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Recent Progress of Transition Metal Nitrides for Efficient Electrocatalytic Water Splitting
Abstract
The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) constitute the two main processes in electrochemical water splitting to produce high-purity hydrogen and oxygen as alternatives to fossil fuel. Catalysts are crucial to high-efficiency conversion of water to hydrogen and oxygen. Although transition metal nitrides (TMNs) are promising HER and OER catalysts due to the unique electronic structure and high electrical conductivity, single-phase nitrides have inferior activity compared to Pt-group metals because of the unsatisfactory metal-hydrogen (M-H) bonding strength. TMNs-based composites in combination with other metals, carbon, and metallic compounds have been demonstrated to possess improved catalytic properties because the modified electronic structure leads to balanced M-H bonding strength, synergistic effects, and improved electrochemical stability. Herein, recent progress pertaining to TMNs is reviewed from the perspective of advanced catalysts for electrochemical water splitting. The challenges and future opportunities confronting TMNs-based catalysts are also discussed.
... 12 In particular, transition metal nitrides (TMNs) have high conductivity, high activity, and high selectivity. 13,14 Transition metal nitrides (TMNs) change the dband structure of metal atoms due to their unique physical and chemical properties and when metal atoms bond with nitrogen atoms, so that the d-band contraction of metal atoms can change the activity of catalytic sites. Therefore, TMNs show great research potential in the direction of electrolytic water. ...
The importance of efficient and stable hydrogen evolution reaction (HER) electrocatalysts for hydrogen production in alkaline conditions to energy crisis resolution and environmental pollution is immense. In general, the quantity of catalytic sites in the electrocatalyst limits the current density of HER. In response to such problems, the bimetallic effect of non-noble bimetallic nitrides has been shown to regulate the corresponding catalytic sites. Here, a microrod-like non-noble bimetallic nitride catalyst with Ni3Mo3N microrods uniformly modified on nickel foam was synthesized by hydrothermal and nitriding processes. The catalyst showed high catalytic activity for HER in 1 M KOH solution. The overpotential was only 28 mV at a current density of 10 mA·cm⁻², demonstrating exceptional electrochemical performance. Furthermore, it exhibited remarkable long-term stability under the same current density. This work will open up a low-cost and simple way for the synthesis of bimetallic nitrides as functional electrode materials for HER and electrochemical detection.
... It is well known that RuO 2 and IrO 2 are the state-of-the-art OER electrocatalysts, but they are severely limited by their high price and scarcity. To this end, people have been engaged in searching for new materials, which including transitionmetal oxides/hydroxides/oxyhydroxides, [5][6][7][8][9][10][11][12][13] transition metals nitrides, [14][15][16] transition metals carbides [17][18][19] and transition metals suldes, [20][21][22] as highly active and abundant OER catalysts. Among them, transition metal phosphides (TMPs) have gained tremendous attention in the eld of OER owing to their adjustable composition, high stability and metallic properties. ...
Designing active and stable electrocatalysts with economic efficiency for oxygen evolution reaction (OER) is essential for developing water splitting process at an industrial scale. Herein, we rationally designed a tungsten doped iron cobalt phosphide incorporated with carbon (Wx–FeCoP2/C), prepared by a mechanochemical approach. X-ray photoelectron spectroscopy (XPS) revealed that the doping of W led to an increasing of Co³⁺/Co²⁺ and Fe³⁺/Fe²⁺ molar ratios, which contributed to the enhanced OER performance. As a result, a current density of 10 mA cm⁻² was achieved in 1 M KOH at an overpotential of 264 mV on the optimized W0.1–FeCoP2/C. Moreover, at high current density of 100 mA cm⁻², the overpotential value was 310 mV, and the corresponding Tafel slope was measured to be 48.5 mV dec⁻¹, placing it among the best phosphide-based catalysts for OER. This work is expected to enlighten the design strategy of highly efficient phosphide-based OER catalysts.
... The development of efficient and cost-effective catalysts for the hydrogen evolution reaction (HER) is important to advanced water electrolysis and the widespread adoption of hydrogen as a clean and sustainable energy source [1,2] . While noble metals such as Pt and Pd exhibit exceptional HER activity, their limited natural reserve and high cost pose significant challenges for large-scale implementation [3,4] . As a result, there is a growing interest in exploring nonprecious metal-based catalysts as alternatives. ...
The development of non-precious metal-based catalysts for the hydrogen evolution reaction (HER) is a promising research area with the potential to advance water electrolysis and enable the widespread use of hydrogen as a clean energy source. While noble metals like Pt and Pd exhibit excellent HER activity, their limited availability and high cost present significant challenges. Non-precious transition metals such as Fe, Co, and Ni have emerged as alternative catalyst materials due to their natural abundance. However, these metals often encounter obstacles related to their hydrogen adsorption behavior. This commentary highlights the various strategies employed to optimize the electronic structures of non-precious metal-based catalysts to enhance the HER performance. The outlook of non-precious metal-based catalysts is bright, with ongoing and future research activities mainly focusing on improving their properties, integrating these catalysts into commercial water electrolysis systems, and improving the scalability for large-scale hydrogen production. The development of high-performance non-precious metal-based catalysts for HER is crucial to future sustainable and efficient hydrogen production in the transition from fossil fuels to clean energy.
... Those insufficiencies will become an obstacle to further development and application. Moreover, the doping amounts of heteroatoms in the catalysts are usually very low, and the doping types are difficult to control [115][116][117][118] and the OER electrocatalysts with complex structures are faced with the difficulty of identifying active sites in complicated electrochemical environments [119][120][121][122][123], which may become obstacles to the further improvement of catalytic activity. Furthermore, the properties of individual 2D carbon nanosheets may be affected because they can aggregate, overlap, or restack due to the Van Der Waals attraction between the slices and the high surface energy. ...
Water splitting is considered a renewable and eco−friendly technique for future clean energy requirements to realize green hydrogen production, which is, to a large extent, hindered by the oxygen evolution reaction (OER) process. In recent years, two−dimensional (2D) carbon−based electrocatalysts have drawn sustained attention owing to their good electrical conductivity, unique physicochemical properties, and excellent electrocatalytic performance. Particularly, it is easy for 2D carbon−based materials to form nanocomposites, which further provides an effective strategy for electrocatalytic applications. In this review, we discuss recent advances in synthetic methods, structure−property relationships, and a basic understanding of electrocatalytic mechanisms of 2D carbon−based electrocatalysts for water oxidation. In detail, precious, non−precious metal−doped, and non−metallic 2D carbon−based electrocatalysts, as well as 2D carbon−based confined electrocatalysts, are introduced to conduct OER. Finally, current challenges, opportunities, and perspectives for further research directions of 2D carbon−based nanomaterials are outlined. This review can provide significant comprehension of high−performance 2D carbon−based electrocatalysts for water-splitting applications.
... 26,27 Advanced electrocatalysts for OER have been identified in the form of cobalt-based catalysts, which include hydroxides, 28,29 oxides/peroxides, 30−32 sulfides, 33−35 phosphates/phosphides, 36,37 and nitrides. 38,39 In 2012, Stahl et al. synthesized a series of binuclear Co III bridging peroxo complexes that emphasize the significance of a stable ligand framework to prevent ligand exchange and decomposition of the Co complex during water oxidation. 32 In 2016, Shi and co-workers synthesized a robust, homogeneous cobalt-based catalyst capable of electrocatalyzing water oxidation at high pH and low overpotential (η = 520 mV) in a phosphate buffer. ...
... Various energy sources are available for splitting water, including solar, wind, nuclear, photocatalysts, and electrocatalysis. [11][12][13][14][15][16][17][18][19][20] A simple, cost-effective, and environmentally friendly way to split water is by using electrocatalysts. Oxygen and hydrogen gas produced by this process can be used to power a wide variety of applications. ...
A simple, scalable, and environmentally friendly process was demonstrated for the synthesis of Co3O4 nanostructures using lemon juice and hydrothermal chemistry. The reducing, capping, and stabilizing agents in lemon juice result in improved performance in oxygen evolution reactions and supercapacitors due to their positive effects on morphology, crystal size, and surface defects. Several techniques were used to characterize Co3O4 nanostructures grown with different quantities of lemon juice, including field emission scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. The results show that lemon juice alters the size and homogeneity of Co3O4 nanostructures as well as surface defects like oxygen vacancies and interstitial Co. A sample prepared with 4 mL of lemon juice (sample 1) performed best, demonstrating an overpotential of 260 mV at 10 mA cm−2 and good stability at 20 mA cm−2 for 40 h. With the prepared nanomaterial, supercapacitors were developed with a specific capacitance of 398 F g−1 at 0.8 A g−1, a specific capacity retention percentage of 97%, a high energy density of 9.5 Wh kg−1, and excellent stability during 880 galvanic charge and discharge cycles. Co3O4 nanostructures have experienced dramatic improvements in electrochemical performance as a result of morphological changes and oxygen vacancy concentrations on their surfaces. By reducing, capping, and stabilizing lemon juice, a new generation of electroactive electrodes have been developed for storage and conversion of energy.
... The rising overuse of conventional fossil fuels in recent years has severely impacted the environment, which has made using clean energy sources an urgent aspect of future sustainable development [1][2][3]. Hydrogen, due to its potential utilization in electrochemical processes, superior gravimetric energy density compared to conventional fuels, and its capacity to generate substantial amounts of energy, avails itself as a prominent contender among the green energy sources with the most potential in the twenty-first century [4][5][6]. Electrochemical splitting of water into hydrogen and oxygen, (Hydrogen/Oxygen evolution reaction) has been shown to be a renewable, effective, and ecologically benign alternative to commercial H 2 generating technologies [7]. In the context of water electrolysis, the evolution of hydrogen and oxygen occurs continuously at the anode and cathode, respectively. ...
The advancement of renewable energy technologies like water electrolysis and hydrogen fuel cells relies on the fabrication of effective and reliable catalysts for the hydrogen evolution process (HER). In this regard, we report gold nanoparticles embedded in laser-induced graphene electrodes for regulation of overpotential and electrocatalytic performance of hydrogen evolution reaction. Gold nanoparticles were deposited onto the LIG surface using electrode deposition via cyclic voltammetry (CV) at different cycle lengths. The catalyst fabrication technique enables the manipulation of many electrochemical parameters, such as overpotential value, charge transfer resistance, electrochemical active surface area, and tafel slope, through the adjustment of cyclic voltammetry (CV) cycles. The LIG-Au@50 sample demonstrates remarkable electrocatalytic characteristics, as evidenced by its low overpotential of 141 mV at a current density of 10 mA/cm2 and reduced tafel slope of 131 mV/decade in an acidic environment. Furthermore, the presence of an augmented electrochemical active surface area, a mass activity of 8.80 A/g, and a high turnover frequency of 0.0091 s−1 suggest elevated and significant accessibility to plentiful active sites. A significant decrease in charge transfer resistance resulted in an enhanced rate of the water-splitting reaction.
... It has therefore been a pressing task to continue developing high-efficient NPM-based HER electrocatalysts for producing hydrogen. Since then, a lot of advancements have been achieved, leading to the creation of the electrode materials phosphides, carbides, sulfides, nitrides, oxides, and nanocarbon free of metal particles [220][221][222][223][224]. However, two major issues remain the low electrical conductivity, which causes the active coating to thicken, and activity to drop rapidly. ...
The unique properties of two-dimensional (2D) materials have piqued the interest of the technical community. Titanium carbide (MXene) is a member of a rapidly expanding family of 2D materials with exceptional physiochemical characteristics and a wide range of uses in the environmental feld. 2D MXene has long been a topic of interest in environmental applica�tions, including wastewater treatment, electromagnetic interference (EMI) shielding, photocatalysis, and hydrogen evolution reactions (HER) due to its high conductivity, varied band gap, hydrophilic nature, and exceptional structural stability. This study covers important developments in 2D MXene and discusses how design, synthetic methods, and stability have changed over time. In this review paper, we have discussed the strategy synthesizing of conventional, afordable heterojunctions and Schottky junctions, as well as the development, mechanisms, and trends in the deterioration of environmental organic con�taminants, HER, and EMI Shielding. We also explore the obstacles and restrictions that prevent the scientifc community from producing practical MXene with regulated characteristics and structures for environmental applications and analyzing its present usage. The hazardous-environmental aspects of MXene-based materials and the problems and future possibilities of these applications are also examined and emphasized. This review paper focused on environmental applications such as heavy metal detection and removal, EMI shielding, and hydrogen generation using MXenes. The issues related to wastewa�ter, electromagnetic interference, and clean energy production are very persistent in the environment, and a better material is required to address these challenges. Thus, MXene is a kind of material that could be a better alternative to address these persistent issues, and hence, this review becomes very important, which can pave the way for the development of MXene�based materials to address these issues.
... Different non-noble metal catalysts that are tuned for HER and OER have recently come to light as cutting-edge materials for water splitting [12][13][14]. OER components may be fabricated from a wide variety of materials, which include transition-metal (TM) nitrides [15,16], TM carbides [17], TM sulfides [18], perovskites [19], TM oxides, and hydroxides [20,21]. It can be difficult to develop electro-catalysts that are advantageous for system simplicity and cost reduction while simultaneously being efficient and long-lasting for both HER and OER in the same electrolyte. ...
For the water-splitting process, it is essential to improve the search for low-cost, highly active materials that can catalyze the oxygen evolution reaction (OER). Based on this, the current work suggests a unique method for creating g-C3N4/CdS nanocomposite. The g-C3N4/CdS nanocomposite loaded on nickel foam (NF) required overpotential of 279.6 mV for the OER, which is higher than overpotentials required by g-C3N4 and CdS for attaining desired standard current density of 10 mA cm⁻² under the same circumstances. Findings elucidate high activity of composite material through increased active sites with ECSA of 130 cm², very low charge-transfer resistance Rct value of 2.5 (Ω) and decreased tafel slope value of 44.5 mV dec⁻¹. All these factors are accountable for the improved OER activity and faster reaction kinetics. The material was characterized through XRD, FTIR, SEM, EDS, and XPS techniques.
Graphical abstract
Two new heteroleptic cobalt(III)diakyldithiophosphate complex cations with 1,2-bis(diphenylphosphino)ethane (dppe) ancillary ligand having formula [Co{S2P(OR)2}2(dppe)](B(C6H5)4) (R = -C2H5 (Co-Et); -CH(CH3)2 (Co-Pr)) have been synthesized and characterized spectroscopically as well as by...
Electrochemical energy storage and conversion systems (EESCSs), including batteries, supercapacitors, fuel cells, and water electrolysis technologies, enabling the direct conversion between chemical and electrical energies. They are key to the flexible storage and utilization of renewable energy and play an important role in future energy technologies. The physical and chemical properties of electrode materials significantly influence the performance of EESCSs, necessitating the development of materials with both high cost‐effectiveness and superior electrochemical storage and catalytic capabilities. Layered double hydroxides (LDHs), due to their unique properties as high surface area, evenly distributed active sites, and tunable compositions, makes themselves and the derivatives have become focal points in the EESCSs. This review summarizes recent advances of LDH and their derivates for diverse EESCSs applications, aims to elucidate the modification strategies of LDH materials and provide valuable insights for exploring LDH‐derived materials in various electrochemical devices, offering interdisciplinary perspectives for the rational design of LDH‐based materials.
The multi-interface nanotube structured phosphorus-doped bimetallic oxide P-CoMoO 4 /CF-1 exhibits remarkable water splitting catalytic activity. The nanotube structure decorated with MOFs arrays with unique surfaces provides abundant active sites.
Recent development and expansion in electrochemical water splitting processes have driven the research community to explore an efficient, economical and eco-friendly electrocatalyst. Within this domain, the electrocatalytic oxygen evolution reaction (OER) presents a notable challenge due to its inherent inefficiency arising from a sluggish four-electron transfer process. In the present study, we investigated a hydrothermal technique for synthesizing an electrocatalyst featuring MnO-embedded CoFe2O4 spinel oxide, which is firmly anchored onto a nickel foam (NF) substrate. The electrocatalyst demonstrated impressive performance, exhibiting exceptional stability over an 82-h endurance test. A significantly smaller overpotential was required for OER, achieving a notable decrease of 179 mV. Furthermore, it displayed a Tafel value of approximately 68 mV dec−1 at current density of 10 mA cm−2 for OER, underscoring its exceptional electrocatalytic performance. In light of these compelling findings, the current research has introduced a feasible, environmentally friendly, and potentially high-impact strategy towards the development of cost-effective transition metal-based catalysts, highly suitable for use as electrodes in electrochemical water splitting applications.
The advancement of a sustainable and scalable catalyst for hydrogen production is crucial for the future of the hydrogen economy. Electrochemical water splitting stands out as a promising pathway for sustainable hydrogen production. However, the development of Pt‐free electrocatalysts that match the energy efficiency of Pt while remaining economical poses a significant challenge. This review addresses this challenge by highlighting latest breakthroughs in Pt‐free catalysts for the hydrogen evolution reaction (HER). Specifically, we delve into the catalytic performance of various transition metal phosphides, metal carbides, metal sulphides, and metal nitrides toward HER. Our discussion emphasizes strategies for enhancing catalytic performance and explores the relationship between structural composition and the performance of different electrocatalysts. Through this comprehensive review, we aim to provide insights into the ongoing efforts to overcome barriers to scalable hydrogen production and pave the way for a sustainable hydrogen economy.
Heterogeneous catalysts have attracted extensive attention among various emerging catalysts for their exceptional oxygen evolution reaction (OER) capabilities, outperforming their single‐component counterparts. Nonetheless, the synthesis of heterogeneous materials with predictable, precise, and facile control remains a formidable challenge. Herein, a novel strategy involving the decoration of catalysts with CeO 2 is introduced to concurrently engineer heterogeneous interfaces and adjust phase composition, thereby enhancing OER performance. Theoretical calculations suggest that the presence of ceria reduces the free energy barrier for the conversion of nitrides into metals. Supporting this, the experimental findings reveal that the incorporation of rare earth oxides enables the controlled phase transition from nitride into metal, with the proportion adjustable by varying the amount of added rare earth. Thanks to the role of CeO 2 decoration in promoting the reaction kinetics and fostering the formation of the genuine active phase, the optimized Ni 3 FeN/Ni 3 Fe/CeO 2 ‐5% nanoparticles heterostructure catalyst exhibits outstanding OER activity, achieving an overpotential of just 249 mV at 10 mA cm ⁻² . This approach offers fresh perspectives for the conception of highly efficient heterogeneous OER catalysts, contributing a strategic avenue for advanced catalytic design in the field of energy conversion.
Electrochemical water splitting is one of the promising approaches for the production of molecular hydrogen as well as to meet the clean and sustainable energy demand of the modern world. However, the key task for the research communities is to design a cost‐effective and efficient electrocatalyst to contribute positively to recent world crises. This study presents a novel SiO2@TiN nanocomposite and utilize it for oxygen evolution reaction (OER) as an electrocatalysts. The different techniques use for the characterization of SiO2@TiN nanocomposite. The electrochemical investigations encompass linear sweep voltammetry (LSV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) which collectively yield critical parameters for assessing electrocatalytic performance. At a current density of 10 mAcm⁻² the SiO2@TiN nanocomposite has a substantially lower overpotential of 256 mV compared to pure SiO2 and TiN. The composite also shows smaller tafel slope of 40 mV dec⁻¹ as well as lower overpotential. The SiO2@TiN nanocomposite also demonstrates the enhanced redox activity as a result of its synergistic effect. Consequently, the increased electrical conductivity of TiN facilitates the attachment of metal oxides and more active sites are exposed to improve the OER activity of the fabricated materials.
Transition metal selenides (TMSes) have gained significant attention as viable non-noble metal catalysts for water splitting due to their low cost and potential electrocatalytic activity. However, the electrocatalytic activity of...
Nickel nitride (Ni 3 N) is a promising electrocatalyst for hydrogen evolution reaction (HER) owing to its excellent metallic features, and has been demonstrated to exhibit considerable interest for water oxidation. However,...
This study successfully prepared porous single crystal niobium nitride microcubes with abundant active sites, which greatly enhances the catalytic activity and stability of the electrode.
In order to decrease the overpotentials required for the electrocatalytic water splitting reaction, high-performance and abundant-element based-electrocatalysts have to be developed. Especially, high-surface-area materials are considered as promising candidates to drive the oxygen evolution reaction (OER) at low overpotentials in alkaline and acidic media owing to a large amount of available active surface sites. In this context, mesoporous spinel cobalt oxide (meso-Co3O4) thin films on conductive substrates were prepared for the first time by the dip-coating and soft-templating approach using cobalte nitrate as precursor and commercially available, low-cost Pluronic® F-127 as structure-directing agent. By making use of the evaporation-induced self-assembly (EISA) process, citric acid was applied as structural stabilizer reported yet to be only compatible with customized polymers for formation of mesoporous thin films. The usage of commercial Pluronic® F-127 was reported to result in breakdown of the mesoporous framework. However, this work shows that both Pluronic® F-127 and citric acid are compatible and can be utilized to produce uniform mesoporous networks after annealing. The meso-Co3O4 thin film was found to be crack-free on the nano- and macroscale, thus offering a highly accessible nanoarchitecture ensuring a large interface to any electrolyte allowing for efficient mass transport. The surface and bulk morphology, crystallographic structure, and surface composition of the mesostructured Co3O4 thin film were correlated to its OER activity. The Co3O4 nanostructure showed, when applied as OER catalyst, a low overpotential of 340 mV vs. RHE at 10 mA cm⁻² in 1 M KOH. The electrochemical performance was evaluated by means of impedance spectroscopy and Tafel plot analysis confirming enhanced electron transfer at the electrode/electrolyte interface. The Co3O4 electrocatalyst exhibited a promising stability under alkaline conditions over more than 4 hours upon chronopotentiometry (OER-activity loss of only 2% at 10 mA cm⁻²). Our preparation procedure reveals the general capability of combining commercial copolymer templates with citric acid and can be transferred to other metal oxides to produce low-cost and high-surface-area materials for electrochemical applications.
To increase the effectiveness of both the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER), significant efforts are made to produce bifunctional water‐splitting electrocatalysts. In this study, bismuth oxide/nickel oxide (Bi2O3/NiO)‐based composite is supported over the nickel foam (Bi2O3/NiO‐NF) and carbon nanotube fiber (Bi2O3/NiO‐CNTF) to develop two different electrode systems for water‐splitting studies. For OER, Bi2O3/NiO‐NF and Bi2O3/NiO‐CNTF require overpotential of 401 and 369 mV, respectively, to achieve the current density of 50 mA cm⁻² in alkaline media, while the current density of 50 mA cm⁻² is achieved at overpotential of 398 and 304 mV, respectively, in neutral media. For HER, Bi2O3/NiO‐NF and Bi2O3/NiO‐CNTF achieve the current density of 50 mA cm⁻² at overpotential of 301 and 268 mV, respectively, in neutral media. For overall water splitting in neutral media, Bi2O3/NiO‐CNTF achieves the current density of 50 mA cm⁻² at cell voltage of 1.654 V. The promising performance of synthesized electrocatalysts reveals that the mixed metal oxides (p‐block and d‐block elements)‐based electrocatalysts can be potential candidates for practical water splitting in basic (1 M KOH) as well as neutral media (1 M phosphate‐buffered saline).
The unique catalytic activities of high‐entropy alloys (HEAs) emerge from the complex interaction among different elements in a single‐phase solid solution. As a “green” nanofabrication technique, inert gas condensation (IGC) combined with laser source opens up a highly efficient avenue to develop HEA nanoparticles (NPs) for catalysis and energy storage. In this work, the novel N‐doped non‐noble HEA NPs are designed and successfully prepared by IGC. The N‐doping effects of HEA NPs on oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are systematically investigated. The results show that N‐doping is conducive to improving the OER, but unfavorable for HER activity. The FeCoNiCrN NPs achieve an overpotential of 269.7 mV for OER at a current density of 10 mA cm⁻² in 1.0 M KOH solution, which is among the best reported values for non‐noble HEA catalysts. The effects of the differences in electronegativity, ionization energy and electron affinity energy among mixed elements in N‐doped HEAs are discussed as inducing electron transfer efficiency. Combined with X‐ray photoelectron spectroscopy and the extended X‐ray absorption fine structure analysis, an element‐design strategy in N‐doped HEAs electrocatalysts is proposed to improve the intrinsic activity and ameliorate water splitting performance.
Transition metal nitrides (TMNs), an encouraging and new class of emerging materials for energy storage devices , such as supercapacitors (SCs) and batteries, including Lithium-ion batteries (LIBs), Potassium-ion batteries (KIBs), Zn-air battery, Lithium-S battery (Li-S), Sodium sulfur (Na-S), and Lithium-O 2 battery (Li-O 2) due to their wide bandgap, flat and adjacent potential similar to lithium-metal, high capacity, superior conductivity, ideal chemical stability, and tunable structure. From this perspective, Fe 2 N is the best electrode for electrochemical energy storage devices due to its brilliant electrical conductivity, high capacity, environmental friendliness, low resistance, economical and natural abundance. Large strains, due to the nano-size effect, offer large exposed areas and more active centers for charge accommodations. In the existing literature, no single review article outlines the energy storage performance of adorable Fe 2 N, a rising star in the TMNs family, and its composite electrodes for advanced energy storage technologies. The recent research progress in Fe 2 N, Fe 2 N-based nano-structures for advanced SCs, LIBs together with Na-ion, Li-S, Na-S, KIBs, Li-O 2 , and Zn-air batteries are briefly oulined in this review report. Howevetr, a sustainable strategies, structural features of various nanostructured electrodes, and the current research progress are advocated for future evaluation.
Hydrogen (H2) is now deemed one of the prominent energy solutions in the 21st century due to the significant scientific and technological efforts entailed for the renewable carbon-free H2-based economy....
Developing abundant Earth‐element and high‐efficient electrocatalysts for hydrogen production is crucial in effectively reducing the cost of green hydrogen production. Herein, a strategy by comprehensively considering the computational chemical indicators for H* adsorption/desorption and dehydrogenation kinetics to evaluate the hydrogen evolution performance of electrocatalysts is proposed. Guided by the proposed strategy, a series of catalysts are constructed through a dual transition metal doping strategy. Density Functional Theory (DFT) calculations and experimental chemistry demonstrate that cobalt‐vanadium co‐doped Ni3N is an exceptionally ideal catalyst for hydrogen production from electrolyzed alkaline water. Specifically, Co,V‐Ni3N requires only 10 and 41 mV in alkaline electrolytes and alkaline seawater, respectively, to achieve a hydrogen evolution current density of 10 mA cm⁻². Moreover, it can operate steadily at a large industrial current density of 500 mA cm⁻² for extended periods. Importantly, this evaluation strategy is extended to single‐metal‐doped Ni3N and found that it still exhibits significant universality. This study not only presents an efficient non‐precious metal‐based electrocatalyst for water/seawater electrolysis but also provides a significant strategy for the design of high‐performance catalysts of electrolyzed water.
Developing bifunctional catalysts that can catalyze both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is pivotal to commercializing large-scale water splitting. Herein, a novel hollow nanotriangle composed of NiFe LDH-CoMoSx heterojunction (H-CMSx@NiFe LDH) is proposed as a highly efficient bifunctional electrocatalyst for both OER and HER. To fabricate a heterojunction system, ultra-thin nickel–iron layered double hydroxide (NiFe LDH) nanosheets are uniformly electrodeposited onto a metal–organic framework-derived hollow CoMoSx nanotriangle. The strong coupling of CoMoSx and NiFe LDH catalysts forms the intimate heterojunction interfaces to facilitate interfacial charge transfer, which is favorable to enhance the bifunctional catalytic activity. Moreover, the large void of CoMoSx nanotriangles and interconnected ultra-thin NiFe LDH nanosheets result in good electrolyte penetration and gas release. Therefore, the as-prepared H-CMSx@NiFe LDH on nickel foam (NF) exhibits an impressive catalytic activity and durability for OER and HER activities, delivering a current density of 100 mA·cm−2 at the small overpotentials of 214 and 299 mV in OER and HER, respectively. Meanwhile, H-CMSx@NiFe LDH/NF proves to be an effective electrode for an alkaline electrolyzer, as a voltage of only 1.99 V is enough to achieve a current density voltage of only 1.99 V is enough to achieve a current density of 400 mA·cm−2 with no degradation in performance over 50 h.
Planar supercapacitors have recently attracted much attention owing to their unique and advantageous design for 2D nanomaterials based energy storage devices. However, improving the electrochemical performance of planar supercapacitors still remains a great challenge. Here we report for the first time a novel, high-performance in-plane supercapacitor based on hybrid nanostructures of quasi-2D ultrathin MnO2/graphene nanosheets. Specifically, the planar structures based on the δ-MnO2 nanosheets integrated on graphene sheets not only introduce more electrochemically active surfaces for absorption/desorption of electrolyte ions, but also bring additional interfaces at the hybridized interlayer areas to facilitate charge transport during charging/discharging processes. The unique structural design for planar supercapacitors enables great performance enhancements compared to graphene-only devices, exhibiting high specific capacitances of 267 F/g at current density of 0.2 A/g and 208 F/g at 10 A/g and excellent rate capability and cycling stability with capacitance retention of 92% after 7000 charge/discharge cycles. Moreover, the high planar malleability of planar supercapacitors makes possible superior flexibility and robust cyclability, yielding capacitance retention over 90% after 1000 times of folding/unfolding. Ultrathin 2D nanomaterials represent a promising material platform to realize highly flexible planar energy storage devices as the power back-ups for stretchable/flexible electronic devices.
Lithium-sulfur batteries (LSBs), with large specific capacity (1,675 mAh g⁻¹), are regarded as the most likely alternative to the traditional Lithium-ion batteries. However, the intrinsical insulation and dramatic volume change of sulfur, as well as serious shuttle effect of polysulfides hinder their practical implementation. Herein, we develop three-dimensional micron flowers assembled by nitrogen doped carbon (NC) nanosheets with sulfur encapsulated (S@NC-NSs) as a promising cathode for Li-S to overcome the forementioned obstacles. The in situ generated S layer adheres to the inner surface of the hollow and micro-porous NC shell with fruitful O/N containing groups endowing both efficient physical trapping and chemical anchoring of polysulfides. Meanwhile, such a novel carbon shell helps to bear dramatic volume change and provides a fast way for electron transfer during cycling. Consequently, the S@NC-NSs demonstrate a high capacity (1,238 mAh g⁻¹ at 0.2 C; 1.0 C = 1,675 mA g⁻¹), superior rate performance with a capacity retention of 57.8% when the current density increases 25 times from 0.2 to 5.0 C, as well as outstanding cycling performance with an ultralow capacity fading of only 0.064% after 200 cycles at a high current density of 5.0 C.
The nitrogen/hydrogen (N2/H2) plasma-treated strontium titanate (SrTiO3) crystals with different orientations of (111), (110) and (100) were obtained using microwave plasma chemical vapor deposition, which was proved to be a simple and effective strategy to fundamentally improve the photocatalytic performance. It is found that plasma-treated SrTiO3 crystals exhibit different photocatalytic properties in relation to crystalline anisotropy, plasma types and microwave power. The N: SrTiO3 samples display higher photocatalytic activity compared to the untreated sample and N2/H2-treated sample. The (111) N: SrTiO3 which is treated using N2 plasma of 600 W shows the best photocatalytic performance in the current research. The dopants of nitrogen can serve as electron donors, which introduce impurity states in various positions in the band gap of SrTiO3 and lead to different degrees of modification in electrical conductivity. The enhancement for photocatalytic properties and the effects of N2 plasma treatment on the charge separation and transfer efficiency will be discussed.
Practical application of hydrogen production from water splitting relies strongly on the development of low-cost and high-performance electrocatalysts for hydrogen evolution reaction (HER). The previous researches mainly focused on transition metal nitrides as HER catalysts due to their electrical conductivity and corrosion stability under acidic electrolyte, while tungsten nitrides have reported poorer activity for HER. Here the activity of tungsten nitride is optimized through rational design of a tungsten nitride-carbon composite. More specifically, tungsten nitride (WN
x
) coupled with nitrogen-rich porous graphene-like carbon is prepared through a low-cost ion-exchange/molten-salt strategy. Benefiting from the nanostructured WN
x
, the highly porous structure and rich nitrogen dopant (9.5 at%) of the carbon phase with high percentage of pyridinic-N (54.3%), and more importantly, their synergistic effect, the composite catalyst displays remarkably high catalytic activity while maintaining good stability. This work highlights a powerful way to design more efficient metal-carbon composites catalysts for HER.
In this work, a reaction coupling self-propagating high-temperature synthesis (RC-SHS) method was developed for the in situ controlled synthesis of novel, high activity TiB2/(TiB2-TiN) hierarchical/heterostructured nanocomposites using TiO2, Mg, B2O3, KBH4 and NH4NO3 as raw materials. The as-synthesized samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray energy dispersive spectroscopy (EDX), transition electron microscopy (TEM), high-resolution TEM (HRTEM) and selected-area electron diffraction (SAED). The obtained TiB2/TiN hierarchical/heterostructured nanocomposites demonstrated an average particle size of 100-500 nm, and every particle surface was covered by many multibranched, tapered nanorods with diameters in the range of 10-40 nm and lengths of 50-200 nm. In addition, the tapered nanorod presents a rough surface with abundant exposed atoms. The internal and external components of the nanorods were TiB2 and TiN, respectively. Additionally, a thermogravimetric and differential scanning calorimetry analyzer (TG-DSC) comparison analysis indicated that the as-synthesized samples presented better chemical activity than that of commercial TiB2 powders. Finally, the possible chemical reactions as well as the proposed growth mechanism of the TiB2/(TiB2-TiN) hierarchical/heterostructured nanocomposites were further discussed.
Well-dispersed and highly efficient molybdenum nitrides on nitrogen-doped carbon matrix (Mo2N@NC) are reported as new and active electrocatalyst for hydrogen evolution in alkaline electrolyte. The key point of fabricating this catalyst is using HNO3-treated melamine, other than pristine melamine, as carbon and nitrogen pool to realize the complete nitridation of MoO3 to Mo2N nanoparticles in size of 4 nm and at the same time to generate nitrogen-doped carbon matrix to support these nanoparticles by thermolysis under Ar atmosphere. The as-prepared Mo2N@NC exhibits excellent HER activity in 1 M KOH with a pretty low overpotential of 85 mV to achieve the current density of 10 mA cm-2 and a small Tafel slope of 54 mV dec-1, which is among the best for Mo-based compounds and better than most non-noble metal electrocatalysts to date in alkaline media. It is also much better than the incomplete nitride compounds (MoO2/Mo2N@NC) and mixture of nitrides and carbides (Mo2N/Mo2C@NC) fabricated under similar conditions, from aspects of overpotential, Tafel slope, exchange current density, conductivity, active surface area and turnover frequencies. Therefore Mo2N represents a new kind of very active HER catalyst in alkaline electrolyte. Also this work provides an effective method to fabricate metal nitrides/carbon composites for other applications.
A noble-metal-free and high-efficient bifunctional catalyst for overall water splitting is greatly desirable to generate clean and sustainable energy carrier such as hydrogen, but remains enormous challenges. Herein, we design and grow the porous interconnected iron-nickel nitride nanosheets on the carbon fiber cloth (FeNi-N/CFC) combing a facile electrodeposition method and in situ nitrogenization process. The as-synthesized FeNi-N/CFC with a low mass loading of 0.25 mg cm-2 exhibits excellent catalytic activities for both oxygen evolution reaction (OER) with 20 mA cm-2 at overpotential (η) of 232 mV and hydrogen evolution reaction (HER) with 10 mA cm-2 at η = 106 mV. Moreover, as bifunctional electrocatalyst for overall water splitting FeNi-N/CFC only requires a cell voltage of 1.55 V to drive a current density (j) of 10 mA cm-2 and shows robust long-term durability at j > 360 mA cm-2 with a negligible change in current density over 60 h, revealing its promising application in commercial electrolyzer.
Two-dimensional (2D) transition metal nitrides just recently entered the research arena, but already offer a potential for high-rate energy storage, which is needed for portable/wearable electronics and many other applications. However, lack of efficient and high-yield synthesis methods for 2D metal nitrides have been a major bottleneck for manufacturing of those potentially very important materials, and only MoN, Ti4N3 and GaN have been reported so far. Here we report a scalable method that uses reduction of 2D hexagonal oxides in ammonia to produce 2D nitrides, such as MoN. MoN nanosheets with subnanometer thickness have been studied in depth. Both theoretical calculation and experiments demonstrate the metallic nature of 2D MoN. The hydrophilic restacked 2D MoN film exhibits a very high volumetric capacitance of 928 F cm-3 in sulfuric acid electrolyte with an excellent rate performance. We expect that the synthesis of metallic 2D MoN and two other nitrides (W2N and V2N) demonstrated here will provide an efficient way to expand the family of 2D materials and add many members with attractive properties.
Exploring efficient and durable catalysts from earth-abundant and cost-effective materials is highly desirable for the sluggish anodic oxygen evolution reaction (OER), which plays a key role in water splitting, fuel cells, and rechargeable metal-air batteries. First-row transition metal (Ni, Co, and Fe)-based compounds are promising candidates as the OER catalysts to substitute the benchmark of noble metal-based catalysts, such as IrO2 and RuO2. Although Fe is the cheapest and one of the most abundant transition metal elements, there are seldom papers reported on Fe-only compounds with outstanding catalytic OER activities. Here we propose an interesting strategy by growing iron nitride (Fe3N/Fe4N)-based nanoporous film on three-dimensional (3D) highly conductive graphene/Ni foam, which is demonstrated to be a robust and durable self-supported 3D electrode for the OER featured by a very low overpotential of 238 mV to achieve a current density of 10 mA/cm2, small Tafel slope of 44.5 mV/dec, good stability and 96.7% Faradaic yield. The high OER efficiency is by far one of the best for single metal (Fe, Co, and Ni)-based catalysts, and even better than the benchmark IrO2, which is attributed to the fast electron transfer, high surface area, and abundant active sites of the catalyst. This development introduces another member to the family of cost-effective and efficient OER catalysts.
In order to improve the corrosion and wear resistance of biomedical Ti-6Al-4V implants, a Ta2N nanoceramic coating was synthesized on a Ti-6Al-4V substrate by the double glow discharge plasma process. The Ta2N coating, composed of fine nanocrystals, with an average grain size of 12.8 nm, improved the surface hardness of Ti-6Al-4V and showed good contact damage tolerance and good adhesion strength to the substrate. The corrosion resistance of the Ta2N coating in Ringer's physiological solution at 37 °C was evaluated by different electrochemical techniques: potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), potentiostatic polarization and capacitance measurements (Mott-Schottky approach). The evolution of the surface composition of the passive films at different applied potentials was determined by X-ray photoelectron spectroscopy (XPS). The results indicated that the Ta2N coating showed higher corrosion resistance than both commercially pure Ta and uncoated Ti-6Al-4V in this solution, because of the formed oxide film on the Ta2coating showed highern coating having a smaller carrier density (Nd) and diffusivity (Do) of point defects. The composition of the surface passive film formed on the Ta2N coating changed with the applied potential. At low applied potentials, the oxidation of the Ta2N coating led to the formation of tantalum oxynitride (TaOxNy) but, subsequently, the tantalum oxynitride (TaOxNy) could be chemically converted to Ta2O5 at higher applied potentials.
All-polymer solar cells (All-PSCs) have attracted a lot of attention in the recent years due to broad absorption spectra, adjustable chemical structures, high morphological stability, better donor-acceptor compatibility and better mechanical durability. This review summarizes the recent development of perylene diimides (PDI)-based electron acceptors used in all-PSCs because these polymers are promising candidates. The photovoltaic performances of non-fullerene polymer acceptors were compared, and the structure-performance relationship was discussed when the same donor material was used.
The n-type semiconductor sodium bismuth molybdate and p-type multiwall carbon nanotube (n-NaBi(MoO4)2/p-MWCNT) composites were synthesized by solvothermal method. MWCNT were added to the mixed solution of NaBi(MoO4)2 precursor before solvothermal. All the as-prepared NaBi(MoO4)2 were the same tetragonal scheelite nanocrystal, the composites have similar specific surface area and higher than pure NaBi(MoO4)2. SEM results showed that the composites were composed of NaBi(MoO4)2 nanoparticles coated MWCNT, the morphology of the NaBi(MoO4)2 in composites was nanoparticles and different from nanorods in the pure NaBi(MoO4)2. The low MWCNT content composites show good gas sensitivity. The sensors based on 1 wt% MWCNT doping NaBi(MoO4)2 shows the highest gas response and selectivity to n-butanol at 300 °C. The 1 wt% MWCNT doping NaBi(MoO4) sensor can be appiled as n-butanol gas sensors.
The development of acceptor-donor-acceptor (A-D-A) type fused-ring electron acceptors boosted the energy conversion efficiency of organic solar cells. Certified record power conversion efficiencies of single junction organic solar cells have exceeded 14%. In this paper, we briefly reviewed the development of A-D-A type fused-ring electron acceptors which were reported since 2014. The planarity of the central donor moieties, the effects of bulky side-chain and the end-group modification were highlighted.
The Fe2(MoO4)3 nanoparticles were prepared by hydrothermal method using polyvinyl pyrrolidone (PVP) as surfactant. The crystal phase, morphology and microstructure were characterized by x-ray diffraction, scanning electron microscopy. The results indicated the Fe2(MoO4)3 nanoparticles were composed of sphere-like monoclinic nanocrystals with average size of 50 nm. The sensor based on the Fe2(MoO4)3 nanoparticles exhibits good gas-sensing performances, especially to acetone. The response to acetone was significantly higher than that to other gases. The responses of the sensor were 2.45, 24.7, respectively, to 1 ppm and 100 ppm acetone at the optimal operating temperature of 340 °C. The Fe2(MoO4)3 nanoparticles can be potential material for high response and low concentration acetone selective sensor which can be applied in diabetes diagnosis.
The addition of tin (Sn) is commonly used as a design strategy for catalyst optimization of platinum-based catalysts. The mechanistic understanding of this class of systems is, however, obscured by the structural complexity. Herein, a series of catalyst characterization techniques including X-ray absorption fine structure (XAFS) and in-situ CO diffuse reflectance infrared fourier transform spectroscopy (CO-DRIFTS) were utilized to study the catalyst structure. It was found that the structure and catalytic properties are closely related with the interaction between Pt and SnO2 (specifically the Pt-SnO2 strong metal-support interaction (SMSI)), which can be continuously tuned by thermal treating the Pt-Sn/SiO2 precursor at different atmospheres and temperatures. The treatment in an oxidative atmosphere (O2) also can generate Pt-SnO2 SMSI, which became weak at higher temperatures and led to the growth of Pt nanoparticles (NPs). Pt-SnO2 SMSI became stronger when the oxygen atmosphere was changed to an inert (N2) atmosphere. Small metallic Pt NPs were formed and their dispersion was increased with increasing treatment temperature with inert gas. The catalyst presented a moderate activity in the dehydrogenation of lower alkanes. The treatment in a reductive atmosphere (H2) produced the strongest Pt-SnO2 SMSI and most active catalyst. Highly dispersed Sn surface-enriched Pt–Sn alloy NPs were formed on SiO2, in which Pt was most electron rich. The apparent activation energy in n-butane dehydrogenation is higher on Pt–Sn/SiO2_1073 K H2 than the corresponding one on Pt–Sn/SiO2_1073 K N2. The kinetic studies revealed that the extreme isolation of Pt on Pt–Sn/SiO2_1073 K H2 (geometrical effects) dominantly contributed to its superior catalytic performance. The present work highlights the effects of thermal treatment-induced Pt-SnO2 SMSI, providing a new insight into the structure of Pt–Sn bimetallic catalysts and the promotional role of Sn in the dehydrogenation of lower alkanes to olefins on Pt surfaces.
Non-noble-metal electrocatalysts for water splitting hold great promises for developing sustainable and clean energy sources. Herein, a highly efficient bifunctional electrode consisting of Ni-doped molybdenum nitride nanorods on Ni foam is prepared through topotactic transformation of NiMoO4 nanorods that are in situ hydrothermally grown on Ni foam. The electrode not only contains rich, accessible, electrochemically active sites, but also possesses extraordinary chemical stability. It exhibits excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance in 1.0 M KOH with low overpotentials of 15 mV and 218 mV, respectively, at a current density of 10 mA cm⁻², superior to the commercial benchmark materials Pt/C and RuO2 under the same condition. A simple water electrolyzer using the obtained electrode as both the anode and cathode needs a very low cell potential of 1.49 V to reach a current density of 10 mA cm⁻² and maintains stability for 110 h without degradation. The excellent performance of the electrode could be attributed to the formation of highly conductive, corrosion- and oxidation-resistant metal nitrides and the synergetic effect between intimately interconnected, electrochemically active nickel molybdenum nitride and Ni or NiO nanoparticles. This study shows that the use of transition metal nitrides in combination of nanostructured heterojunctions of multiple active components enables one to develop highly stable and efficient water electrolyzers without precious metals. The preparative strategy used in this work could be applied to devise new electrocatalysts.
Efficient and low-cost non-precious-metal-based electrocatalysts are crucial to the commercial success of the hydrogen evolution reaction (HER) under alkaline conditions. Herein, a step-by-step strategy to prepare a hierarchical structure assembled from Ni-doped amorphous FeP nanoparticles, porous TiN nanowires, and graphitic carbon fibers (Ni-FeP/TiN/CC) is described. The FeP/TiN/CC composite is plasma-implanted with Ni ions to modify the electronic structure and produce an amorphous surface. Simultaneous doping and amorphization of FeP by Ni ion implantation to enhance the HER activity is achieved for the first time. The flexible and freestanding Ni-FeP/TiN/CC catalyst produced on a carbon cloth can serve directly as an electrode in HER in an alkaline medium. The Ni-FeP/TiN/CC catalyst delivers excellent HER performance including an overpotential of 75 mV to generate a cathodic current density of 10 mA cm⁻², a Tafel slope close to that of commercial Pt/C catalysts, and long lifetime indicated by a more constant cathodic current density during continuous operation for 10 h. The remarkable HER activity is attributed to the combined effects rendered by the Ni and Fe atoms in the Ni-doped FeP nanoparticles, active amorphous surface, as well as conductive nanowire scaffold, which expose a large amount of active sites, enhance the charge transfer efficiency, and prevent the catalysts from migration and aggregation.
A series of molybdenum nitride films, viz., Mo3N2, Ag-Mo3N2, V-Mo3N2 and Cu-Mo3N2 have been fabricated by magnetron co-sputtering technique and evaluated as HER electrocatalysts in near-neutral pH (pH 5) buffer medium. An optimal HER activity has been observed at about 1.8 M phosphate buffer with Cu-Mo3N2 showing highest activity. Under strongly buffered and oxygen saturated conditions the molybdenum nitride films have consistently shown very high HER selectivity in the presence of oxygen. The stability of the molybdenum nitride films has been enhanced retaining almost 100% of the initial activity in a durability test, whereas, a significant loss in the stability has been observed for the same catalysts in 0.5 M H2SO4 solution.
Developing advanced materials with high catalytic activity for electrocatalytic applications is of vital importance to mitigate the energy crisis. In this work, we for the first time report a novel method to prepare bimetallic vanadium‑molybdenum nitride (MoVN) thin films by magnetron co-sputtering and further demonstrate their applications for hydrogen evolution reaction (HER). When used as HER catalysts, the resulting MoVN thin film electrodes show superior electrocatalytic activity especially in alkaline electrolyte in contrast to bare VN and Mo2N, delivering a low overpotential of 108 mV to afford a current density of 10 mA cm⁻², a Tafel slope of 60 mV dec⁻¹, as well as excellent long-term durability. Most importantly, our study opens opportunities to explore new HER catalyst materials in the family of bimetallic transition metal nitrides.
Monolithic interwoven composite of V2O5 nanobelts and carbon nanotubes (designated as VNTs⊂CNTs-40) is prepared via one-pot hydrothermal synthesis and subsequent vacuum filtration. The strong synergistic effect between versatile CNTs and in situ produced V2O5 nanobelts in hydrothermal process leads to the formation of 3D interwoven mesh intermediate with relatively loose and well-reticulated channels which facilitate mass transfer in ultrafast hetero-assembly (∼30s) of film-like monolithic VNTs⊂CNTs-40 composite during vacuum filtration. The interconnected CNTs network and interstitial porous channels in the monolithic VNTs⊂CNTs-40 composite not only improve charge transport during the redox reactions of the active materials, but also serve as a robust and flexible buffer to accommodate the volume change during repetitive ion insertion/extraction. In the evaluation of binder-free cathodes in alkali-ion batteries, the monolithic VNTs⊂CNTs-40 composite exhibits outstanding alkali-ion storage properties such as high initial capacity (215.2/295.8 mAhg⁻¹ for SIBs/LIBs at a current density of 200 mAg⁻¹), high-rate capability (137.8/156.2 mAhg⁻¹ for SIBs/LIBs at a current density of 800/2000 mAg⁻¹), and superior cycling stability (167/223.5 mAhg⁻¹ for SIBs/LIBs at a current density of 200 mAg⁻¹ after 200 cycles). The monolithic VNTs⊂CNTs-40 composite has large potential in high-performance alkali-ion batteries.
The growing extent of antibiotics pollution by human activities has engendered an urgent need for adjustable approaches to their removal. The adsorption-photocatalysis technique is attractive and widely employed to address the above issue, since it does not involve other chemicals, but could achieve pollutant mineralization by the reactive species generated under the light irradiation. In this paper, three kinds of mesoporous nano-TiO2 synthesized from titanium glycolate precursor with three different post-treatment methods [hydrothermal, calcination, and hydrothermal-calcination, denoted as TiO2 (hydr), TiO2 (calc), and TiO2 (hydr + calc), respectively] were employed for the removal of ciprofloxacin (CIP) antibiotic. The variations in crystal phase and structure of TiO2 nanocrystals from the precursor were studied in detail. The impact of post-treatment approaches on the titanium glycolate precursor in terms of adsorption capability and photocatalytic activity of TiO2 nanocrystallite aggregates was evaluated on the removal of CIP solution. Compared to TiO2 (calc), and TiO2 (hydr + calc), TiO2 (hydr) material exhibited superior capability towards CIP adsorption and photodegradation. Among the three kinds of post-processing methods, the hydrothermal treatment contributed larger surface areas and weaker hydrophilic properties which could improve the CIP molecule adsorption on the surface of the TiO2 (hydr) materials. On the other hand, the obtained TiO2 (hydr) displayed efficient electron-hole separation and fast charge transfer capabilities, resulting in higher photocatalytic activity towards CIP degradation initiated by holes and [rad]OH radicals than the other materials. In addition, the results of an antibacterial activity assay demonstrated that the degradation products of CIP solution were less harmful to the environment. This work could demonstrate that development of suitable post-processing modes for the precursor is a key issue in producing favorable materials with designed functionality.
Highly crystalline semimetallic 1T’-WTe2nanorods (WTe2 NRs) and WTe2nanoflowers (WTe2 NFs) are applied as the anode materials for sodium ion battery (SIB) for the first time. WTe2 NRs and NFs are synthesized through a novel two-step process with hydrothermal derived WO3 transformed into WTe2 NRs and NFs after a chemical vapor deposition process. The performance of WTe2 SIB anode is highly influenced by WTe2 morphology. WTe2 NRs have shown high capacity in sodium ions storage with excellent rate and cycling stability. The initial discharge capacity for WTe2 NRs is 442 mA h g-1 at the current density of 0.1 A g-1, and remains 221 mA h g-1 after 100 cycles, while WTe2 NFs show 324 mA h g-1 initial capacity and remain 260 mA h g-1 after 40 cycles. The coulombic efficiency of both WTe2 NRs and NFs anodes are as high as 98.83% and 97.96% from the second cycle, respectively.
Titanium nitride (TiN) is an attractive electrode material in fast charging/discharging supercapacitors because of the excellent conductivity. However, the low capacitance and mechanical brittleness of TiN restrict itself for further application in flexible supercapacitor with high energy density, thus, it is still a challenge for rational designing TiN electrode with both high electrochemical and mechanical properties. Herein, the hierarchical TiN nanoparticles assembled nanopillars (H-TiN NPs) array as binder free electrode are obtained by nitriding of hierarchical titanium dioxide (TiO2) nanopillars, which is produced by a simple hydrothermal treatment of anodic TiO2 nanotubes (NTs) array in water. The porous TiN nanoparticles connect each other to form ordered nanopillars arrays, effectively providing larger specific surface area and more active sites for charge storage. The H-TiN NPs deliver a high volumetric capacitance of 120 F cm-3 at 0.83 A cm-3, which is better than that of TiN NTs arrays (69 F cm-3 at 0.83 A cm-3). After assembling into all-solid-state devices, the H-TiN NPs based supercapacitors have an outstanding volumetric capacitance of 5.9 F cm-3 at 0.02 A cm-3 and a high energy density of 0.53 mWh cm-3. Our results reveal a new strategy to optimizate the supercapacitive performance of metal nitride.
Molybdenum carbide/molybdenum nitride hybrid N-doped graphene (abbreviated as Mo2C/MoN/NG), as an efficient electrocatalyst for the hydrogen evolutionreaction (HER), was synthesized via simple ion-exchange resin synthesis followed by a two-step annealing process, which increased the dispersion degree of theelectrocatalyst’s active sites on the support skeleton and simplified the syntheticconditions. Additionally, N-doped graphene (NG) enhanced the electron transferand reduced the inner resistance. The material has a graphene-like morphology and highly dispersed Mo2C/MoN nanoparticles about 2 nm in diameter on the NG. X-ray photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy revealed that Mo2C/MoN/NG consisted of Mo2C and MoN composited together. Finally, Mo2C/MoN/NG exhibited remarkable performance as an electrocatalyst for the HER with a small overpotentialof 78.82 mV and a small Tafel slope of 39.3 mV·dec−1 in a 0.5 mol·L−1 H2SO4solution. Its activity was approximately 30% lower than that of 20% Pt/C and 60% higherthan that of NG. Also, it exhibited a low onset overpotential of 24.82 mV, which is similar to the theoretical HER potential. Our work provides a foundation for advanced HER applications of molybdenum compounds.
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Developing cost-effective and highly efficient bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of great interest for overall water splitting, but still remains challenging issue. Herein, a self-template route is employed to fabricate a unique hybrid composite constructed by encapsulating cobalt nitrides (Co5.47N) nanoparticles within three-dimensional (3D) N-doped porous carbon polyhedra (Co5.47N NP@N-PC), which can be served as highly active bifunctional electrocatalyst. To afford a current density of 10 mA cm−2, the as-fabricated Co5.47N NP@N-PC only requires overpotentials as low as 149 mV and 248 mV for HER and OER, respectively. Moreover, an electrolyzer with Co5.47N NP@N-PC electrodes as both the cathode and anode catalyst in alkaline solutions can drive a current density of 10 mA cm−2 at a cell voltage of only 1.62 V, superior to that of the Pt/IrO2 couple.The excellent electrocatalytic activity of Co5.47N NP@N-PC can be mainly ascribed to the high inherent conductivity and rich nitrogen vacancies of Co5.47N lattice, the electronic modulation of N-doped carbon towards Co5.47N as well as the hierarchically porous structure design.
The electrochemical performance of carbon nanofibers (CNFs) as the electrode material of the supercapacitor should be improved to meet requirements of renewable energy systems. We report here the synthesis of nitrogen-doped carbon nanofibers (RGO-AgNP/N-CNF) with a meso-microporous structure by the supplement of reduced graphene oxide–silver nanoparticles (RGO-AgNPs) into N-CNFs. The usage of polyacrylonitrile (PAN) is aimed to supply nitrogen doped in carbon bulk, which can enhance fast migration of electrolyte ions during the electrochemical process. Decoration of AgNPs on RGO surface improves electrical conductivity of RGO-AgNP/N-CNF composites and alleviates the aggregation of AgNPs. The addition of RGO-AgNPs elevates the specific surface area and mesoporous content of CNFs. The assembled RGO-AgNP/N-CNF symmetric supercapacitor possesses high specific capacitance of 188.0 F g⁻¹ at a current density of 0.5 A g⁻¹, delivers an ultrahigh energy density of 26.1 Wh kg⁻¹ and displays an excellent cycling performance (97.5% retention after 5000 cycles), which suggest its big potential as energy storage devices.
Flexible supercapacitors (SCs) are desirable for elastic and clothing electronic products owning to their considerable safety, high foldability and outstanding power density. Herein, multilayered films composed of alternating mesoporous Nb4N5 nanobelts and rGO nanosheets (Nb4N5/rGO) are designed and fabricated exhibiting good flexibility. The folding Nb4N5/rGO film electrode reveals an areal capacitance of 141 mF cm-2 (at 1 mA cm-2) along with remarkable cycling stability (the capacitance retention is 90% after 6,000 cycles). The flexible SCs devices were constructed by interlayer couple films of Nb4N5/rGO electrodes with PVA/H2SO4 gel as the electrolyte, which exhibited huge volumetric capacitance of 19 F cm-3 (at 0.1 A cm-3) and a considerable energy density of 0.98 mW h cm-3 with a power density of 0.029 W cm-3. Additionally, the as-obtained folding devices bode outstanding cycling stability with capacitance retention of 89% after 4,000 cycles measured by cyclic voltammetry method (at 100 mV s-1). Above results about niobium nitride based flexible electrodes and devices exploit a platform for wearable electronics and flexible devices.
WTe2 is one of most important layered transition metal dichalcogenides (TMDs) and exhibits various prominent physical properties. All the present methods for WTe2 preparation need strict conditions such as high temperature or cannot be applied in large scale which limit the practical applications. In addition, most studies on WTe2 focus on its physical properties while the electrochemical properties are still illusive with little investigation. Here we develop a facile and scalable two-step method to synthesize high quality WTe2 nanoribbon crystal with 1T’Weyl semimetal phase for the first time. We can get highly crystalline 1T’-WTe2 nanoribbon on a large scale through this two-step method. In addition, the electrochemical tests show that WTe2 nanoribbon exhibits smaller overpotential and much better hydrogen evolution reaction (HER) catalytic performance than other tungsten-based sulfide and selenide (WS2, WSe2) nanoribbons under same morphology and preparation condition. WTe2 nanoribbons show a Tafel slope of 57 mV/dec, which is one of best values for TMDs catalysts and about 2 and 4 times smaller than that 135 mV/dec for 2H-WS2 nanoribbon and 213 mV/dec for 2H-WSe2 nanoribbon, respectively. 1T’-WTe2 nanoribbon also show ultrahigh stability in 5000 cycles and 20 h at 10 mA/cm2. The better performance is attributed to high conductivity of semimetallic 1T’-phase-stable WTe2 nanoribbon with one or two order higher charge transfer rate than normally semiconducting 2H-stable WS2 and WSe2 nanoribbons. These results open the door of electrochemical applications of Weyl semimetallic TMDs.
It is of great importance to design and exploit high-efficiency low-cost electrocatalysts for the oxygen evolution reaction (OER) under mild conditions for applications. In this Article, we propose that formation of a thin amorphous Ni carbonate layer on Ni3N nanoarray supported on carbon cloth (Ni3N NA/CC) is an effective strategy to boost its OER activity in at near-neutral pH. When used as a 3D non-noble-metal OER electrocatalyst, the resulting core–shell Ni3[email protected] NA/CC displays superior catalytic activity with extremely small overpotential of 400 mV for 20 mA cm⁻² in 1.0 M KHCO3 (bulk pH: 8.3). Moreover, it also exhibits considerable long-term electrochemical durability with its activity being preserved for at least 12 h. Conductive Ni3N nanoarray not only provides as the Ni source for in-situ electrochemical derivation of 3D Ni-Ci catalyst with high surface area, more exposed active sites and facilitated mass diffusion, but effectively prompts the electron transport from Ni-Ci shell to CC, enabling more efficient water oxidation electrocatalysis.
A series of ZrN-Ag films with various Ag contents (Ag/(Zr + Ag), at.%) were deposited by reactive magnetron sputtering and their microstructure, mechanical and tribological properties at various testing temperatures were investigated by the energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), nanoindenter and high temperature tribometer. The results showed that face-centered cubic (fcc) ZrN and fcc-Ag coexisted in the ZrN-Ag films. The hardness of the films, which was influenced by the fine-grain strengthening and the contents of soft Ag, initially increased gradually and reached a summit, then decreased with the increase of the Ag contents in the films and the maximum value was about 29 GPa at 0.3 at.% Ag. At room temperature, the average friction coefficient of the films first decreased and then almost remained stable with the increase of the Ag contents and the minimum value was 0.62 at 26.6 at.% Ag. The wear rate of the films first decreased slightly and reached a summit, then decreased with the increase of the Ag contents and the minimum value was 1.1 × 10⁻⁸mm³·N⁻¹mm⁻¹ at 0.3 at.% Ag. With the rise of the testing temperature from 200 °C to 600 °C, the combination of Ag into ZrN matrix could decrease the average friction coefficient of the films significantly and led to a relatively steady tendency of the average friction coefficient at the wide testing temperatures. However, the wear rate decreased with the increase of Ag content at the same temperature. Average friction coefficient and wear rate of the films regardless of the testing temperature were influenced by the soft lubricant Ag phase significantly.
Large-scale energy storage technologies are in high demand for effective utilization of intermittent electricity generations and efficient electric power transmission. The feasibility of lithium-ion batteries for large-scale energy storage is under debate due to the scarcity and uneven distribution of lithium resources in the Earth’s crust. Therefore, there arise tremendous interests in pursuing alternative energy storage systems based on earth-abundant materials. Recently, non-aqueous potassium-ion batteries (KIBs) are emerging as a promising energy storage system due to the abundance of potassium and the encouraging battery performance. Here, the recent research progress in non-aqueous KIBs is summarized, including electrode materials, electrolytes, battery architectures and fundamental electrochemical processes. The challenges and future research opportunities are also briefly discussed.
Exploring highly efficient and durable bifunctional electrocatalyst from the earth-abundant low-cost transition metals is central to obtain clean hydrogen energy via the large scale electrolytic water splitting. Herein, we demonstrate in-situ synthesis of porous nickel-cobalt nitride nanosheets on macroporous Ni foam (NF) via a facile electro-deposition process followed by one-step annealing process in NH3 atmosphere. The transformation from metal hydroxide to metal nitride could efficiently enhance the electrocatalytic performance for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Interestingly, we found that the incorporation of nickel could further boost the catalytic activity of cobalt nitride. Typically, when used as bifunctional electrocatalysts, the obtained nickel-cobalt nitride electrocatalyst shows superior catalytic performance toward both HER and OER with a low overpotential of 0.29 and 0.18 V to achieve a current density of 10 mA cm-2, respectively and good stabilities. The good electrocatalytic performance was also evidenced by the as-fabricated electrolyzer for overall water splitting, exhibiting a high gas generation rate for hydrogen and oxygen with the excellent stability in the prolonged alkaline water electrolysis. The present work provides an efficient approach to preparing 3D interconnected porous nickel-cobalt nitride network with exposed inner active sites for overall water splitting.
Development of non-noble metal electrocatalysts for hydrogen evolution reaction (HER) has attracted much attention. Metal-nitrides are considered as promising alternatives in recent years. Nevertheless, the preparation of tungsten nitride still suffer from environmentally unfriendly source and poor morphology, which induces the relative low activity. Herein we employed clean N2-plasma to develop 3D WN nanowires array on carbon cloth (WN NW/CC) with a porous structure. As expected, the resulting WN NW/CC are highly active, giving a small η10 (overpotential to drive a current of 10 mA cm-2) of 134 mV, and Tafel slope of 59.6 mV dec-1 in acid solution, and η10 of 130 mV, and Tafel slope of 57.1 mV dec-1 in alkaline solution, respectively. Additionally, it maintains its catalytic activity for at least 14500 s in both acidic and alkaline media.
The development of new corrosion-resistant coatings is often challenging, but strongly driven by the potential benefits such coatings hold. A nanostructured Ta2N coating was deposited on a Ti-6Al-4V substrate in an Ar-N atmosphere using a double cathode glow discharge plasma method with the aim being to improve its corrosion resistance in oral environments. The microstructure of the coating was investigated by a range of methods including XRD, SEM-EDS and TEM. The as-deposited coating exhibited densely packed fibrous structure and the individual fibers were composed of equiaxed grains with an average grain size 13nm, arranged along the longitudinal axis of the individual fibers. The electrochemical behavior of the Ta2N nanocrystalline coating was characterized in artificial saliva containing different NaF concentrations by a range of electrochemical techniques, including potentiodynamic measurement, EIS, capacitance and PZFC measurements. It was shown that the coating possessed superior corrosion resistance compared to uncoated Ti-6Al-4V, because its passive film exhibited higher stability against the fluoride ion attack.
Hazardous hexavalent chromium removal from wastewater is an urgent issue in industry environmental pollution. In this work, hollow Bi2S3 nanospheres have been successfully synthesized from unique Bi2O3 porous nanospheres via Kirkendall effect through hydrothermal process. It was found that the sulfur source and the initial Bi2O3 templates played key roles in the formation of the uniform morphologies and structures through an anion exchange process. Compared with other Bi2S3 samples, the synthesized hollow Bi2S3 nanospheres exhibited much enhanced photocatalytic ability for Cr(VI) photoreduction. XPS analysis demonstrated that Cr(VI) was reduced to less harmful Cr(III) species over hollow Bi2S3 nanospheres under visible-light irradiation. More importantly, the hollow Bi2S3 nanospheres remained high efficiency and good stability in the recycling Cr(VI) photoreduction, and exhibited remarkable Cr(VI) removal ability in actual electroplating industry wastewater treatment.
A general ionic-assisted microwave-ultrasonic combined synthetic strategy was developed to fabricate Bi2E3 (E=S, Se, and Te) hierarchitectures. To understand the crystal phase transformation and morphological evolution of Bi2S3 hierarchical nanostructures, the fabrication of Bi2S3 hierarchitectures was investigated by varying sulfidation time and chlorination time. A topotactic transformation from BiOCl microsphere to Bi2S3 hierarchitectures was proposed. It was found that the structure, size, and morphology of Bi2S3 hierarchitectures could be delicately engineered by varying chlorination time, alkyl chain length, and concentration of ionic liquid. Moreover, the as-prepared Bi2S3 hierarchitectures displayed superior capacity of Cr(VI) photoreduction to P25 and irregular Bi2S3 nanostructures under visibe light irradiation. Effects of morphology, pH value of reaction system, Cr(VI) concentration, and catalyst dosage on the Cr(VI) photoreduction capacity of Bi2S3 hierarchitectures were also discussed. The enhancement of photoreduction capacity is not only attributed to the intrinsic good electron transfer ability of Bi2S3, but also to synergetic effects of special architectures, wide photoresponse range, high light photoadsoprtion, high BET surface area and good electron-hole separation performance. The systematic condition experiments and Cr(VI) photoreduction in electroplating and tannery wastewater experiments further demonstrated that the hierarchical Bi2S3 nanospheres can be used in the actual Cr(VI)-containing wastewater treatment.
TiO2 modification via TiCl4 treatment has been widely used to improve the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs), in which the effects usually attribute to the inhibition of charge recombination by barrier effect. Niobium pentoxide (Nb2O5) is considered a promising photoelectrode material for DSSCs. Here we prepared urchin-like orthorhombic Nb2O5 nanospheres consisting of ultrathin nanorods by a hydrothermal method, which were further developed as photoelectrodes for DSSCs. The TiO2 modification on the urchin-like orthorhombic Nb2O5 nanospheres increases the photocurrent and PCE of the DSSCs. However, the impedance spectroscopy showed that charge recombination was not reduced by the TiO2 modification. The improvement in the photocurrent and PCE has been attributed to the enhanced absorption of dye molecules (N719). The results indicate that the enhancement of dye absorption for orthorhombic Nb2O5 photoelectrodes is the desirable approach to improve the performance of orthorhombic Nb2O5-based DSSCs.
Molybdenum based materials are gaining importance as electrocatalysts for hydrogen evolution reaction because of their low cost and good electrocatalytic efficiency. Introducing iron nitride with molybdenum nitride as a composite results in efficient hydrogen evolution activity with current density of \({\sim }120\) \(\hbox {mA/cm}^{2}\) at \(-400 \hbox { mV}\) vs. RHE. The nanocomposites were characterized using powder XRD, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Electron Diffraction, Thermogravimetric Analysis and FTIR Spectroscopy. The electrochemical investigations suggest that the electrocatalytic activity of the composite increases with iron nitride content. The composite exhibits good electrochemical stability upto 42 hours in acidic medium. The hydrogen evolution reaction (HER) follows Volmer-Heyrovsky mechanism where Volmer reaction is the rate determing step.
Graphical Abstract
SYNOPSIS Introducing iron nitride in composite with molybdenum nitride leads to higher HER activity in acidic media. The in-situ growth of CNTs in the composites enhances the conductivity and decreases the charge transfer resistance. Open image in new window
There are wide interests in developing high-performance electrode materials for electrochemical energy storage and conversion devices. Among them, transition metal nitrides (TMNs) are suitable for a wide range of devices because they have better electrical conductivity than the oxides and excellent catalytic properties. In particular, properly designed nanostructured TMNs offer additional advantages for performance enhancement. However, reviews of the rapid utilization of metal nitrides as electrode materials are still not much. In this mini-review, we present a recent (mostly since 2015) update on nanostructured TMNs as high-performance electrode materials for energy storage devices and water splitting; we discussed how a judicious nanostructure design will lead to improving performance in lithium ion battery, supercapacitor and Li-ion capacitor, as well as in electrochemical water splitting (oxygen and hydrogen evolution reactions). Knowledge about this review on metal nitrides is aimed at sharing a wide view in recent TMNs synthetic development, applications, prospects and challenges.
Nanohybrid material containing carbon-supported molybdenum carbide and nitride nanoparticles of size ranging from 8 to 12 nm, exhibits excellent HER catalytic activity. This molybdenum based catalyst (MoCat) is designed as a highly efficient, low-cost (precious-metal-free), highly stable electrocatalysts for water electrolysis in acidic medium, synthesized using simple methodology. These nanoparticles (β-Mo2C and γ-Mo2N) were produced in-situ using a metal precursor and C/N source in a controlled solid state reaction. An overpotential of 96 mV for driving 10 mA cm-2 of current density was measured for MoCat catalyst, which is very close to commercially available Pt/C catalysts (61mv).
Conventionally, nanostructured ceramics are susceptible to brittle fracture due to processing-induced flaws such as porosity. In this study, the microstructure and deformation behavior of two nanostructured Ta2N coatings, one with a fully-dense structure and the other with a nanoporous structure, both prepared by double cathode glow discharge technique, were investigated. It was found that the elastic modulus of the Ta2N coatings is more sensitive to the presence of nanoporosity than their hardnesses. Compared with the fully-dense Ta2N coating, the nanoporous Ta2N coating exhibits a marked increase in the damage tolerance, as well as a good potential for wear-resistance.
Metallic Cobalt nanoparticles segregated in situ on conductive vanadium nitride (Co/VN) nanosheets synthesized by ammonia nitridation of hydrothermally prepared Co2V2O7 nanosheets are investigated as high-performance oxygen evolution reaction (OER) electrocatalysts. The metallic Co nanoparticles with a large number of exposed active sites are distributed uniformly and adhere firmly to the VN substrate to enhance the OER efficiency, facilitate fast charge transfer, and improve the stability. As a result, a small overpotential of 320 mV is required to achieve a current density of 10 mA cm⁻² with a small Tafel slope of 55 mV dec⁻¹. The excellent stability is indicated by an overpotential shift of only 34 mV after 2,000 cyclic voltammetry cycles at a large current density of 200 mA cm⁻². The precious-metal-free Co/VN nanosheets deliver outstanding OER performance and are promising as electrocatalysts in water splitting and related applications.
Hybrid organic–inorganic perovskites (HOIPs) can have a diverse range of compositions including halides, azides, formates, dicyanamides, cyanides and dicyanometallates. These materials have several common features, including their classical ABX3 perovskite architecture and the presence of organic amine cations that occupy the A-sites. Current research in HOIPs tends to focus on metal halide HOIPs, which show promise for use in solar cells and optoelectronic devices; however, the other subclasses also exhibit a diverse range of physical properties. In this Review, we summarize the chemical variability and structural diversity of all known HOIP subclasses. We also present a comprehensive account of their intriguing physical properties, including photovoltaic and optoelectronic properties, dielectricity, magnetism, ferroelectricity, ferroelasticity and multiferroicity. Moreover, we discuss the current challenges and future opportunities in this exciting field.
TiO2-modified nitrogen-doped carbon (TiO2-NC), prepared by a polymerization-pyrolysis process, is used to support the Pd catalyst for ethanol oxidation reaction (EOR) in alkaline media. X-ray photoelectron spectroscopy characterization indicates that the incorporation of TiO2 and nitrogen into the carbon matrix could improve the percentage of Pd⁰ in Pd/TiO2-NC catalyst. Electrochemical characterization shows that the Pd/TiO2-NC catalyst presents higher electrocatalytic activity and stability for EOR than the nitrogen-doped carbon-supported Pd (Pd/NC) catalyst and the carbon black-supported Pd (Pd/CB) catalyst, which can be mainly attributed to the high percentage of Pd⁰ in Pd/TiO2-NC catalyst (65%) than those in Pd/NC (48%) and Pd/CB (31%) catalysts. The results indicate that the Pd/TiO2-NC catalyst holds great potential as high-performance anode catalyst for direct ethanol fuel cells.
In this study, a 3D hierarchical ternary metal oxide Bi2MoO6 (BMO) microspheres coupled with layered reduced graphene oxide (rGO) composite (rGO/BMO) was synthesized by a facile ultraviolet light reduction method. By means of a series of characterizations, it was found that the reduction of graphene oxide plays a key role in raising photo-induced charge carrier separation efficiency as an electron collector through the interaction between rGO and BMO. As a result, the as-prepared rGO/BMO composite exhibits enhanced photocatalytic water oxidation, which is higher than that of pure BMO under simulated solar light irradiation. In addition, the photocatalytic oxidation performance for organic pollutant degradation has also been evaluated and the coupled photocatalyst displayed an improved activity over pure BMO. Thus, the strategy provides an efficient approach for the fabrication of graphene composites containing hierarchical ternary oxides for photocatalysis.
Great advances in the subfield of non-fullerene acceptors have been achieved in the last few years. Perylene diimides are among the most investigated due to their excellent electron mobility, high electron affinity and feasible chemical modification. In this review, we summarize reports of small molecule acceptors based on perylene diimides in recent years and highlight the effect of molecular structure on their performance in bulk heterojunction organic solar cells with the hope of providing criteria for designing acceptors based on perylene diimides.
Designing highly active, earth-abundant and stable bifunctional electrocatalysts for both the oxygen (OER) and hydrogen (HER) evolution reactions is very crucial to overall water splitting. Herein, we developed nanoparticle-stacked porous Co3FeNx (NSP-Co3FeNx) nanowires as bifunctional electrocatalysts, exhibiting excellent OER and HER activity with a low overpotential of 222 mV at 20 mA cm(-2) and 23 mV at 10 mA cm(-2), respectively, due to their unique structural advantages with grain boundaries, defects and dislocations. Moreover, the electrocatalysts as bifunctional electrodes show a high performance with 10 mA cm(-2) at a cell voltage of 1.539 V.