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![Volcano plot for HER on various metal surfaces in acidic media. The experimentally obtained j0 versus the hydrogen chemisorption energy DEH is represented for each surface.
Reproduced with permission from Ref. [24], © 2005 The Electrochemical Society](publication/336444050/figure/fig11/AS:963460871487500@1606718380122/Volcano-plot-for-HER-on-various-metal-surfaces-in-acidic-media-The-experimentally.png)
Volcano plot for HER on various metal surfaces in acidic media. The experimentally obtained j0 versus the hydrogen chemisorption energy DEH is represented for each surface. Reproduced with permission from Ref. [24], © 2005 The Electrochemical Society
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Sustainable and high performance energy devices such as solar cells, fuel cells, metal–air batteries, as well as alternative energy conversion and storage systems have been considered as promising technologies to meet the ever-growing demands for clean energy. Hydrogen evolution reaction (HER) is a crucial process for cost-effective hydrogen produc...
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Pursuing efficient, economical, and stable electrodes on hydrogen production by water splitting is of great significance for new energy sources. In this work, Ni-Co-P self-supported electrocatalyst at macroporous nickel mesh electrode (NCP/NM) was prepared by a combination of hydrothermal and phosphorylation reactions. The Ni-Co with spherical form...
Hydrogen production from natural resourses and industrial waste water is of vital and duel importance to the energy and environmental issues. Urea oxidation based on cost effictive catalyst and which is substuation to the noble based electrolysers like Pt, Pd and Rh of great challange. Herein, we have fabricated effective decoration of Ni NPs on GO...
MoS2 materials have been extensively studied as hydrogen evolution reaction (HER) catalysts. In this study nanoparticulate MoS2 is explored as a HER catalyst through impact voltammetry. The onset potential was found to be -0.10 V (vs RHE) at pH 2, which was confirmed to be due to HER by scale-up of the impact experiment to generate and collect a su...
This review brings out the key advancements made in the field of alkaline HER with metal hydroxides and their heterostructures and also provides a detailed and critical analysis of strategies and perspectives used with highlights on future prospects at the end.
Abstract
Transition metal hydroxides (M‐OH) and their heterostructures (X|M‐OH, where X...
Water splitting provides clean hydrogen via different technologies such as alkaline water electrolysis, proton exchange membrane electrolyzers, solid oxide electrolysis cells, and photoelectrolysis, each with advantages and challenges. The focus on alkaline water electrolysis highlights its maturity compared to emerging methods. Non-noble metal cat...
Citations
... Current-overpotential plots (Tafel plots) are used to further assess the kinetics and mechanism of OER [81]. The anodic polarization curves for OER were recorded in 1 M KOH and 1 M Methanol at the scan rate of 100 mV s −1 . ...
Electrochemical water splitting presents an optimal approach for generating hydrogen (H 2 ), a highly promising alternative energy source. Nevertheless, the slow kinetics of the electrochemical oxygen evolution reaction (OER) and the exorbitant cost, limited availability, and susceptibility to oxidation of noble metal-based electrocatalysts have compelled scientists to investigate cost-effective and efficient electrocatalysts. Bimetallic nanostructured materials have been demonstrated to exhibit improved catalytic performances for the oxygen evolution reaction (OER). Herein, we report carbon aerogel (CA) decorated with different molar ratios of Fe and Ni with enhanced OER activity. Microwave irradiation was involved as a novel strategy during the synthesis process. Inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM), Energy dispersive X-ray spectroscopy (EDAX spectra and EDAX mapping), Transmission Electron Microscope (TEM), High-Resolution Transmission Electron Microscope (HR-TEM), and Selected Area Electron Diffraction (SAED) were used for physical characterizations of as-prepared material. Electrochemical potential towards OER was examined through cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy (EIS). The FeNi/CA with optimized molar ratios exhibits low overpotential 377 mV at 10 mAcm ⁻² , smaller Tafel slope (94.5 mV dec ⁻¹ ), and high turnover frequency (1.09 s ⁻¹ at 300 mV). Other electrocatalytic parameters were also calculated and compared with previously reported OER catalysts. Additionally, chronoamperometric studies confirmed excellent electrochemical stability, as the OER activity shows minimal change even after a stability test lasting 3600 s. Moreover, the bimetallic (Fe and Ni) carbon aerogel exhibits faster catalytic kinetics and higher conductivity than the monometallic (Fe), which was observed through EIS investigation. This research opens up possibilities for utilizing bi- or multi-metallic anchored carbon aerogel with high conductivities and exceptional electrocatalytic performances in electrochemical energy conversion.
... In summary, bimetallic single-atom catalysts supported on 2D materials are at the forefront of developing active, robust, and inexpensive systems for clean hydrogen generation [20,25]. Further mechanistic insights into bimetallic synergies [22] and synthetic strategies to incorporate different metal pairs will be imperative to guide the rational design of optimized catalysts for hydrogen production [26,[26][27][28][29]. The choice of appropriate support materials and engineering optimal catalyst-support interfaces continue to be key focuses in this emerging field. ...
Electrocatalytic and photocatalytic hydrogen evolution reactions (HERs) provide a promising approach to clean energy generation. Bimetallic single-atom catalysts have been developed and explored to be advanced catalysts for HER. It is urgent to review and summarize the recent advances in developing bimetallic single-atom HER catalysts. Firstly, the fundamentals of bimetallic single-atom catalysts are presented, highlighting their unique configuration of two isolated metal atoms on their supports and resultant synergistic effects. Secondly, recent advances in bimetallic single-atom catalysts for electrocatalytic HER under acidic/alkaline conditions are then reviewed, including W-Mo, Ru-Bi, Ni-Fe, Co-Ag, and other dual-atom systems on graphene and transition metal dichalcogenides (TMDs) with enhanced HER activity versus monometallic analogs due to geometric and electronic synergies. Then, photocatalytic bimetallic single-atom catalysts on semiconducting carbon nitrides for solar H2 production are also discussed. Finally, an outlook is provided on opportunities and challenges in precisely controlling bimetallic single-atom catalyst synthesis and gaining in-depth mechanistic insights into bimetallic interactions. Further mechanistic and synthetic studies on bimetallic single-atom catalysts will be imperative for developing optimal systems for efficient and sustainable hydrogen production.
... In summary, bimetallic single-atom catalysts supported on 2D materials are at the forefront of developing active, robust, and inexpensive systems for clean hydrogen generation [20,25]. Further mechanistic insights into bimetallic synergies [22] and synthetic strategies to incorporate different metal pairs will be imperative to guide the rational design of optimized catalysts for hydrogen production [26,[26][27][28][29]. The choice of appropriate support materials and engineering optimal catalystsupport interfaces continue to be key focuses in this emerging field. ...
Electrocatalytic and photocatalytic hydrogen evolution reaction (HER) provides a promising approach to clean energy generation. Bimetallic single-atom catalysts raised and have been explored to be advanced catalysts for HER. It is urgent to review and summarize the recent advances in developing bimetallic single-atom HER catalysts. Firstly, the fundamentals of bimetallic single-atom catalysts are presented, highlighting their unique configuration of two isolated metal atoms on supports and resultant synergistic effects. Secondly, recent advances in bimetallic single-atom catalysts for electrocatalytic HER under acidic/alkaline conditions are then reviewed, including W-Mo, Ru-Bi, Ni-Fe, Co-Ag, and other dual-atom systems on graphene and transition metal dichalcogenides (TMDs) with enhanced HER activity versus monometallic analogs due to geometric and electronic synergies. Then, Photocatalytic bimetallic single-atom catalysts on semiconducting carbon nitrides for solar H2 production are also discussed. Finally, an outlook is provided on opportunities and challenges in precisely controlling bimetallic single-atom catalyst synthesis and gaining in-depth mechanistic insights into bimetallic interactions.
... Several studies indicated that combining noble metals with metal compounds can significantly improve noble metal utilization while also lowering the cost of HER electrocatalysis [207,208]. Furthermore, noble metal-free cocatalysts, such as transition metal phosphides (TMPs) [209][210][211], cobalt compounds [212][213][214][215], nickel-based materials [216,217], and chalcogenides [218][219][220][221], and their hybrid structure [222] are considered promising candidates to replace noble metal catalysts due to their availability, low processing cost, and good electrochemical properties [223][224][225][226]. Because of the adequate hydrogen adsorption free energy and moderate bond strength of metal-intermediate (M-OH), Ni has been identified as one of the most efficient non-noble-metal HER and OER catalysts. ...
... Moreover, Co 9 S 8 -based materials are known as an important and promising class of electrocatalysts [226]. They have shown great potential in hydrogen and oxygen electrocatalysis applications [223]. ...
Hydrogen fuel has been considered a sustainable, green, and alternative energy source to fossil fuels for future energy supply. Electro- and photochemical water splitting systems are reported as simple, pollutant-free, low-cost, highly efficient techniques for hydrogel production in large quantities and with high purity. As featured by high porosity, self-supportability, and large surface area, aerogels-based catalysts meet all the required criteria for efficient electro and photocatalysts design for water splitting. Besides the traditional sol-gel technique, today, aerogel synthesis and processing have advanced significantly, mainly because of the emergence of various molecular precursors and low dimensional noble, non-noble metals, and carbon-based building blocks, which require the implementation of different network formation strategies. This versatility in the synthesis and fabrication approaches combined with the unique highly 3D porous microstructural feature enhances the aerogel performance for targeted catalytic reactions with improved efficiencies. Herein, an all-embracing overview of the design and processing aspects of aerogel and aerogel-inspired-based materials with various building blocks is given to provide an insight into their electro- and photo-catalysts performance for the water-splitting process and hydrogen production. We also review the recent theoretical studies based on density functional theory (DFT) for unfolding the mechanism and physics of catalytic reactions on the studied aerogel-based materials. Considering their bright prospects, aerogel-based catalysts can pave the way for the advancement of new high-performance binder-free and free-standing electro-and photo-catalytic materials for water-splitting techniques and, ultimately, the production of green hydrogen, a fuel of the future.
... In recent years, numerous and effective techniques have been used to identify or eliminate pollutants such as heavy metals and pesticides in the agricultural industry. For example, the manufacture of electrocatalytic composites based on intermediate metals such as cobalt and nickel has been developed as a technology for the disposal of wastewater in the agricultural industry [8][9][10][11][12]. Other methods such as electrochemical [13], photocatalytic degradation [14], electrochemical sensors [15], biodegradation [16], biosensor [17] and adsorption [18] have also been used for this purpose. ...
Today, high consumption and increasing use of pesticides and chemical fertilizers to control pests of agricultural products, and the entry of these pollutants into the environment, is one of the most important environmental and health problems. Their non-biodegradability, as well as their toxicity and carcinogenicity, have generally made these compounds one of the most dangerous pollutants that cause inevitable pollution of the environmental. Among the various methods used to remove agricultural pesticide residues from the water sources, the adsorption method has received more attention due to its simplicity, cost and higher efficiency. In this research, nanocomposite of Co/Ni/Al-LTH@ZIF-8 was synthesized by in-situ growth of ZIF-8 on the Co/Ni/Al-LTH and used for the removal of diazinon (DIZ) pesticide from aqueous solution. Characterizations of the nanocomposite were performed by various techniques, including Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and thermal analysis. Statistical evaluation was studied by BOX-Behnken design. In addition, the response surface methodology was used to optimize the factors affecting on the adsorption process. Parameters such as adsorbent dose (mg), pH, and contact time (min) were considered in this experiment. The results showed that the removal efficiency of diazinon is improved significantly (from 64 to 84%) by loading ZIF-8 on Co/Ni/Al-LTH. Statistical studies showed the optimum conditions achieved under pH = 6.9, adsorbent dosage 25 mg, and contact time 12 min.
Graphical Abstract
... The PVA as a polymer matrix is vigorously studied for various kinds of nanofillers such as metals, nonmetals, metal oxides, sulphides, inorganic, or mixtures of these elements [15][16][17]. Further this doping of these above mentioned fillers has lead to the formation of PVA nanocomposites with very peculiar properties [14][15][16][17][18][19]. ...
The solid state method was used to prepare ceramic LaFeO3 (LFO) nanoparticles. The solution casting method was employed to create the nanocomposite thick film of this ceramic (as filler) with polyvinyl alcohol (PVA). These films were characterized by x-ray diffraction (XRD) and Fourier transform Infrared (FT-IR) spectroscopy techniques. The XRD technique verifies that our samples are in single phase with orthorhombic crystal structure. Powder X software was used to determine the lattice parameters, which were found to decrease with increase in the doping content. To measure the size of crystallites and strain in the LFO; peak broadening, the Williamson–Hall (W–H) method, and the size-strain approach were used. For all XRD reflection peaks, the physical parameters such as strain, stress, and energy density were calculated using the W–H plot, uniform deformation model (UDM), uniform stress deformation model (USDM), uniform deformation energy density model (UDEDM), and the size-strain plot method (SSP). FT-IR data show finger print function groups associated with this polymer. However slight shifts in these functional groups show the possible coulomb interactions with the ceramic oxygen atom. From this vibrational data, different parameters like force constant (K), the stiffness constant (C11 = C12), bulk modulus (B), rigidity modulus (R), Young’s modulus (Y), Poisson ratio (σ), longitudinal elastic wave velocity (Vl), transverse elastic wave velocity (Vt), mean elastic wave velocity (Vm), Debye temperature (θ*D and θD) and lattice energy (UL) were calculated. The variation in elastic parameters with different doping concentration has been observed and discussed. The various physical parameters obtained from these models were compared and a possible explanation was also proposed.
... The samples prepared with different chemicals were directly used as working electrodes to investigate the performance of HER catalytic activity in 1 M KOH, while the three basic reaction mechanisms included in HER in alkaline electrolytes are shown in the following three formulas [60]. HER are subjected to the Volmer reaction, Volmer-Heyrovsky, or Volmer-Tafel reaction mechanism [61][62][63]. The electrochemical workstation automatically applies iR compensation to eliminate its effects. ...
... The lowest Tafel slope of 97.71 mV·dec −1 is obtained for the Ni x P y / NiCoP sample in which the NaH 2 PO 2 ·H 2 O content was 16 mmol, while the other samples has higher Tafel slopes of 126. 63, 130.55, 168.02, and 245.31 mV·dec −1 [61][62][63]. It can be seen from the Tafel slope that the Ni x P y /NiCoP synthesized in a proper amount of NaH 2 PO 2 ·H 2 O has better activity, indicating that the appropriate amount of P atoms endows the material better electronegativity and promotes H 2 production from H atoms absorbed at the catalyst surface, which facilitates the efficiency of hydride absorption and dehydrogenation. ...
Transition metal phosphides have high catalytic performance and stability among non-precious metal electrocatalysts, particularly exhibiting good hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance in alkaline solutions, due to the platinum-like electronic structure of transition metal phosphides. In this study, we successfully synthesized nickel phosphide and nickel cobalt phosphate hybrid on the three-dimensional nickel foam by a facile hydrothermal method. It is worth noting that the NixPy/NiCoP in 1 M KOH only needs the overpotential of 95 mV to reach the current density of 10 mA∙cm⁻² for hydrogen evolution reaction (HER) and the overpotential of 231 mV at 10 mA∙cm⁻² for oxygen evolution reaction (OER), which is superior to most electrocatalysts. The obtained results indicate that there is a synergistic effect between the three elements of Ni, Co, and P, facilitating the process of electrocatalysis. Meanwhile, the synthesized electrode not only has a large active surface area, but also good electrical conductivity, effectively facilitating the electrocatalytic reaction kinetics. Thus, this work provides an effective route to a low-cost, high-performance catalyst for electrocatalytic hydrogen production.
Graphical abstract
... In this regard, controlling the structural characteristics of these compounds via relatively simple means can greatly reduce the overall cost and renovate their performances, thereby enlarging their large-scale usage [14][15][16][17]. Accordingly, considerable pursuits have been enshrined to rationally construct active transition metals and eliminate their several inevitable difficulties as well as achieve satisfactory activities [18][19][20][21][22][23]. In particular, optimizing the capacitance and operating voltage range are key issues to raise up the energy density. ...
Manipulating the structure of electroactive materials with hierarchical frameworks can boost the electrochemical properties. The soaring fidelity of mixed nanostructured materials in electrochemistry verifies their candidature as appropriate electrodes for sustainable energy storage and conversion devices. Herein, we present facile and economical techniques to develop three-dimensional (3D) hierarchical nanoframes-like sulfurized nickel aluminum (sulfurized NiAl) as a positive electrode material and ternary bismuth cerium sulfide (Bi-Ce-S) as the negative electrode material for constructing an aqueous asymmetric supercapacitor system. These hierarchical architectures with well-developed pores and hollow spaces can capitalize the surface-to-volume ratio and maximize the contact area between the active material and electrolyte, therefore immensely reduce the ion penetration distances and promote the electron transport rates. Tuning the conductivity of electrode materials affords rich contact sites and integrates the features of all components, thus resulting in better electrochemical enhancements. As expected, sulfurized NiAl nanosheet arrays with unique porous architectures exhibit a good electrochemical performance with commendable specific capacitance of 1230.6 F g–1 at 1 A g–1 current density and stable rate capability (69.8% up to 20 A g–1). In addition, the obtained Bi-Ce-S hybrid provides a high specific capacitance (411.7 F g–1 at 1 A g–1) with 92.2% capacitance retention even after 4000 cycles. An asymmetric supercapacitor (ASC) device is established with the designed composites, which realizes a high energy density of 38.5 Wh kg–1 at a power density of 750 W kg–1 and reveals an enhanced cycle stability (80.6% retention after 8000 GCD times).
Graphical abstract
... For example, Rao et al. observed a similar trend when the ORR electrocatalytic activity of N-doped CNTs was increased with the increase of pyridinic-N content. N-doped CNTs synthesized from metal organic frameworks (MOFs) are characterized by high content of graphitic-N, and hollow structure and displayed competitive electrocatalytic ORR performance, stability, and tolerance to that of commercial Pt/C as shown in Fig. 6g, h (Rao et al. 2010;Khalafallah et al. 2019b). Boron-Doped CNTs for ORR Boron "B" and carbon atoms are comparable in size and this minimizes the graphene lattice distortion during the formation of B-doped CNTs which is essential for preserving the CNTs structural and mechanical stability in the resulting materials. ...
Carbon nanotubes (CNTs) can be doped or intercalated with nonmetal heteroatoms, metal atoms or metal clusters to act as electron donors or acceptors, analogous to conjugated polymers and graphene. The doped CNTs reveal favorable features including tuned electrical conductivity, more elastic electron conduction, better mechanical stability, and cyclability. The exceptionally high surface area of CNTs, combined with their selective enrichment of electronic properties is advantageous in determining their corresponding applications in sustainable energy conversion and storage sectors. Functionalization of CNTs can be done through the introduction of heteroatoms into the CNTs graphene surface layers to modify their electronic structure. Substitutional doping of CNTs with heteroatoms is an excellent strategy to promote their electrocatalytic properties and provide manipulation of pathways for efficient electron transfer processes. Moreover, heteroatom doping improves not only the electrical conductivity of CNTs but also their chemical affinity and wettability, allowing them to be used extensively in electrocatalytic reactions due to their excellent conductivity and tunable multifunctionality. With these considerations, great advances in functional heteroatoms-doped CNTs continue to be made with the goal of cost-effective, easily processed, and environmentally friendly pathways on the rise. The present chapter addresses versatile dopant introduced into CNTs and the changes to their properties and potential applications. The recent developments in the use of CNTs-based electrode materials in the next generation energy conversion and storage technologies are discussed along with some promising experimental studies.
... Compositional attributes of a hybrid electrode material to achieve a better structural stability and an enhanced electrochemical activity have become an attractive research topic. Moreover, the synergism between the active constituents can significantly elevate the pseudocapacitive performance [25][26][27]. Realizing the charge balance between the positive and negative electrodes is a critical issue to reduce the overall weight of the resulting device and optimize the energy storage efficiency [28]. Hence, it is imperative to design negative electrode materials with reinforced electrochemical effects to fulfill the need for effective energy storage appliances [29]. ...
Hybrid metal chalcogenides incorporating prolific redox-active transition metal selenides with optimized interactions are suitable candidates to boost the electrochemical properties of supercapacitors. The present study elaborates the design and application of selenium (Se)-enriched reduced graphene oxide hybridized heterostructured nickel bismuth selenide (RGO/Ni-Bi-Se) and bismuth selenide (RGO/Bi2Se3)-based electrode materials by a simple in-situ growth solvothermal reaction for advanced battery-type supercapacitors. Integrating the advantages of different components, good electrical conductivity of RGO and Se-enrichment induce a strong collaborative effect on redox reactions. The favourable structural and compositional features are not only desirable for the capacitive and rate performance enhancement but also for volume change mitigation during successive charge–discharge processes. The heterostructured RGO/Ni-Bi-Se delivers a boosted electrochemical behavior with an exceptional specific capacity (220.2 mAh g–1 at 1 A g–1) and good rate performance (54.8% capacity retention at 50 A g–1). The strong synergy between the Ni and Bi active components with multielectron reversible Faradic redox reactions optimizes the overall electrochemical performances and modifies the charge storage capability of the electrode material. The interconnected porous nanoarchitectures are regulated with abundant interface engineering and disorders, thereby achieving a large electrode/electrolyte area at junction and shortening the ion diffusion paths as well as accelerating the electron-transmission ability during operation. On the other hand, the as-obtained RGO/Bi2Se3 negative electrode material exhibits better pseudocapacitive properties with favourable reversibility and displays a large specific capacitance of 464 F g–1 at 1 A g–1. The RGO fabric not only offers a solid skeleton for the self-assembly of building units but also enlarges the specific area for more electrochemical active sites and decreases the charge transfer resistance. The formation of weak electronegative Se is profitable to adjust the electronic configuration of exposed Ni/Bi sites. More significantly, the heterostructured RGO/Ni-Bi-Se reveals a well-matched performance with the capacitive RGO/Bi2Se3 and the established aqueous battery supercapacitor hybrid (BSH) device achieves admirable energy density of 62.3 Wh kg⁻¹ at a power density of 949.7 W kg⁻¹ together with 89.2% retention after 10 000 cycles.
