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Interface-rich Au-doped PdBi alloy nanochains as multifunctional oxygen reduction catalysts boost the power density and durability of a direct methanol fuel cell device
Abstract
The development of cathode oxygen reduction reaction (ORR) catalysts with high characteristics for practical, direct methanol fuel cells (DMFCs) has continuously increased the attention of researchers. In this work, interface-rich Au-doped PdBi (PdBiAu) branched one-dimensional (1D) alloyed nanochains assembled by sub-6.5 nm particles have been prepared, exhibiting an ORR mass activity (MA) of 6.40 A·mgPd⁻¹ and long-term durability of 5,000 cycles in an alkaline medium. The MA of PdBiAu nanochains is 46 times and 80 times higher than that of commercial Pt/C (0.14 A·mgPt⁻¹) and Pd/C (0.08 A·mgPd⁻¹). The MA of binary PdBi nanochains also reaches 5.71 A·mgPd⁻¹. Notably, the PdBiAu nanochains exhibit high in-situ carbon monoxide poisoning resistance and high methanol tolerance. In actual DMFC device tests, the PdBiAu nanochains enhance power density of 140.1 mW·cm⁻² (in O2)/112.4 mW·cm⁻² (in air) and durability compared with PdBi nanochains and Pt/C. The analysis of the structure—function relationship indicates that the enhanced performance of PdBiAu nanochains is attributed to integrated functions of surficial defect-rich 1D chain structure, improved charge transfer capability, downshift of the d-band center of Pd, as well as the synergistic effect derived from “Pd-Bi” and/or “Pd-Au” dual active sites. [Figure not available: see fulltext.].
... 138 Chain-like PdBi and PdBiAu structures can be synthesized via a hydrothermal method, with DMF and oleylamine as the solvent and F127 as the additive. 139 Alternatively, NP-40 as the structure-directing agent can be used to produce PdCu as well as PdFePb (and PdPb or PdFe) alloy nanowires. 140,141 Both reports employ the borohydride reducing system, with either NaBH 4 or KBH 4 as the reducing agent in ice-cold aqueous solution. ...
... A recent work investigated in detail the effect of Ni in the PtNi alloy nanowires for alkaline HOR. 139,186 PtNi alloy nanowires with the Ni presented either at the core or the surface of the nanowires were compared, and it was found that the surface Ni could enhance the HOR activity more significantly by increasing the adsorption of both *H and *OH species. ...
Benefiting from both one-dimensional (1D) morphology and alloy composition, metal alloy nanowires have been exploited as advanced electrocatalysts in various electrochemical processes. In this review, the synthesis approaches for metal alloy nanowires are classified into two categories: direct syntheses and syntheses based on preformed 1D nanostructures. Ligand systems that are of critical importance to the formation of alloy nanowires are summarized and reviewed, together with the strategies imposed to achieve the co-reduction of different metals. Meanwhile, different scenarios that form alloy nanowires from pre-synthesized 1D nanostructures are compared and contrasted. In addition, the characterization and electrocatalytic applications of metal alloy nanowires are briefly discussed.
... The theoretical calculation proves that methanol tolerance in their catalyst was arisen due to weak adsorption of methanol molecules, produced from the lower downshift of the d-band center, and electronic interaction between Pt and Cu components. Li et al. prepared interfacerich Au-doped PdBi (PdBiAu) branched one-dimensional (1D) alloyed nanochains through the single-step liquid phase method [57]. Their PdBiAu nanochains catalysts show excellent ORR performance and also demonstrate high methanol resistance. ...
... A summary of the effects of methanol feeding on the electrocatalyst. (a) Pt based catalyst and carbon coating for methanol tolerance, reproduced with permission from Ref.[57]. Copyright from American Chemical Society 2017. ...
Methanol cross-over effects from the anode to the cathode are important parameters for reducing catalytic performance in direct methanol fuel cells. A promising candidate catalyst for the cathode in direct methanol fuel cells must have excellent activity toward oxygen reduction reaction and resistance to methanol oxidation reaction. This review focuses on the methanol tolerant noble metal-based electrocatalysts, including platinum and palladium-based alloys, noble metal-carbon based composites, transition metal-based catalysts, carbon-based metal catalysts, and metal-free catalysts. The understanding of the correlation between the activity and the synthesis method, electrolyte environment and stability issues are highlighted. For the transition metal-based catalyst, their activity, stability and methanol tolerance in direct methanol fuel cells and comparisons with those of platinum are particularly discussed. Finally, strategies to enhance the methanol tolerance and hinder the generation of mixed potential in direct methanol fuel cells are also presented. This review provides a perspective for future developments for the scientist in selecting suitable methanol tolerate catalyst for oxygen reduction reaction and designing high-performance practical direct methanol fuel cells.
... MEA performance is also affected by the way that the catalyst layer is fabricated, and significant research efforts have been exerted in investigating novel fabrication procedures [22][23][24][25][26][27]. Tsai et al. placed Pt-Ru nanoparticles in dense carbon nanotubes that directly grow on carbon cloth, and this method decreased the Pt-Ru load to 0.4 mg cm −2 and increased the power density by 27% [23]. ...
This paper presents a membrane electrode assembly (MEA) with a double-catalytic layered structure to improve the performance of the micro direct methanol fuel cell. The inner and outer parts of the double-catalytic layer comprise an unsupported and carbon-supported catalyst, respectively. A two-dimensional two-phase model of mass transport and electrochemical reaction is established and simulated to analyze the superiority of the double-catalytic layered structure. Simulation results show that this structure has a more uniform current density distribution and less over-potential across the catalyst layer. Methanol crossover is also reduced. Experimental results confirm that the MEA with the double-catalytic layered structure exhibits better performance than the traditional MEA. The adoption of a gas diffusion electrode as the outer catalytic layer and a catalyst-coated membrane as the inner layer of the double-catalytic layered structure can further improve the performance of the MEA. Both simulation and experimental results show the existence of an optimum number of metal loadings of the inner and outer parts of the double-catalytic layer.
... Among them, the PdAu nanochain catalysts have enhanced ORR performance and improved methanol resistance after heat treatment at 500°C for 1 h. In addition, Li et al. [106] based on the strategy that the introduction of a few third transition metals in binary nanoalloys can improve the catalytic performance of electrocatalysts as "active auxiliaries". [90,91] The Pd 0.60 Bi 0.35 Au 0.05 nanochains were synthesized by a one-step hydrothermal method based on the study of PdAu nanochains with the addition of the transition metal Bi. ...
In fuel cells, the generally low oxygen reduction reactions (ORR) rate at the cathode is a major factor limiting the overall performance of fuel cell, so the development of high‐performance, stable and inexpensive ORR electrocatalysts is a major researching direction. Nano‐electrocatalysts, especially one‐dimensional (1D) electrocatalysts, exhibit good catalytic behavior in fuel cell reactions due to their unique anisotropic structure, large specific surface area, high elasticity and excellent stability. To date, many advanced 1D electrocatalysts have been reported for optimizing the cathode ORR of fuel cells. Therefore, a comprehensive review of the structural design of 1D nano‐electrocatalysts and a systematic analysis of their enhanced performance still need further summarized and concluded. In this review, we firstly introduce the main synthetic methods of 1D electrocatalysts, and then discuss the recent advances and advantages of different structured 1D electrocatalysts involving nanofibers, nanotubes, nanorods, nanochains, nanowires, nanobelts, nanoneedles, nanowhiskers, and coaxial nanocables. In addition, we also introduce 1D electrocatalysts while highlighting advanced strategies and preparation methods for these different structured 1D electrocatalysts to improve ORR performance. Finally, we prospect the future development of 1D ORR electrocatalysts.
Enhancing the catalytic efficiency of the methanol electro-oxidation reaction (MOR) holds paramount importance in expediting the commercialization of direct methanol fuel cells (DMFCs). In this study, we unveil a novel...
Shape-controlled metal-based nanomaterials provide a special platform to regulate the surface physicochemical properties for optimizing the electrocatalytic performance, due to their homogeneously arranged surface atomic structures. Accordingly, owing to the solely {100} facets-ended surfaces, highly uniform Pt nanocubes (NCs) are utilized in this study, to probe the effects of synergizing with Ir species (a very effective metal for various electrocatalysis) on the electrocatalytic performance for the oxygen reduction reaction (ORR). Electrochemical results present that carbon-supported Pt1Ir1 NCs with surface Ir–O species (Pt1Ir1–O NCs/C) have much enhanced electrocatalytic activity and electrochemical stability than both Pt NCs/C and commercial Pt/C. Physicochemical characterization and theoretical calculation analyses further elucidate the mechanism of the improved electrocatalytic performance: the strong electronic interaction between Pt and Ir, the lowered d-band center of the surface metal atoms, and especially the synergistic effect induced by the surface Ir–O species. This study not only develops a highly active and stable ORR electrocatalyst, but also demonstrates an effective and universal research paradigm to explore the surface engineering effects on the electrocatalytic performance, which can be further applied in other crystalline facets for other (electro)catalytic reactions.
Pd‐based electrocatalysts are the most effective catalysts for ethylene glycol oxidation reaction (EGOR), while the disadvantages of poor stability, low resistance to neutrophilic, and low catalytic activity seriously hamper the development of direct ethylene glycol fuel cells (DEGFCs). In this work, defect‐riched PdCoZn nanosheets (D‐PdCoZn NSs) with ultrathin 2D NSs and porous structures are fabricated through the solvothermal and alkali etching processes. Benefiting from the presence of defects and ultrathin 2D structures, D‐PdCoZn NSs demonstrate excellent electrocatalytic activity and good durability against EGOR in alkaline media. The mass activity and specific activity of D‐PdCoZn NSs for EGOR are 9.5 A mg⁻¹ and 15.7 mA cm⁻², respectively, which are higher than that of PdCoZn NSs, PdCo NSs, and Pd black. The D‐PdCoZn NSs still maintain satisfactory mass activity after long‐term durability tests. Meanwhile, in situ IR spectroscopy demonstrates that the presence of defects attenuated the adsorption of intermediates, which improves the selectivity of the C1 pathway with excellent anti‐CO poisoning performance. This work not only provides an effective synthetic strategy for the preparation of Pd‐based nanomaterials with defective structures but also indicates significant guidance for optimum C1 pathway selectivity of ethylene glycol and other challenging chemical transformations.
To alleviate the world's current energy crisis, fuel cells play a significant role. The efficiency of a fuel cell primarily depends on the electrochemical catalytic activity of the catalysts used....
Understanding the relationship between crystallographic structure and electrocatalytic performance is important to successfully design an efficient electrocatalyst. With finely controlled thermal H2-reduction condition, herein, binary Pd-Cr nanofiber was fabricated as...
To find a low-Pt electrocatalyst that is functionally integrated and superior to the state-of-the-art single-Pt electrocatalyst is expectedly a challenge. We have in this study found that the reactivity of the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR), in both acidic and alkaline electrolytes (viz., four half-cell reactions), can be modified and greatly enhanced by the electronic and/or synergistic effects of a low-Pt octahedral PtCuCo alloy. For the ORR, the mass activity (MA) of Pt0.23Cu0.64Co0.13/C in an acidic or alkaline electrolyte was 14.3 or 10.7 times that of the commercial Pt/C. For the MOR, the MA of Pt0.23Cu0.64Co0.13/C in an acidic or alkaline electrolyte was 7.2 or 3.4 times that of the commercial Pt/C. In addition, Pt0.23Cu0.64Co0.13/C exhibited an increased durability and CO tolerance, as compared with the commercial Pt/C. Density functional theory calculations demonstrated that the PtCuCo(111) surface can effectively optimize the O* binding energy. This work has successfully shown an example of how both acidic and alkaline ORR and MOR activities can be significantly synchronously enhanced.
Direct ethanol fuel cells (DEFCs) have received increasing attention as one of the most promising energy conversion devices. However, developing catalysts with high activity, long durability and strong anti-poisoning ability for ethanol oxidation is still challenging. Here, using Pd nanosheets as sacrificial templates, we have successfully synthesized PdPtBi networked nanowires (NWs) to improve the activity and stability for ethanol oxidation reaction (EOR) due to the addition of Bi. Density functional theory (DFT) calculations demonstrated the downshift of d-band center of Pd, which is beneficial to suppress CO poisoning and boost reaction kinetics for EOR. Impressively, the PdPtBi networked NWs exhibited the highest activity (\(11.08\,{\rm{A}} \cdot {\rm{m}}{{\rm{g}}_{{\rm{Pd}} + {\rm{Pt}}}}^{-1}\) and 92.52 mA·cm−2) with an enhancement of 4.4 and 17.5 times relative to those of Pd/C, respectively and best stability with a 47.2% left versus only a 5.8% left for Pd/C of mass activity after 3,600 s towards EOR. This work deepens the understanding of controllable preparation of networked NWs and provides an effective strategy to design advanced catalysts with high activity and stability.
The design of the nanostructure of palladium-based nanocatalysts is considered to be a very effective way to improve the performance of nanocatalysts. Recent studies have shown that multiphase nanostructures can increase the active sites of palladium catalysts, thus effectively improving the catalytic efficiency of palladium atoms. However, it is difficult to regulate the phase structure of Pd nanocatalysts to form a compound phase structure. In this work, PdSnP nanocatalysts with different compositions were synthesized by fine-regulating the doping amount of phosphorus atoms. The results show that the doping of phosphorus atoms not only changes the composition of PdSn nanocatalysts but also changes the microstructure, forming amorphous and crystalline multiphase structures. This multiphase nanostructure contains abundant interfacial defects, which effectively promotes the electrocatalytic oxidation efficiency of Pd atoms in small-molecule alcohols. Compared with the undoped PdSn nanocatalyst (480 mA mgPd-1 and 2.28 mA cm-2) and the commercial Pd/C catalyst (397 mA mgPd-1 and 1.15 mA cm-2), the mass (1746 mA mgPd-1) and specific activities (8.56 mA cm-2) of PdSn0.38P0.05 nanocatalysts in the methanol oxidation reaction were increased by 3.6 and 3.8 times and 4.4 and 7.4 times, respectively. This study provides a new synthesis strategy for the design and synthesis of efficient palladium-based nanocatalysts for the oxidation of small-molecule alcohols.
Incorporation of oxophilic metals into Pd-based nanostructures has shown great potential in small molecule electrooxidation owing to their superior anti-poisoning capability. However, engineering the electronic structure of oxophilic dopants in Pd-based catalysts remains challenging and their impact on electrooxidation reactions is rarely demonstrated. Herein, we have developed a method for synthesizing PdSb-based nanosheets, enabling the incorporation of the Sb element in a predominantly metallic state despite its high oxophilic nature. Moreover, the Pd90Sb7W3 nanosheet serves as an efficient electrocatalyst for the formic acid oxidation reaction (FAOR), and the underlying promotion mechanism is investigated. Among the as-prepared PdSb-based nanosheets, the Pd90Sb7W3 nanosheet exhibits a remarkable 69.03% metallic state of Sb, surpassing the values observed for the Pd86Sb12W2 (33.01%) and Pd83Sb14W3 (25.41%) nanosheets. X-ray photoelectron spectroscopy (XPS) and CO stripping experiments confirm that the Sb metallic state contributes the synergistic effect of their electronic and oxophilic effect, thus leading to an effective electrooxidation removal of CO and significantly enhanced FAOR electrocatalytic activity (1.47 A mg-1; 2.32 mA cm-1) compared with the oxidated state of Sb. This work highlights the importance of modulating the chemical valence state of oxophilic metals to enhance electrocatalytic performance, offering valuable insights for the design of high-performance electrocatalysts for electrooxidation of small molecules.
Finding a high-performance low-Pt bipolar electrocatalyst in actual direct alcohol fuel cells (DAFCs) remains challenging and desirable. Here, we developed a crystalline PdPtCu@amorphous subnanometer Pd-Pt "dual site" layer core-shell structure for the oxygen reduction reaction (ORR) and alcohol (methanol, ethylene glycol, glycerol, and their mixtures) oxidation reaction (AOR) in an alkaline electrolyte (denoted D-PdPtCu). The prepared D-PdPtCu/C achieved a direct 4-electron ORR pathway, a full oxidation pathway for AOR, and high CO tolerance. The ORR mass activity (MA) of D-PdPtCu/C delivered a 52.8- or 59.3-fold increase over commercial Pt/C or Pd/C, respectively, and no activity loss after 20000 cycles. The D-PdPtCu/C also exhibited much higher AOR MA and stability than Pt/C or Pd/C. Density functional theory revealed the intrinsic nature of a subnanometer Pd-Pt "dual site" surface for ORR and AOR activity enhancement. The D-PdPtCu/C as an effective bipolar electrocatalyst yielded higher peak power densities than commercial Pt/C in actual DAFCs.
The construction of efficient and durable electrocatalysts with highly dispersed metal clusters and hydrophilic surface for alkaline hydrogen evolution reaction (HER) remains a great challenge. Herein, we prepared hydrophilic nanocomposites of Ru clusters (∼ 1.30 nm) anchored on Na+, K+-decorated porous carbon (Ru/Na+, K+-PC) through hydrothermal method and subsequent annealing treatment at 500 °C. The Ru/Na+, K+-PC exhibits ultralow overpotential of 7 mV at 10 mA·cm−2, mass activity of 15.7 A·mgRu−1 at 100 mV, and long-term durability of 20,000 cycles potential cycling and 200 h chronopotentiometric measurement with a negligible decrease in activity, much superior to benchmarked commercial Pt/C. Density functional theory based calculations show that the energy barrier of H-OH bond breaking is efficiently reduced due to the presence of Na and K ions, thus favoring the Volmer step. Furthermore, the Ru/Na+, K+-PC effectively employs solar energy for obtaining H2 in both alkaline water and seawater electrolyzer. This finding provides a new strategy to construct high-performance and cost-effective alkaline HER electrocatalyst.
The design of bifunctional catalysts with high performance and low platinum for the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) is of significant implication to promote the industrialization of fuel cells. In our work, Pt/carbon nanotube (CNT), Pt3Ru/CNT, and PtRu/CNT catalysts were synthesized by plasma heat treatment, in which the pyrolysis reduction of organometallic salts and the dispersion of CNTs were achieved simultaneously, and catalytic nanoparticles with uniform particle size were anchored on the dispersed CNT surface. Later, Fe was further introduced, and PtFe/CNT, Pt3RuFe/CNT, and PtRuFe/CNT catalysts were synthesized by calcination, and the structure and electrochemical properties in both MOR and ORR of all as-synthesized catalysts were investigated. The results indicated that plasma thermal treatment has the advantage of rapidness and immediacy in the synthesis of catalysts, and the Pt/CNT, Pt3Ru/CNT, and PtRu/CNT catalysts exhibited better electrocatalytic properties than commercial platinum (JM-Pt/C) catalysts. Meanwhile, the introduction of Fe during the calcination further changed the surface electronic properties of catalytic nanoparticles and enhanced the graphitization degree of catalysts; the PtRuFe/CNT catalyst exhibited outstanding electrocatalytic properties with a mass activity of 834.3 mA mg-1 for MOR and a half-wave potential of 0.928 V in alkaline media for ORR. The combination of plasma thermal treatment and calcination puts forward a novel strategy for the optimization of catalysts, and the synthesis method based on plasma dispersion needs to be further optimized to achieve its large-scale promotion.
The introduction of functional groups or oxygen vacancies into Pd-based electrocatalysts is a powerful strategy for enhancing the electrocatalytic performances for many electrocatalytic reactions. Herein, an amorphous ceria-modified Pd nanocomposite anchored on D-4-amino-phenylalanine (DAP)-functionalized graphene nanosheets (Pd-CeO2-x/FGS) was prepared by a facile and effective one-pot synthetic strategy and further used as an electrocatalyst for the ethanol oxidation reaction (EOR) in alkaline electrolytes. The obtained Pd-CeO2-x/FGS exhibits relatively high electrocatalytic activity, fast kinetics and excellent antipoisoning ability as well as robust durability for EOR, outperforming the comparable electrocatalysts as well as commercial Pd/C. The experimental results show that the enhanced EOR properties of Pd-CeO2-x/FGS can be attributed to the DAP-functionalization and CeO2-x-modification. Adequate functional groups (amino and carboxyl groups) and abundant oxygen vacancies were introduced in Pd-CeO2-x/FGS by DAP-functionalization and CeO2-x-modification. The functional groups facilitate the anchoring of small nanoparticles onto the substrate as well as modulate the electron density of Pd. The oxygen vacancies boost the adsorption ability of the reactive oxygen species (OHads) and accelerate the kinetics of the potential-limiting step for EOR. This study proposes a new strategy for the rational design of highly efficient catalysts for the electro-oxidation reaction.
Achieving stable surface structures of metal catalysts is an extreme challenge for obtaining long-term durability and meeting industrial application requirements. We report a new class of metal catalyst, Pt-rich PtCu heteroatom subnanoclusters epitaxially grown on an octahedral PtCu alloy/Pt skin matrix (PtCu1.60), for the oxygen reduction reaction (ORR) in an acid electrolyte. The PtCu1.60/C exhibits an 8.9-fold enhanced mass activity (1.42 A·mgPt−1) over that of commercial Pt/C (0.16 A·mgPt−1). The PtCu1.60/C exhibits 140,000 cycles durability without activity decline and surface PtCu cluster stability owing to unique structure derived from the matrix and epitaxial growth pattern, which effectively prevents the agglomeration of clusters and loss of near-surface active sites. Structure characterization and theoretical calculations confirm that Pt-rich PtCu clusters favor ORR activity and thermodynamic stability. In room-temperature polymer electrolyte membrane fuel cells, the PtCu1.60/C shows enhanced performance and delivers a power density of 154.1/318.8 mW·cm−2 and 100 h/50 h durability without current density decay in an air/O2 feedstock.
Proton exchange membrane fuel cells (PEMFCs) have received a sustained world-wide attention owing to their promising applications based on clean energy. However, their widespread applications are still restricted by the sluggish oxygen reduction reaction (ORR) process. Over the past decades, significant efforts have been devoted to developing efficient ORR catalysts, which have been summarized in numerous previous reviews. Unfortunately, most of them mainly focused on ORR activity on the rotating disk electrode (RDE) level, which cannot truly represent the performance in real applications. Developing and showcasing efficient catalysts evaluated at the membrane electrode assembly (MEA) level is of vital importance. In this review, we first briefly showcased the recent development of ORR catalysts and then put more emphasis on the discussion of designing efficient catalysts at MEA and full-cell level, aiming to help stimulate more attention on their practical applications.
In severe traumatic brain injury (sTBI), acute oxidative stress and inflammatory cascades rapidly spread to cause irreversible brain damage and low survival rate within minutes. Therefore, developing feasible solution for the quick‐treatment of life‐threatening emergency is urgently demanded to earn time for hospital treatment. We herein carefully constructed Janus catalysis‐driven nanomotors (JCNs) via plasma‐induced alloying technology and sputtering‐caused half coating strategy. The theoretical calculation and experiment results indicated that heteroatom‐doping alloyed engine endowed JCNs much higher catalytic activity for removing reactive oxygen species (ROS) and reactive nitrogen species (RNS) than common Pt‐based engine. When JCNs were dropped to the surface of ruptured skull, they can effectively catalyze endogenous hydrogen peroxide, which induces movement as fuels to promote JCNs to deep brain lesions for further nanocatalysts‐mediated cascade‐blocking therapy (CBT). Results demonstrated that JCNs successfully blocked the inflammatory cascades, thereby reversing multiple behavioral defects and dramatically declining the mortality of sTBI mice. Together, this work provides a revolutionary nanomotors‐based strategy to sense brain injury and scavenge oxidative stress. Meanwhile, our JCNs provide a feasible strategy to adapt various first aid scenarios due to their self‐propelled movement combined with highly multienzymes‐like catalytic activity, exhibiting tremendous therapeutic potential to help people for emergency pretreatment. This article is protected by copyright. All rights reserved
Chemical functionalization is an effective approach to address interfacial deterioration caused by environmental exposure in cellulose nanofiber (CNF)-epoxy nanocomposites. However, how functionalization affects interfacial deterioration and durability of nanocomposites in erosive environment is still lacked. In this work, the global mechanical properties and local interfacial intermolecular behavior of pristine and functionalized CNF-reinforced nanocomposites are investigated through molecular dynamics simulations. The results show that functionalization can enhance the interfacial energy barrier and debonding stress by 43% and 57%, respectively. Functionalized CNF inhibits the slippage of epoxy chains, ensuring better interfacial adhesion and efficient stress transfer between fiber and matrix. Functional groups promote the formation of interfacial bridging and topological structures and weaken the hydrogen bonding ability of water molecules, leading to stronger intermolecular adsorption effect and better interfacial integrity. The epoxy molecular configuration evolution and intermolecular interactions, caused by the functionalization of CNF in the interfacial region, enhance the interfacial erosion resistance, contributing to the durability of the nanocomposites. This study reveals the in-depth interfacial deterioration mechanism of functionalized nanocomposites under erosive environment, inspiring a novel strategy for the design of durable CNF-reinforced nanocomposites.
Platinum (Pt) is considered as the preferred metal catalyst for methanol oxidation reactions. However, the application prospects of Pt catalysts are limited due to the inherent scarcity and cost. Enabling a trace amount of Pt to exert satisfactory catalytic activity and durability has become a key issue in designing electrocatalysts. Here, Ru-doped PtSn alloy nanoplates ([email protected] NP) with an average particle size of less than 5 nm were controllably synthesized by adjusting the Pt–Sn atomic ratio. Compared with Ru-doped PtSn alloy nanospheres ([email protected] NS/C, 714.7 mA/mgPt), PtSn bimetallic nanoplates (PtSn NP/C, 880.2 mA/mgPt) and commercial Pt/C (299.6 mA/mgPt), the prepared [email protected] NP/C (1105.1 mA/mgPt) exhibited an extraordinary methanol oxidation mass activity. Furthermore, the peak oxidation current retention of [email protected] NP/C was as high as at 87.5% after 1000 accelerated durability tests. The significantly enhanced catalytic performance and durability were attributed to the synergistic effect of the alloy components and morphological advantages. This work has led us to think more deeply about the constitutive relationship between structure and performance.
Pd-based catalysts are attractive anodic electrocatalysts for direct methanol fuel cells owing to their low cost and natural abundance. However, they suffer from sluggish reaction kinetic and insufficient electroactivity in methanol oxidation reaction (MOR). In this work, we developed a facile one-pot approach to fabricate low Pt-doped Pd12P3.2 nanowires with crystalline/amorphous heterophase (termed Pt-Pd12P3.2 NWs) for MOR. The unique crystalline/amorphous heterophase structures promote the catalytic activity by the plentiful active sites at the phase boundaries and/or interfaces and the synergistic effect between different phases. Moreover, the incorporation of trace Pt into Pd lattices modifies the electronic structure and improves the electron transfer ability. Therefore, the obtained Pt-Pd12P3.2 NWs display significantly enhanced electrocatalytic performance toward MOR with the mass activity of 2.35 A mgPd+Pt-1, which is 9.0, 2.9, and 2.0 times higher than those of the commercial Pd/C (0.26 A mgPd-1), Pd12P3.2 NWs (0.82 A mgPd-1), and commercial Pt/C (1.19 A mgPt-1). The high mass activity enables the Pt-Pd12P3.2 NWs to be the promising Pd-based catalysts for MOR.
To overcome the limited potency of energy devices such as alkaline water electrolyzers, the construction of active materials with dramatically enhanced oxygen evolution reaction (OER) performance is of great importance. Herein we developed an ion diffusion-induced doping strategy that is capable of producing Ni 2+ /Co 2+ doped two-dimensional (2D) Au-Fe 7 S 8 nanoplatelets (NPLs) with exceptionally high OER activity outperforming the benchmark RuO 2 catalyst. The coexistence of Co and Ni in Au-Fe 7 S 8 NPLs led to the lowest OER overpotential of 243 mV at 10 mA cm-2 and fast kinetics with a Tafel slope of 43 mV dec-1. Density functional theory (DFT) calculations demonstrated that Ni 2+ /Co 2+ doping improves the binding of OOH species on the {001} surfaces of Au-Fe 7 S 8 NPLs and lowers the Gibbs free energy of the OER process, which are beneficial to outstanding OER activity of the nanoplatelets.
Ultrathin 2D metal nanostructures have sparked a lot of research interest because of their improved electrocatalytic properties for fuel cells. So far, no effective technique for preparing ultrathin 2D Pd‐based metal nanostructures with more than three compositions has been published. Herein, a new visible‐light‐induced template technique for producing PdAuBiTe alloyed 2D ultrathin nanosheets is developed. The mass activity of the PdAuBiTe nanosheets against the oxygen reduction reaction (ORR) is 2.48 A mgPd−1, which is 27.5/17.7 times that of industrial Pd/C/Pt/C, respectively. After 10 000 potential cyclings, there is no decrease in ORR activity. The PdAuBiTe nanosheets exhibit high methanol tolerance and in situ anti‐CO poisoning properties. The PdAuBiTe nanosheets, as cathode electrocatalysts in direct methanol fuel cells, can thus give significant improvement in terms of power density and durability. In O2/air, the power density can be increased to 235.7/173.5 mW cm−2, higher than that reported in previous work, and which is 2.32/3.59 times higher than Pt/C. Ultrathin quaternary PdAuBiTe alloyed 2D nanosheets are first achieved by a new visible‐light‐induced template strategy. As high‐performance oxygen reduction reaction (ORR) catalysts, the PdAuBiTe nanosheets can greatly increase power densities and durability in direct methanol fuel cell devices. The maximum power densities of PdAuBiTe nanosheets are up to 235.7/173.5 mW cm–2 in O2/air, respectively.
The electrochemical oxygen reduction reaction (ORR) is the key energy conversion reaction involved in fuel cells, metal‐air batteries, and hydrogen peroxide production. Proliferation and improvement of the ORR requires wider use of new and existing high performance catalysts; unfortunately, most of these are still based on precious metals and become uneconomical in mass‐use applications. Recent progress suggests that low cost and durable carbon materials can potentially be developed as efficient ORR catalysts. Significant efforts have been made in discovering fundamental catalytic mechanisms and engineering techniques to guide and enable viable regulation of both the ORR activity and selectivity of these carbon catalysts. Starting from the fundamental understanding, this report reviews recent progress in engineering carbon materials from exotic chemical doping to intrinsic geometric defects for improved ORR. On the basis of both theoretical and experimental investigations reported so far in this area, future improvements in carbon catalysts are also discussed, providing useful pathways for more efficient and reliable energy conversion technologies.
The core@shell structure dimension of the Pd‐based nanocrystals deeply impacts their catalytic properties for C1 and C2 alcohol oxidation reactions. However, the precise simultaneous control on the synthesis of core@shell nanocrystals with different shell dimensions is difficult, and most synthesis on Pd‐based core@shell nanocatalysts involves the surfactants participation by multiple steps, thus leads to limited catalytic properties. Herein, for the first time, a facile one‐step surfactant‐free strategy is developed for shell dimension reconstruction of PdAu@Pd core@shell nanocrystals by altering volume ratios of mixed solvents. The Pd‐based sunflower‐like (SL) and coral grass‐like (CGL) nanocrystals are obtained with different 2D hexagonal nanosheet assembles and 3D network shells, respectively. Benefitting from the clean surface shell of 2D ultrathin nanosheets structure, high atom utilization efficiency, and robust electronic effect. The PdAu@Pd SL achieves the ascendant methanol/ethanol/ethylene glycol oxidation reaction (MOR/EOR/EGOR) activities, much higher than Pd/C catalysts, as well as the improved antipoisoning ability. Notably, this one‐step construction shell dimension of PdAu@Pd core@shell catalysts not only provide a significant reference for the improvement of surfactant‐free synthetic routes, but also shed light on the advanced engineering on shell dimensions in core@shell nanostructures for electrocatalysis and so forth.
The preparation of metal electrocatalysts with excellent comprehensive properties for application in alcohol fuel cells is an urgent issue. This study reports a novel 3D Au‐doped PtBi intermetallic phase woven by sub‐7 nm building blocks. The high‐efficiency “active auxiliary” Au advances the activity and in situ anti‐CO poisoning upon ethylene glycol electrooxidation on 3D PtBiAu, along with high CC bond cleavage and attainment of a ten‐electron complete electrooxidation via a CO‐free pathway. The interface‐rich 3D structure with “nanocontainer” function, electronic effect, and dual functional sites of “Pt–Au” or “Pt–Bi” enable the 3D PtBiAu to outperform industrial Pt black and 3D PtBi intermetallics significantly. The mass activity on the 3D Pt53.1Bi43.4Au3.5 intermetallics boosts to 28.72 A mgPt−1, higher than that reported in a previous study. The 3D Pt53.1Bi43.4Au3.5 exhibits superior performance to industrial Pt/C in direct ethylene glycol fuel cells (DEGFCs). The peak power density of 3D Pt53.1Bi43.4Au3.5 is 145/92 mW cm−2 in O2/air (80 °C). Importantly, the cell voltage shows a negligible decay in both O2 and air during the 20 h durability testing. This study results in the development of novel 3D PtBiAu intermetallics as high‐performance anode electrocatalysts for application in DEGFCs. A novel 3D structure for the Au‐doped PtBi intermetallics woven by sub‐7 nm building blocks is achieved. The 3D Pt53.1Bi43.4Au3.5 as a high‐performance anode electrocatalyst promotes excellent power density and long‐term durability for practical, direct ethylene glycol fuel cells in both O2 and air.
Dual-doping of carbon, especially the combination of nitrogen and a secondary heteroatom, has been demonstrated efficient to optimize the oxygen reduction reaction (ORR) performance. However, the optimum dual-doping is still not clear due to the lack of strong experimental proofs, which rely on a reliable method to prepare carbon materials that can rule out the interference factors and then emphasize only the doping effects. In this work, an inside-out doping method is reported to prepare carbon submicrotubes (CSTs) as a material to study the principles of designing dual-doping catalysts for ORR. The interference factors including the metal impurities and doping gradient in the bulk phase are excluded, and the doping effects including the structural and chemical variation of carbon are studied. P-doping exhibited a higher pore-forming ability to perforate carbon and a lower doping content, but a higher ORR catalytic activity as compared with S- and B-doped N-CSTs, demonstrating the N,P co-doping is more efficient in making carbon-based catalysts for ORR. First-principle calculations reveal that the edge C situated around the oxidized P site nearby a graphitic N atom is the active site that shows the lowest ORR overpotential comparable to Pt-based catalysts. This study suggests that the catalytic activity of dual-heteroatoms-doped carbons not only depends on the intrinsic chemical bonding between heteroatoms and carbon, but also is affected by the structural variation generated by introducing different atoms, which can be extended to the study of other kinds of functionalization of carbon and potential reactions besides ORR.
Atomically dispersed oxide‐on‐metal inverse nanocatalysts provide a blueprint to amplify the strong oxide–metal interactions for heterocatalysis but remain a grand challenge in fabrication. Here we report a 2D inverse nanocatalyst, RuOx‐on‐Pd nanosheets, by in situ creating atomically dispersed RuOx/Pd interfaces densely on ultrathin Pd nanosheets via a one‐pot synthesis. The product displays unexpected performance toward the oxygen reduction reaction (ORR) in alkaline medium, which represents 8.0‐ and 22.4‐fold enhancement in mass activity compared to the state‐of‐the‐art Pt/C and Pd/C catalysts, respectively, showcasing an excellent Pt‐alternative cathode electrocatalyst for fuel cells and metal–air batteries. Density functional theory calculations validate that the RuOx/Pd interface can accumulate partial charge from the 2D Pd host and subtly change the adsorption configuration of O2 to facilitate the O−O bond cleavage. Meanwhile, the d‐band center of Pd nanosubstrates is effectively downshifted, realizing weakened oxygen binding strength.
Metallic nanostructures are commonly densely packed into a few packing variants with slightly different atomic packing factors. The structural aspects and physicochemical properties related with the vacancies in such nanostructures are rarely explored because of lack of an effective way to control the introduction of vacancy sites. Highly voided metallic nanostructures with ordered vacancies are however energetically high lying and very difficult to synthesize. Here, we report a chemical method for synthesis of hierarchical Rh nanostructures (Rh NSs) composed of ultrathin nanosheets, composed of hexagonal close-packed structure embedded with nanodomains that adopt a vacated Barlow packing with ordered vacancies. The obtained Rh NSs exhibit remarkably enhanced electrocatalytic activity and stability toward the hydrogen evolution reaction (HER) in alkaline media. Theoretical calculations reveal that the exceptional electrocatalytic performance of Rh NSs originates from their unique vacancy structures, which facilitate the adsorption and dissociation of H 2 O in the HER.
The development of new electrode approaches from highly active electrocatalysts to replace the state-of-the-art Pt/C is most desirable for enhancing power performance and durability in proton exchange membrane fuel cells. However, the deployment of advanced, often shape-controlled Pt alloy electrocatalysts in actual electrodes has remained challenging due to their small quantities in preparation and poor power performance in operating fuel cells. In this study, a new electrocatalyst approach is presented for Au integrated one-dimensional AgPt alloy nanorods. The atom arrangement is tuned through precisely controlling the metal ion reduction procedure to improve the catalyst activity. With 5 at% Au, nanorods with an average length of 20 nm and diameter of 3-4 nm are achieved. The test of Au-AgPt nanorods as cathode catalysts shows 1.2-fold higher fuel cell power density than commercial Pt/C catalysts, and a lower decline rate of 39.63% compared to 44.19% after the accelerated degradation test.
The methanol crossover effect in direct methanol fuel cells (DMFCs) can severely reduce cathodic oxygen reduction reaction (ORR) performance and fuel efficiency. As a result, developing efficient catalysts with simultaneously high ORR activity and excellent antipoisoning methanol capability remains challenging. Here, we report a class of Pd-Te hexagonal nanoplates (HPs) with a Pd 20 Te 7 phase that simultaneously overcome the activity and methanol-tolerant issues in alkaline DMFC. Because of the specific arrangement of Pd atoms deviated from typical hexagonal close-packing, Pd-Te HPs/C displays extraordinary methanol tolerance with high ORR performance compared with commercial Pt/C. DFT calculations reveal that the high performance of Pd-Te HPs can be attributed to the breakthrough of the linear relationship between OOH* and OH* adsorption, which leaves sufficient room to improve the ORR activity but suppresses the methanol oxidation reaction. The concurrent high ORR activity and excellent methanol tolerance endow Pd-Te HPs as practical electrocatalysts for DMFC and beyond.
The development of advanced transition metal/nitrogen/carbon-based (M/N/C) catalysts with high activity and extended durability for oxygen reduction reaction (ORR) is critical for platinum-group-metal (PGM) free fuel cells but still remains great challenging. In this review, we summarize the recent progress in two typical M/N/C catalysts (atomically dispersed metal-nitrogen-carbon catalysts (M-N-C) and carbon-supported metal nanoparticles with N-doped carbon shells (M@NC)) with an emphasis on their potential applications in fuel cells. Starting with understanding the active sites in these two types of catalysts, the representative innovative strategies for enhancing their intrinsic activity and increasing the density of these sites are systematically introduced. The synergistic effects of M-N-C and M@NC are subsequently discussed for those M/N/C catalysts combining both of them. To translate the material-level catalyst performance into high-performance devices, we also include the recent progress in engineering the porous structure and durability of M/N/C catalysts towards efficient performance in fuel cell devices. From the viewpoint of industrial applications, the scale-up cost-effective synthesis of M/N/C catalysts has been lastly briefed. With this knowledge, the challenges and perspectives in designing advanced M/N/C catalysts for potential PGM-free fuel cells are proposed.
Au‐incorporation is a promising strategy to retard composition‐loss in Pt‐based catalyst. However, the unclear mechanism limits guided catalyst design and the performance optimization. Here, direct evidence is provided to validate the outward diffusion of Au atoms in Au‐core/Pt‐based‐shell structures. A Co interlayer is built between the Au‐core and PtCo‐based shell to exclude the possibility of atomic diffusion caused by interfacial alloying. In conjunction with the improved catalytic durability of the Au‐core@Pt‐based‐shell structure, it is reasonable to conclude that it is the subsurface segregated Au atoms rather than interfacial interaction that boosts the catalytic durability of Au‐core/Pt‐based‐shell structured catalysts towards oxygen reduction reaction. More importantly, by constructing Au‐core@Co‐interlayer@PtCoAu‐shell multilayer structure, the specific (1.730 mA cm⁻²) and mass (0.692 A mg⁻¹Pt) activities are enhanced 7‐ and 4‐ fold relative to the commercial Pt/C. After 10 000 cycles of accelerated durability test, the mass activity loss for the multilayered catalyst is as low as 6.14% while the loss exceeds 35% for the commercial Pt/C catalyst. The improved catalytic performance of the Au@Co@PtCoAu multilayer structure can be ascribed to the finely modulated electronic structure and the compensated composition loss owing to the delicate structure and composition profile design.
Unique palladium‐gold hollow nanochains (PdAu HCs) with 1D architecture and an ultrathin Pd‐rich skin exhibit fantastic oxygen reduction reaction (ORR) enhancements due to their high conductivity, structural stability, and maximized atomic utilization. More importantly, such PdAu HCs possess periodic concave structures that boost ORR performance. These structures readily form high‐density high‐index facets, and fewer arc edges. Concave structures can deliver strong strain effects and surface charge accumulation is revealed by off‐axis electron holography. In addition, periodic concave structures can provide strong localized surface–plasmon coupling, which means that PdAu HCs have great potential as efficient surface‐enhanced Raman scattering (SERS) substrates. This study offers a novel and general approach for the design of complex noble metal‐based nanostructures as efficient ORR catalysts and SERS substrates.
Tuning the intrinsic strain of Pt‐based nanomaterials has shown great promise for improving the oxygen reduction reaction (ORR) performance. Herein, reported is a tunable surface strain in penta‐twinned ternary Pt–Cu–Mn nanoframes (NFs). Pt–Cu–Mn ultrafine NFs (UNFs) exhibit ≈1.5% compressive strain compared to Pt–Cu–Mn pentagonal NFs (PNFs) and show the superior activity toward ORR in an alkaline environment. Specifically, the specific and mass activity of Pt–Cu–Mn UNFs are 3.38 mA cm−2 and 1.45 A mg−1, respectively, which is 1.45 and 1.71 times higher than that of Pt–Cu–Mn PNFs, demonstrating that compressive strain in NFs structure can effectively enhance the catalytic activity of ORR. Impressively, Pt–Cu–Mn UNFs exhibit 8.67 and 9.67 times enhanced specific and mass activity compared with commercial Pt/C. Theoretical calculations reveal that compression on the surface of Pt–Cu–Mn UNFs can weaken the bonding strengths and adsorption of oxygen‐containing intermediates, resulting in an optimal condition for ORR. The surface strain in penta‐twinned Pt–Cu–Mn nanoframes (NFs) is effectively tuned. Pt–Cu–Mn ultrafine NFs exhibit ≈1.5% compressive strain compared to Pt–Cu–Mn pentagonal NFs and show the superior activity toward oxygen reduction reaction in an alkaline environment.
Recently, in order to improve the energy conversion efficiency of direct polyol fuel cells, the engineering of effective Pd‐ and/or Pt‐based electrocatalysts to rupture CC bonds has received increasing attention. Here, an example is shown to synthesize highly uniform sub‐10 nm Pd‐Cu‐Pt twin icosahedrons by controlling the nucleation phase. Because of the synergies of the electronic effect, synergistic effect, geometric effect, and abundant surface active sites originating from the formation of near surface alloy and special icosahedral shape, the Pd‐Cu‐Pt twin icosahedrons exhibit excellent electrocatalytic performance in glycerol electrocatalysis at the operating temperature of direct alcohol fuel cells (70 °C) in KOH electrolyte. The Pd50.2Cu38.4Pt11.4 icosahedrons show mass activities of 9.7 A mg−1Pd+Pt and 13.7 A mg−1Pd. Furthermore, the Pd50.2Cu38.4Pt11.4 icosahedrons demonstrate long‐term durability in current–time test for 36 000 s and high in situ anti‐CO poisoning performance. In addition, the introduction of CO can enhance electro‐oxidation endurance on Pd50.2Cu38.4Pt11.4 icosahedrons, and the peak mass activity can reach to 14.4 A mg−1Pd+Pt. The in situ Fourier transform infrared spectroscopy spectra indicate that the Pd50.2Cu38.4Pt11.4 icosahedrons possess a high capacity to break CC bonds and may efficiently convert glycerol into CO2, thus improving the utilization efficiency of energy‐containing molecule glycerol. Ultrasmall Pd‐Cu‐Pt trimetallic twin icosahedrons have been achieved as effective electrocatalysts toward glycerol oxidation at the operating temperature of fuel cells (70 °C). The Pd50.2Cu38.4Pt11.4 icosahedrons exhibit a high capacity to break CC bonds, long‐term durability in current–time test for 36 000s, and high in situ anti‐CO poisoning performance.
Nanocage-chain fuel cell catalysts
The expense and scarcity of platinum has driven efforts to improve oxygen-reduction catalysts in proton-exchange membrane fuel cells. Tian et al. synthesized chains of platinum-nickel alloy nanospheres connected by necking regions. These structures can be etched to form nanocages with platinum-rich surfaces that are highly active for oxygen reduction. In fuel cells running on air and hydrogen, these catalysts operated for at least 180 hours.
Science , this issue p. 850
PdMo bimetallene, a highly curved and sub-nanometre-thick nanosheet of a palladium–molybdenum alloy, is an efficient and stable electrocatalyst for the oxygen reduction and evolution reactions under alkaline conditions.
Harnessing self-tuned strain
Strain can modify the electronic properties of a metal and has provided a method for enhancing electrocatalytic activity. For practical catalysts, nanomaterials with high surface areas are needed. However, for nanoparticles, strain is often induced with overlayers (adsorbates or heteroatoms) that can undergo reconstruction during operation that releases the induced strain. Wang et al. show that freestanding palladium nanosheets (three to five monolayers thick) form with an internal compressive strain of 1 to 2% and can be much more active for both the oxygen and hydrogen evolution reactions under alkaline conditions compared with nanoparticles.
Science , this issue p. 870
It is generally accepted that the interface effect and surface electronic structure of catalysts have vital impact on catalytic properties. Understanding and tailoring the atomic arrangement of interface structure are of great importance for electrocatalysis. Herein, we proposed a simple method to synthesize etching-PtNiCu nanowires (e-PtNiCu NWs) enclosed by both (110) and (100) facets evolving from PtNiCu nanowires (PtNiCu NWs) mainly with (111) facets by selectively etching process. After acetic acid etching treatment, the e-PtNiCu NWs possess high total proportions (88.3%) of (110) and (100) facets, whereas the (111) facet is dominant in PtNiCu NWs (64%) by qualitatively and quantitatively evaluation. Combining the structure characterizations and performance tests of ethanol electrooxidation reaction (EOR), we find that the e-PtNiCu NWs display remarkably performance for EOR, which is nearly 4.5 times and 1.5 times enhancement compared with the state-of-the-art Pt/C catalyst, as well as 2.2 and 1.4 times of PtNiCu NWs, in specific activity and mass activity, respectively. The improved performance of e-PtNiCu NWs is attributed to synergistic catalytic effect between (110) and (100) facets that not only significantly decreases the onset potentials of adsorbed CO (COads) but also favors the oxidation of COads on the surface of catalyst. Furthermore, thermodynamics and kinetic studies indicate that the synergistic effect of both (110) and (100) facets in e-PtNiCu NWs can decrease the activation energy barrier and facilitate the charge transfer during the reaction. This work provides a promising approach to construct catalysts with tunable surface electronic structure towards efficient electrocatalysis.
Tuning the crystal phase of bimetallic nanocrystals offers an alternative avenue to improving their electrocatalytic performance. Herein, we present a facile and one-pot synthesis approach that is used to enhance the catalytic activity and stability toward oxygen reduction reaction (ORR) in alkaline media via control of the crystal structure of Pd-Bi nanocrystals. By merely altering the types of Pd precursors under the same conditions, the monoclinic structured Pd5Bi2 and conventional face-centered cubic (fcc) structured Pd3Bi nanocrystals with comparable size and morphology can be precisely synthesized, respectively. Interestingly, the carbon-supported monoclinic Pd5Bi2 nanocrystals exhibit superior ORR activity in alkaline media, delivering a mass activity (MA) as high as 2.05 A/mgPd. After 10,000 cycles of ORR durability test, the monoclinic structured Pd5Bi2/C nanocatalysts still remain a MA of 1.52 A/mgPd, which is 3.6 times, 16.9 times, and 21.7 times as high as those of the fcc Pd3Bi/C counterpart, commercial Pd/C, and Pt/C electrocatalysts, respectively. Moreover, structural characterizations of the monoclinic Pd5Bi2/C nanocrystals after the durability test demonstrate the excellent retention of the original size, morphology, composition, and crystal phase, greatly alleviating the leaching of the Bi component. This work provides new insight for the synthesis of multimetallic catalysts with a metastable phase and demonstrates phase-dependent catalytic performance.
Although Pt-based alloy catalysts have been considered promising candidates for fuel cell applications, constructing highly efficient, multifunctional Pt-based catalysts that simultaneously boost the three key reactions (MOR, ORR and HOR) in proton exchange membrane fuel cells (PEMFCs) remains a huge challenge. Herein, PtMo-CeOx hybrids with interesting ultrathin and ultralong nanowire assemblies (NAs) structure are synthesized by a one-pot solvothermal method without templates. The PtMo-CeOx-NAs catalyst exhibits 5.2-fold, 6.9-fold and 2.4-fold higher mass activity than commercial Pt/C towards the MOR, ORR and HOR simultaneously and shows excellent durability and CO poisoning tolerance. Detailed experiments reveal that the enhancement should be due to strain and ligand effects. Most impressively, when PtMo-CeOx-NAs membrane electrode assemblies (MEAs) fabricated by a catalyst-coated method are used both as the anode and cathode in PEMFCs, the performance of fuel cells is dramatically boosted compared to those with Pt/C.
To overcome the limited potency of energy devices such as alkaline water electrolyzers, the construction of active materials with dramatically enhanced oxygen evolution reaction (OER) performance is of great importance. Herein we developed an ion diffusion-induced doping strategy that is capable of producing Ni²⁺/Co²⁺ doped two-dimensional (2D) Au-Fe7S8 nanoplatelets (NPLs) with exceptionally high OER activity outperforming the benchmark RuO2 catalyst. The co-existence of Co and Ni in Au-Fe7S8 NPLs led to the lowest OER overpotential of 243 mV at 10 mA cm⁻² and fast kinetics with a Tafel slope of 43 mV dec⁻¹. Density functional theory (DFT) calculations demonstrated that Ni²⁺/Co²⁺ doping improves the binding of OOH species on the {001} surfaces of Au-Fe7S8 NPLs and lowers the Gibbs free energy of the OER process, which are beneficial to outstanding OER activity of the nanoplatelets.
Concentrating active Pt atoms in the outer layers of electrocatalysts is a very effective approach to greatly reduce the Pt loading without compromising the electrocatalytic performance and the total electrochemically active surface area (ECSA) for the oxygen reduction reaction (ORR) in hydrogen-based proton-exchange membrane fuel cells. Accordingly, a facile, low-cost, and hydrogen-assisted two-step method is developed in this work, to massively prepare carbon-supported uniform, small-sized, and surfactant-free Pd nanoparticles (NPs) with ultrathin ∼3-atomic-layer Pt shells (Pd@Pt3L NPs/C). Comprehensive physicochemical characterizations, electrochemical analyses, fuel cell tests, and density functional theory calculations reveal that, benefiting from the ultrathin Pt-shell nanostructure as well as the resulting ligand and geometric effects, Pd@Pt3L NPs/C exhibits not only significantly enhanced ECSA, electrocatalytic activity, and noble-metal (NM) utilization compared to commercial Pt/C, showing 81.24 m2/gPt, 0.710 mA/cm2, and 352/577 mA/mgNM/Pt in ECSA, area-, and NM-/Pt-mass-specific activity, respectively; but also a much better electrochemical stability during the 10,000-cycle accelerated degradation test. More importantly, the corresponding 25-cm2 H2-air/O2 fuel cell with the low cathodic Pt loading of ∼ 0.152 mgPt/cm2geo achieves the high power density of 0.962/1.261 W/cm2geo at the current density of only 1,600 mA/cm2geo, which is much higher than that for the commercial Pt/C. This work not only develops a high-performance and practical Pt-based ORR electrocatalyst, but also provides a scalable preparation method for fabricating the ultrathin Pt-shell nanostructure, which can be further expanded to other metal shells for other energy-conversion applications.
Ultra-small size metal nanoparticles (u-MNPs) have broad applications in the fields of catalysis, biomedicine and energy conversion. Herein, by means of a ligand-controlled synthesis strategy, series of Ru-based NPs with high dispersity and ultra-small size (marked as u-Ru/C), or sparse and aggregated state (marked as a-Ru/C) anchored on the surface of hollow porous carbon shells are prepared. Systematical in-situ thermogravimetry-mass spectrometry-Fourier transform infrared spectra tests suggest that the different ligands in these Ru-based precursors can regulate the nucleation, growth and fixation of metal sites during the pyrolysis process, thus contributing to Ru NPs with various size and dispersity. As a result, when applied to hydrogen evolution reaction, the u-Ru-1/C catalyst displays a low Tafel slope of 26 mV·dec−1, overpotential of 31 mV (at 10 mA·cm−2) and a large exchange current density of 1.7 mA·cm−2 in 1.0 M KOH, significantly better than that of the a-Ru-2/C, hollow carbon and even commercial 20% Pt/C. This is mainly because that the u-Ru-1/C sample owns both smaller particle size, more electrochemical active sites, higher intrinsic activity and optimized surface H adsorption ability than that of the a-Ru-2/C counterpart. Such ligand-modulated growth strategy is not only applicable to Ru, but also can be extended to other similar metals, offering a step forward in the design and synthesis of highly dispersed u-MNPs.
Carbon-supported transition metal single atoms are promising oxygen reduction reaction (ORR) electrocatalyst. Since there are many types of carbon supports and transition metals, the accurate prediction of the components with high activity through theoretical calculations can greatly save experimental time and costs. In this work, the ORR catalytic properties of 180 types single-atom catalysts (SACs) composed of the eight representative carbon-based substrates (graphdiyne, C2N, C3N4, phthalocyanine, C-coordination graphene, N-coordination graphene, covalent organic frameworks and metal-organic frameworks) and 3d, 4d, and 5d transition metal elements are investigated by density functional theory (DFT). The adsorption free energy of OH* is proved a universal descriptor capable of accurately prediction of the ORR catalytic activity. It is found that the oxygen reduction reaction overpotentials of all the researched SACs follow one volcano shape very well with the adsorption free energy of OH*. Phthalocyanine, N-coordination graphene and metal-organic frameworks stand out as the promising supports for single metal atom due to the relatively lower overpotentials. Notably, the Co-doped metal-organic frameworks, Ir-doped phthalocyanine, Co-doped N-coordination graphene, Co-doped graphdiyne and Rh-doped phthalocyanine show extremely low overpotentials comparable to that of Pt (111). The study provides a guideline for design and selection of carbon-supported SACs toward oxygen reduction reaction.
A reasonable design strategy to improve the utilization of noble metal electrocatalysts for the hydrogen evolution reaction (HER) is crucial to simplify the process flow and accelerate the future renewable energy economy. Here, abundant defects were created on 2.4-nm Ru nanoparticles to achieve unprecedently high mass-specific reactivity in harsh acidic and alkaline electrolytes. The obtained defect-enriched Ru (DR-Ru) exhibits an ultrahigh HER turnover frequency of 16.4 s−1 with a 100-mV overpotential in alkaline media, and it also retains an excellent value of 20.6 s−1 in acidic media; these results are superior to those reported for other Ru catalysts. Accordingly, a record-low loading of 2.5 µg cm−2 for the DR-Ru catalysts and low overpotentials of 28.2 and 25.1 mV at 10 mA cm−2 can be realized in alkaline and acidic media, respectively. Furthermore, the less coordinated Ru surface sites and partial lattice oxygen introduction weaken the bonding between H and DR-Ru catalysts, facilitate fast acidic HER kinetics and help dissociate the water molecule to overcome the major challenge of HER in alkaline electrolytes, leading to an activity comparable to that under acidic conditions. This result provides a guideline for defect engineering on noble metal nanocatalysts to effectively improve the utilization of the catalysts and optimize reactivities.
Interfacial electron engineering between noble metal and transition metal carbide is identified as a powerful strategy to improve the intrinsic activity of electrocatalytic oxygen reduction reaction (ORR). However, this short-range effect and the huge structural differences make it a significant challenge to obtain the desired electrocatalyst with atomically thin noble metal layers. Here, we demonstrated the combinatorial strategies to fabricate the heterostructure electrocatalyst of Mo2C-coupled Pd atomic layers (AL-Pd/Mo2C) by precise control of metal-organic framework confinement and covalent interaction. Both atomic characterizations and density functional theory calculations uncovered that the strong electron effect imposed on Pd atomic layers has intensively regulated the electronic structures and d-band center and then optimized the reaction kinetics. Remarkably, AL-Pd/Mo2C showed the highest ORR electrochemical activity and stability, which delivered a mass activity of 2.055 A mgPd-1 at 0.9 V, which is 22.1, 36.1, and 80.3 times higher than Pt/C, Pd/C, and Pd nanoparticles, respectively. The present work has developed a novel approach for atomically noble metal catalysts and provides new insights into interfacial electron regulation.
Neutral Zn-air batteries (ZABs) have attracted much attention due to the enhanced lifespan and stability. However, their development is suppressed by the poor catalytic properties of the air-electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Hence, the exploration of highly efficient electrocatalysts for neutral ZABs is critical. Herein, we designed an economical heterostructure of Pt nanoparticle-modified Zn nanoplates (Pt/Zn NPs). Compared with commercial Pt/C electrocatalyst, our Pt/Zn heterostructure exhibits comparable catalytic properties and ultrahigh stability in neutral media. The heterostructure can reduce the dosage of Pt and offer sufficient active sites, resulting in enhanced catalytic properties for ORR/OER in neutral media. When applied to neutral ZABs as air cathode, our heterostructure exhibits a high power density of 45 mW cm−2 and excellent stability of more than 850 cycles with negligible decay, making it the most efficient and robust one in neutral electrolyte. This approach opens a new avenue to strategically design catalysts with high activity for neutral ZABs, rendering them potential in portable and wearable electronic devices.
Regulating the selectivity of catalysts in selective hydrogenation reactions at the atomic level is highly desirable but remains a grand challenge. Here we report a simple and practical strategy to synthesize a monolithic single-atom catalyst (SAC) with isolated Pd atoms supported on bulk nitrogen-doped carbon foams (Pd-SAs/CNF). Moreover, we demonstrate that the single-atom Pd sites with unique electronic structure endow Pd-SAs/CNF with an isolated site effect, leading to excellent activity and selectivity in 4-nitrophenylacetylene semi-hydrogenation reaction. In addition, benefiting from the great integrity and excellent mechanical strength, monolithic Pd-SAs/CNF catalyst is easy to separate from the reaction system for conducting the subsequent recycling. The cyclic test demonstrates the excellent reusability and stability of monolithic Pd-SAs/CNF catalyst. The discovery of isolated site effect provides a new approach to design highly selective catalysts. And the development of monolithic SACs provides new opportunities to advance the practical applications of single-atom catalysts.
A facile non-template assisted mechanical ball milling technique has been employed to generate PdBi alloy catalyst. The induced lattice strain upon milling time caused a shift of the d-band centre thereby enhancing oxygen reduction reaction (ORR) catalytic activity. Also, Pd-O reduction potential and adsorbed OH coverage used as descriptors stipulated the cause for enhanced ORR activity upon increased milling interval. Redox properties of surface Pd is directly correlated with positive shift in Pd-O reduction potential and OH surface coverage. Hence, deconvoluting the lattice strain and role of descriptor species we achieved a catalyst system with specific activity 5.4 times higher than commercial Pt/C and improved durability. The experimental observation is well corroborated by theoretical simulation by inducing strain externally into the system.
Current concerns on material-design induced mass transfer processes during small molecule electrocatalysis are on the ones assisted by external forced convection generally via electrode rotating, demonstrating the intrinsic activity of catalysts. Of note is that, in practical battery configurations there is no the forced convection around electrode micro-environments. Therefore, the establishment of effective strategies in tuning the inherent mass transfer process, the one with no assistance by external forced convection, is also greatly significant, but rarely reported, retarding further advances. Herein, a size-induced inherent mass-transfer strategy is scrupulously established through designed kinetic investigations and also controllable construction of uniform Co, N co-doped carbon materials with a wide range of tunable particle sizes from 10 nm to 2 μm. The catalysts are synthesized by a pyrolysis of zeolitic imidazolate framework (ZIF) [email protected], in which the wrapped shell layer avoids evident metal aggregations, and also contributes to rich porous environments after carbonizations. It is unclosed that particle size has a considerable effect on inherent mass transfer processes, even for the porous carbon catalysts. A particle size at around 700 nm is revealed to be most favorable for the inherent mass transfer process within the probed range, revealed by the smallest difference of Tafel slopes obtained with no electrode rotation and with infinite rotation speed. The latter is achieved via extrapolating rotation speeds to infinity in the Koutecký-Levich plots, by which the external mass transfer limitation can be completely eliminated. Contributed by the great inherent mass transfer process, the catalyst with a particle size of around 700 nm exhibits an impressive ORR activity in both three-electrode systems and zinc-air batteries. This work not only establishes a novel strategy in tuning inherent mass transfer process for small molecule electrocatalysis, more importantly, it provides a new dimension in kinetic investigations and oriented design of advanced energy materials.
Platinum (Pt) is an efficient catalyst for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), but the debate of the relevance between the Pt particle size and its electrocatalytic activity still exist. The strong metal-support interaction (SMSI) between the metal and carrier causes the charge transfer and mass transport from the support to the metal. Herein, Pt species (0.5 wt.%) with various particle sizes supported on carbon nanotubes (CNTs) have been synthesized by a photo-reduction method. The ~1.5 nm-sized Pt catalyst shows much higher HER performance than the counterparts in all pH solutions, and the mass activity of it is even 23–36 times that of Pt/C. While for ORR, the ~3 nm-sized Pt catalyst exhibits the optimal performance, and the mass activity is 3 times and even 16 times that of Pt/C in acidic and alkaline media, respectively. The high HER and ORR performances of the ~1.5 nm- and ~3 nm-sized Pt catalysts benefit from the SMSI between Pt and the CNTs matrix and the higher ratio of face sites to edge sites, which is meaningful for the design of efficient electrocatalysts for renewable energy application.
Systematic control of grain boundary densities in various platinum (Pt) nanostructures was achieved by specific peptide-assisted assembly and coagulation of nanocrystals. A positive quadratic correlation was observed between the oxygen reduction reaction (ORR) specific activities of the Pt nanostructures and the grain boundary densities on their surfaces. Compared to commercial Pt/C, the grain-boundary-rich strain-free Pt ultrathin nanoplates demonstrated a 15.5 times higher specific activity and a 13.7 times higher mass activity. Simulation studies suggested that the specific activity of ORR was proportional to the resident number and the resident time of oxygen on the catalyst surface, both of which correlate positively with grain boundary density, leading to improved ORR activities.
The rational design and preparation of efficient Pt-based electrocatalysts towards the oxygen reduction reaction (ORR) is a key issue for the widespread application of hydrogen fuel cells. Despite many Pt/support hybrid materials that have been reported as promising electrocatalysts for the ORR, precisely controlling the contact facet between the Pt and the support has never been demonstrated to mediate the ORR. Herein, based on theoretical calculations, we constructed an interesting Pt/support electrocatalyst by chemically coupling Pt nanoparticles (NPs) with single crystal (Sc) LiTiO2 nano-octahedra (Pt NPs/Sc-LiTiO2) for the first time. Specifically, the Pt {111} atomic crystal planes are in contact with the highly lattice-matched Sc-LiTiO2 {111} crystal planes to form specific crystal-plane coupling heterostructures, leading to strong cooperative effects between the Sc-LiTiO2 and the Pt as well as to the epitaxial growth and favorable exposed facets of Pt on the surface of Sc-LiTiO2. These key features endow Pt NPs/Sc-LiTiO2 with a mass activity of 1.44 A mg⁻¹Pt and specific activity of 1.78 mA cm− 2 at 0.9 V, which are 8.0 and 7.1-fold higher than those of the state-of-the-art Pt/C, respectively. Meanwhile, it can undergo 20000 sweep cycles with negligible activity decay and no obvious changes in morphology or composition, showing excellent ORR durability. The resulting ORR performance is also comparable to or even better than those of most first-class Pt-based electrocatalysts. Our synthetic strategy could be easily extended to the design and fabrication of other robust metal/support electrocatalysts.
Carbon-supported Pt-Co (Pt-Co/C) nanoparticles with a high Pt loading are regarded as promising cathode catalysts for practical applications of proton exchange membrane fuel cells (PEMFCs). Unfortunately, with high loading, it is difficult to improve the catalytic durability while maintaining the particle size between 2-5 nm to ensure the initial catalytic activity. Thus, it is of great significance to prepare high-loading Pt-Co/C catalysts with enhanced activity and durability. Herein, we proposed an efficient way to prepare high-Pt-loading (>50 wt.%) Pt-Co/C catalysts without using any further surfactants. Furthermore, due to the one-step selective acid etching and surface Au modification, the as-prepared catalysts only need to undergo thermal treatment at as low as 150℃ to achieve a surface structure rich of Pt and Au. The average particle size of the as-prepared Au-Pt-Co/C-0.015 is 3.42 nm and the Pt loading of it is up to 50.2 wt.%. The atomic ratio of Pt, Co and Au is 94:5:1. The mass activity (MA) is nearly 1.9 times that of Pt/C (60 wt.%, JM) and the specific activity (SA) is also improved. The MA loss after the 30,000-cycle accelerated degradation test (ADT) is only 9.4%. The remarkable durability is mainly due to the surface Au modification, which can restrict the dissolution of Pt and Co. This research provides an effective synthesis strategy to prepare high-loading carbon-supported Pt-based catalysts beneficial to practical PEMFC applications.
Integration of two metal constituents into core-shell structures is an efficient strategy to prepare advanced materials for a variety of applications. The controllable synthesis of targeted bimetallic core-shell nanostructures is an important yet challenging task. Herein, bimetallic nanoparticles comprising a gold multipod nanoparticle (GMN) core and distinctive Pd shell ([email protected] NPs) are successfully synthesized in a facile and controllable manner. Epitaxial or islanded growth of Pd on the GMNs can be readily achieved using appropriate stabilizing agents. The controllable growth mode of the Pd layers, coupled with the unique topologies of GMNs, are advantageous for enhancing the density of active interfacial surfaces in the composites. Particularly, I[email protected] NPs show substantially enhanced ORR activity compared with monometallic counterparts and excellent durability and better tolerance to the crossover effect than that of Pt/C, rendering the materials highly desirable for practical use.
Exploring the high-performance non-Pt electrocatalysts for oxygen reduction reaction (ORR), the bottleneck process in fuel cells, is desirable, but challenging. Here we report the [email protected] core-shell icosahedra as an active and durable electrocatalyst toward ORR in alkaline conditions, which feature a three-atomic-layer tensile-strained PdFe overlayer on Pd icosahedra. Our optimized catalyst shows 2.8-fold enhancement in mass activity and 6.9-fold enhancement in specific activity than commercial Pt/C catalyst toward ORR, respectively, representing one of the best non-Pt electrocatalysts. Moreover, the boosted ORR catalysis is strongly supported by the assembled fuel cell performance using [email protected] core-shell icosahedra as the cathode electrocatalyst. The density functional theory calculations reveal that the synergistic coupling of tensile strain and alloy effects enables the optimum binding strength for intermediates, thus causing the maximum activity. The present work suggests the coupling between multiple surface modulations endows larger room for the rational design of remarkable catalysts.
Developing high-performance electrocatalysts for ethanol oxidation reaction (EOR) is critical for the commercialization of direct ethanol fuel cells. However, current EOR catalysts suffer from high cost, low activity, and poor durability. Here we report the preparation of PdBi-Bi(OH)3 composite nanochains with outstanding EOR activity and durability. The incorporation of Bi can tune the electronic structure and downshift the d-band center of Pd, while the surface decoration of Bi(OH)3 can facilitate the oxidative removal of CO and other carbonaceous intermediates. As a result, the nanochains manifest an exceptional mass activity (5.30 A mgPd-1, 4.6-fold higher than that of commercial Pd/C) and outstanding durability (with a retained current density of ~ 1.00 A mgPd-1 after operating for 20,000 s). More importantly, the nanochains catalyst can be re-activated, and negligible activity loss has been observed after operating for 200,000 s with periodic re-activation, making it one of the best EOR catalysts.
Pd-based nanocatalyst is a potential oxygen reduction oxidation (ORR) catalyst because of its high activity in alkaline medium and low cost. In this work, bimetallic PdAu nanocatalysts are prepared by one-pot hydrothermal method using triblock pluronic copolymers, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO19-PPO69-PEO19)(P123) as reducer and stabilizer, and heat-treatment method is applied to regulate catalyst structure and improve catalyst activity. The results show that the heat treatment can agglomerate the catalyst to a certain extent, but effectively improve the crystallinity and alloying degree of the catalyst. The ORR performance of the PdAu nanocatalysts obtained under different heat treatment conditions is systematically investigated. Compared with commercial Pd black and PdAu catalyst before heat treatment, the ORR performance of AuPd nanocatalyst obtained after heat treatment for one hour at 500 °C has been enhanced. The PdAu nanocatalysts after heat treatment also display enhanced anti-methanol toxicity ability in acidic medium.
The hydrogen evolution reaction (HER) is an ideal model to explore the effect between the activity and the surface vacancy of catalysts. Compared to the anion vacancy, the cation vacancy is more challenging to selectively generate due to the large formation energy, and the serious lack of insight into the structure-activity relationship of cation vacancy-rich catalysts. Herein, we report a facile solid-liquid phase chemical strategy for in situ formation of cation vacancies in a five-fold twinned PtPdRuTe anisotropic structure (v-Pd3Pt29Ru62Te6 AS). Five-fold twinned AS with metal vacancies preferentially produced are confirmed by both X-ray photoelectron spectroscopy (XPS) and High-angle annular dark-field scanning transmission electron microscope (HAADF-STEM). Due to the synergy of metal vacancies and twinned structural advantages, including the appropriate hydrogen binding energy, large exposed surface, anisotropic structure and fast mass/charge transport, v-Pd3Pt29Ru62Te6 AS exhibits significantly enhanced HER electrocatalytic performance in both alkaline and acidic solutions, with ultrasmall overpotentials of 22 and 39 mV to achieve 10 mA cm-2, respectively, and remarkable long-term stability (at least 30 h). These results herald a promising strategy to utilize defective twinned materials for advanced energy storage applications.
Exploring Pt-free electrocatalysts with high activity and long durability for the oxygen reduction reaction (ORR) has been long pursued by the renewable energy material community. In this work, we have designed an ordered intermetallics PdZn/C (O-PdZn) with a several atomic-layer Pd shell, which achieved a three-fold enhancement in ORR mass activities (MA) in alkaline media, relative to Pd/C and Pt/C. Further Au incorporation in O-PdZn/C (Au-O-PdZn/C) yielded a catalyst with superior durability with less than 10% loss in MA after 30,000 potential cycles. These effects have attributed to the rationally designed ordered structure and stabilizing effect of Au atoms. Aberration-corrected scanning transmission electron microscopy (STEM) and synchrotron-based X-ray fluorescence spectroscopy were employed to show that Au not only galvanically replaced Pd and Zn on the surface, but also penetrated through the PdZn lattice and distributed uniformly within the particles. Au-O-PdZn/C was also tested as an effective oxygen cathode in broad applications in rechargeable Li-air and Zn-air batteries.
Proton exchange membrane fuel cells (PEMFCs) are promising mobile power supply systems, and operate without noise or polluting emissions. Because the oxygen reduction reaction (ORR) at the cathode suffers from high overpotential and sluggish kinetics, many catalysts have been developed in efforts to enhance activity and durability for the ORR. However, most of them have complicated synthetic procedures which cannot be scaled-up easily, and have only been tested in a half-cell. High activity in a half-cell does not necessarily guarantee better performance in a single-cell. In this work, we synthesized an Au-doped PtCo/C catalyst using a simple method of gas-phase reduction and subsequent galvanic replacement, and its activity and durability were tested in a single-cell. When current densities were compared at 0.6 V after a durability test of 30,000 cycles in 0.6–1.0 V, the values were 1.40, 0.81, and 0.63 A cm⁻² for the Au-doped PtCo/C, acid-treated PtCo/C, and commercial Pt/C catalysts, respectively. Co leaching was much less in the Au-doped PtCo/C. Density functional theory (DFT) calculations confirmed that surface oxygen species bound more weakly at the catalyst surface and migration of a Co atom (Co segregation) to the surface was suppressed in the presence of Au. This facile method can provide a more realistic strategy to design better ORR catalysts for PEMFC application.
The instable structure of Pt based high-indexed facets (HIFs) facile reconstructed is a key obstacle for further practical applications due to its high surface energy and amounts of undercoordinated surface atoms. Herein, a strategy to advance fundamental surface study on Pt-based HIFs materials is addressed by implanting non-noble metal or nonmetals as “active auxiliaries” into the near-surface of noble metal nanocrystals bounded with HIFs to engineer a stable structured catalyst. Then the Mo/Pt3Mn catalysts serving as proof-of-concept examples are designed and show enhanced catalytic performance of ethylene glycol (EG). According to the electrochemical in situ Fourier transform infrared spectroscopy results, the Mo modified Pt3Mn alloys with HIFs promote not only the C-C cleavage of EG but also the direct conversion of COHX to CO2, without the formation of COL poison species. In this case, the Mo/Pt3Mn catalysts show the greatly significant increase of the catalytic activity in copamprison with Pt3Mn CNC and the commercial Pt/C, as well as the enhanced stability. The high resolution transmission electron microscopy and X-ray photoelectron spectrum assisted by Ar surface etching experiments accompanied with density functional theory calculations are further used to explore the structure-performance relationship of Mo/Pt3Mn CNC for electro-oxidation of EG. This study addresses a promising strategy to fabricate a stable structured catalysts, which will shed a very promising methodology for developing Pt-based catalysts for further application of fuel cell.
Developing efficient and durable bifunctional electrocatalysts for oxygen reduction and evolution reaction (ORR/OER) is highly desirable in energy conversion and storage systems. This study prepares nickel-ruthenium layered double hydroxide (NiRu-LDHs) nanosheets subjected to decorate with conductive silver nanoparticles (Ag NP/NiRu-LDHs) that interestingly induce their multivacancies associated with catalytic site activity and populations. The as-prepared Ag NP/NiRu-LDH shows substantially marvellous catalytic activity toward both OER and ORR features with low onset overpotential of 0.21 V and -0.27 V, respectively, with 0.76 V potential gap between OER potential at 10 mA cm−2 and ORR potential at－3 mA cm−2, demonstrating the preeminent bifunctional electrocatalyst reported to date. Compared to pristine NiRu-LDHs, the resulting Ag NP/NiRu-LDHs nanosheets require only an overpotential of 0.31 V to deliver 10 mA cm−2 with excellent durability. The superb bifunctional performance of Ag NP/NiRu-LDH is ascribed to the formation of multivacancies, mutual benefits of synergistic effect between metal LDHs and silver nanoparticles, and increased accessible active sites together with site activity are the key to the perceived performance. This work provides a new strategy to decorate LDHs and to engineer multivacancies to enhance site activity and populations simultaneously as ORR/OER bifunctional electrocatalysts.