Direct atomic-level insight into oxygen reduction reaction on size-dependent Pt-based electrocatalysts from density functional theory calculations

Developing novel oxygen reduction reaction(ORR)catalysts with high activity is urgent for proton exchange membrane fuel cells.Herein,we investigated a group of size-dependent Pt-based catalysts as promising ORR catalysts by density functional theory calculations,ranging from single-atom,nanocluster to bulk Pt catalysts.The results showed that the ORR overpotential of these Pt-based catalysts increased when its size enlarged to the nanoparticle scale or reduced to the single-atom scale,and the Pt_(38)cluster had the lowest ORR overpotential(0.46 V)compared with that of Pt_(111)(0.57 V)and single atom Pt(0.7 V).Moreover,we established a volcano curve relationship between the ORR overpotential and binding energy of O*(ΔE_(O*),confirming the intermediate species anchored on Pt38cluster with suitable binding energy located at top of volcano curve.The interaction between intermediate species and Pt-based catalysts were also investigated by the charge distribution and projected density of state and which further confirmed the results of volcano curve.

Durable hierarchical phosphorus‐doped biphase MoS_(2)electrocatalysts with enhanced H^(*)adsorption

Phase engineering is an efficient strategy for enhancing the kinetics of electrocatalytic reactions.Herein,phase engineering was employed to prepare high‐performance phosphorous‐doped biphase(1T/2H)MoS_(2)(P‐BMS)nanoflakes for hydrogen evolution reaction(HER).The doping of MoS_(2)with P atoms modifies its electronic structure and optimizes its electrocatalytic reaction kinetics,which significantly enhances its electrical conductivity and structural stability,which are verified by various characterization tools,including X‐ray photoelectron spectroscopy,high‐resolution transmission electron microscopy,X‐ray absorption near‐edge spectroscopy,and extended X‐ray absorption fine structure.Moreover,the hierarchically formed flakes of P‐BMS provide numerous catalytic surface‐active sites,which remarkably enhance its HER activity.The optimized P‐BMS electrocatalysts exhibit low overpotentials(60 and 72 mV at 10 mA cm^(−2))in H_(2)SO_(4)(0.5 M)and KOH(1.0 M),respectively.The mechanism of improving the HER activity of the material was systematically studied using density functional theory calculations and various electrochemical characterization techniques.This study has shown that phase engineering is a promising strategy for enhancing the H*adsorption of metal sulfides.

Data-Driven Design of Single-Atom Electrocatalysts with Intrinsic Descriptors for Carbon Dioxide Reduction Reaction

The strategic manipulation of the interaction between a central metal atom and its coordinating environment in single-atom catalysts(SACs)is crucial for catalyzing the CO_(2)reduction reaction(CO_(2)RR).However,it remains a major challenge.While density-functional theory calculations serve as a powerful tool for catalyst screening,their time-consuming nature poses limitations.This paper presents a machine learning(ML)model based on easily accessible intrinsic descriptors to enable rapid,cost-effective,and high-throughput screening of efficient SACs in complex systems.Our ML model comprehensively captures the influences of interactions between 3 and 5d metal centers and 8 C,N-based coordination environments on CO_(2)RR activity and selectivity.We reveal the electronic origin of the different activity trends observed in early and late transition metals during coordination with N atoms.The extreme gradient boosting regression model shows optimal performance in predicting binding energy and limiting potential for both HCOOH and CO production.We confirm that the product of the electronegativity and the valence electron number of metals,the radius of metals,and the average electronegativity of neighboring coordination atoms are the critical intrinsic factors determining CO_(2)RR activity.Our developed ML models successfully predict several high-performance SACs beyond the existing database,demonstrating their potential applicability to other systems.This work provides insights into the low-cost and rational design of high-performance SACs.

Engineering Two-Phase Bifunctional Oxygen Electrocatalysts with Tunable and Synergetic Components for Flexible Zn-Air Batteries

Metal-air batteries,like Zn-air batteries(ZABs)are usually suffered from low energy conversion efficiency and poor cyclability caused by the sluggish OER and ORR at the air cathode.Herein,a novel bimetallic Co/CoFe nanomaterial supported on nanoflower-like N-doped graphitic carbon(NC)was prepared through a strategy of coordination construction-cation exchange-pyrolysis and used as a highly efficient bifunctional oxygen electrocatalyst.Experimental characterizations and density functional theory calculations reveal the formation of Co/CoFe heterostructure and synergistic effect between metal layer and NC support,leading to improved electric conductivity,accelerated reaction kinetics,and optimized adsorption energy for intermediates of ORR and OER.The Co/CoFe@NC exhibits high bifunctional activities with a remarkably small potential gap of 0.70 V between the half-wave potential(E_(1/2))of ORR and the potential at 10 mA cm^(-2)(E_(j=10))of OER.The aqueous ZAB constructed using this air electrode exhibits a slight voltage loss of only 60 mV after 550-cycle test(360 h,15 days).A sodium polyacrylate(PANa)-based hydrogel electrolyte was synthesized with strong water-retention capability and high ionic conductivity.The quasi-solid-state ZAB by integrating the Co/CoFe@NC air electrode and PANa hydrogel electrolyte demonstrates excellent mechanical stability and cyclability under different bending states.

Ultrathin NiO/Ni_(3)S_(2)Heterostructure as Electrocatalyst for Accelerated Polysulfide Conversion in Lithium-Sulfur Batteries

The practical application of Lithium-Sulfur batteries largely depends on highly efficient utilization and conversion of sulfur under the realistic condition of high-sulfur content and low electrolyte/sulfur ratio.Rational design of heterostructure electrocatalysts with abundant active sites and strong interfacial electronic interactions is a promising but still challenging strategy for preventing shuttling of polysulfides in lithium-sulfur batteries.Herein,ultrathin nonlayered NiO/Ni_(3)S_(2)heterostructure nanosheets are developed through topochemical transformation of layered Ni(OH)_(2)templates to improve the utilization of sulfur and facilitate stable cycling of batteries.As a multifunction catalyst,NiO/Ni_(3)S_(2)not only enhances the adsorption of polysulfides and shorten the transport path of Li ions and electrons but also promotes the Li_(2)S formation and transformation,which are verified by both in-situ Raman spectroscopy and electrochemical investigations.Thus,the cell with NiO/Ni_(3)S_(2)as electrocatalyst delivers an area capacity of 4.8 mAh cm^(-2)under the high sulfur loading(6 mg cm^(-2))and low electrolyte/sulfur ratio(4.3 pL mg^(-1)).The strategy can be extended to 2D Ni foil,demonstrating its prospects in the construction of electrodes with high gravimetric/volumetric energy densities.The designed electrocatalyst of ultrathin nonlayered heterostructure will shed light on achieving high energy density lithium-sulfur batteries.

Transition metal clusters with precise numbers of atoms anchored on graphdiyne as multifunctional electrocatalysts for OER/ORR/HER:a computational study

Subnanometer metal clusters play an increasingly important role in heterogeneous catalysis due to their high catalytic activity and selectivity.In this work,by means of the density functional theory(DFT) calculations,the catalytic activities of transition metal clusters with precise numbers of atoms supported on graphdiyne(TM_(1-4)@GDY,TM=V,Cr,Mn,Fe,Co,Ni,Cu,Ru,Rh,Pd,Ir,Pt) were investigated for oxygen evolution reactions(OER),oxygen reduction reactions(ORR) and hydrogen evolution reactions(HER).The computed results reveal that the Pd_(2),Pd_(4) and Pt_(1) anchored graphdiyne can serve as trifunctional catalysts for OER/ORR/HER with the overpotentials of 0.49/0.37/0.06,0.45/0.33/0.12 and 0.37/0.43/0.01 V,respectively,while Pd_(1) and Pt_(2)@graphdiyne can exhibit excellent catalytic performance for water splitting(OER/HER) with the overpotentials of 0.55/0.17 and 0.43/0.03 V.In addition,Ni_(1) and Pd_(3) anchored GDY can perform as bifunctional catalysts for metal-air cells(OER/ORR) and fuels cells(ORR/HER) with the overpotentials of 0.34/0.32 and 0.42/0.04 V,respectively.Thus,by precisely controlling the numbers of atoms in clusters,the TM_(1-4) anchored graphdiyne can serve as promising multifunctional electrocatalysts for OER/ORR/HER,which may provide an instructive strategy to design catalysts for the energy conversation and storage devices.

Heterometallic cluster-based organic frameworks as highly active electrocatalysts for oxygen reduction and oxygen evolution reaction:a density functional theory study

Recently,metal–organic frameworks are one of the potential catalytic materials for electrocatalytic applications.The oxygen reduction reaction and oxygen evolution reaction catalytic activities of heterometallic cluster-based organic frameworks are investigated using density functional theory.Firstly,the catalytic activities of heterometallic clusters are investigated.Among all heterometallic clusters,Fe_(2)Mn–Mn has a minimum overpotential of 0.35 V for oxygen reduction reaction,and Fe_(2)Co–Co possesses the smallest overpotential of 0.32 V for oxygen evolution reaction,respectively 100 and 50 mV lower than those of Pt(111)and RuO_(2)(110)catalysts.The analysis of the potential gap of Fe_(2)M clusters indicates that Fe_(2)Mn,Fe_(2)Co,and Fe_(2)Ni clusters possess good bifunctional catalytic activity.Additionally,the catalytic activity of Fe_(2)Mn and Fe_(2)Co connected through 3,3′,5,5′-azobenzenetetracarboxylate linker to form Fe_(2)M–PCN–Fe_(2)M is explored.Compared with Fe_(2)Mn–PCN–Fe_(2)Mn,Fe_(2)Co–PCN–Fe_(2)Co,and isolated Fe_(2)M clusters,the mixed-metal Fe_(2)Co–PCN–Fe_(2)Mn possesses excellent bifunctional catalytic activity,and the values of potential gap on the Mn and Co sites of Fe_(2)Co–PCN–Fe_(2)Mn are 0.69 and 0.70 V,respectively.Furthermore,the analysis of the electron structure indicates that constructing a mixed-metal cluster can efficiently enhance the electronic properties of the catalyst.In conclusion,the mixed-metal cluster strategy provides a new approach to further design and synthesize high-efficiency bifunctional electrocatalysts.

Two-dimensional titanium carbonitride MXene as a highly efficient electrocatalyst for hydrogen evolution reaction

In this paper,we report,for the first time,on the electrochemical catalytic activity of 2D titanium carbonitride MXene for hydrogen evolution reaction(HER).According to our study,2D titanium carbonitride exhibited much higher electrocatalytic activity than its carbide analogues,achieving an onset overpotential of 53 mV and Tafel slope of 86 mV dec^(-1),superior to the titanium carbide with onset overpotential of 649 mV and Tafel slope of 303 mV dec^(-1).The obtained onset overpotential for 2D titanium carbonitride is lower than those of all the reported transition metal carbides MXene catalysts without additives,so far.Density functional theory calculations were conducted to further understand the electrochemical performance.The calculation results show that a greater number of occupied states are active for Ti_(3)CNO_(2),revealing free energy for the adsorption of atomic hydrogen closer to 0 than that of Ti_(3)C_(2)O_(2).Both experimental and calculation studies demonstrate the excellent electrocatalytic behavior of titanium carbonitride.The investigation of 2D titanium carbonitride opens up a promising paradigm for the conscious design of high-performance non-precious metal catalyst for hydrogen generation.

Transition metal decorated bismuthene for ammonia synthesis:A density functional theory study

The electrochemical nitrogen reduction reaction(NRR)for the ammonia production under ambient conditions is regarded as a sustainable alternative to the industrial Haber-Bosch process.However,the electrocatalytic systems that efficiently catalyze nitrogen reduction remain elusive.In the work,the nitrogen reduction activity of the transition metal decorated bismuthene TM@Bis is fully investigated by means of density functional theory calculations.Our results demonstrate that W@Bis delivers the best efficiency,wherein the potential-determining step is located at the last protonation step of^(*)NH_(2)+H^(+)+e^(-)→*NH_(3)via the distal mechanism with the limiting potential ULof 0.26 V.Furthermore,the dopants of Re and Os are also promising candidates for experimental synthesis due to its good selectivity,in despite of the slightly higher ULof NRR with the value of 0.55 V.However,the candidates of Ti,V,Nb and Mo delivered the relative lower ULof 0.35,0.37,0.41 and 0.43 V might be suffered from the side hydrogen evolution reaction.More interestingly,a volcano curve is established between ULand valence electrons of metal elements wherein W with 4 electrons in d band located at the summit.Such phenomenon originates from the underlying acceptance-back donation mechanism.Therefore,our work provides a fundament understanding for the material design for nitrogen reduction electrocatalysis.

Insight into coupled Ni-Co dual-metal atom catalysts for efficient synergistic electrochemical CO_(2)reduction

The development of highly active,selective,and stable electrocatalysts can facilitate the effective implementation of electrocatalytic CO_(2)conversion into fuels or chemicals for mitigating the energy crisis and climate problems.Therefore,it is necessary to achieve the goal through reasonable material design based on the actuality of the operational active site at the molecular scale.Inspired by the stimulating synergistic effect of coupled heteronuclear metal atoms,a novel Ni-Co atomic pairs configuration(denoted as NiN_(3)?CoN_(3)-NC)active site was theoretically screened out for improving electrochemical CO_(2)reduction reaction(CO_(2)RR).The structure of NiN_(3)?CoN_(3)-NC was finely regulated by adjusting Zn content in the precursors Zn/Co/Ni-zeolite imidazolate frameworks(Zn/Co/Ni-ZIFs)and pyrolysis temperature.The structural features of NiN_(3)?CoN_(3)-NC were systematically confirmed by aberration-corrected HAADF-STEM coupled with 3D atom-overlapping Gaussian-function fitting mapping,XAFS,and XRD.The results of theoretical calculations reveal that the synergistic effect of Ni-Co atomic pairs can effectively promote the*COOH intermediate formation and thus the overall CO_(2)RR kinetic was improved,and also restrained the competitive hydrogen evolution reaction.Due to the attributes of Ni-Co atomic pairs configuration,the developed NiN_(3)?CoN_(3)-NC with superior catalytic activity,selectivity,and durability,with a high turnover frequency of 2265 h^(-1)at-1.1 V(vs.RHE)and maximum Faradaic efficiency of 97.7%for CO production.This work demonstrates the great potential of DACs as highly efficient catalysts for CO_(2)RR,provides a useful strategy to design heteronuclear DACs,exploits the synergistic effect of multiple metal sites to facilitate complex CO_(2)RR catalytic reactions,and inspires more efforts to develop the potential of DACs in various fields.

W-doped FeNi_(2)S_(4)/Ni_(3)S_(2)/NF with interfacial effect as efficient bifunctional electrocatalyst for overall water splitting

Given the current shortage of resources and environmental pollution,rationally designing and developing low-cost and highefficiency bifunctional electrocatalysts is an urgent and challenging task.It is widely recognized that element doping can effectively improve the electrocatalytic activity by adjusting the microstructure,morphology,and electronic structure.Therefore,this work rationally designs and prepares three-dimensional flower-like structured W-doped FeNi_(2)S_(4)/Ni_(3)S_(2)/NF heterojunctions as efficient bifunctional electrocatalysts for overall water splitting.In 1 M KOH,the prepared W-FeNi_(2)S_(4)/Ni_(3)S_(2)/NF electrocatalyst can effectively drive both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)processes,and only needs overpotentials of 93 and 210 mV to reach current densities of 10 and 50 mA·cm^(−2).In the double electrode cell composed by WFeNi_(2)S_(4)/Ni_(3)S_(2)/NF electrocatalyst,a low cell voltage of 1.52 V was required to reach a current density of 10 mA·cm^(−2),and 91.6%of this value was preserved after 24 h electrolysis operation.The performance of FeNi_(2)S_(4)/Ni_(3)S_(2)/NF electrocatalyst is superior to most of the current bifunctional electrocatalytic materials.Density functional theory(DFT)theoretical calculations also revealed a more intense electron transfer process that can be facilitated by constructing FeNi_(2)S_(4)and Ni_(3)S_(2)/NF interface,which may be the main reason for the archived excellent electrochemical performance.

CO在Pt及其合金表面电化学氧化和吸附的理论研究

文本综述了CO在Pt及其它过渡金属上电化学氧化机理的量子化学研究现状。系统论述了密度泛函理论计算在催化剂对CO电氧化的作用机制和CO与金属间吸附、成键及振动频率方面所给出的详细信息, 并指出了量子化学计算结果对于电极催化剂设计的指导意义。最后, 指出了目前量子化学计算的局限性并展望来其未来发展趋势。

Defective ZnS nanoparticles anchored in situ on N-doped carbon as a superior oxygen reduction reaction catalyst

Defect engineering has been used to develop low-cost and effective catalysts to boost oxygen reduction reactions.However,the development of catalysts that use metal cation vacancies as the active sites for oxygen reduction reaction is lacking.In this study,ZnS nanoparticles on N-doped carbon serve as an oxygen reduction reaction catalyst.These catalysts were prepared via a one-step method at 900℃.Amazingly,the high-resolution transmission electron microscope image revealed obvious defects in the ZnS nanoparticles.These facilitated the catalyst synthesis,and the product displayed good electrocatalytic performance for the oxygen reduction reaction in an alkaline medium,including a lower onset potential,lower mid-wave potential,four electron transfer process,and better durability compared with 20 wt%Pt/C.More importantly,the density functional theory results indicated that using the Zn vacancies in the prepared catalyst as active sites required a lower reaction energy to produce OOH*from*OO toward oxygen reduction reaction.Therefore,the proposed catalyst with Zn vacancies can be used as a potential electrocatalyst and may be substitutes for Pt-based catalysts in fuel cells,given the novel catalyst’s resulting performance.

Commercial indium-tin oxide glass:A catalyst electrode for efficient N_(2)reduction at ambient conditions

The typical Haber technical process for industrial NH_(3)production involves plenty of energy-consumption and large quantities of greenhouse gas emission.In contrast,electrochemical N_(2)reduction proffers environment-friendly and energy-efficient avenues to synthesize NH_(3)at mild conditions but demands efficient electrocatalysts for the N_(2)reduction reaction(NRR).Herein we report for the first time that commercial indium-tin oxide glass(ITO/G)can be used as a catalyst electrode toward artificial N_(2)fixation,as it demonstrates excellent selectivity at mild conditions.Such ITO/G delivers excellent NRR performance with a NH_(3)yield of 1.06×10^(-10) mol s^(-1) cm^(-2) and a faradaic efficiency of 6.17%at-0.40 V versus the reversible hydrogen electrode(RHE)in 0.5 M LiClO4.Furthermore,the ITO/G also possesses good electrochemical stability and durability.Finally,the possible reaction mechanism for the NRR on the ITO catalysts was explored using first-principles calculations.

Fe, V-co-doped C_(2)N for electrocatalytic N_(2)-to-NH_(3) conversion

Designing providential catalyst is the key to drive the electrochemical nitrogen reduction reactions(NRR),which is referring to multiple intermediates and products. By means of density functional theory(DFT)calculations, we studied heteronuclear bi-atom electrocatalyst(HBEC) for NRR. Our results revealed that compared to homonuclear bi-atom electrocatalyst(Fe_2@C_2N, V_2@C_2N), Fe, V-co-doped C_2N(Fe V@C_2N)had a smaller limiting potential of-0.17 V and could accelerate N_2-to-NH_3 conversion through the enzymatic pathway of NRR. Importantly, N–N bond length monotonically increases with increasing the Bader charges of adsorbed N_2 molecule but decreases with increasing the Bader charge difference of two adsorbed N atoms. Additionally, the Fe V@C_2N could suppress the production of H_2 by the preferential adsorption and reduction of N_2 molecule. Thus, the as-designed HBEC may have the outstanding electrochemical NRR performance. This work opens a new perspective for NRR by HBECs under mild conditions.

高催化活性M-BHT(M=Co,Cu)电催化还原CO_(2)为CH_(4)的密度泛函理论研究

具有独特电子结构和丰富催化位点的二维金属有机框架材料是具有高活性的CO2还原反应的电催化剂.本文基于密度泛函理论(DFT)计算,发现单层Co-BHT(BHT=benzenehexathiol,苯六硫醇)将CO2还原为CH4时具有很高的催化活性.吉布斯自由能变化计算结果表明,在Co-BHT上将CO2还原成CH4的最佳反应路径为CO_(2)→^(*)COOH→^(*)CO→*CHO→^(*)CHOH→*CH→*CH_(2)→^(*)CH_(3)→CH_(4);整个反应的速度控制步骤为*CO→*CHO;速度控制步骤的吉布斯自由能变化(ΔGL)为0.66 eV,比在二维Cu-C3N4(ΔG_(L)=0.75 eV)和传统的Cu(211)表面(ΔG_(L)=0.74 eV)将CO2还原为CH4的吉布斯自由能变化都小.而在单层Cu-BHT表面的反应路径和速度控制步骤(CO2→^(*)COOH)与Co-BHT均不同,且ΔG_(L)为0.76 eV.与Cu-BHT相比,Co-BHT将CO_(2)还原为CH_(4)的ΔG_(L)更低,这可能归因于Co-BHT的d能带中心高于Cu-BHT,导致Co-BHT与中间体的相互作用更强.

Engineering of Co_(3O)_(4)@Ni_(2)P heterostructure as trifunctional electrocatalysts for rechargeable zinc-air battery and self-powered overall water splitting

Rational design of highly efficient,robust and nonprecious electrocatalysts for the oxygen reduction reaction(ORR),oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)is highly demanded and challenging.Here,heterostructural Co_(3O)_(4)@Ni_(2)P arrays with numerous reaction sites,unique interfacial electronic structure and fast charge transfer kinetics are developed as electrocatalysts for rechargeable Zn-air batteries and overall water splitting.Both density functional theory calculation and X-ray absorption fine structure analysis manifest that the synergistic structural and abundant electronic modulations interfaces are formed,thus simultaneously promoting the electrocatalytic kinetics,activities and stabilities.Specifically,it can achieve an ultralow overpotential of 270 m V and 28 m V at 10 m A cm^(-2) for OER and HER,respectively.The water electrolyzer delivers a current density of 10 m A cm^(-2) at 1.563 V;furthermore,rechargeable Zn-air batteries triggered by this heterostructure can achieve excellent cyclic stability of 177 h(2 h per cycle)at 10 m A cm^(-2);both devices are superior to the Pt/C+Ir/C.This work not only designs an efficient trifunctional electrocatalyst but also paves an avenue to understand the heterostructure engineering for catalysts development and disclose the underlying relationship of interfacial electronic structures and catalytic properties.

析氢反应中氮掺杂石墨烯负载金属单/双原子催化活性起源

电催化析氢反应(HER)是极具潜力的氢能转化手段,发展高性能、低成本的析氢催化剂是制氢技术的关键。本文选取了以过渡金属(Fe、Ni、Co)为活性中心、以氮掺杂石墨烯(N-graphene)为基底的单、双原子催化剂(SAC、DAC),首先通过理论计算对其结构稳定性做出了讨论,证明了所选催化材料的可行性。然后,采用H吸附能为描述符,对催化剂的HER活性进行了分析讨论。结果表明CoN_(4)表现出最优异的HER活性,FeN_(3)、FeN_(4)、Fe_(2)N_(6)三种结构的Fe原子活性中心次之。最后,系统讨论了催化剂的电子结构,揭示了HER催化活性的来源。本文从理论计算角度对SAC、DAC的HER活性进行了对比,结果表明DAC具有较差的HER活性,SAC中CoN_(4)、FeN_(3)、FeN_(4)在HER中展现出优异的催化性能,可作为取代常用的贵金属(Pt/C)HER催化剂的理想选择。

Ni_(3)S_(2) nanocrystals in-situ grown on Ni foam as highly efficient electrocatalysts for alkaline hydrogen evolution

The exploitation of cost-efficient electrocatalysts is critical to develop the hydrogen evolution reaction(HER) for hydrogen production.Herein,Ni_(3)S_(2)/NF-x h(x=12,16 and 20,reaction time) nanocrystals in-situ grown on Ni foam(NF) were prepared via a facile hydrothermal method.The results demonstrate that the reaction time plays key roles in the morphology,the hydrogen evolution performance of the samples,and the hydrogen brittleness of NF substrate.Interestingly,the Ni_(3)S_(2)/NF-16 h displays outstanding catalytic activity for HER in alkaline solution and avoids the hydrogen brittleness of the NF skeletons simultaneously.To afford a catalytic current of20 mA·cm^(-2),Ni_(3)S_(2)/NF-16 h presents ultra-low overpotential of 48 mV for hydrogen evolution and sufficient stability for 40 h.Moreover,the density functional theory(DFT) calculations revealed that the excellent electrocatalytic HER activity of Ni_(3)S_(2) could be attributed to its exposed(015) plane,which exhibited good capability for water adsorption and dissociation in an alkaline electrolyte,leading to the optimal free energy for H^(*) adsorption.The present work offers a novel strategy to design,synthesize and develop highly efficient electrocatalysts for HER.

A Pt/MnV_(2)O_(6) nanocomposite for the borohydride oxidation reaction

Problems associated with carbon support corrosion under operating fuel cell conditions require the identification of alternative supports for platinum-based nanosized electrocatalysts.Platinum supported on manganese vanadate(Pt/MnV_(2)O_(6))was prepared by microwave irradiation method and characterized using X-ray diffraction,Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy,scanning electron microscopy with energy dispersive spectroscopy,and transmission electron microscopy.The borohydride oxidation reaction(BOR)on Pt/MnV_(2)O_(6) was studied in highly alkaline media using voltammetry,chronoamperometry,and electrochemical impedance spectroscopy.BOR electrocatalytic activity of Pt/MnV_(2)O_(6) was also compared with that of commercial Pt/C(46 wt%Pt)electrocatalyst.The apparent activation energy of BOR at Pt/MnV_(2)O_(6) was estimated to be 32 k J mol^(-1) and the order of reaction to be 0.51,indicating that borohydride hydrolysis proceeds in parallel with its oxidation.Long-term stability of Pt/MnV_(2)O_(6) under BOR typical conditions was observed.A laboratory-scale direct borohydride fuel cell assembled with a Pt/MnV_(2)O_(6) anode reached a specific power of 274 W g^(-1).Experimental results on Pt/MnV_(2)O_(6) were complemented by DFT calculations,which indicated good adherence of Pt to MnV_(2)O_(6),beneficial for electrocatalyst stability.