Synthesis And Electrocatalytic Performance Of PtZn And PtFe-based Intermetallic Nanoparticles

Proton Exchange Membrane Fuel Cells(PEMFCs)fuelled with hydrogen as the clean and efficient energy device have attracted considerably increasing attention to help with solving urgent social issues including both energy shortage and environmental pollution.Oxygen reduction reaction(ORR)is the essential process in PEMFCs due to its sluggish kinetics and large overpotentials on the cathode compared with hydrogen oxidation reaction(HOR)on the anode.Although carbon-supported platinum(Pt/C)nanoparticles have long been thought as ideal ORR catalysts,it is now generally reckoned to be an unrealistic choice owing to their high costs and scarcity.Here,the atomic orderd intermetallic Pt-Fe series catalysts have been synthesized to improve the catalytic performance and decrease the usage of Pt.The structurally ordered Pt-Fe/C series nanoparticles with face-centered cubic(fcc)type or face-centered tetragonal(fct)type intermetallic phase are successfully obtained via an impregnation reduction method followed by a post-annealing strategy.The Pt-Fe intermetallic nanoparticles with ordered structure serve as a robust electrocatalyst with enhanced activity and stability(superior to corresponding disordered phase and Pt/C)towards ORR.Furthermore,different from the dissolution of Fe on ordered fcc-PtFe3 and the destruction of ordered structure,ordered fcc-Pt3 Fe and orderd fct-PtFe exhibited preferable long-term durability against Fe dissolution throughout the harsh operating conditions.Taking account of security and portability,small organic molecules such as methanol and formic acid replacing the hydrogen as the fuel represent a new generation of environmentally friendly technology.Especially aiming to transportation which represents a significant portion of world energy consumption and contributes considerably to atmospheric pollution,the development of an appropriate fuel cell system,such as direct methanol fuel cells(DMFCs)or direct formic acid fuel cells(DFAFCs)has arouse considerable interest in recent years.One of the most challenging problems is to find electrocatalysts which can effectively enhance the electrode-kinetics of methanol oxidation reaction(MOR)and formic acid oxidation reaction(FAOR),the reaction rates of which are far slower than that of HOR.Here,atomic ordered ternary alloy PtFexCu1-x has been perpared to accurately and flexibly tune the structure and performance of nanoparticle catalysis.The presence of copper in alloy PtFexCu1-x(0 < x < 1)facilitates PtFe phase structure transformation from disordered fcc structure to ordered fct structure at desirable lower temperature.Ordered fct-PtFe/C exhibits both enhanced activity and stability towards MOR than disordered fcc-PtFe/C,furthermore,ternary alloy PtFexCu1-x/C catalysts with ordered intermetallic fct-PtFe phase exhibit a significant enhancement in durability compared to that of ordered fct-PtFe catalyst.In addition,contributed to lower surface enenry of Zn and the evaporation of the zinc element at high temperature,the clean PtZn ordered intermetallic nanoparticles,which are well dispersed on the carbon support with ultrasmall mean particle sizes of around 3 nm in diameter,has been successfully synthesized here.It was less susceptible to CO poisoning relative to Pt/C and exhibited enhanced catalytic activity and stability toward FAOR.