Synthesis And Electrocatalytic Properties Of Pt Alloy Nanocatalysts

As a clean and efficient new energy technology,fuel cells are the current research hotspot.The noble metal platinum（Pt）is the most important catalyst for the cathodic oxygen reduction reaction（ORR）,but its low abundance,high cost,and susceptibility to poisoning severely limit the large-scale commercial application of this catalyst.The catalyst cost can be reduced by introducing other low-cost and good catalytic performance earth-rich transition metals and Pt to form an alloy,and at the same time,the geometric and electronic structure of the catalyst can be adjusted to improve the performance of the catalyst.In this paper,the synthesis and characterization of Pt-based alloy catalysts,their ORR electrocatalytic activity and stability related to the fuel cell cathode are studied.The main research contents are as follows:1.Pt Ni nano-alloy catalysts with octahedral structure were prepared in an aqueous solvent by a simple one-pot method without using any surfactants.DMF is found to be an ideal reaction solvent through comparative experiments.On this basis,the effects of reducing agent type,precursor dosage and calcination temperature on the morphology and properties of nanocrystals were investigated,and the stability of the Pt Ni/C-DMF catalyst with high ORR activity was studied.The results show that the oxygen reduction half-wave potential of the octahedral Pt Ni/C-DMF nanocatalyst is 0.931 V,which is 56m V higher than that of commercial Pt/C,and the mass activity at 0.9 V is 1.77Amg _Pt^-1,which is 6.8%higher than that of commercial Pt/C.The area activity is 3.21 m A cm _Pt^-2,which is 8.2 times that of commercial platinum carbon.Stability tests were carried out in the voltage range of 0.3 V-0.8 V,and the area activity of the catalyst decreased by 49%and the mass activity decreased by 54%after 4000 CV cycles.The catalyst was treated with acid washing and then calcined with nitrogen,and it was found that the stability of the catalyst was significantly improved.After 4000 CV cycles,its half-wave potential did not decay,and it was considered that its mass activity and area activity did not decrease within the error range.2.The surface-doped ternary platinum alloy catalyst M-Pt Ni（M=Mo,Cr,W,Mn,Cu,Fe,Co）was successfully prepared by a two-step method.The effect of the third metal element on the stability of the catalyst was explored,the effects of different metal elements on the morphology and oxygen reduction activity of the catalyst were analyzed,and the effects of synthesis method and post calcination treatment on the catalyst were also explored.The results showed that the catalyst exhibited better stability and higher areal activity than the binary alloy catalyst Pt Ni/C-DMF in 0.1M HCl O₄.The areal activity was4.26 m A cm _Pt^-2,which decreased by only 27%after 4000 CV cycles.The XPS test results show that the doping of 3d transition metal Mn induces the alloying effect,adjusts the surface electronic structure and oxygen adsorption energy of Pt and Ni,and further improves the stability.