Structurally Ordered Ternary Pt-Based Alloy Nanoparticles As Oxygen Reduction Electrocatalysts

Proton exchange membrane?PEM?fuel cells,due to their high efficiency,low temperature start and environmentally friendly,have been attracted the worldwide attention.Electrocatalysts,whose catalytic properties affect the performance,service life and cost of the battery directly,are the core materials of fuel cells.The development of Catalysts with low cost and high redox performance is of vital important to realize the commercialization of fuel cells.Binary disordered Pt-based alloy catalysts are one of the most widely applied catalysts.However,there are still a series of problems,during the operation of the fuel cell,such as poor stability,insufficient catalytic activity and metal dissolution.Aimed to solve the problems above,we synthesised the structure-ordered ternary alloy depending on the spatial confinement and high-temperature interface diffusion principle and explored the influence of alloy composition and structure on the catalytic activity and stability in this paper.The experimental results proved that adding the third metal Fe and Ni to the PtCo binary ordered alloy not only maintained its ordered structure,but also enhanced its catalytic activity.it was confirmed that the PtCoFe system showed the superior catalystic performance and stability in comparison with the PtCoNi system,.The electrochemical test results indicated that PtCoFe-1-0.6?representing the molar ratio of the catalyst Pt:Co:Fe=1:1:0.6?shows the optimal oxygen reduction catalytic activity.Compared with the binary ordered PtCo-1?representing the molar ratio of catalyst in the Pt:Co=1:1?catalyst(0.97 A/mg_Pt,1.34 mA/cm²),the mass activity and specific surface activity of PtCoFe-1-0.6 catalyst at 0.9 V was 1.43 A/mg_Pt and 2.23 mA/cm²individually,which was increased by 1.5 times and 1.7 times,respectively.Meanwhile,it was 8.4 times and 9.6 times higher than commercial Pt/C catalysts(0.17 A/mg_Pt,0.23mA/cm²),respectively.After 20,000 laps of aging test,the half-wave potential of the oxygen reduction polarization curve of PtCoFe-1-0.6 catalyst was only attenuated by 8mV,the PtCo-1 catalyst was attenuated by 13 mV,and the commercial Pt/C catalyst was attenuated by 32 mV,indicating that the ordered PtCoFe-1-0.6 catalyst possesses the higher electrocatalytic activity and higher stability.Secondly,We added a third alloying element,Fe,Co,and Ni,based on the PtFe and PtNi binary alloys.It was found that these trimetallic alloy catalysts exhibit higher catalytic performance while maintaining their ordered structure compared to binary alloys.Among them,PtFeCo-1-0.6?indicating the molar ratio Pt:Fe:Co=1:1:0.6 in the catalyst?shows the best oxygen reduction catalytic activity.Compared with the binary ordered PtFe-1?representing the molar ratio of catalyst Pt:Fe=1:1?catalyst(0.81 A/mg_Pt,0.91 mA/cm²),the mass activity and specific surface activity at 0.9 V of PtFeCo-1-0.6 were 1.69 A/mg_Pt and 2.18 mA/cm² individually,which was increased by2.1 times and 2.4 times,respectively.In the same time,the catalyst obtained shows 9.9times and 9.4 times higher than that of the commercial Pt/C catalyst(0.17 A/mg _Pt,0.23mA/cm²),respectively.After 20,000 laps of aging test,the half-wave potential of the oxygen reduction polarization curve of PtFeCo-1-0.6 was only attenuated by 11 mV,the PtFe-1 catalyst was attenuated by 16 mV,and the commercial Pt/C catalyst was attenuated by 32 mV,indicating that the ordered PtCoFe-1-0.6 catalyst has the higher electrocatalytic activity and higher stability.In comparsion with the study of the three systems obove,it is confirmed that the catalytic activity of the ternary ordered alloy based on PtFe alloy is superior to the ternary ordered alloy synthesized on the basis of PtCo and PtNi alloy,among which PtFeCo-1-0.6 shows the best mass activity and specific surface activity.