Preparation And Electrocatalytic Activity Of Ternary Platinum-gold-nickel Alloy Catalyst

Proton exchange membrane fuel cells(PEMFCs)are expected to realize large-scale commercialization.Because the PEMFCs have many advantages,such as high energy conversion rate,no pollution to the environment,rapid start-up capability,wide range of applications and so on.The electrocatalyst is one of the key materials to determine the cost,performance and life of the PEMFCs.Up to now,the cathode oxygen reduction reaction(ORR)catalysts in PEMFCs are still dominated by Pt catalysts,but the high cost,low ORR activity and poor stability of Pt catalysts limit its commercialization process.Alloying Pt with other metals can not only reduce the use of Pt,but also improve the electrocatalytic activity of the catalysts.Binary Pt-Ni catalysts usually exhibit high ORR activity.However,these catalysts usually suffer from low stability because nickel can be easily leached out in an acid medium.Au can be used to improve the stability of the electrocatalysts due to its high redox potential.In this paper,the stability of the catalyst could be improved by adding Au into the binary Pt-Ni/C catalyst.The main research works are listed as follows:The ternary Pt-Au-Ni/C catalyst was synthesized by the microwave-assisted ethylene glycol(EG)method.The TEM images indicate that the catalyst nanoparticles are dispersed uniformly on the surface of the carbon support,and the particle size distribution is narrow.The catalyst nanoparticles composed of Pt,Au and Ni was confirmed by the EDS element mapping.For Pt-Au-Ni/C catalyst,the enlarged lattice distance of the Pt(111)was demonstrated by both of HRTEM and XRD,which further proved the formation of an alloy by Au with other metal elements.According to the results of XPS,the binding energy of Pt0 4f shifts positively,demonstrating the electronic effect between the three elements of Pt,Au and Ni.The electrocatalytic activity of the catalyst was evaluated by half-sell test,and the results showed that the ORR activity of the Pt-Au-Ni/C catalyst was higher than both of commercial Pt/C and Pt-Ni/C.At 0.9 V,the Pt-Au-Ni/C catalyst exhibits the mass activity(MA)and special activity(SA)of 0.83 A mg-1 pt and 1.1 mA cm-2ECSA,respectively,which are 6.0 and 6.7 times that of the commercial Pt/C.The results of the half-cell accelerated degradation test(ADT)shows that the Pt-Au-Ni/C catalyst was much more stable than both of commercial Pt/C and Pt-Ni/C catalyst.After10 000 cycles of ADT,the commercial Pt/C and Pt-Ni/C lost 57.1%and 77.1%of its initial MA,respectively.However,the Pt-Au-Ni/C catalyst only lost 16.8%of its initial MA.The MA of the Pt-Au-Ni/C was still as high as 0.69 A mg-1 pt after ADT,which was 5.0 times that of the initial Pt/C.According to the TEM image of the Pt-Au-Ni/C after ADT,the Pt-Au-Ni/C still exhibited good dispersion and the average particle size has almost unchanged.In single-cell test,the current density of the Pt-Au-Ni/C catalyst at 0.6 V(774.4 mA cm-2)was higher than that of the Pt/C(705.7 mA cm-2).Moreover,the Pt-Au-Ni/C exhibited only a loss of 17.1%in current density at 0.6 V after 5 000 cycles of ADT.However,a loss of 49.7%in current density for the Pt/C was observed after ADT.Finally,the ORR activity of the high-load ternary Pt-Au-Ni/C catalysts were studied.By regulating the ratio of the three elements of Pt,Au and Ni,it was found that the ORR activity of ternary Pt41 Au10Ni9/C catalyst was the highest.This paper proved that adding Au into Pt-Ni/C catalyst could improve the activity and stability of the catalyst,which provides a certain guidance and reference significance for synthesizing Pt-based alloy catalysts with high activity and long-term stability.