Preparation And Oxygen Reduction Performance Of Fuel Cell Cathode Catalysts On Graphene

Fuel Cells have attracted widespread attention as alternative clean energy technologis with high energy conversion efficiency and energy density. However, the high cost of fuel cells prevents their commercialization, one of the most important factors is the high cost of cathode catalyst. In this paper, the microwave-assisted preparation of Pt/graphene cahthode catalysts with ethylene glycol as reducing reagent was conducted to reduce the cost of catalysts, and further to improve the electrochemical activity and stability.Firstly, the graphite oxide was prepared by the modified Hummers and Offeman method, and dried in a conventional drying and freeze-drying respectively. Then, the thermal expanded graphite oxide was obtained after expansion of the powder of graphitic oxide. The Pt/graphene cahthode catalysts were prepared by using the expanded graphite oxide as support of carbon precursor and chloroplatinic acid as Pt precursor. The influence of microwave time, concentration of the solvents and pH value during the preparation process was well studied. The as-prepared catalysts were further characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry curve (CV), linear sweep voltammetry (LSV), time current curve (i-t), etc. It is found that the Pt nanoparticles with a size of c.a.2.4nm were dispersed uniformly on the surface of the graphene when the30%ethylene glycol as reducing reagent and microwave time of50s-(30s)-60s-(40s)-60s were. Half-wave potential of the catalyst (0.65V) was smaller than commercial catalysts (0.66V), meanwhile the electrochemical stability was much higher than commercial catalyst, indicating that the catalyst possessed superior electrocatalytic property.In order to further reduce the amount of platinum, the Pt-Ni/graphene catalysts (total amotic mass%:20%) were prepared under the same conditions, and the electrochemical properties of Pt-Ni/graphene catalysts with different Pt-Ni ratio (mass%) were also compared. It is found that the catalysts were alloy structure, uniformly dispersed on the supports with a alloy structure, and the interplanar distance was0.223nm. Although the half-wave potential of the catalyst (0.55V) is smaller than the half-wave potential commercial catalysts, the electrochemical stability is higher than commercial catalysts. In addition, the Pt3Ni/graphene-2catalyst (total amotic mass%:20%, Pt:Ni=3:1) with freeze-drying was also prepared. The physical characterization showed that the nanoparticles of Pt3Ni/graphene-2were also alloy particles, and the particle size was3.7nm. Half-wave potential of the catalyst (0.50V) was smaller than the half-wave potential of the commercial catalyst, but the electrochemical stability was better than the commercial catalyst. In summary, graphene is an excellent fuel cell cathode catalyst support which can not only increase the utilization of the particle load, but also improve the corrosion resistance and electrochemical stability of catalysts.