▎ 摘　　要

The graphene-supported nano Pt-Pd bimetallic catalysts with various chemical compositions (Pt/Pd molar ratio 4 : 1, 1 : 1, 1 : 4) were prepared via simple ethanol reduction method by reflux of graphene oxide (GO) and metallic salts in ethanol/water solvent for 5.5 h at 88 degrees C. For comparison, graphene-supported Pt, Pd monometallic catalysts were also synthesized under the same experimental conditions. The morphology of as-prepared catalysts was characterized by XRD and TEM, the results indicate that chemical composition of metallic catalysts shows distinct influence on the particle morphology and size, the Pt-Pd bimetallic catalyst particles disperse on the surface of graphene support most evenly with the average diameter of approximately 5.6 nm when the Pt/Pd molar ratio was set as 1 : 1. Their catalytic activities for hydrolysis reaction of alkaline potassium borohydride (pH = 12. 0) were investigated, the catalytic experiment results demonstrate that the catalytic activities significantly depend on chemical composition of metallic catalyst, among them the Pt-Pd bi-metallic catalyst with the molar ratio of 1 : 1 displays higher activity than other Pt-Pd bimetallic catalysts (Pt/ Pd molar ratios of 1 : 4 and 4 : 1) and Pt, Pd monometallic catalysts, the hydrogen generation efficiency of graphene-supported nano Pt-Pd (molar ratio 1 : 1) bimetallic catalysts is about 4380 mol(H2) . mol(M)(-)(1) . h(-1), which is higher than graphene-supported Pt catalyst by 52% and approximately as fkmr-fold as graphene-supported Pd catalyst. Investigation on the catalytic durability demonstrated that about 83% of the initial catalytic activity was retained even after three cycles. Catalytic reaction kinetics studies manifest the activation energy of borohydride hydrolysis reaction catalyzed by graphene supported Pt/Pd (molar ratio 1 : 1) bimetallic catalyst is about 20.90 kJ/mol, which is distinctly lower than those of the reaction catalyzed by Pt/C and Ru/C catalysts. DFT calculations based on M55 model revealed that the barrier height of rate-determining step catalyzed by Pt25Pd30 are distinctly lower than that catalyzed by Pd55 and Pt55, indicating the graphene supported Pt-Pd(Pt/Pd molar ratio 1 : 1) possess more excellent catalytic activity.