Promoting Effect of Ni in PtNi Bimetallic Electrocatalysts for the Methanol Oxidation Reaction in Alkaline Media: Experimental and Density Functional Theory Studies

Abstract

Carbon-supported bimetallic PtmNin electrocatalysts with different Pt/Ni atomic ratios were synthesized through a modified polyol process. The as-prepared electrocatalysts were characterized by X-ray diffraction, transmission electron microscopy, voltammetry techniques, and single-cell tests. It was revealed that the PtmNin bimetallic nanoparticles were uniformly distributed on carbon supports with average diameters of about 3 nm. Pt and Ni were partially alloyed, indicated by the decreased Pt lattice constants compared with that of pure Pt. The results of the electrochemical measurements showed that the PtmNin/C catalysts, compared with the Pt/C, have superior specific activity toward the methanol electrooxidation reaction (MOR) in alkaline media as well as a higher power density in a direct methanol fuel cell test with the Pt3Ni1/C as the anode catalyst. Density functional theory studies further revealed that the electronic structure of Pt was modified by Ni due to the charge transfer from Ni to Pt atom...