Reversible Electrocatalytic Activity of Carbon-Supported Ptx Ni1-x in Hydrogen Reactions.

ABSTRACT

Hydrogen oxidation and evolution reactions (HOR and HER) are studied on Ptx Ni1-x /C materials synthesized by the bromide anion exchange method. Physicochemical characterization shows that this surfactant-free method enables the preparation of well-dispersed and effective catalysts for the processes involved in the anode of H2 /O2 fuel cells (HOR) and the cathode of water electrolyzers (HER). The Pt-based materials are modified with different Ni contents to decrease the amount of costly precious metal in the electrode materials. These modified Pt-based materials are found to be electroactive for both reactions without additional overpotential. Kinetic parameters such as the Tafel slope, exchange (j0 ) and kinetic current densities, and the rate-determining steps of the reaction mechanisms are determined for each Pt-Ni catalyst and compared to those obtained at the Pt/C surface in alkaline medium. The high j0 values that are obtained indicate a probable contribution of the surface structure of the catalysts due to their roughness and the presence of oxygenated Ni species even at low potentials.