Carbon-supported Pt0.75M0.25 (M = Ni or Co) electrocatalysts for borohydride oxidation

Abstract

Electrochemical oxidation of sodium borohydride (NaBH4) at carbon-supported platinum (Pt/C) and carbon-supported bimetallic platinum alloys (Pt0.75M0.25/C, with M=Ni or Co) is studied in alkaline media using cyclic voltammetry and linear scan voltammetry with rotating disc electrode. Main kinetic parameters (e.g., charge transfer coefficients, number of electrons exchanged, standard heterogeneous rate constants and activation energies) for NaBH4 oxidation on these electrocatalysts are determined. Results indicate the highest catalytic activity of Pt0.75Ni0.25/C alloy electrocatalyst, followed by Pt0.75Co0.25/C, while the lowest activity is observed for Pt/C electrocatalyst. The influence of electrolyte composition and temperature on NaBH4 electrooxidation at the three materials is also explored. The good performance of these bimetallic alloys makes them a lower cost alternative to single Pt as electrocatalysts for the direct borohydride fuel cell anode.