Kinetics of sodium borohydride direct oxidation on carbon supported Cu-Ag bimetallic nanocatalysts

Carbon supported Cu-Ag (Cu-Ag/C) bimetallic nanoparticles prepared by the impregnation reduction method in aqueous solution are evaluated as anode catalysts for sodium borohydride (NaBH₄) oxidation. The physical properties of the as-prepared electrocatalysts are investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM). Electrochemical oxidation of NaBH₄ at carbon-supported Ag/C and Cu-Ag/C is studied in 2 M NaOH/0.1 M NaBH₄ using linear scan voltammetry with rotating disc electrode (LSV RDE), chronoamperometry (CA) and in situ Fourier transform infrared spectroscopy (in situ FTIR). Main kinetic parameters (e.g. Tafel slope, apparent rate constant, number of electrons exchanged, and exchange current density) for NaBH₄ oxidation on these electrocatalysts are determined. Results show that the average size of the Cu-Ag/C particles is approximately 14 nm. The kinetic parameters for the NaBH₄ oxidation are better for Cu-Ag/C than for Ag/C. Among all the as-prepared catalysts, the Cu₆₇Ag₃₃/C catalyst presents the highest catalytic activity.