Kinetic study of oxygen reduction reaction on an amorphous Ni ₅₉Nb₄₀Pt_0.6Ru_0.4 catalyst in acid media

The aim of this work was to investigate the molecular oxygen reduction on an amorphous Ni₅₉Nb₄₀Pt_0.6Ru_0.6 electrocatalyst, with the intention to produce an amorphous metallic alloy with corrosion resistant with temperature in acid media. The catalyst was synthesized by mechanical milling technique during 40h. Kinetic parameters were deduced from steady state measurements with a rotating disk electrode (RDE) in 0.5M H₂SO₄ in the range of temperature of 293-313 K. For this study the electrocatalyst powder was incorporated in a disk of carbon paste matrix. It was found from the analysis of the electrochemical data, an independent variation of Tafel slope (-120 mV dec^-1) with temperature and a corresponding linear variation of the charge transfer coefficient with temperature, da /dT = 2.3 × 10^-3 K ^-1. In order to explain this behavior, the enthalpic and entropic components of the charge transfer coefficient were evaluated and the apparent activation enthalpy of this process and its variation with overpotential was determined from an electrochemical Arrhenius plot.