Unveiling Oscillatory Behavior in the Electro-Oxidation of Ethanol on Nickel Electrodes

Ethanol derived from renewable sources is a carbon-neutral fuel, and its electro-oxidation offers a pathway for sustainable energy generation, reducing dependence on fossil fuels. Nickel, as a cost-effective alternative to noble metals, enhances the economic feasibility of large-scale applications in energy systems such as alkaline fuel cells and electrolyzers. This study presents an experimental investigation of ethanol electro-oxidation on nickel electrodes in alkaline media, focusing on electrocatalytic activity and the emergence of oscillatory kinetics. The results demonstrate that ethanol electro-oxidation is facilitated by NiOOH species, with the oxidation of ethanol identified as the rate-determining step. Cyclic voltammetry revealed that the conversion of Ni-(OH)₂ to NiOOH plays a crucial role, and an increase in current density was observed, correlating with ethanol oxidation and the formation of additional anodic peaks. Stable potential oscillations persisted even under enhanced mass transport, indicating a dynamic interplay between the continuous formation and consumption of NiOOH species during ethanol oxidation at lower potentials and the oxygen evolution reaction at higher potentials.