The electrochemical oxidation of sulphite on gold electrodes

The electro-oxidation of sulphite is studied in acid media on gold macroelectrodes and Au particle array modified boron doped diamond electrodes. The sulphite oxidation proceeds through a one-electron transfer process followed by a chemical step of second order (EC2 mechanism), as evidenced by experimental voltammetry and digital simulation for both gold macroelectrodes and gold particle modified substrates. The diffusion coefficient of sulphite is calculated consistently for both cases at about 4×10−9 m2 s−1, with the reverse peak behaviour concentration dependent. The arrays are made by electrodeposition and show a morphological transition from a quasi-spherical to a star shape as the growth time of the particles increases. Kinetic parameters inferred from the electro-oxidation at the macroelectrode can be successfully applied to model the gold particle modified electrode data to confirm the EC2 mechanism, whilst recognising the overlapping diffusion layers of adjacent gold particles