Mass and electron-transfer conditions for the electrochemical oxidation of hydrogen sulfide at vanadium pentoxide film modified electrode

A mechanistic scheme for the electrochemical oxidation of hydrogen sulfide at vanadium pentoxide film modified electrode was proposed to account for the steady-state current responses as a function of both electrode rotation rate and sulfide concentration. The mechanism indicates that the primary electron-transfer reaction is the re-oxidation of reduced vanadium species (V⁴⁺) into oxidized species (V⁵⁺) after the metal oxide film had previously been reduced by sulfide ions. The electrode reaction was found to be controlled by both mass and electron-transfer processes by which the apparent diffusion coefficient and the heterogeneous electron-transfer rate constant were evaluated applying general hydrodynamic theories. Three modes of inhibition were suggested to describe potential poisoning of the metal oxide surface sites due to sulfur adsorption. The phase boundary condition of the film for mass and electron-transfer processes is discussed also.