Spontaneous adsorption of heteropolytungstates and heteropolymolybdates on the surfaces of solid electrodes and the electrocatalytic activity of the adsorbed anions

Heteropolytungstate and heteropolymolybdate anions spontaneously adsorb from aqueous solutions onto mercury, gold, pyrolytic graphite and glassy carbon electrodes. The adsorption persists when the electrodes are transferred to pure supporting electrolyte solutions where the electrochemical responses from the adsorbed anions can be observed. The adsorption is much less extensive from non-aqueous solvents. The adsorbed anions can serve as catalysts for various electrode reactions. Examples are given of the electrocatalytic reductions of hydrogen peroxide to water and of nitrite to ammonia.