Electrolysis of CO2+ in phosphate, m ethyl phosphonate, and borate electrolytes effects the electrodeposition of an amorphous highly active water oxidation catalyst as a thin film on an inert anode. Electrodeposition of a catalytically competent species immediately follows oxidation of CO2+ to CO3+ in solution. M ethyl phosphonate and borate electrolytes support catalyst activity comparable to that observed for phosphate. Catalytic activity for O-2 generation in aqueous solutions containing 0.5 M NaCl is retained for catalysts grown from phosphate electrolyte.