Mn-W oxide anodes prepared by thermal decomposition for oxygen evolution in seawater electrolysis

Manganese-tungsten oxide electrodes have high efficiency for oxygen evolution in seawater electrolysis. Manganese oxide, tungsten oxide and manganese-tungsten oxides were coated on the IrO₂-coated titanium (IrO₂/Ti electrode) by thermal decomposition. The oxygen evolution efficiencies at 200 A · m^-2 of the manganese oxide and tungsten oxide electrodes in 0.5 M NaCl solution at pH 8 and 30°C were 70 and 68%, respectively. The efficiency for oxygen evolution is enhanced by small amounts of mutual additions into manganese oxide or tungsten oxide. In particular, the efficiencies of α-Mn₂O₃-type oxide with 15 mol% W⁶⁺ and WO₃-type oxide with 10 mol% Mn²⁺ go up to over 92 and 86%, respectively. Further increase in additives leads to the formation of MnWO₄ and to a significant decrease in the oxygen evolution efficiency.