Nanocrystalline Manganese-Molybdenum-Tungsten Oxide Anodes for Oxygen Evolution in Acidic Seawater Electrolysis

In an attempt to tailor new oxygen evolution anodes for acidic seawater electrolysis, manganese-molybdenum-tungsten oxide anodes were prepared by anodic deposition on IrO2/Ti substrate using 0.2 kmol m−3 MnSO4-(0.00–0.006) kmol m−3 Na2MoO4-(0.0–0.03) kmol m−3 Na2WO4 electrolytes at pH −0.1∼+1.0 and 363 K at 600 Am−2. The deposits consist of a nanocrystalline single γ-MnO2 type phase in the form of triple Mn1−x−yMoxWyO2+x+y oxide. Anodic deposition in 0.2 kmol m−3 Mn2+-0.003 kmol m−3 Mo6+-0.006 kmol m−3 W6+ electrolyte at pH 0.0 resulted in the formation of an electrode with 100% and 99.8% oxygen evolution efficiencies before and after electrolysis for 691.2 ks in 0.5 kmol m−3 NaCl solution of pH 2 at 1000 Am−2. Thus, Mn1−x−yMoxWyO2+x+y electrodes were promising oxygen evolving anodes for acidic seawater electrolysis. It has been concluded that additions of both tungsten and molybdenum beneficially bring about an increase in the real electro-catalytic activity along with the formation of deposits with optimum thickness and good adherence to the IrO2/Ti substrate.