Nanocrystalline manganese-molybdenum-tungsten oxide anodes for oxygen evolution in acidic seawater electrolysis

Abstract

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 Na2MoO 4-(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 IrO 2/Ti substrate. ©2005 The Japan Institute of Metals.