Anodically deposited Mn-Mo-Fe oxide anodes for oxygen evolution in hot seawater electrolysis

Abstract

In order to avoid chlorine evolution on the anode in hot seawater electrolysis, the oxygen evolution anodes were tailored, γ- MnO2type Mn1-x-yMoxFeyO 2-x-0.5y anodes consisting of Mn4-, Mo6- and Fe3+ were prepared by anodic deposition. The anodes with the 100% oxygen evolution efficiency in the electrolysis of 0.5 kmol m-3 NaCl at pH 12, 353 K and a current density of 1000 Am-2 were prepared in solutions consisting of 0.003 kmol m-3 Na2MoO 4, 0.1 kmol m-3 Fe(NH4) (SO4) 2 and 0.2 kmol m-3 or higher concentrations of MnSO 4 at pH 0.33-0.5, 363 K and a current density of 600 Am -2. In the outside of this range, generally because of lower deposition efficiency, the electrode surface was not completely covered with anodically deposited oxides with a consequent lower oxygen evolution efficiency.