The durability of different elements doped manganese dioxide-coated anodes for oxygen evolution in seawater electrolysis

Manganese-molybdenum (Mn-Mo), manganese-molybdenum-vanadium (Mn-Mo-V), manganese-molybdenumiron (Mn-Mo-Fe) and manganese-iron-vanadium (Mn-Fe-V) anodes were prepared by anodic electrodeposition on iridium oxide-coated titanium substrates for oxygen evolution in seawater electrolysis. XRD, FESEM, EDX and oxygen evolution efficient analysis revealed that the prepared anodes had a gamma-MnO2 structure and show a unique mesh-like nanostructure. Oxygen evolution efficiencies were all measured to be more than 99%. The durability tests were performed at 1000 A.m(-2) in 3.5 wt% NaCl solution at pH 12 and 90 degrees C. The Mn-Fe-V anode was the most stable electrode during the sea water electrolysis, and maintained an oxygen evolution efficiency of 87.96% even after 500 h. It has been found that the main reason for the eventual decrease in oxygen evolution efficiency was partly because of the peeling and electrochemical dissolution of the oxide layer after electrolysis. Also, it was found that the addition of iron and vanadium would maintain a high level of oxygen evolution efficiency during electrolysis. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.