The Effect of Antimony in the Intermediate IrO_2-SnO_2-Sb₂O₅ Oxide Layer on Titanium Substrate for Oxygen Evolution Mn_1-x-yMo_xSn_yO_2+x Anodes in Seawater Electrolysis

Abstract

An attempt is made to find out the optimal compositions for the intermediate oxide layer of IrO_2-SnO_2-Sb₂O₅ in preventing insulating titanium oxide formation on titanium substrate for the oxygen evolution Mn_1-x-yMo_xSn_yO_2+x anodes in electrolysis of 0.5 M NaCl of pH 1 at 1000 A.m^-2. Effects of antimony and iridium in the intermediate IrO_2-SnO_2-Sb₂O₅ layer are discussed. The 75 % of the iridium content in the intermediate layer of the oxygen evolution anodes can be substituted by SnO₂ and small amount of Sb₂O₅ to increase the electronic conductivity of the intermediate layer as well as the activity of the Mn_1-x-yMo_xSn_yO_2+x/IrO_2-SnO_2-Sb₂O₅/Ti anodes for seawater electrolysis at pH 1. Although Sb⁵⁺ addition is effective in decreasing the Ir⁴⁺ concentration in the intermediate layer of the anodes, the Ir_1-x-ySn_xSb_yO_2+0.5y intermediate layers with the Sb⁵⁺/Sn⁴⁺ between 0.125-0.285 in the coating solution showed excellent performance of the oxygen evolution efficiency. All the examined manganese-molybdenum-tin triple oxides, Mn_1-x-yMo_xSn_yO_2+x, prepared by anodic deposition on the IrO_2-SnO₂-Sb₂O₅-coated titanium substrate showed around 99% initial oxygen evolution efficiency at a current density of 1000 A.m^-2 in 0.5 M NaCl of pH 1 at 25ºC.

Keywords: global CO₂ recycling, hydrogen production electrode, IrO_2-SnO_2-Sb₂O₅ layer, 0.5 M NaCl, titanium substrate.

DOI: 10.3126/jncs.v23i0.2093

J. Nepal Chem. Soc., Vol. 23, 2008/2009

Page: 21-32