Effects of Antimony and Tin Additions in the Intermediate Ir_1-x-y Sn_xSb_yO_2+0.5y Layer of Mn–Mo–Sn–O Electrocatalyst for Hydrogen Production from Seawater Electrolysis

Abstract

The oxygen production anode for seawater electrolysis is composed of two layers on the titanium substrate. The outermost layer is electrocatalysts of ?-MnO₂ type Mn_1-x-yMo_xSn_yO_2+x triple oxides and the intermediate layer preventing insulating oxide formation on the titanium substrate is generally IrO₂. Due to limited amount of iridium, alternative materials to the intermediate IrO₂ having sufficient durability and conductivity at high potentials for anodic polarization are required. In this context, decrease in the amount of IrO₂ by substitution with SnO₂ and increase in the electronic conductivity of the intermediate layer by Sb₂O₅ addition is performed in this works. The additions of SnO₂ with Sb₂O₅ to the intermediate layer of the Mn-Mo-Sn-O/Ir_1–x–ySn_xSb_yO_2+0.5y/Ti anodes was effective to decrease the use of IrO₂, maintaining the high electronic conductivity of the intermediate Ir_1–x–ySn_xSb_yO_2+0.5y layer and the high activity of oxygen evolution in seawater electrolysis at pH 1 for about 1550 h. The oxygen evolution efficiency of the nanocrystalline ?-MnO₂ type Mn-Mo-Sn-O/Ir_1–x–ySn_xSb_yO_2+0.5y/Ti anodes with 0.208 M Ir⁴⁺, 0.208-0.416 M Sn⁴⁺ and 0.104 M Sb⁵⁺ in the intermediate layers was about 98.5 % during electrolysis for about 1550 hours without any degradation in 0.5 M NaCl solution of pH 1 at 25°C.

DOI: http://dx.doi.org/10.3126/jncs.v27i1.6664

J. Nepal Chem. Soc., Vol. 27, 2011 78-85