The Oxygen Evolution Reaction at Sn-Sb Oxide Anodes: Influence of the Oxide Preparation Mode

Abstract

Stannous and antimony oxide electrodes were prepared by metallic electrodeposition followed by thermal oxidation. For the metal deposition, two methodologies were tested: alternate and simultaneous Sn and Sb electrodepositions. Metals were deposited onto titanium foil or titanium foil covered with platinum or copper. For both preparation methods, the SnO2 crystalline phase was identified, with Sb2O3 or Sb2O4 only present when alternate Sn and Sb electrodepositions were performed. The roughness factor depends on the electrodeposition method and on the substrate morphology. The introduction of a Pt or Cu metallic interlayer increases the current intensity for equal applied potential due to the increases in the substrates' conductivity and real surface area. The presence of composite Sn and Sb oxides leads to lower current intensity because the existence of distinct phases introduces resistance in the grain boundaries. Concerning the apparent activation energy for the oxygen evolution reaction, values of 73, 74 and 63 kJ mol−1 were found for Ti/Pt/SnO2-Sb, Ti/Cu/SnO2-Sb and Ti/Cu/SnO2-Sb2O3, respectively, pointing to HO− adsorption as the rate determining step at these electrodes' surfaces. For Ti/SnO2-Sb, Ti/SnO2-Sb2O4 and Ti/Pt/SnO2-Sb2O4, much higher apparent activation energies were obtained. Of the tested materials, the most appropriate for oxygen evolution is Ti/Cu/SnO2-Sb.