Direct Synthesis of Two Inorganic Catalysts on Carbon Fibres for the Electrocatalytic Oxidation of Water

Two electrodes for anodic water oxidation made by direct synthesis of inorganic catalysts onto conductive carbon fibre sheets are evaluated. As catalysts two Co- and Sb-containing phases were tested, that is, Co₃ Sb₄ O₆ F₆ and the new compound CoSbO₄ . The compounds express large differences in their morphology: CoSbO₄ grows as thin needles whereas Co₃ Sb₄ O₆ F₆ grows as larger facetted crystals. Despite the smaller surface area the latter compound shows a better catalytic performance. When the compound Co₃ Sb₄ O₆ F₆ was used it gave a low increase of +0.028 mV h^-1 at an overpotential of η=472 mV after 10 h and a stability of +0.48 mV h^-1 at an overpotential of η=488 mV after 60 h. The leakages of Co and Sb were negligible and only <0.001 at % Co and approximately 0.02 at % Sb were detected in the electrolyte.