Composite materials for electrocatalysis of O_2 evolution: IrO_2 + SnO_2 in acid solution

摘要

IrO_2 + SnO_2 mixed oxide electrodes were prepared by thermal decomposition at 400 ℃ over the whole composition range. Data of XPS and cyclic voltammetry (CV) have shown considerable surface enrichment with IrO_2. Consistently, O_2 evolution from acid solution (H_2SO_4), for precious metal oxide contents >10%, proceeds with kinetic parameters close to those of pure IrO_2. The Tafel slope, IR-drop, reaction order (H~+ and surface sites), electrocatalytic activity and stability have been scrutinized as functions of active layer composition. A reaction mechanism has been proposed. For some of the compositions the effect of the solution temperature was also investigated. The kinetics of O_2 evolution appear to conform to the 'standard' Butler-Volmer model. IrO_2 + SnO_2 electrodes were found to be stable under O_2 evolution within the time scale of the present work.