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With the aim of obtaining a highly stable and active catalyst for oxygen evolution reaction (OER), a core–shell-like IrO2@RuO2material was synthesized by using a surface modification/precipitation method in ethanol medium. The comparison of this catalyst with pure RuO2and pure IrO2showed that the obtained mixed oxide catalyst displayed the highest amount of active sites as well as a good accessibility for water. Moreover, this catalyst was shown to be highly stable toward repetitive redox cycling. Polarization curves of the three catalysts showed that the IrO2@RuO2was the most active for the OER due to the large number and high accessibility of active sites. These catalytic benefic effects are attributed to an intimate contact between the two oxides in the IrO2-covered RuO2nanocatalyst that combines the RuO2intrinsic activity and the IrO2stability. The present study contributes therefore to the rational design of efficient and stable electrocatalysts for water splitting in acidic media.

Ru and Ir based materials were prepared by the thermal decomposition of polymeric precursor's method. The anode catalysts free from carbon substrate were obtained by tailoring the reaction process to avoid occurrence of CO2formation during water electrolysis. Various Ir contents were added in the Ru catalytic compositions for improving the oxidation-resistance of RuO2which was the best metallic oxide in H2O splitting. Their physical characterizations revealed the presence of agglomerates due probably to the heat treatment process consisting in the removal of organic carbon at 400 ºC. The prevalent existence of RuO2 and IrO2 in the anode materials was confirmed by XPS experiments and the electrochemical measurements enabled to show that RuxIr1-xO2materials were more active towards water oxidation than IrO2catalyst. The O2evolution process started at 1.45 V with Ru0.9Ir0.1O2in the anodic compartment of a 25 cm2Proton Exchange Membrane Water Electrolyzer at 60ºC.