Electroactivity of RuO2–IrO2 mixed nanocatalysts toward the oxygen evolution reaction in a water electrolyzer supplied by a solar profile

• Ruthenium iridium mixed oxide materials are synthesized from the hydrolysis method.
• A 25 cm2 single PEM Water electrolyzer is supplied by a solar power profile.
• In Galvanodynamic mode, the electrolyzer delivers 1.75 V at 1 A cm−2 and at 80 °C.

Pure crystalline ruthenium–iridium oxide materials were synthesized with high surface area by co-precipitation method in ethanol medium. Cyclic and linear scan voltammetries were then undertaken to evaluate the effect of mixing iridium and ruthenium oxides on the oxygen evolution reaction (OER). The activity of these anode catalysts was evidenced through the determination of their capacitances, surface charges and Tafel slopes. It was found that the Ru0.9Ir0.1O2 catalyst presented catalytic properties close to those of RuO2, in particular for low overpotentials. The proposed synthesis method was also shown to be suitable for recovering large catalyst amount for O2 production in a large surface proton exchange membrane water electrolyzer (PEMWE). Polarization measurements were therefore performed in a single PEMWE cell and the durability of the catalytic materials was evaluated by supplying a solar power profile. The efficiency loss at 1 A cm−2 and 80 °C was only 90 μV h−1 for 1000 h under galvanodynamic operating conditions for Ru0.9Ir0.1O2 as anode, while the cell voltage varied between 1.75 and 1.85 V.