Investigation of IrO2 electrocatalysts prepared by a sulfite-couplex route for the O2 evolution reaction in solid polymer electrolyte water electrolyzers

IrO2 electrocatalysts were prepared and electrochemically characterized for the oxygen evolution reaction in a Solid Polymer Electrolyte (SPE) electrolyzer. By using a sulfite complex-based preparation procedure, an amorphous iridium oxide precursor was obtained at 80 °C, which was, successively, calcined at different temperatures: 350 °C, 400 °C and 450 °C. A physico-chemical characterization was carried out by X Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray-photoelectron spectroscopy (XPS). The various IrO2 catalysts were sprayed onto a Nafion 115 membrane with a loading of 2.5 mg cm−2 to form the anode. A Pt/C catalyst (Pt loading 0.5 mg cm−2) was used as cathode. The best electrochemical performance was obtained for the cell based on the IrO2 calcined at 350 °C. The maximum current density at high potentials (1.8  V) was about 1.75 A cm−2. Accelerated time-tests at 2 A cm−2 demonstrated a suitable stability of the IrO2 calcined at 350 °C; however, the intrinsic stability appeared to increase with the calcination temperature. The sample calcined at 400 °C could represent a good compromise between performance and intrinsic stability.