Nanosized IrO electrocatalysts for oxygen evolution reaction in an SPE electrolyzer.

Nanosized IrO electrocatalysts ( d ~ 7-9 nm) with specific surface area up to 100 m g were synthesized and characterized for the oxygen evolution reaction in a solid polymer electrolyte (SPE) electrolyzer. The catalysts were prepared by a colloidal method in aqueous solution and a subsequent thermal treatment. An iridium hydroxide hydrate precursor was obtained at ~100 °C, which was, successively, calcined at different temperatures from 200 to 500 °C. The physico-chemical characterization was carried out by X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry (TG-DSC) and transmission electron microscopy (TEM). IrO catalysts were sprayed onto a Nafion 115 membrane up to a loading of 3 mg cm. A Pt catalyst was used at the cathode compartment with a loading of 0.6 mg cm. The electrochemical activity for water electrolysis of the membrane-electrode assemblies (MEAs) was investigated in a single cell SPE electrolyzer by steady-state polarization curves, impedance spectroscopy and chrono-amperometric measurements. A maximum current density of 1.3 A cm was obtained at 1.8 V and 80 °C for the IrO catalyst calcined at 400 °C for 1 h. A stable performance was recorded in single cell for this anode catalyst at 80 °C. The suitable catalytic activity and stability of the most performing catalyst were interpreted in terms of proper combination between nanostructure and suitable morphology. [ABSTRACT FROM AUTHOR]