Electrodeposited amorphous thin films of IrO₂ are annealed at different temperatures to produce amorphous/crystalline interfaces. During oxygen evolution reaction at high current density their presence is found to influence both activity and stability/solubility of the electrode. Although increased performance is found, films are still prone to dissolution.

Abstract

A major challenge with water splitting technology is to develop highly active and stable electrocatalysts for the oxygen evolution reaction (OER). IrO₂ – based electrocatalysts are one of the most active electrocatalysts for proton exchange membrane (PEM) electrolysers, due to their excellent activity for the OER in acidic conditions. However, IrO₂ often suffers from dissolution during electrolysis due to phase transitions into more soluble forms. Herein, a range of electrodeposited IrO₂ films annealed to different temperatures of up to 500^°C are prepared to understand the influence that crystalline/amorphous interfaces have on performance during accelerated degradation tests in concentrated acidic solutions. This study showed that an IrO₂ film annealed at 300 °C exhibited the highest catalytic activity with a low overpotential of 150 mV at 10 mA cm⁻², the smallest Tafel slope of 51 mV dec⁻¹, with a less progressive decay in activity over a period of 8 h of accelerated degradation testing. This contrasts with both fully amorphous or more crystalline IrO₂ films that decayed much more rapidly within 1 h of testing indicating the role that amorphous/crystalline regions have on OER performance.