Investigating the Influence of Amorphous/Crystalline Interfaces on the Stability of IrO₂ for the Oxygen Evolution Reaction in Acidic Electrolyte

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.

Investigating the Potential Use of Ni‐Mn‐Co (NMC) Battery Materials as Electrocatalysts for Electrochemical Water Splitting

“…The catalysts were then analysed after repetitive potential cycling in the OER region to provide a more accurate representation of the active form of the catalyst rather than the initial pristine state. It is now well recognised that the majority of OER electrocatalysts undergo significant changes in either their morphology or composition when exposed to the harsh conditions of oxygen evolution [37,68–73] and in particular when exposed to repetitive potential cycling. SEM analysis of NMC 622‐NF (Figure 5a, b) shows that the even distribution of catalyst particles on the NF remains in tact while EDS mapping (Figure 5c‐f) also shows an even distribution of Ni, Mn, Co and O elements.…”