Recent developments of iridium-based catalysts for the oxygen evolution reaction in acidic water electrolysis

Proton exchange membrane water electrolysis (PEMWE) is one of the central technologies to enable the widespread use of intermittent renewable energy, thereby solving the problems caused by the global warming and the energy crisis associated with fossil fuels. Due to the harsh reaction conditions and sluggish kinetics of the four-electron transfer involved oxygen evolution reaction (OER) at the anode, precious metal Ir-based electrocatalysts are necessary to enable active and durable acidic water electrolysis. However, the high price and scarcity of Ir spur intensive research on designing robust OER catalysts with decreased Ir loading. In this review, we provide a systematic review on the recent development of Ir-based OER catalysts, initiated with understanding of the reaction mechanism and the degradation process. Particularly, the adsorbate evolution mechanism (AEM) and lattice oxygen participation mechanism (LOM) are discussed in detail, which then serve as guiding principles for catalyst design. Second, the latest progress of Ir-based catalysts in terms of morphology engineering, heteroatom doping and controllable crystal phase design is summarized, with the real world performance of OER electrocatalysts in practical electrolyzers provided. Finally, we put forward our perspective of challenges and prospects for future development of Ir-based OER catalysts.