Iridium-based catalysts for oxygen evolution reaction in proton exchange membrane water electrolysis

Proton exchange membrane water electrolysis (PEMWE) is a favorable technology for producing high-purity hydrogen under high current density using intermittent renewable energy. The performance of PEMWE is largely determined by the oxygen evolution reaction (OER), a sluggish four-electron reaction with a high reaction barrier. Nowadays, iridium (Ir)-based catalysts are the catalysts of choice for OER due to their excellent activity and durability in acidic solution. However, its high price and unsatisfactory electrochemical performance severely restrict the PEMWE's practical application. In this review, we initiate by introducing the current OER reaction mechanisms, namely adsorbate evolution mechanism and lattice oxygen mechanism, with degradation mechanisms discussed. Optimized strategies in the preparation of advanced Ir-based catalysts are further introduced, with merits and potential problems also discussed. The parameters that determine the performance of PEMWE are then introduced, with unsolved issues and related outlooks summarized in the end.