Enhancing the Activity and Stability of IrO₂ for the Oxygen Evolution Reaction over a Wide pH Range using Electrodeposited BaO₂

Abstract Electrochemical water splitting holds great promise for converting intermittent renewable energy into chemical energy in the form of hydrogen. A major challenge is developing highly active and stable electrocatalysts, in particular for the demanding oxygen evolution reaction (OER). IrO 2 is renowned as one of the most efficient electrocatalysts for this reaction but still requires improvement in performance. Here we present an electrochemically synthesized IrO 2 /BaO 2 electrocatalyst where the incorporation of BaO₂ is believed to elevate the oxygen activity within the composite, allowing it to sustain higher current densities with improved stability. In acidic media, the stability of the Ba‐IrO 2 ‐300 °C sample showed significant improvement, with the initial current density of 100 mA cm −2 decreasing to 80 mA cm −2 after 8 h of testing. The resultant electrocatalysts show high catalytic activity over a wide range of pH values (1–14).At low current densities, neutral and alkaline conditions are more favourable compared to an acidic electrolyte where the stability at neutral pH was maintained for up to 70 h of testing. The enhanced performance of Ba‐incorporated IrO₂ may be attributed to access to oxygen activating Ba sites, offering valuable insights into the development of cost‐effective, efficient, and reliable IrO₂‐based catalysts for water splitting.