Iridium‐Based Catalysts for Solid Polymer Electrolyte Electrocatalytic Water Splitting

Chemical energy conversion/storage through water splitting for hydrogen production has been recognized as the ideal solution to the transient nature of renewable energy sources. Solid polymer electrolyte (SPE) water electrolysis is one of the most practical ways to produce pure H2. Electrocatalysts are key materials in the SPE water electrolysis. At the anode side, electrode materials catalyzing the oxygen evolution reaction (OER) require specific properties. Among the reported materials, only iridium presents high activity and is more stable. In this Minireview, an application overview of single iridium metal and its oxide catalysts—binary, ternary, and multicomponent catalysts of iridium oxides and supported composite catalysts—for the OER in SPE water electrolysis is presented. Two main strategies to improve the activity of an electrocatalyst system, namely, increasing the number of active sites and the intrinsic activity of each active site, are reviewed with detailed examples. The challenges and perspectives in this field are also discussed. SPEctacular splits: Solid polymer electrolyte (SPE) water electrolysis is one of the most practical ways to produce pure H2. Water electrolysis at the anode produces O2 and four protons near the electrode surface for each oxygen molecule. Hydrogen ions are transported through the proton exchange membrane to generate H2 gas near the cathode. An overview of various electrocatalysts for the oxygen evolution reaction in SPE water electrolysis is presented.