Boosting Oxygen Evolution Electrocatalysis Through Hydrogen Intercalation‐Induced Phase Transformation in Iridium Dioxide

Iridium dioxide (IrO₂) is an industrial anode catalyst in proton exchange membrane water electrolyzers (PEMWEs), and the development of effective methods to enhance its activity and durability is required. Here, we demonstrate a strategy to boost the catalytic performance of IrO₂ by introducing hydrogen atoms into the crystal lattice using glycerol as a hydrogen source. This hydrogen intercalation drives a tetragonal-to-monoclinic phase transition, with a refinement of the nanoparticles down to the sub-2 nm scale. Due to the synergetic modification of the atomic, electronic, and morphological structures, the hydrogen-intercalated nanocatalyst achieves a boost in catalytic activity for acidic oxygen evolution reaction and reduces Ir leaching by over 80% relative to pristine IrO₂. When integrated into a practical PEMWE, the hydrogen-intercalated nanocatalyst shows high activity at current densities of 1.0, 2.0, and 3.0 A cm^-2, and operates stably for more than 1000 h at each current density. Integrated operando spectroscopy, isotopic tracing, and theoretical modeling reveal a mixed oxygen evolution mechanism, with the dominant adsorbate evolution route and a limited lattice oxygen participation. This work deepens the understanding of hydrogen intercalation chemistry of inorganic oxides, and provides a novel way to design efficient Ir-based electrocatalysts without sacrificing catalytic stability.