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Iridium has the exclusive chemistry guaranteeing both high catalytic activity and sufficient corrosion resistance in a strong acidic environment under anodic potential. Complex iridates thus attract considerable attention as high-activity electrocatalysts with less iridium utilization for the oxygen evolution reaction (OER) in water electrolyzers using a proton-exchange membrane. Here we demonstrate the effect of chemical doping on the durability of hexagonal-perovskite Bax(M,Ir)yOz-type iridates in strong acid (pH ~ 0). Some aliovalent cations are directly visualized to periodically locate at the octahedral sites bridging the two face-sharing Ir2O9 dimer or Ir3O12 trimers in hexagonal-perovskite polytypes. In particular, highly ionic bonding of the d0 Nb5+ and Ta5+ cations with oxygen anions results in notable suppression of lattice oxygen participation during the OER and thus effectively preserves the connectivity between the Ir3O12 trimers without lattice collapse. Providing an in-depth understanding of the correlation between the electronic structure and bonding nature in crystals, our work suggests that proper control of chemical doping in complex oxides promises a simple but efficient tool to realize OER electrocatalysts with markedly improved durability. Iridium-based materials are promising for mentioning high catalytic activity and durability for the oxygen evolution reaction in acidic water electrolysis. Here the authors report Ba-based complex iridate with distinct atomic scale cation ordering for enhanced durability and activity for acidic water oxidation.
Sim et al. (Sun,) studied this question.