Effect of ionic-bonding d<sup>0</sup> cations on structural durability in barium iridates for oxygen evolution electrocatalysis.
basic_science · Level V
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- Record sourced from PubMed, PMID 40320410.
- Also identified by DOI 10.1038/s41467-024-55290-y and PMC identifier 12050298.
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Abstract
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 Ba<sub>x</sub>(M,Ir)<sub>y</sub>O<sub>z</sub>-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 [Ir<sub>2</sub>O<sub>9</sub>] dimer or [Ir<sub>3</sub>O<sub>12</sub>] trimers in hexagonal-perovskite polytypes. In particular, highly ionic bonding of the d<sup>0</sup> Nb<sup>5+</sup> and Ta<sup>5+</sup> cations with oxygen anions results in notable suppression of lattice oxygen participation during the OER and thus effectively preserves the connectivity between the [Ir<sub>3</sub>O<sub>12</sub>] 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.