Active Origin of Ordered Mesoporous Ir-Based Electrocatalysts for Acidic Water Oxidation

Iridium (Ir)-based electrocatalysts are widely explored as benchmarks for acidic oxygen evolution reaction (OER), but further enhancing their catalytic activity has been retarded by the unidentified active species and unfavorable architectures. In this work, we first report two-dimensional (2D), ordered mesoporous Ir-IrOx/C catalysts with mixed valent species (Ir0, IrIV, and IrV) through a nanoconfined self-assembly strategy. The mesoporous Ir-IrOx/C catalyst has highly ordered layered nanochannels (~20 nm) and uniformly dispersed Ir-IrOx nanoparticles (~2 nm). Benefits from the mixed valence states and favorable mesostructured architecture, the resultant catalyst displays the lowest overpotential (η) of 198 mV at 10 mA cm-2geo for Ir-based OER electrocatalysts in an acid medium. Both experimental and computational results reveal that the IrV moiety of 2D mesoporous Ir-IrOx/C catalysts with a shortened Ir-O(II-δ)- bond (1.91 A) is the key active species for the enhancement of OER by balancing the adsorption free energy of oxygen-containing intermediates. This study provides a model for an in-depth understanding of the active origin of the ordered mesoporous Ir-based electrocatalysts and role of V species in OER, as well as opens an avenue for designing high-efficient 2D ordered mesoporous electrocatalysts for water oxidation.