Activating Lattice Oxygen Oxidation Mechanism in Asymmetric [IrO6] Octahedra of Ir‐Based Oxides Toward Superior Acidic Electrochemical Water Oxidation

Abstract

AbstractThe activation of lattice oxygen oxidation mechanism (LOM) will endow iridium‐based electrocatalysts with desired acid‐available water oxidation activity, compared to the conventional adsorbate evolution mechanism (AEM). However, the inherent symmetric [IrO6] octahedra of commercial Ir‐based catalysts generally thermodynamically favor the AEM pathway contributing to the moderate water oxidation performance. Here, based on typical layered Ca2IrO4 (CIO) modeled materials, the d‐orbitals electron repulsion strategy is demonstrated, via constructing asymmetrically polarized Ir‒O‒Ru configuration in Ru‐CIO, to effectively activate the lattice oxygen participating in water oxidation process for decent oxygen‐related electrocatalytic activity. Specifically, a great increase of ≈700‐fold and ≈170‐fold in mass activity and turnover frequency, respectively, has been realized for the optimal Ru‐CIO electrocatalyst in an acid medium relative to the commercial IrO2 electrocatalysts, where a small overpotential of only 175 mV is required for achieving 10 mA cmgeo‒2. In situ X‐ray fine structure spectroscopies combined with in situ 18O‐ isotope‐labeled differential electrochemical mass spectrometry analyses reveal that desirable LOM has been boosted by the activated lattice oxygen and the flexible Ir(3+δ)+ active sites of asymmetric [IrO6] octahedra, which results in superior OER kinetics for Ir‐based oxide catalysts.