Rhenium Suppresses Iridium (IV) Oxide Crystallization and Enables Efficient, Stable Electrochemical Water Oxidation

Abstract

IrO2 as benchmark electrocatalyst for acidic oxygen evolution reaction (OER) suffers from its low activity and poor stability. Modulating the coordination environment of IrO2 by chemical doping is a methodology to suppress Ir dissolution and tailor adsorption behavior of active oxygen intermediates on interfacial Ir sites. Herein, the Re‐doped IrO2 with low crystallinity is rationally designed as highly active and robust electrocatalysts for acidic OER. Theoretical calculations suggest that the similar ionic sizes of Ir and Re impart large spontaneous substitution energy and successfully incorporate Re into the IrO2 lattice. Re‐doped IrO2 exhibits a much larger migration energy from IrO2 surface (0.96 eV) than other dopants (Ni, Cu, and Zn), indicating strong confinement of Re within the IrO2 lattice for suppressing Ir dissolution. The optimal catalysts (Re: 10 at%) exhibit a low overpotential of 255 mV at 10 mA cm−2 and a high stability of 170 h for acidic OER. The comprehensive mechanism investigations demonstrate that the unique structural arrangement of the Ir active sites with Re‐dopant imparts high performance of catalysts by minimizing Ir dissolution, facilitating *OH adsorption and *OOH deprotonation, and lowering kinetic barrier during OER. This study provides a methodology for designing highly‐performed catalysts for energy conversion.

Reducing the Ir−O Coordination Number in Anodic Catalysts based on IrOx Nanoparticles towards Enhanced Proton‐exchange‐membrane Water Electrolysis

“…[18] Thus, the OER intermediate species (OH*, O* and OOH*) are favorably adsorb/desorption in metal active sites with Angewandte Chemie unsaturated coordination environment, which promotes their better OER activity. [19] Moreover, we also noted that such an oxidation state is stable even after removing the reaction potential. On the other hand, EXAFS spectra show that the IrÀ O bond length at the low-coordinated samples is shortened from 1.66 Å to 1.6 Å as the OCV increased up to 1.6 V (vs. RHE), in sharp contrary to unchanged bond length at rutile-IrO 2 , which could effectively adjust the d-band center and electronic structure of IrO 2 , causing a good affinity of the active site to oxygenate intermediates.…”

Reducing the Ir−O Coordination Number in Anodic Catalysts based on IrOx Nanoparticles towards Enhanced Proton‐exchange‐membrane Water Electrolysis

“…Chemie Forschungsartikel unsaturated coordination environment, which promotes their better OER activity. [19] Moreover, we also noted that such an oxidation state is stable even after removing the reaction potential. On the other hand, EXAFS spectra show that the IrÀ O bond length at the low-coordinated samples is shortened from 1.66 Å to 1.6 Å as the OCV increased up to 1.6 V (vs. RHE), in sharp contrary to unchanged bond length at rutile-IrO 2 , which could effectively adjust the d-band center and electronic structure of IrO 2 , causing a good affinity of the active site to oxygenate intermediates.…”

Electrochemical Etching Switches Electrocatalytic Oxygen Evolution Pathway of IrOx/Y2O3 from Adsorbate Evolution Mechanism to Lattice‐Oxygen‐Mediated Mechanism

“…Determined by the scaling relationship between the adsorption energy of *OH and *OOH on the active sites, this mechanism is theoretically limited by a considerable overpotential of 370 mV for OER. [ 2,13–14 ] In the LOM‐mediated pathway, lattice oxygens are electrochemically activated, presenting as intermediates to release oxygen. [ 15 ] In this way, the LOM approach can bypass the generation of *OOH, thereafter breaking the scaling relationship as shown in the AEM‐mediated pathway.…”