Alkali Metal-Induced Core-Shell Hybrid with Mixed Ir Valence State Boosts Acidic Water Oxidation

Abstract

Iridium (Ir)-based electrocatalysts have long been employed as the benchmark for the oxygen evolution reaction (OER) in acid, but further to improve their catalytic activity still facing great challenges. Herein, alkali metal K is incorporated to induce the in situ construction of a core-shell hybrid of K-IrOx thin skin-wrapped metallic Ir (K-IrOx/Ir) to boost the acidic OER. The K-IrOx/Ir exhibits exceptional catalytic performance with a long lasting stability of 3000 h operation and a low overpotential of 199 mV to reach the 10 mA cm-2. Electrochemical and spectroscopic studies revealed that the enrichment of K in the low-coordination IrOx shell induces a significant compressive strain, which regulates the Ir & horbar;O bond properties and further optimizes the adsorption energy of rate-limiting intermediates, favoring of the enhanced catalytic activity. Furthermore, the surface IrOx active layer is well maintained during the OER process thanks to the mixed-valence state and intensified electronic interaction in core-shell hybrid that inhibit the overoxidation and dissolution of Ir, responsible for the outstanding stability. This work offers a novel strategy for developing high performance acidic OER catalysts by the design of favorable mesostructured architectures with mixed metal states to enable the intensified electronic interaction and strain effect.