Synergy of high-entropy support with Ir single-atom cluster for boosting oxygen evolution reaction

The sluggish kinetics of oxygen evolution reaction (OER) is one of the critical challenges for electrochemical water splitting. Rational design of single atom on metal-support interactions (MSI) using deposition method is essential for electrocatalytic materials. Herein, we report the single-atomic-site and cluster-site iridium stabilized on high-entropy oxides (FeCoNiCrMoO_x) with deposition method using choline chloride/urea deep eutectic solvent (ChCl/U). The resulting Ir single atoms and clusters exhibit an average interatomic distance of approximately 0.77 nm. Ir_1&n-FeCoNiCrMoO_x delivers an ultralow overpotential of 193 mV at a current density of 100 mA·cm^-2, and a long-term stability over 240 h for OER by precisely regulating the local coordination environments of the active sites in catalyst. DFT calculations reveal that closely distance single atoms and clusters exhibit stronger interactions with the high-entropy substrate. These strong interactions lead to a shift in the rate-determining step, and Ir_1&n-FeCoNiCrMoO_x demonstrates the lowest theoretical OER overpotential. This work introduces DES as an effective electrochemical deposition method with synthesizing closely spaced single atoms and clusters for superior OER activity.