Low‐Spin‐Induced Optimization of Intermediate Adsorption in Selenium‐Incorporated Layered Double Hydroxides for Enhanced Electrochemical Water Splitting

Abstract

The rational manipulation of spin configurations in cobalt‐based electrocatalysts offers a viable strategy for optimizing oxygen and hydrogen evolution activities. Nevertheless, the intermediate spin (IS) configuration of Co2+ sites, featuring partially occupied d orbitals, triggers suboptimal adsorption with oxygenated species. In this work, selenium incorporation into CoCr layered double hydroxides (LDH) is demonstrated to induce spin‐state transition, activating inert sites and stabilizing the low‐spin (LS) Co2+ configuration. The low spin‐state materials exhibit superior electrocatalytic activity, requiring overpotentials of merely 284.0 and 130.0 mV for oxygen and hydrogen evolution reactions, respectively, at 10 mA cm−2, while maintaining excellent durability over 168 h. The lowered eg occupancy in low‐spin Co2+ results in electronic asymmetry and enhances electron density at the metal center. This electronic configuration facilitates robust Co 3d‐O 2p orbital hybridization, which enhances the adsorption of oxygenated intermediates by elevating the d‐band center toward the Fermi level, optimizing adsorption energetics. Moreover, low‐spin Co2+’s paired d‐orbital electron configuration minimizes high‐energy antibonding eg orbital occupancy, enhancing crystal lattice stability. Overall, this work establishes that spin state modulation in transition metals significantly lowers reaction energy barriers, offering a promising strategy for developing high‐performance electrocatalysts.