Recent Advances in Anion-Doping Transition Metal Layered Double Hydroxide for Water Oxidation to Hydrogen Evolution

Electrochemical water splitting for hydrogen production is limited by the slow kinetics of the oxygen evolution reaction (OER). The tunable structure and anion-exchange capability of layered double hydroxides (LDHs) underpin their promise as OER catalysts. Consequently, the strategic incorporation of foreign anions is viewed as a powerful approach to engineer their active sites and boost catalytic activity. This review summarizes how doping with anions such as NO3−, PO43−, Cl−, F−, and Sq2− modifies the electronic structure of LDHs. These anions regulate the local coordination environment, induce oxygen vacancies, and alter metal oxidation states, thereby synergistically optimizing both the adsorption–evolution mechanism (AEM) and the lattice oxygen oxidation mechanism (LOM). For instance, NO3− promotes surface reconstruction, F− activates lattice oxygen, PO43− stabilizes the interface, Cl− reshapes reaction pathways, and Sq2− maintains interfacial alkalinity. Collectively, rational anion engineering lowers the overpotential, increases current density, and improves stability, establishing an effective design framework for advanced LDH-based OER electrocatalysts.