Electronic and Interfacial Engineering via Tungsten Incorporation for Robust Overall Water Splitting and Seawater Electrolysis

We report the rational design of a high-performance bifunctional electrocatalyst by incorporating tungsten into oxygen-deficient NiFe layered double hydroxide (NiFeW-LDH) nanosheets grown in situ on nickel foam via a one-pot hydrothermal method. The resulting NiFeW-LDH@NF electrode features a porous nanosheet network that enhances the surface area and interfacial electron transport. Tungsten integration tunes the electronic structure, increases oxygen vacancy concentration, and facilitates water molecule adsorption, thereby improving both oxygen evolution reaction and hydrogen evolution reaction (OER and HER) kinetics in 1.0 M KOH. The optimized catalyst achieves low overpotentials of 325 mV and 356 mV at 100 mA cm^-2 for OER and HER, respectively. In a two-electrode configuration, it enables efficient overall water splitting and seawater electrolysis with cell voltages of 1.646 and 1.693 V, respectively. Electrochemical analyses, including impedance spectroscopy, pH- and temperature-dependent kinetics, and turnover frequency measurements, confirm enhanced charge transfer, reduced activation energy, and accelerated reaction rates. Density functional theory calculations further reveal favorable d-band center shifts and intermediate adsorption energetics, supporting the experimental observations. These results demonstrate that NiFeW-LDH@NF is a cost-effective, robust, and scalable electrocatalyst for sustainable hydrogen production in both freshwater and seawater environments.