Complementary Multisite Turnover Catalysis toward Superefficient Bifunctional Seawater Splitting at Ampere‐Level Current Density

Abstract The utilization of seawater for hydrogen production via water splitting is increasingly recognized as a promising avenue for the future. The key dilemma for seawater electrolysis is the incompatibility of superior hydrogen‐ and oxygen‐evolving activities at ampere‐scale current densities for both cathodic and anodic catalysts, thus leading to large electric power consumption of overall seawater splitting. Here, in situ construction of Fe 4 N/Co 3 N/MoO 2 heterostructure arrays anchoring on metallic nickel nitride surface with multilevel collaborative catalytic interfaces and abundant multifunctional metal sites is reported, which serves as a robust bifunctional catalyst for alkaline freshwater/seawater splitting at ampere‐level current density. Operando Raman and X‐ray photoelectron spectroscopic studies combined with density functional theory calculations corroborate that Mo and Co/Fe sites situated on the Fe 4 N/Co 3 N/MoO 2 multilevel interfaces optimize the reaction pathway and coordination environment to enhance water adsorption/dissociation, hydrogen adsorption, and oxygen‐containing intermediate adsorption, thus cooperatively expediting hydrogen/oxygen evolution reactions in base. Inspiringly, this electrocatalyst can substantially ameliorate overall freshwater/seawater splitting at 1000 mA cm −2 with low cell voltages of 1.65/1.69 V, along with superb long‐term stability at 500–1500 mA cm −2 for over 200 h, outperforming nearly all the ever‐reported non‐noble electrocatalysts for freshwater/seawater electrolysis. This work offers a viable approach to design high‐performance bifunctional catalysts for seawater splitting.