Interfacial solar vapor electrolyzer for efficient and durable hydrogen production directly from seawater

Solar-powered water splitting from seawater offers a sustainable pathway for hydrogen production, yet current methods are challenged by the complex composition of seawater, as well as intrinsic thermodynamic and kinetic limits when using liquid water as reactants. This work proposes an interfacial solar vapor electrolyzer (ISVE), which synergistically utilizes interfacial vapor generation driven by dissipated solar-thermal energy and solar-powered electricity to enable efficient and stable hydrogen (H₂) production directly from seawater. Abundant solar-thermal vapor as the reactant during electrolysis not only significantly enhances durability due to intrinsically purified properties, but also fundamentally increases the solar-to-hydrogen (STH) efficiency owing to reduced thermodynamic and kinetic barriers. As a demonstration, ISVE achieves a 15.2% STH efficiency at an average electrolysis current density of over 140 mA cm^{- 2}, and also exhibits stable operation for over 1400 h with seawater. This design enables efficient and durable solar H₂ production directly from widely available water sources, offering a cost-effective solution with high potential for practical applications.