Efficient solar-assisted seawater splitting in alkaline solution using perovskite–graphene–Si tandem integration†

Utilization of seawater represents an attractive opportunity to establish a sustainable hydrogen economy that is less reliant on finite freshwater resources. Photoelectrochemical (PEC) water splitting, which converts sunlight into clean hydrogen fuel, has emerged as an attractive technology for developing clean hydrogen energy. However, this technology faces critical challenges such as corrosion of photoelectrodes and the chloride oxidation reaction (COR) in seawater. The introduction of alkaline electrolytes, which raise the pH level, can effectively suppress the COR and enhance the sluggish oxygen evolution reaction (OER) simultaneously. In this work, we propose using an atomic layer of graphene as a protective interfacial layer to facilitate the direct growth of bifunctional Ni–Fe LDH catalysts on graphene/silicon heterojunction photoanodes and photocathodes. By integrating the perovskite–graphene–silicon tandem structures with Ni–Fe LDH catalysts, efficient bias-free solar-assisted seawater splitting can be achieved, yielding solar-to-hydrogen (STH) conversion efficiencies of 13.26% for simulated seawater and 13.09% for natural seawater under 1 sun illumination (100 mW cm⁻², AM 1.5G). Utilizing graphene as a protective interfacial layer on the perovskite–Si tandem absorber enables efficient and stable solar-assisted seawater splitting under alkaline conditions, offering a promising platform for utilizing the abundant natural resources of solar energy and seawater.