Confined Heterojunction in Hollow-Structured TiO₂ and Its Directed Effect in Photodriven Seawater Splitting

The high salinity of seawater often strongly affects the activity and stability of photocatalysts utilized for photodriven seawater splitting. The current investigation is focused on the photocatalyst H-TiO₂/Cu₂O, comprised of hydroxyl-enriched hollow mesoporous TiO₂ microspheres containing incorporated Cu₂O nanoparticles. The design of H-TiO₂/Cu₂O is based on the hypothesis that the respective hollow and mesoporous structure and hydrophilic surfaces of TiO₂ microspheres would stabilize Cu₂O nanoparticles in seawater and provide efficient and selective proton adsorption. H-TiO₂/Cu₂O shows hydrogen production performances of 45.7 mmol/(g·h) in simulated seawater and 17.9 mmol/(g·h) in natural seawater, respectively. An apparent quantum yield (AQY) in hydrogen production of 18.8% in water (and 14.9% in natural seawater) was obtained at 365 nm. Moreover, H-TiO₂/Cu₂O displays high stability and can maintain more than 90% hydrogen evolution activity in natural seawater for 30 h. A direct mass- and energy- transfer mechanism is proposed to clarify the superior performance of H-TiO₂/Cu₂O in seawater splitting.