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

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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.