Solar energy is an inexhaustible renewable energy source. Among the various methods for solar energy conversion, photocatalytic hydrogen (H₂) production is considered as one of the most promising ways. Since Fujishima pioneered this field in 1972, photocatalytic water splitting to produce H₂ has received widespread attention. Up to now, abundant semiconductor materials have been explored as photocatalysts for pure water splitting to produce H₂. However, photocatalytic seawater splitting is more in line with the concept of sustainable development, which can greatly alleviate the problem of limited freshwater resource. At present, only few studies have focused on the process of H₂ production by photocatalytic seawater splitting due to the complex composition of seawater and lack of suitable photocatalysts. In this review, we outline the most recent advances in photocatalytic seawater splitting. In particular, we introduce the H₂ production photocatalysts, underlying mechanism of ions in seawater on photocatalytic seawater splitting, current challenges and future potential advances for this exciting field.

The TiO₂-H₂O₂ system possesses excellent oxidation activity even under dark conditions. However, the mechanism of this process is unclear and inconsistent. In this work, the binary component system containing TiO₂ nanoparticles (NPs) with single electron-trapped oxygen vacancy (SETOV, V_O·) and H₂O₂ exhibit excellent oxidative performance for tetracycline, RhB, and MO even without light irradiation. We systematically investigated the mechanism for the high activity of the TiO₂-H₂O₂ under dark condition. Reactive oxygen species (ROS) induced from H₂O₂ play a significant role in improving the catalytic degradation activities. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) results firstly confirm that H₂O₂ is primarily activated by SETOVs derived from the TiO₂ NPs through direct contribution of electrons, producing both ·O₂^-/·OOH and ·OH, which are responsible for the excellent reactivity of TiO₂-H₂O₂ system. This work not only provides a new perspective on the role of SETOVs playing in the H₂O₂ activation process, but also expands the application of TiO₂ in environmental conservation.