Photocatalytic water splitting (PWS) has attracted widespread attention as a sustainable method for converting solar to green hydrogen energy. So far PWS research has mainly focused on the development of artificial photocatalytic hydrogen production systems for pure water. It is more practically attractive to create systems for seawater, i.e., to reduce the cost of hydrogen production and make better use of naturally occurring water resources. Herein, brookite, anatase, and rutile TiO₂ nanoparticles are investigated as photocatalysts to explore the feasibility of such thought and have shown attractive hydrogen production performance under full solar spectrum without any sacrificial agent. It is worth noting that, brookite TiO₂, has more suitable band gap position and excellent photoelectric properties compared with anatase and rutile TiO₂, and has higher efficiency and stability in the process of hydrogen production. The photocatalytic hydrogen production rate of brookite TiO₂ can reach up to 1,476 μmol/g/h, the highest value reported for TiO₂-based systems and most other photocatalysts in seawater splitting under full spectrum. As the Cl⁻ ions in seawater go through a cycle of oxidation and reduction, no Cl₂ is detected in the solar hydrogen production from seawater.