A homogeneous Cu-based polyoxometalate coupled with mesoporous TiO₂ for efficient photocatalytic H₂ production

Developing a photocatalytic system for water splitting to H₂ is a promising strategy to address fossil fuel consumption. Exploring photocatalysts with high-performance, steady and low-cost has been the essential goals toward photo-reduction of water. Herein, noble-metal-free polyoxometalate Na₁₂[(α-SbW₉O₃₃)₂Cu₃(H₂O)₃]·46H₂O (Cu₃POM) was coupled with mesoporous, multiphase TiO₂ (Meso-TiO₂) for the first time to catalyze hydrogen production. The composite system exhibited excellent photocatalytic hydrogen production activity. After 2.5 h of illumination, the activity was enhanced 77 times (1284.8 μmol/g) in the presence of Cu₃POM compared to the blank Meso-TiO₂ (16.6 μmol/g). Nitrogen adsorption-desorption isotherms results reveal the mesoporous characteristics of Meso-TiO₂ which could increase the active sites of the reaction. The cycling experiment demonstrated the composite system remained stable after five cycles without activity loss. Multiple characterizations reveal that Ti³⁺ is generated after the reaction, which further narrows the band gap and promotes the photocatalytic performance of the composite system. The suitable LUMO energy level of Cu₃POM was confirmed by electrochemical tests. It accelerates the transfer of photo-generated electrons from the CB of Meso-TiO₂ to the protons in the solution, resulting in a high photocatalytic H₂ production performance. The combination of Meso-TiO₂ with reductive polyoxometalate innovatively provides novel insights into the design of efficient photocatalytic materials for H₂ production.