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.