Charge transfer between Ti4+, Sn4+ and Pt in the tin doped TiO2 photocatalyst for elevating the hydrogen production efficiency

The valence of tin is the critical factor affecting the photocatalytic performance of TiO 2 when using tin as dopant. Sn 4+ acts as the intermediate step for the electron transfer from Ti 4+ to Sn 4+ and then to the adjacent Pt, while Sn 2+ plays as the defect site for carrier recombination. The intermediate step permit a long carrier lifetime, and enable the electron transfer to the surface adsorbed O 2 to form massive superoxide radical. Function of tin doping, light illumination and Pt loading are clarified. • The Sn6 achieved a high hydrogen production efficiency of 39.4 mmol·h -1 ·g -1 . • Sn 4+ dopingcan promote electron transfer, while Sn 2+ doping causes carrier recombination. • The intermediate step on Sn 4+ site between Ti 4+ and Pt leads to a longer carrier lifetime. • Function of tin doping, light illumination and Pt loading are clarified. Hydrogen production has been considered as the most promising approach for obtaining sustainable and clean energy source. Modification of TiO 2 photocatalyst with the aim of enhancing the photocatalytic efficiency has always been the top importance. In this work, Tin ions have been used as dopant to adjust the crystal phase and to improve the catalytic performance of TiO 2 . The results showed that Sn 4+ doping transferred the mixed phase TiO 2 photocatalyst into single rutile phase TiO 2 and increased the water splitting efficiency. Photoluminescence, X-ray photoelectron spectroscopy and UV–vis spectrometer characterization suggested that charge transfer between Ti 4+ and Sn 4+ is the key reason for the suppression of carrier recombination and the improvement of the photocatalytic efficiency. Sn 2+ doping did not adjust the rutile/anatase mix phase formation considerably, charge transfer from Ti 4+ to Sn 4+ is also proved to be the reason for the slightly enhanced water splitting efficiency. This work suggests that the ion valence of tin is the critical factor affecting the photocatalytic performance of TiO 2 .