Effect of loading of Pt at different positions on the photocatalytic hydrogen production performance of TiO2 hollow spheres☆

Insufficient charge density is a major bottleneck limiting the improvement of photocatalytic efficiency. To overcome this limitation, researchers often adopt the strategy of co-catalyst loading to improve the photocatalytic efficiency. However, it is not clear whether the difference in the loading position of the co-catalysts would cause the difference in charge distribution and the effect on the photocatalytic performance. Whereas in many co-catalysts, the loading of noble metals has been shown to significantly improve the photocatalytic performance. Therefore, in this paper, the specific effects of different loading positions on the photocatalytic performance of the composites were investigated in detail by precisely controlling the loading positions of the noble metal Pt on the inner and outer surfaces of TiO2 hollow spheres. The results showed that when 0.5 % Pt was loaded on the outer surface of TiO2 hollow spheres, a significant increase in the electron-hole separation efficiency was observed, leading to a significant increase in the hydrogen production rate of the 0.5Pt@TiO2 composite to 11.71 mmolg-1h- 1, which is an increase of about 69-fold compared to that of monomeric TiO2. When the same mass of Pt was deposited in the inner layer of TiO2 hollow spheres, the photocatalytic hydrogen production rate was only 4.64 mmolg-1h- 1 due to the limited number of active sites, which was about 29 times higher than that of the monolithic TiO2 hollow spheres, but the activity was significantly lower than that of the outer layer loaded with 0.5Pt@TiO2. This comparison further confirms the important influence of the noble metal loading position on the photocatalytic performance and shows the advantage of the outer layer loading in improving the photocatalytic efficiency.