A novel etching and reconstruction route to ultrathin porous TiO2 hollow spheres for enhanced photocatalytic hydrogen evolution

Abstract Decreasing the shell thickness of TiO 2 hollow spheres is a promising route to achieve an overall enhanced photocatalytic performance. However, in traditional synthetic approaches, the thin shell can not guarantee the structural stability of the TiO 2 hollow spheres in the following calcination process to achieve a high degree of crystallinity. In this paper, ultrathin porous TiO 2 hollow spheres with good structural stability, high degree of crystallinity as well as in small grain size were prepared through a novel etching and reconstruction route using amorphous SiO 2 /TiO 2 hollow spheres as precursor. With hot water as etchant, the removal of SiO 2 leads to the reconstruction of TiO 2 hollow spheres and receiving a thinner and thinner shell. Such thin shell enables the exposure of more catalytic active sites of TiO 2 nanocrystals and the improved photogenerated charge transfer and separation. Meanwhile, the residual SiO 2 on the TiO 2 shell protects the TiO 2 nanocrystals from growing larger during high-temperature calcinations. The as-obtained ultrathin porous TiO 2 hollow spheres exhibited enhanced photocatalytic activity in hydrogen production from water in comparison with those with thicker shell.