Raspberry-like TiO2 hollow spheres consisting of small nanocrystals towards efficient NO removal

Abstract

The conversion of nitrogen oxide (NO) by photocatalysis is promising to solve the increasingly serious air pollution. Herein, raspberry-like TiO₂ hollow spheres consisting of small nanocrystals (less than 10 nm) were created using hollow carbon spheres as templates by controlling the synthesis parameters. These raspberry-like hollow spheres were well dispersed and revealed large specific surface area (172.6 m² g⁻¹) which was about 3 times that of commercial TiO₂ powders (P25). The raspberry-like hollow spheres with an anatase phase composition and high crystallinity revealed high NO₂ selectivity for NO conversion. Compared with P25, the hollow spheres exhibited excellent removal performance and high stability for NO, in which ∼60% of NO at a concentration of 600 ppb was removed while P25 removed ∼40% of NO. This is ascribed to the large specific surface area and pore volume, exposed (001) facets with high energy, and the reflection and scattering of light in the hollow sphere structure improving the utilization of light. Based on the diffuse reflection spectra, Mott–Schottky curves, and band gap structures, the removal mechanism is discussed.