Enhanced Photocatalytic Activity of P25 TiO₂ after Modification with Phosphate-Treated Porous SiO₂

In general, an increase in O₂ adsorption is highly desirable for efficient photocatalysis. Herein, commercial P25 TiO₂ is modified with an F127-containing SiO₂ sol, and post-treated with phosphoric acid. It is confirmed, on the basis of O₂ temperature-programmed desorption measurements, that the O₂ adsorption of commercial P25 TiO₂ is greatly promoted through its modification with porous SiO₂, especially in the phosphate-treated case. The promotion of O₂ adsorption is attributed to the introduction of -Si-OH and -P-OH as surface ends, and to the slightly increased surface area. Interestingly, it is concluded that the promotion of O₂ adsorption is favorable for the separation of photogenerated charge carriers, as seen from the steady-state surface photovoltage spectra, transient-state surface photovoltage responses, and measurements of the hydroxyl radicals produced. This is responsible for the clear enhancement in the photocatalytic activity of modified TiO₂ for the degradation of gas-phase acetaldehyde and liquid-phase phenol as colorless pollutants. This work provides a feasible route for improving the photocatalytic activity of TiO₂.