Highly Active TiO₂₋xNx Visible Photocatalyst Prepared by N-Doping in Et₃N/EtOH Fluid under Supercritical Conditions

TiO 2- x N x nanocrystallines were prepared by treating the TiO 2 precursor in triethylamine/ethanol (Et 3 N/EtOH) fluid under supercritical conditions. During photodegradation of p -chlorophenol under irradiation with visible lights, this catalyst exhibits much higher activity than the N-doped TiO 2 obtained via direct calcination. The promoting effect of the supercritical treatment could be attributed to the high surface area, the highly crystallized anatase, and the strong interaction of N-dopants with TiO 2, leading to the enhanced light harvesting and reactant adsorption as well as quantum efficiency of photocatalysis via inhibiting the recombination between photoinduced electrons and holes. Supercritical treatment using Et 3 N/EtOH fluid results in higher N-content in the TiO 2- x N x than that using NH 3 /EtOH fluid. Even with the same N-content, the TiO 2- x N x obtained in Et 3 N/EtOH is still much more active than that obtained in NH 3 /EtOH fluid, possibly owing to the enhanced surface hydrophobicity which could promote the adsorption of reactant molecules for degradation.