Highly active TiO2-xNx visible photocatalyst prepared by N-doping in Et3N/EtOH fluid under supercritical conditions

TiO2-xNx nanocrystallines were prepared by treating the TiO2 precursor in triethylamine/ethanol (Et3N/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 TiO2 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 TiO2, 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 Et3N/EtOH fluid results in higher N-content in the TiO2-xNx than that using NH3/EtOH fluid. Even with the same N-content, the TiO2-xNx obtained in Et3N/EtOH is still much more active than that obtained in NH3/EtOH fluid, possibly owing to the enhanced surface hydrophobicity which could promote the adsorption of reactant molecules for degradation.