Enhancement on the performance of TiO2 photocatalysts under weak UV light irradiation via asorbed-layer nanoreactor technique

Abstract

Because the light source is weak in most environmental systems, photocatalysis under the irradiation of weak light need to be developed urgently. Herein, the effects of catalyst microstructure on their activities under weak UV light irradiation were studied. TiO2 photocatalysts doped with La3+ were prepared via asorbed-layer nanoreactor technique (ANT) to improve their catalytic activity under weak UV light excitation. From the analysis by XRD, BET, PL spectroscopy, DSR, HRTEM, Raman spectroscopy, and XPS, it was found that the structure–activity relationships of the catalysts under weak UV light irradiation were more sensitive than those under strong UV light irradiation. Even trace amounts of amorphous TiO2 caused significant changes in the activity under weak light irradiation. La3+ doping showed two opposite effects: at low doping content, La3+ doping introduced lattice distortions that acted as shallow trapping sites for the photogenerated charge carriers, and that promoted the catalytic activity. The optimum activity of the ANT photocatalysts was more than two-fold higher than that of P25 TiO2. However, the TiO2 crystallization was strongly inhibited when the La3+ doping content exceeded 0.20%. A large amount of amorphous TiO2 became deep trapping sites for the charge carriers in photocatalysis and caused a significant decline in the activity.