Visible Light Photocatalytic Activity of NaYF4:(Yb,Er)-CuO/TiO2 Composite

Abstract

TiO2 photocatalysts are limited to ultraviolet light photo-activation, however, by coupling with NaYF4:(Yb,Er) they can utilize visible light activation, but with low efficiencies. In order to enhance visible light photo-activity, CuO nanoparticles were coupled with NaYF4:(Yb,Er) by mechanical ball-milling and coated with TiO2-sol. The coupling of CuO nanoparticles with NaYF4:(Yb,Er)/TiO2 caused the formation of a NaYF4:(Yb,Er)-CuO/TiO2 composite capable of visible absorption with a remarkably reduced band gap of ~2.5 eV. The NaYF4:(Yb,Er)-CuO/TiO2 composite in H2O2 showed the most efficient methylene blue (MB) degradation efficiency of more than 99.5% after exposure to visible light.

Enhanced Photocatalytic Activity of CuWO4 Doped TiO2 Photocatalyst Towards Carbamazepine Removal under UV Irradiation

“…As can be seen, the photocatalytic activity of CuWO 4 -doped TiO 2 decreased with an increase in loading amount of CuWO 4 from 0.05 wt.% to 4 wt.% ( Figure 7a) following a CBZ removal trend of 0.05CuWO 4 -TiO 2 > 1CuWO 4 -TiO 2 > 2CuWO 4 -TiO 2 > 3CuWO 4 -TiO 2~= 4CuWO 4 -TiO 2 . Generally, the observed trend of decrease in photocatalytic activity with increase in weight percentage load of CuWO 4 can be attributed to the absorption of incident light by the excess CuWO 4 , thereby reducing the number of photons reaching the TiO 2 , particle agglomeration leading to active site blockage, effects of dissolved cupric species, and possibility of charge transfer from composite to O 2 or target molecules during photocatalysis [9,17,20,30,40,47,48], hence, why the minute added 0.05CuWO 4 onto TiO 2 produced a better photocatalytic activity in the series. From Figure 7b, apparent degradation rate constants of the photocatalyst materials were recorded highest for the 0.05CuWO 4 modified TiO 2 material at~2 h −1 compared to 0.89 h −1 for TiO 2 and negligible for CuWO 4 material due to lack of photocatalytic activity during 4 h irradiation time.…”

EPR and CV studies cast further light on the origin of the enhanced hydrogen production through glycerol photoreforming on CuO:TiO2 physical mixtures

“…Band-gap values were determined by diffuse reflectance UV-vis spectroscopy using a Cary 1E (Varian) instrument and polytetraethylene (density = 1 g•cm -3 and thickness = 6 mm) as the refence material. The plot of the modified Kubelka-Munk function [F(R)•E] 1/2 or [F(R)•E] 2 for TiO2 and CuO, respectively, versus the energy of the absorbed light E was used to obtain the value of band gap as described in the literature [37,38].…”