Enhanced photocatalytic degradation of xylene by blackening TiO2 nanoparticles with high dispersion of CuO.

To enhance the photocatalytic activity of TiO2, a new preparation method has been proposed to synthesize the catalysts by introducing Cu-MOF as a precursor and performing a blackening process via a mixture with NaBH4 for TiO2 nanoparticles (CuO-TiO2(mb)). The results showed that the removal efficiency of xylene under ultraviolet and visible light over CuO-TiO2(mb) was 3.45 times higher than that of the catalysts prepared by impregnation of CuO on the surfaces of TiO2 (CuO-TiO2(d)) and 12.12 times higher than that of pure TiO2 nanoparticles. Analyses by the X-ray diffraction, scanning electron microscopy, and transmission electron microscopy indicated that the introduction of Cu-MOF as a precursor on the surface of the catalyst resulted in CuO-TiO2(mb) presenting a lower grain size compared with TiO2 nanoparticles and CuO-TiO2(d). The results of X-ray photoelectron spectroscopy, diffuse reflectance spectrum and photoluminescence indicated that blackening process narrowed the bind gap width and shortened the band gap from 2.95 eV to 1.32 eV, introduced the coexistence of Ti4+, Ti3+, Cu2+ and Cu+ in CuO-TiO2(mb) decreased the recombination rate of e--h+, which greatly improved the light response of CuO-TiO2(mb) under ultraviolet and visible light, resulting in the benefit to the photocatalytic reaction.