Effect of the calcination temperature on the visible light photocatalytic activity of direct contact Z-scheme g-C3N4-TiO2 heterojunction

Z-scheme g-C3N4-TiO2 heterojunctions containing g-C3N4 nanosheets with different thickness were prepared by sintering the mixture of g-C3N4 and nanotube titanic acid (denoted as NTA) at different temperatures in air. As-prepared Z-scheme g-C3N4-TiO2 heterojunctions were characterized by X-ray diffraction, transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible light diffuse reflectance spectrometry, electron spin resonance, and photoluminescence spectrometry. Findings indicate that the annealing temperature has crucial effects on the visible-light photocatalytic activity (a.> 420 nm) of the as-prepared Z-scheme g-C3N4-TiO2 heterojunctions. The Ti3' and porous g-C3 N4 nanosheets formed upon the calcination at 600 degrees C as well as the low concentration of bulk single-electron trapped oxygen vacancy are favorable to the transport of the photoexcited charge carriers. This, in association with the Z-scheme system, contributes to improving the photocatalytic activity of g-C3N4-TiO2 photocatalysts. As a result, g-C3N4-TiO2 photocatalyst prepared at 600 degrees C exhibits good photocatalytic activity towards the degradation of propylene and hydrogen generation by water-splitting under visible light irradiation. (C) 2017 Elsevier B.V. All rights reserved.