Significantly enhanced visible-light photocatalytic activity of g-C3N4 via ZnO modification and the mechanism study

The highly effective ZnO/g-C3N4 photocatalysts with different ZnO amount were prepared by an economic and environmentally friendly method. The photocatalysts were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, and Brunauer–Emmett–Teller surface area. The results showed that photocatalytic activity of the photocatalyst was much higher than that of pure g-C3N4 via photodegradation of Rhodamine B under visible light irradiation. The kinetic constant of RhB degradation over ZnO(15 wt.%)/g-C3N4 was 3.1 times that of pure g-C3N4. Effect of ZnO content on the photocatalytic activity of ZnO/g-C3N4 was studied in detail. The active species in RhB degradation were examined by adding a series of scavengers. The study on photocatalytic mechanism revealed that the electrons injected directly from the conduction band of g-C3N4 to that of ZnO, resulting in the production of O2− and OH radicals in the conduction band of ZnO. Simultaneously, the rich holes in the valence band of g-C3N4 oxidized Rhodamine B directly to promote the photocatalytic degradation reaction. This work may provide some insight into solving the unsatisfactory catalytic activity and low efficiency converting solar radiation for practical applications of g-C3N4.

Compared to pure C3N4 and ZnO, the as-prepared ZnO/C3N4 photocatalysts exhibit excellent visible light photocatalytic activity. The photocatalytic activity of ZnO/C3N4 improves remarkably with increasing ZnO content from 5 wt.% to 15 wt.%, although it decreases slightly at the higher ZnO level. The enhanced photocatalytic activity of ZnO/C3N4 photocatayst is attributed to the effective separation efficiency of photogenerated electrons and holes in the system.Figure optionsDownload high-quality image (176 K)Download as PowerPoint slideHighlights
► The ZnO/C3N4 photocatalysts with various ZnO contents were successfully prepared.
► Rate constant of RhB degradation over ZnO(15 wt.%)/C3N4 is 3.1 times that of C3N4.
► Effect of ZnO content on the photoactivity of ZnO/C3N4 was studied in detail.
► Reactive species in RhB degradation were examined by adding a series of scavengers.
► Visible light degradation mechanism of RhB over ZnO/C3N4 was systematically studied.