Abstract
Graphitic-C3N4 nanosheets (CN)/ZnO photocatalysts (CN/ZnO) with different CN loadings were successfully prepared via a simple precipitation-calcination in the presence of exfoliated C3N4 nanosheets. Their morphology and structure were thoroughly characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectra (PL). The results showed that hexagonal wurzite-phase ZnO nanoparticles were randomly distributed onto the CN nanosheets with a well-bonded interface between the two components in the CN/ZnO composites. The performance of the photocatalytic Cr(VI) reduction indicated that CN/ZnO exhibited better photocatalytic activity than pure ZnO under visible-light irradiation and the photocatalyst composite with a lower loading of CN sheets eventually displayed higher activity. The enhanced performance of CN/ZnO photocatalysts could be ascribed to the increased absorption of the visible light and the effective transfer and separation of the photogenerated charge carriers.
Highlights
Hexavalent chromium (Cr(VI)) is the most toxic of the chromium species and has been listed as one of the priority pollutants by the US Environmental Protection Agency (EPA) due to its notoriously toxic, mutagenic and carcinogenic activity to human beings [1,2]
Compared to pure ZnO, the photoluminescence spectra (PL) peak intensity at 498 nm for both C3N4 nanosheets (CN)/ZnO photocatalysts was significantly reduced, indicating that the modification of ZnO with few-layered CN nanosheets could effectively suppress the recombination of photoinduced electron-hole pairs in the composites and efficiently separate the photoinduced electrons in electron-transfer processes [53,54]
CN/ZnO photocatalysts were successfully prepared via a facile precipitation-calcination in the presence of exfoliated C3N4 nanosheets
Summary
Hexavalent chromium (Cr(VI)) is the most toxic of the chromium species and has been listed as one of the priority pollutants by the US Environmental Protection Agency (EPA) due to its notoriously toxic, mutagenic and carcinogenic activity to human beings [1,2]. Compared to pure ZnO, the PL peak intensity at 498 nm for both CN/ZnO photocatalysts was significantly reduced, indicating that the modification of ZnO with few-layered CN nanosheets could effectively suppress the recombination of photoinduced electron-hole pairs in the composites and efficiently separate the photoinduced electrons in electron-transfer processes [53,54]. The improved photoreduction activity could be ascribed to the increased absorption in the visible-light range and the enhanced charge separation efficiency at the interface of ZnO and CN nanosheets [16,36] Compared to those reports where better activities were obtained with the use of additional scavengers [11,55,57,59], this method described will be highly desirable for environmental remediation due to no additional scavengers in this pFFriiggouucrereess88.. Scheemmaattiicc illussttrraattiioonn off the mechanism of electron-hole separation and transport and photocatalytic activity of CN//ZZnnOOpphhoottooccaattaallyyssttuunnddeerr vviissiibbllee--lliigghhtt iirrrraaddiiaattiioonn
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