BACKGROUND: The photocatalytic activity of a pristine semiconductor is unsatisfactory due to the rapid recombination of photogenerated electrons and holes. Constructing composite photocatalysts has proven to be an effective method to suppress electron-hole recombination. The composites composed of two materials usually are synthesized through a two-step process. However, in this work, a simple one-step solvothermal method employing an homogeneous reaction system was adopted to synthesize a tungsten trioxide (WO 3 )-copper sulfide (CuS) nanosheet heterojunction with enhanced photocatalytic properties.
RESULTS: The formation of the WO 3 -CuS heterojunction was confirmed by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray and X-ray photoelectron spectroscopy analysis. The composites showed improved visible light harvesting ability, and enhanced photoelectric and photocatalytic properties compared with pure WO 3 . The optimized composite displayed a photocurrent almost five-fold greater than the sum of the photocurrents of WO 3 and CuS, and had superior performance for methylene blue (MB) degradation and hexavalent chromium [Cr(VI)] reduction. The MB degradation and Cr(VI) reduction efficiencies were both improved when they co-existed in the photocatalytic system. Interferential ions Cl − and NO 3− were much less effective in the degradation of MB than in the reduction of Cr(VI). CONCLUSIONS: Improved photocatalytic activity was achieved after coupling CuS with WO 3 , due to the enhanced visible light absorption and efficient electron-hole separation. Photogenerated holes were found to be the dominant reactive species in the MB photodegradation process. A synergistic effect existed between MB degradation and Cr(VI) reduction. Interferential ions Cl − and NO 3 − had much greater effect on Cr(VI) reduction than MB degradation.
Evaluation of the interference effects of ionsInorganic ions, such as chloride (Cl − ) and nitrate (NO 3 − ) ions, are found widely in natural water sources, and may interfere with the photocatalysis process. Ion interference experiments were conducted herein to investigate the photocatalytic activity of WO 3 -CuS in the presence of Cl − or NO 3 − ions. As shown in Fig. 10, Cl − and NO 3 − had little effect on MB degradation, whereas they J Chem Technol Biotechnol 2020; 95: 665-674