Preparation And Visible-Light Photocatalytic Activities Of ZnS/CuS Composite Material

In recent years, Semiconductor photocatalysis has attracted a wide attention for its outstanding performance on environmental purification. The technology can not only degrade organic dyes, but also kill harmful microorganisms such as bacteria and viruses. However, the application of conventional semiconductor photocatalysts is hampered by the only responsivity in the UV range and high recombination rate between the photogenerated electron and hole pairs. Hence, to develop photocatalytic semiconductor materials with visible-light response and low recombination rate between carriers has important scientific significance and applicant value.Semiconductor composite technology is an effective method to enhance the efficiency of photocatalytic degradation reactions by effectively separating the photogenic charge carriers or changing the band gap of semiconductors. This paper systematically studied the preparation and photocatalytic properties of ZnS/CuS composite photocatalysts. The photocatalytic activities of these photocatalysts are evaluated using the photodegradation of methylene blue and the inactivation of E.coli under the irradiation of Xenon light???420 nm?.ZnS/CuS composite photocatalysts with good dispersion were prepared using simple coprecipitation method and characterized by the XRD, TEM, UV-Vis and XPS. Results found that ZnS/CuS composite photocatalysts were composed of cubic ?-ZnS and hexagonal CuS. And the size of Zn_0.3Cu_0.7S nanoparticles was smaller than pure CuS nanoparticles. Meanwhile, compared with the pure ZnS product, ZnS/CuS composite photocatalysts have a good responsivity in the vsible light range.The experiments of photocatalytic degredation of samples to methylene blue found that Zn_0.3Cu_0.7S composite showed highest visible light catalysis activity with H₂O₂ as the co-catalysis, for the degradationrate of MB exceed 99%.In the same conditions the degradation rates of MB catalysed by ZnS and CuS respectively were 15.2% and 92.6%. the degradation of ZnS/CuS composites against MB assumed first-order kineticsand L-H model. After five cyclic utilizations, the degradation of MB exceeded 95%, which indicated that Zn_0.3Cu_0.7S showed good cycle stability.The results of the photocatalytic antibacterial activity of Zn_0.3Cu_0.7S composite against E.coli showed that Zn_0.3Cu_0.7S composite with concentration of 200 mg/L could inactivate 7-log of E.coli under visible lightfor 90 min. Inthe same condition, pure ZnS almost could not make E.coli inactive, and pure CuS only inactivate about 5-log of E.coli. Hance, among which, Zn_0.3Cu_0.7S composite exhibited the best antibacterial activity. Here h+ and H₂O₂ resulted in the bacterial inactivation efficiency of Zn_0.3Cu_0.7S composite. And H₂O₂ was derived from the photogenenrated electrons in conduction band of CuS.