Kinetics and mechanism of enhanced photocatalytic activity employing ZnS nanospheres/graphene-like C3N4

In this work, a novel photocatalyst ZnS nanospheres/graphene-like g-C3N4 (ZnS/GL-C3N4) nanocomposite was synthesized by a simple agitation method. Two-dimensional (2D) nanomaterial GL-C3N4, synthesized by thermal exfoliation from g-C3N4, showed large surface area and manifested efficient photocatalytic activity than bulk g-C3N4. ZnS nanospheres were well anchored and covered on the surface of GL-C3N4 nanosheets and a synergetic effect between the ZnS and GL-C3N4 could highly contributed to improvement of the light adsorption capability of GL-C3N4 as well as increasement of the separation efficiency of photon-generated e(-)-h(+) pairs, therefore, enhancing its photocatalytic performance under the illumination of visible light. Methyl orange (MO, a kind of organic dyes which is hard to be degraded by pure C3N4) and tetracycline (TC, a representative broad-spectrum colorless antibiotic agent) were chosen as the targets of pollutants for degradation in this study. The optimum photocatalytic MO degradation of ZnS/GL-C3N4 (50%) was almost 3.48 and 12.4 times higher than that of pure ZnS and GL-C3N4, respectively. 91% TC was photodegraded in the presence of ZnS/GL-C3N4 (50%) and higher than that of GL-C3N4. Furthermore, kinetics and possible photocatalytic mechanism of MO degradation under visible light was proposed in detail. Except for the synergetic effect, the trapping experiments and ESR spectra demonstrated that not only O-2(center dot-) and holes, but also (OH)-O-center dot were active species playing an importing role in this system for effective degradation. Our research results open an easy pathway for developing highly efficiency photocatalyst. (C) 2017 Published by Elsevier B.V.