Abstract
Copper indium sulfide (CuInS(2)) exhibits strong visible light absorption and thus has the potential for good photocatalytic activity; however, rapid charge recombination limits its practical usage. An intriguing strategy to overcome this issue is to couple CuInS(2) with another semiconductor to form a heterojunction, which can improve the charge carrier separation and, hence, enhance the photocatalytic activity. In this study, photocatalysts comprising CuInS(2) with a secondary CuS phase (termed CuIn(x)S(y)) and CuIn(x)S(y) loaded with ZnS (termed ZnS@CuIn(x)S(y)) were synthesized via a microwave-assisted method. Structural and morphological characterization revealed that the ZnS@CuIn(x)S(y) photocatalyst comprised tetragonal CuInS(2) containing a secondary phase of hexagonal CuS, coupled with hexagonal ZnS. The effective band gap energy of CuIn(x)S(y) was widened from 2.23 to 2.71 as the ZnS loading increased from 0 to 30%. The coupling of CuIn(x)S(y) with ZnS leads to long-lived charge carriers and efficient visible-light harvesting properties, which in turn lead to a remarkably high activity for the photocatalytic degradation of brilliant green (95.6% in 5 h) and conversion of 4-nitrophenol to 4-nitrophenolate ions (95.4% in 5 h). The active species involved in these photocatalytic processes were evaluated using suitable trapping agents. Based on the obtained results, photocatalytic mechanisms are proposed that emphasize the importance of h(+), O(2)(•-), and OH(-) in photocatalytic processes using ZnS@CuIn(x)S(y).