Cu2ZnSnS4 (CZTS)-ZnO: A noble metal-free hybrid Z-scheme photocatalyst for enhanced solar-spectrum photocatalytic conversion of CO2 to CH4

Development of photocatalytic materials for achieving the aspects of cost-effectiveness, improved performance and high stability is a subject of enormous interest among the photocatalysis research society. With the aim of achieving above mentioned features, herein we report a noble metal free, solar-light active, efficient and highly stable hybrid Cu2ZnSnS4 (CZTS)-ZnO photocatalyst, synthesized by a simple two-step process. The morphological, crystalline, band alignment, optical and electronic properties of the prepared samples are intensively investigated. Photocatalytic performance is evaluated by measuring, under the simulated solar light, the ability of the photocatalyst to convert CO2 into hydrocarbon fuels, primarily CH4. Our optimum CZTS-ZnO photocatalyst sample exhibits a CH4 yield of 138.90 ppm g(-1) h(-1), a factor of approximate to 31 times greater than the un-sensitized ZnO nanorods, and approximate to 22 times greater than the CZTS nanoparticles; with excellent stability yielding similar CH4 production up to five test-cycles. The enhanced performance of the hybrid, noble metal-free photocatalyst can be attributed to improved light absorption and efficient separation of the photogenerated charge due to the Z-scheme heterojunction interface.