A WS2/sepiolite composite with highly dispersed WS2 nanosheets for photocatalytic wastewater treatment

Abstract

Two-dimensional tungsten disulfide (WS2) nanosheets with large specific surface energies usually suffer from serious aggregation, hindering their catalytic activity and potential applications. In this work, highly dispersed WS2 nanosheets were synthesized in a cost-effective way by employing sepiolite (Sep) nanofibers as the carrier via a hydrothermal treatment followed by calcination under H2/N2 atmosphere, and the mass fraction of the raw materials including ammonium metatungstate, thioacetamide, oxalate acid and sepiolite were determined as 29.3 wt%, 35.7 wt%, 25.0 wt% and 10.0 wt%, respectively. The dispersed WS2 nanosheets were uniformly grown on the Sep, as observed by an electron microscope. First principle calculations further revealed that the favorable bonding between the tungsten of WS2 [W(WS2)] and the oxygen of Sep [O(Sep)] at the WS2/sepiolite interface enables Sep a unique support, superior to other minerals for growing such a highly-dispersed ultrathin WS2 architecture. Compared with pure WS2, the as-prepared WS2/sepiolite composite exhibits about 7 times the specific surface area and 7.4 times the photocatalytic efficiency toward rhodamine B (RhB) degradation due to the better dispersion of WS2 nanosheets and synergetic effects of sepiolite. Besides, the radical trapping experiment indicates that photo-generated hole (h+) plays the leading role, while hydroxyl radical (·OH) and superoxide radical (·O2−) act as the assistants during photocatalysis. This work provides a novel strategy for the low-cost preparation of high-quality two-dimensional materials via assembly on mineral materials.