Synthesis of MoS2 incorporated iron-zinc oxide nanocomposites and investigation of their photoluminescence and photocatalytic properties

Abstract

Abstract In the first part of investigation, a facile one-step ultrasound driven exfoliation technique has been demonstrated for the synthesis of few-layer MoS2 nanosheets from bulk MoS2 powder with a yield of almost 60%. Structural, morphological and optical characterizations of non-ultrasonicated and ultrasonicated MoS2 are carried out in nominally identical conditions to make a direct comparison between their properties. The Rietveld refined powder X-ray diffraction (XRD) patterns elucidate the semiconducting 2H phase of MoS2 nanosheets without any structural deformation caused by ultrasonication. The field emission scanning electron microscopy (FESEM) imaging ensures the successful formation of ultrathin few-layer MoS2 nanosheets having thickness in the range of 8-15 nm. The photoluminescence (PL) spectroscopy reveals the enhanced potential of ultrasonicated MoS2 to suppress photogenerated carrier recombination phenomenon. The ultrasonicated MoS2 manifests 48% higher reaction rate in photocatalytic degradation of Rhodamine B (RhB) dye under visible light irradiation as compared to non-ultrasonicated MoS2. The outcome suggests that this MoS2 nanosheets synthesized by ultrasound assisted exfoliation technique may further lead to engineering heterogeneous structures of different photocatalysts having promising potential for numerous applications. Inspired by the aforementioned improvements, in the second part of this investigation MoS2 incorporated α-Fe2O3/ZnO nanocomposites have been synthesized by adapting a facile hydrothermal reaction technique at low temperatures. The effect of incorporating few-layer MoS2 nanosheets on the visible-light driven photocatalytic performance of photocatalyst nanocomposites has been demonstrated. Structural, morphological and optical characteristics of the as-synthesized nanomaterials are comprehensively investigated and analyzed by performing Rietveld refinement of powder XRD patterns, FESEM imaging and UV-visible spectroscopic analysis, respectively. The PL spectra of the as-prepared nanocomposites elucidate that the recombination of photogenerated electron-hole pairs is highly mitigated due to incorporation of MoS2 nanosheets. Notably, the ultrasonicated MoS2 incorporated α-Fe2O3/ZnO nanocomposite manifests 91% efficiency in degradation of RhB dye under visible light which is considerably higher as compared to non-ultrasonicated MoS2 incorporated α-Fe2O3/ZnO as well as α-Fe2O3/ZnO nanocomposites. The as-synthesized ultrasonicated MoS2 incorporated α-Fe2O3/ZnO nanocomposite has also produced a noticeably larger amount of hydrogen gas by photocatalytic water splitting in comparison with non-ultrasonicated MoS2 incorporated α-Fe2O3/ZnO, α-Fe2O3/ZnO nanocomposites and commercially available Degussa P25 titania nanoparticles. This indicates the promising potential of the incorporation of ultrasonicated MoS2 with α-Fe2O3/ZnO nanocomposite for economical and carbon-free solar hydrogen generation. The substantial increase in the photocatalytic efficiency of α-Fe2O3/ZnO after incorporation of ultrasonicated MoS2 can be attributed to its favorable band structure, large surface to volume ratio, effective segregation and migration of photogenerated electron-hole pairs at the interface of heterojunction and the plethora of exposed active edge sites provided by few-layer MoS2 nanosheets.