Investigation of visible light photocatalytic degradation of organic dyes by MoS2 nanosheets synthesized by different routes

In this work, we have synthesized MoS2 nanosheets (NSs) through hydrothermal as well as liquid-phase sonication methods and studied their ability to degrade organic dyes, methyl red (MR) and methylene blue (MB) under visible light irradiation. The as-synthesized photocatalysts have been characterized by powder X-ray diffraction, Raman Spectroscopy and transmission electron microscopy to confirm their structure and surface morphology. XRD patterns show that crystalline nature of MoS2 NSs prepared by hydrothermal method appears at 160°C for 15 h. In contrast, sharp and intense diffraction peaks appear for liquid exfoliation method even at room temperature, exhibiting better crystallinity of the as-prepared NSs. The difference (∆) of ~25 cm−1 between E12g and A1g modes of Raman spectra indicates formation of 5–6 layers of MoS2 from both the synthesis routes. UV–Vis spectroscopy has been utilized to study the degradation of dyes by MoS2 NSs as catalyst. Hydrothermally assisted synthesis of MoS2 NSs exhibit lesser degradation efficiency with 58.92% for MR and 49.28% for MB, while exfoliation-assisted MoS2 NSs act as better photocatalyst with 63.40 and 62.40% degradation of MR and MB, respectively. Faster degradation rate for MR compared to MB has been attributed to the presence of lesser chromophoric sites in MR.