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

Abstract

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 E¹_2g and A_1g 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.