Sustainable Synthesis of Mos2 and Its Application for Organic Molecule Removal

Molybdenum disulfide (MoS₂) is a low-cost n-type semiconductor, characteristic of a 1.2–1.9 eV band gap and a versatile structure that enables multifunctional properties, which are crucial for various applications [1]. For instance, the photocatalytic/electrochemical properties of MoS2 can be effectively exploited for green hydrogen production or the degradation of organic wastewater pollutants [2]. Typically, hydrothermal synthesis of MoS2 involves using soluble sources of Mo (VI) and sulfur at a relatively high temperature and for extended duration in a synthetic organic-based surface modification and reducing medium [1]. In addition, the mentioned conditions are not energetically efficient and also may lead to emissions of toxic reagents or its decomposition products. Since most of the proposed synthetic pathways are based on low yield production in a toxic reagent’s environment, a greener approach to obtaining MoS2 is necessary for environmental sustainability. In addition, the aim of this research was to develop a sustainable approach to synthesize MoS2 and to apply it for removal of organic molecules. For this reason, ascorbic acid was employed as a green reducing agent, which simultaneously was also used as a green surfactant. MoS2 ­based samples were synthesized in hydrothermal environment at a temperature of 180-220 °C for 8-12 h. Chemical and morphological composition was determined by analysis methods of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller method. The particle size distribution of the samples was also measured, and the band gap of the synthesis products was determined by UV-visible spectroscopy. Lastly, the samples were applied to remove methylene blue and rhodamine B by adsorption and photocatalytic degradation. The findings of this research have revealed that under the applied hydrothermal conditions, defect-rich 2H MoS₂ was formed, with the band gap of 1.55-2.8 eV, in size of 264-592 nm. The results of organic molecules removal revealed that synthetic powder functioned primarily as an adsorbent rather than a photocatalytic material. During the first 10 min of experiment, MoS2 samples have adsorbed 58 % of methylene blue and 45 % of rhodamine B. During 100 min of total experiment, the final values of removal efficiency were 99% and 90.5% for methylene blue and rhodamine B respectively. In addition, the proposed synthesis approach offers a sustainable method for producing MoS₂ with promising properties for removal of organic molecules.