Electrochemical exfoliation of MoS2 nanosheets with ultrahigh stability for lead adsorption

Lead (Pb 2+ ) is one of the most common and harmful heavy metal contaminants that cause water pollution worldwide. Two-dimensional MoS 2 nanomaterials have been reported to possess high capability for the removal of Pb 2+ , whereas the long-term application is limited by the tendency of oxidative decomposition. In this study, we electrochemically exfoliated MoS 2 (E-MoS 2 ) to investigate the adsorption performance and chemical stability as compared with other commonly-studied MoS 2 nanomaterials. The results revealed that E-MoS 2 displayed a Pb 2+ removal capacity of 357.2 mg/g, much higher than that of hydrothermally synthesized MoS 2 although they both are pure 2H phase. More importantly, the E-MoS 2 nanosheets exhibited super stable performance, with the Pb 2+ adsorption barely interfered after 15 days of aging in air, while the 1T-dominated MoS 2 samples decreased by up to 50 %. The unchanged performance of E-MoS 2 derived from the properties of oxidation resistance , whereas other MoS 2 nanomaterials could be oxidized to soluble Mo(VI). Investigations for the mechanisms by XPS, XRD and TEM characterizations suggested that the removal of Pb 2+ was achieved by binding on the surface of E-MoS 2 , without any contribution of PbMoO 4 precipitates like that in other MoS 2 nanomaterials. Relatively high adsorption capacity and excellent chemical stability render E-MoS 2 practical significance for the long-term application in water treatment.