Electrochemical exfoliation of MoS2 nanosheets with ultrahigh stability for lead adsorption

Abstract

Lead (Pb2+) is one of the most common and harmful heavy metal contaminants that cause water pollution worldwide. Two-dimensional MoS2 nanomaterials have been reported to possess high capability for the removal of Pb2+, whereas the long-term application is limited by the tendency of oxidative decomposition. In this study, we electrochemically exfoliated MoS2 (E-MoS2) to investigate the adsorption performance and chemical stability as compared with other commonly-studied MoS2 nanomaterials. The results revealed that E-MoS2 displayed a Pb2+ removal capacity of 357.2 mg/g, much higher than that of hydrothermally synthesized MoS2 although they both are pure 2H phase. More importantly, the E-MoS2 nanosheets exhibited super stable performance, with the Pb2+ adsorption barely interfered after 15 days of aging in air, while the 1T-dominated MoS2 samples decreased by up to 50 %. The unchanged performance of E-MoS2 derived from the properties of oxidation resistance, whereas other MoS2 nanomaterials could be oxidized to soluble Mo(VI). Investigations for the mechanisms by XPS, XRD and TEM characterizations suggested that the removal of Pb2+ was achieved by binding on the surface of E-MoS2, without any contribution of PbMoO4 precipitates like that in other MoS2 nanomaterials. Relatively high adsorption capacity and excellent chemical stability render E-MoS2 practical significance for the long-term application in water treatment.