Metallic 1T/1T′ phase TMD nanosheets with enhanced chemisorption sites for ultrahigh-efficiency lead removal

Abstract

Two-dimensional (2D) materials, as adsorbents, have garnered great attention in removing heavy metal ions (HMIs) from drinking water due to their extensive exposed adsorption sites. Nevertheless, there remains a paucity of experimental research to remarkably unlock their adsorption capabilities and fully elucidate their adsorption mechanisms. In this work, exceptional lead ion (Pb²⁺) (a common HMI) removal capacity (up to 758 mg g⁻¹) is achieved using our synthesized metallic 1T/1T′ phase 2D transition metal dichalcogenide (TMD, including MoS₂, WS₂, TaS₂, and TiS₂) nanosheets, which hold tremendous activated S chemisorption sites. The residual Pb²⁺ concentration can be reduced from 2 mg L⁻¹ to 2 μg L⁻¹ within 0.5 min, meeting the drinking water standards following World Health Organization guideline (Pb²⁺ concentrations <10 μg L⁻¹). Atomic-scale characterizations and calculations based on density functional theory unveil that Pb²⁺ bond to the top positions of transition metal atoms in a single-atom form through the formation of S-Pb bonds. Point-of-use (POU) devices fabricated by our reported metallic phase MoS₂ nanosheets exhibit treatment capacity of 55 L-water g⁻¹-adsorbent for feed Pb²⁺ concentration of 1 mg L⁻¹, which is 1-3 orders of magnitude higher than other 2D materials and commercial activated carbon.

2D materials are known for their ability to remove heavy metal ions from water, however their adsorption mechanism is not well-understood. Here the authors prepared metallic 1T/1T′ phase 2D transition metal dichalcogenide nanosheets, with activated sulfur sites, for rapid removal of Pb²⁺ ions.