Development of high-performance MoS2 with nanofoam architecture for gaseous elemental mercury sequestration: The key role of edge sulfur vacancy

Abstract

Two-dimensional MoS₂ materials exhibit considerable promise for elemental mercury adsorption. However, challenges persist to identify the intrinsic active site in MoS₂ adsorbent for Hg⁰ immobilization. In this work, three MoS₂ samples with different sulfur vacancy concentrations and sulfur vacancy species, namely few-layer MoS₂, multi-layer MoS₂, and edge-rich MoS₂, were engineered to confirm the pivotal active ligand for Hg⁰ capture performance. Theoretical calculation combined with multiple characterizations confirm the critical role of edge sulfur vacancy for Hg⁰ sequestration. MoS₂ with rich edge sulfur vacancies demonstrates commendable Hg⁰ adsorption performance at elevated temperatures, achieving an average adsorption rate of 7.07 μg/g/min, higher than few-layer MoS₂ with rich in-plane sulfur vacancies. The Hg⁰ adsorption capacity of edge-rich MoS₂ achieves 27.62 mg/g at a breakthrough threshold of 25 %, surpassing the capabilities of most reported metal sulfide adsorbents. Moreover, Hg⁰ is peculiarly prone to combine with unsaturated Mo ligand on the edge sulfur vacancy to form Hg-Mo amalgam, then reacts with neighboring sulfide ligand to form stable HgS. Besides, high thermal stability of active sulfide ligand on the edge sulfur vacancy endows the edge-rich MoS₂ with a wide temperature range. This research offers a new insight on the rational adsorbent design of metal sulfides for mercury pollution control.