Rational design of metal sulfide based on quantitative relationship between its mercury adsorption capacity and the abundance of Under-Coordinated sulfur

Abstract

Fundamental barriers remaining yet impeding the rational design of metal sulfide (MS)-based sorbents for efficient elemental mercury (Hg0) capture are the lack of a quantitative understanding between the amount of the most active ligands (i.e., under-coordinated sulfur) and the Hg0 removal performance of MS. The intrinsic diversity and complexity of the sulfur species, which make it difficult to exclusively control the abundance of under-coordinated sulfur in MS while keeping its valence generally unchanged, is the primary challenge to be overcome. A dedicated tin sulfide (SnSx) nanosheet was thus adopted to this end by adjusting its size and the exposure ratio of edge mono-sulfide. Unlike other methods used for the construction of under-coordinated sulfur, e.g., doping heteroatoms, introducing defects, straining lattice, etc., this novel method achieved the independent adjustment of the abundance of under-coordinated sulfur in MS. A linear relationship was hence established, indicating that, with the molar ratio of under-coordinated sulfur in SnSx increased by 1 %, its Hg0 capture capacity was enhanced by ∼ 0.9 mg g−1. This quantitative relationship was further taken as valuable guidance serving the Hg0 capture performance improvement of SnSx with the co-consideration of its textural properties. The applicability of this quantitative relationship may be further extended across the MS community, saving the time spending in experiments and stepping towards the rational design of MS-based Hg0 sorbents.