In-situ low-temperature sulfur CVD on metal sulfides with SO to realize self-sustained adsorption of mercury.

Capturing gaseous mercury (Hg) from sulfur dioxide (SO)-containing flue gases remains a common yet persistently challenge. Here we introduce a low-temperature sulfur chemical vapor deposition (S-CVD) technique that effectively converts SO, with intermittently introduced HS, into deposited sulfur (S) on metal sulfides (MS), facilitating self-sustained adsorption of Hg. ZnS, as a representative MS model, undergoes a decrease in the coordination number of Zn-S from 3.9 to 3.5 after S deposition, accompanied by the generation of unsaturated-coordinated polysulfide species (S, named S) with significantly enhanced Hg adsorption performance. Surprisingly, the adsorption product, HgS (ZnS@HgS), can serve as a fresh interface for the activation of S to S through the S-CVD method, thereby achieving a self-sustained Hg adsorption capacity exceeding 300 mg g without saturation limitations. Theoretical calculations substantiate the self-sustained adsorption mechanism that S ring on both ZnS and ZnS@HgS can be activated to chemical bond S chain, exhibiting a stronger Hg adsorption energy than pristine ones. Importantly, this S-CVD strategy is applicable to the in-situ activation of synthetic or natural MS containing chalcophile metal elements for Hg removal and also holds potential applications for various purposes requiring MS adsorbents.