In-situ low-temperature sulfur CVD on metal sulfides with SO2 to realize self-sustained adsorption of mercury

Abstract Capturing gaseous mercury (Hg 0 ) from sulfur dioxide (SO 2 )-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 2 , with intermittently introduced H 2 S, into deposited sulfur (S d 0 ) on metal sulfides (MS), facilitating self-sustained adsorption of Hg 0 . ZnS, as a representative MS model, undergoes a decrease in the coordination number of Zn–S from 3.9 to 3.5 after S d 0 deposition, accompanied by the generation of unsaturated-coordinated polysulfide species (S n 2– , named S d * ) with significantly enhanced Hg 0 adsorption performance. Surprisingly, the adsorption product, HgS (ZnS@HgS), can serve as a fresh interface for the activation of S d 0 to S d * through the S-CVD method, thereby achieving a self-sustained Hg 0 adsorption capacity exceeding 300 mg g −1 without saturation limitations. Theoretical calculations substantiate the self-sustained adsorption mechanism that S 8 ring on both ZnS and ZnS@HgS can be activated to chemical bond S 4 chain, exhibiting a stronger Hg 0 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 0 removal and also holds potential applications for various purposes requiring MS adsorbents.