A theoretical study on structures of neutral (CuS)n (n=1-10) clusters and their interaction with Hg0

In recent years, CuS materials, especially nanomaterials, were found to have outstanding performance in mercury removal, and were taken as a promising alternative to the traditional mercury sorbents. In this work the mercury removal mechanism of CuS nanomaterials was investigated theoretically. Firstly, the structures of (CuS)(n) (n = 1-10) clusters were revised, and quite a few new ground state structures were located. Then the adsorption of Hg on (CuS)(n) clusters and on graphene supported (CuS)(n) clusters were studied. Results show that the adsorptions of Hg-0 on clusters are stronger than those on the clean CuS (001) surfaces, which agrees with the fact that CuS nanoparticles perform better in mercury removal than CuS bulk. Furthermore, the mercury removal ability of (CuS)(n) cannot be destroyed by the introduction of graphene, in line with the excellent performance of CuS-modified carbon materials reported in experimental studies. It is found that Hg is adsorbed chemically on (CuS)(n) cluster, acting as Cu to expand the Cu-core, and further stabilized by the bridging S atoms. The specialty of CuS in various metal sulfides on mercury removal was discussed, and it is the mix-valence Cu1+/Cu2+ and S1-/S2- in CuS that cause the coexistence of Hg-S and Hg-Cu interaction.

Automated summary

This study theoretically investigates the mercury removal mechanism of CuS nanomaterials and finds that their excellent removal performance is related to strong adsorption of Hg-0 on the clusters. The introduction of graphene does not destroy the removal ability of CuS nanomaterials, consistent with experimental studies. The study reveals that Hg chemically adsorbs on (CuS)(n) clusters, expanding the Cu-core and further stabilized by bridging S atoms.