Amorphous Cobalt Selenide Nanoparticles with a Coral-like Structure for the Removal of Gaseous Elemental Mercury

Mercury in the atmosphere is highly toxic, posing significant risks to human health and causing ecological damage. Nanostructured amorphous cobalt selenide (a-CoSe2) with a coral-like morphology assembled from interconnected nanospheres was successfully synthesized via a liquid-phase aging method at room temperature. This unique nanoarchitecture endows the material with a high specific surface area and abundant adsorption sites, thereby enhancing its immobilization capability toward Hg0. This approach contributes to breaking the mercury cycle and provides an innovative solution for controlling mercury pollution in flue gas. In this study, a-CoSe2 achieved nearly 100% Hg0 removal efficiency at temperatures ranging from 40–120 °C. The equilibrium adsorption capacity of the adsorbent reached 79.81 mg·g–1, outperforming most commercially available adsorbents. The mercury capture mechanism of a-CoSe2 was elucidated through X-ray photoelectron spectroscopy (XPS) analysis and density functional theory (DFT) calculations. Due to the electron-trapping characteristics of under-coordinated selenium, it acts as the primary active site during Hg0 removal, reacting to form stable HgSe species. The nanoscale design of a-CoSe2 enables its outstanding performance in Hg0 removal, offering a high-performance alternative to conventional adsorbents. This work also provides a reference for synthesis strategies of amorphous materials.