Under-Coordinated Selenide Enriched Amorphous Cobalt Selenide Prepared Under Ambient Conditions for Highly Efficient Immobilization of Gaseous Elemental Mercury

The limited adsorption capacity of commercialized sorbents towards elemental mercury (Hg0) remains a major challenge facing their extensive applications under the regulation of the Minamata Convention. Metal selenides were recently found to be promising alternatives to commercialized sorbents for capturing Hg0 from industrial flue gas due to the high affinity between Hg0 and selenide. In metal selenides, under-coordinated selenide sites play critical roles in oxidation and subsequent immobilization of Hg0, while there is still no simple way to increase the abundance of under-coordinated selenide in metal selenides under ambient conditions. In this work, an effective and facile precipitation pathway was proposed to prepare amorphous cobalt selenide (a-CoSe2) with under-coordinated selenide enriched surface under ambient conditions. The a-CoSe2 as synthesized achieved outstanding Hg0 uptake capacity and adsorption rate (534.2 mg g-1 and 483.1 μg g-1 min-1), far surpassing those of crystalline cobalt selenide (c-CoSe2) by magnitudes. The characteristic results demonstrated that the under-coordinated selenide enriched nature of a-CoSe2 is the principal reason causing the significant performance improvement, which is fully in line with our hypothesis and purpose. This work not only proposes a potential sorbent for efficient Hg0 sequestration from industrial flue gas, but also inspires the further development of synthesis strategies for amorphous materials.