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 (Hg 0 ) 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 Hg 0 from industrial flue gas due to the high affinity between Hg 0 and selenide. In metal selenides, under-coordinated selenide sites play critical roles in oxidation and subsequent immobilization of Hg 0 , 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-CoSe 2 ) with under-coordinated selenide enriched surface under ambient conditions. The a-CoSe 2 as synthesized achieved outstanding Hg 0 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-CoSe 2 ) by magnitudes. The characteristic results demonstrated that the under-coordinated selenide enriched nature of a-CoSe 2 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 Hg 0 sequestration from industrial flue gas but also inspires the further development of synthesis strategies for amorphous materials.