Copper selenide anchored on Ti₃C₂ MXene via Lewis acidic etching route for efficient removal of gaseous elemental mercury

A fundamental obstacle that restricts the use of metal selenides for gaseous elemental mercury (Hg0) immobilization is the failure to take both the optimization of intrinsic structure favorable for Hg0 diffusion and adequate exposure of metal selenide towards Hg0 into consideration. In this work, a Ti3C2 MXene/Cu2Se sorbent for Hg0 sequestration was synthesized via a Lewis acid etching route combined with room-temperature selenization pathway. During this strategy, copper chloride plays a dual role, i.e., an etching agent for the Ti3C2 MXene synthesis and a precursor for Cu0 decoration. Cu2Se precursors (Cu0) were dispersedly and firmly pre-anchored on the substrate, effectively avoiding the agglomeration and warranting excellent dispersion of Cu2Se. Compared with pristine Cu2Se, Ti3C2 MXene/Cu2Se exhibits advantageous structural characteristics fully boosting Hg0 diffusion kinetics. Meanwhile, the enhanced dispersion of Cu2Se from the prefixation of Cu0 largely enhances the exposure and utilization of selenide. Consequently, Ti3C2 MXene/Cu2Se shows a Hg0 adsorption capacity of 147.64 mg g-1 , which is much higher than those of Cu2Se and most other metal selenides. Impressively, its uptake rate of 688.99 mu g g-1 min-1 is the highest record rate in metal selenides. Moreover, Ti3C2 MXene/Cu2Se still maintained outstanding Hg0 adsorption performance under relatively high reaction temperature with the shelter of Ti3C2 MXene. Typical fuel gas situations including coal combustion flue gas, smelting flue gas, natural gas have negligible influences on its Hg0 adsorption performance, indicating its extensive applicability and flexibility for actual industrial situations. This work also provides valuable hints for the trade-off of structural properties and ligands exposure to design Hg0 sorbents with satisfactory Hg0 sequestration performances.