Controllable Disordered Copper Sulfide with a Sulfur-Rich Interface for High-Performance Gaseous Elemental Mercury Capture

Abstract

Copper sulfide (CuS) has received increasing attention as a promising material in gaseous elemental mercury (Hg⁰) capture, yet how to enhance its activity at elevated temperature remains a great challenge for practical application. Herein, simultaneous improvement in the activity and thermal stability of CuS toward Hg⁰ capture was successfully achieved for the first time by controlling the crystal growth. CuS with a moderate crystallinity degree of 68.8% showed a disordered structure yet high thermal stability up to 180 °C. Such disordered CuS can maintain its Hg⁰ capture activity stable during longtime test at a wide temperature range from 60 to 180 °C and displayed strong resistance to SO₂ (6%) and H₂O (8%). The significant improvement can be attributed to the synergistic effect of a moderately crystalline nature and a unique sulfur-rich interface. Moderate crystallinity guarantees the thermal stability of CuS and the presence of abundant defects, in which copper vacancy enhances significantly the Hg⁰ capture activity. The sulfur-rich interface enables CuS to provide plentiful highly active S_<i>x</i>^2- sites for Hg⁰ adsorption. The interrelation between structure, reactivity, and thermal stability clarified in this work broadens the understanding toward Hg⁰ oxidation and adsorption over CuS and provides new insights into the rational design and engineering of advanced environmental materials.