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 Sx2- 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.
Keywords: controllable disorder; copper sulfide; crystal structure; mercury; thermal stability.