Synergistic Role of Short-Chain Sulfur and Single-Atom Catalysts for Low-Temperature Mercury Removal in Post-Combustion CO ₂ Capture

Efficient mercury (Hg0) removal under CO2 capture conditions (∼30 °C) remains a critical challenge for ensuring the long-term safe operation of post-combustion carbon capture, utilization, and storage (CCUS) system. Herein, a series of short-chain sulfur-modified single-atom catalysts (Fe, Ni, and Cu) supported on carbon nanospheres (CNs) were developed to achieve low-temperature Hg0 removal. Among them, Fe-CN exhibits the highest activity, maintaining over 70% Hg0 removal efficiency within 2 h through oxidation-escape-dominated way, with HgO as the main product. Appropriate SO2 heat treatment will introduce some short-chain sulfur and generate Fe–S bonds, which transform Hg0 removal from the oxidation-escape to adsorption-dominated way, yielding stable HgS. Fe-CN-3000S achieves an optimal average Hg0 removal efficiency of 86.0% within 2 h, with an Hg0 adsorption ratio of 54.8%. The synergy between Fe single-atom (Fe–N4)/C═O sites, short-chain sulfur, and Fe–S enhances the activation of Hg0 and O2, enabling efficient and stable Hg0 capture under CO2 capture-relevant conditions. This study provides insights into the cooperative mechanism of catalytic oxidation and sulfur-assisted adsorption, offering guidance for Hg0 control in CCUS processes.