Loading mechanism and double-site reaction mechanism of Cu on activated carbon for enhanced oxidation of CO from flue gas

• Carboxyl groups in anchoring Cu enhance the loading amount and dispersibility of Cu. • AC-supported Cu samples follow a Cu 2+ -Cu + double-site L-H mechanism. • Hydroxyl groups and Ce indirectly oxidize CO and enhance resistance to SO 2 and NO. To strengthen the CO oxidation activity of activated carbon for flue gas purification, AC was modified through acid treatment and metal loading. AC-supported Cu shows excellent catalytic oxidation activity compared with other metal-modified AC samples. To investigate the action modes of Cu loaded on activated carbon and the mechanism of CO oxidation, various samples were characterized by XRD, N 2 O titration, SEM, N 2 physisorption, TPD, H 2 -TPR, XPS, in situ DRIFTS and EPR. The results show that oxygen-containing functional groups increase the loading amount and dispersion of Cu. Moreover, Cu species strongly bound to oxygen-containing functional groups are the main contributors to CO oxidation. The roles of oxygen-containing functional groups are further revealed: carboxyl groups are the anchoring sites of Cu, and hydroxyl groups supply oxygen to restore the active structure. Similarly, Ce indirectly promote the oxidation activity of CO by re-oxidizing Cu + to Cu 2+ , which accelerates the catalytic cycle. The reaction mechanism on AC-supported Cu samples has been proposed to follow the double-site Langmuir–Hinshelwood mechanism, with Cu 2+ as oxidation sites, Cu + as adsorption sites and the formation of oxygen vacancies on Cu + during the reaction. AC-Cu performs the highest oxidation activity at a proportion of Cu + of 0.5–0.6. SO 2 causes irreversible chemical poisoning to CO oxidation, while NO leads to reversible poisoning due to competitive adsorption with CO. The novel AC-supported Cu catalyst with Ce improves the resistance against SO 2 and NO, and the reason is explained. These findings provide theoretical guidance for the preparation and application of metal-modified activated carbon.