Mechanistic study of the effect of oxygen vacancy and sulfur poisoning on the reaction of copper ferrite spinel with CO during chemical-looping combustion

Abstract The surface structure has a great influence on the chemistry property and performance of oxygen carrier used for chemical-looping combustion. Based on density functional theory and periodic structure model, the effect of oxygen vacancy and sulfur poisoning on the reaction of copper ferrite spinel with CO during chemical-looping combustion was systematically studied. The results show that Cu–O2 bridging site shows better activity towards CO adsorption on the O-defective and sulfur-poisoned copper ferrite surfaces. The adsorption energies of CO follow the order of Eads (perfect surface) > Eads (sulfur-poisoned surface) > Eads (O-defective surface). The energy barriers of CO oxidation over different surfaces are in the order of O-defective surface (Ea = 22.68 kJ/mol) > sulfur-poisoned surface (Ea = 14.19 kJ/mol) > perfect surface (Ea = 4.85 kJ/mol). The oxygen vacancy and sulfur poisoning not only weaken the reactivity towards CO adsorption, but also have a disadvantageous impact on the CO oxidation process. For the sulfur-poisoned surface, the COS formation is kinetically unfavorable as compared to CO oxidation due to the higher energy barrier (27.13 kJ/mol).