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

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)\xa0>\xa0Eads (sulfur-poisoned surface)\xa0>\xa0Eads (O-defective surface). The energy barriers of CO oxidation over different surfaces are in the order of O-defective surface (Ea\xa0=\xa022.68\xa0kJ/mol)\xa0>\xa0sulfur-poisoned surface (Ea\xa0=\xa014.19\xa0kJ/mol)\xa0>\xa0perfect surface (Ea\xa0=\xa04.85\xa0kJ/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\xa0kJ/mol).