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

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).

Automated summary

The oxygen vacancy and sulfur poisoning significantly affect the CO adsorption and oxidation processes on the copper ferrite surface, with static sulfur and dynamic sulfur showing different reaction mechanisms in CO oxidation.