SO ₂ Binding on CuO during Chemical Looping with Oxygen Uncoupling: Effects of Flue Gas Components and Surface Oxygen Vacancy

CuO is a primary component of Cu-based oxygen carriers used in chemical looping with oxygen uncoupling (CLOU). In this study, density functional theory and ab initio thermodynamics calculations were performed to investigate how flue gas components and oxygen vacancies affect the binding of SO2 on CuO. SO2 forms a sulfite-like species on the CuO(111) surface. Among the flue gas components, water seems to have a favorable effect on the SO2 binding. SO2 binds more strongly on the oxygen-vacant surface. While the sulfite-like structure on the surface is not stable on the fully oxidized CuO at high temperatures representing CLOU conditions, it is found to be stable on the surface with oxygen vacancies. Investigation of the oxygen release mechanism from CuO indicates that the presence of SO2 on the surface causes a slight decrease in the energy cost for the oxygen vacancy creation; therefore, it does not inhibit the release of oxygen from the oxygen carrier.