DFT Study of SO 2 Binding on Cu 2 O during Chemical Looping with Oxygen Uncoupling: Effects of Flue Gas Components and Surface Oxygen Vacancy

In this study, binding of SO 2 on the Cu 2 O(111) surface was investigated by employing DFT and ab initio thermodynamics to explore the possible interactions of SO 2 with copper-based oxygen carriers in the chemical looping with oxygen uncoupling (CLOU) process. SO 2 forms a sulfite-like species on the Cu 2 O(111) surface. The presence of the flue gas components, H 2 O and CO 2, and SO 2 adsorbed on the surface lowers the SO 2 binding energy compared to that on the clean surface. In the presence of an oxygen vacancy, the SO 2 molecule binds to the Cu 2 O(111) surface by occupying the vacant site with one of its oxygen atoms with a higher binding energy compared to the surface without any vacancy, indicating a positive effect of the oxygen vacancy on SO 2 binding. Finally, ab initio thermodynamics calculations indicate that SO 2 on the Cu 2 O(111) surface is thermodynamically unstable within the CLOU operating temperature range of 800–1000 °C.