(654f) A DFT Study of so2 Binding on CuMn2O4 Oxygen Carrier for Chemical Looping with Oxygen Uncoupling

Chemical looping with oxygen uncoupling (CLOU) is a variant of chemical looping combustion (CLC), which is one of the promising carbon capture and storage technologies. In CLOU, the fuel reacts with gaseous O₂ released by a metal oxide, called the oxygen carrier, at suitable temperatures and oxygen partial pressures, unlike the CLC, where only the lattice oxygen reacts with the fuel. The kinetically favored gas-solid reaction makes CLOU more effective than CLC for solid fuels like coal and biomass. As a CLOU oxygen carrier, bi-metallic Cu-Mn has demonstrated high fuel combustion efficiency for both solid and gaseous fuels. However, sulfur compounds of the fuel might poison the oxygen carrier by reacting with the metal oxide; thus, reducing its reactivity. Authors have recently conducted an experimental study on the effects of SO₂ on this oxide’s performance. However, first principle based theoretical studies to examine the interaction of SO₂ on this oxygen carrier surface is scarce in literature.

Therefore, the purpose of this study is to investigate SO₂ binding on the CuMn₂O₄ (100) surface employing density functional theory (DFT) and ab initio thermodynamics. SO₂ binding was studied at various possible sites with different SO₂ molecular orientations. All DFT calculations were performed using the Vienna Ab Initio Simulation Package (VASP). The optimized configurations obtained from the calculations were examined to identify active binding sites and stable adsorption geometries of SO₂. Finally, ab initio thermodynamic calculations were performed to relate the DFT-obtained results to experimental reaction conditions. It was found that SO₂ binding on the surface is energetically favorable. Furthermore, the thermodynamic calculations show that the SO₂-bound CuMn₂O₄(100) surface is thermodynamically stable at the CLOU operating conditions, which is consistent with the authors’ previous experimental observations.