Spatial evolution characteristics of active components of copper-iron based oxygen carrier in chemical looping combustion

Abstract

Reactivity of oxygen carriers (OCs) is a key issue in chemical looping technology. Exploring spatial evolution characteristics of active components and lattice oxygen migration during reduction reaction is of great importance in improving the reactivity of OCs. In this study, thermogravimetric analyzer (TGA) is used to control the reduction degree of OCs. Oxygen migration to the surface of CuFe2O4 (100) and CuO (111) is studied based on density functional theory (DFT). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are used to investigate phase change and valence evolution of active components of the oxygen carriers. The results show that the ratios of lattice oxygen, chemical adsorbed oxygen and physical adsorbed oxygen at three points are very close in OCfresh. As the reduction reaction progresses, lattice oxygen is gradually consumed and the content of Cu0 and Fe2+ is increased. The closer to the edge point, the more lattice oxygen is consumed and the larger ratio of Cu0 and Fe2+. Moreover, there is no Fe0 in sample OC6.24% or OC9.19%, which is caused by the rapid migration and replenishment of lattice oxygen. The calculation results show that bulk oxygen migration to the surfaces of the OCs is exothermic and has a certain energy barrier.