Lattice oxygen migration of iron-based oxygen carrier during chemical looping reaction process

Chemical looping combustion relies on high performance oxygen carriers (OCs). Iron-based OCs have excellent overall properties, but the disadvantage of low reduction reactivity limits their application prospects. Clarification of oxygen transfer pathways and bulk phase properties is essential to improve oxygen transfer rates and increase the reactivity of OCs. High-resolution transmission electron microscopy, electron energy loss spectroscopy and X-ray photoelectron spectroscopy had been used to study the lattice oxygen transport properties, the Fe and O elemental contents and Fe elemental valence changes at different positions on the radial surface of Fe2O3 OC, as well as the related elemental compositions, atomic valence and surface energy distribution on the surface of the OC during the reduction process of OC. The results show that during the reduction process, the active components at different locations of the OC are simultaneously reduced and lattice oxygen is released. Both internal and external lattice oxygen are involved in the reaction. Besides, reaction interface is believed to be fixed at a OC surface. This study reveals the migration direction of the reduction interface and the mechanism of oxygen release in the bulk phase, and would provide a theoretical basis for the structural design of Fe-based OCs.