Lattice oxygen migration-dependent behaviors in CO chemical looping combustion over well-defined Cu₂O

Chemical looping combustion (CLC) is a promising technology for efficient CO₂ capture. However, the intrinsic relationship between lattice oxygen migration and the cycling stability of oxygen carriers (OCs) remains insufficiently understood. In this study, we systematically investigated the structural evolution of Cu₂O model OCs with well-defined morphologies, emphasizing the critical role of lattice oxygen migration in governing their cycling stability. Carbon monoxide (CO) was used as a probe molecule to induce the reduction of Cu₂O, while oxygen (O₂) facilitated its oxidation, thereby completing the CLC cycles. Cu₂O in cubic and dodecahedral forms, which have closed surfaces, exhibit incongruent inward and outward lattice oxygen migration, triggering irreversible structural changes that ultimately result in ineffective cycles. In contrast, octahedral Cu₂O, possessing an open surface and one-coordinate unsaturated Cu atoms, facilitates both CO oxidation and O₂ activation. This open-surface configuration enables congruent lattice oxygen migration during redox cycling, thereby maintaining structural integrity and catalytic activity over ten consecutive cycles at 200 °C. These findings reveal a positive feedback mechanism between lattice oxygen migration and structural stabilization, providing fundamental insights into the origin of the superior cycling stability of well-defined Cu₂O model OCs in CLC.