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.