Tailoring an Fe–O_v–Ce–Triggered Phase‐Reversible Oxygen Carrier for Intensified Chemical Looping CO₂ Splitting

ABSTRACT Advanced oxygen carrier plays a pivotal role in various chemical looping processes, such as CO₂ splitting. However, oxygen carriers have been restricted by deactivation and inferior oxygen transferability at low temperatures. Herein, we design an Fe–O_v–Ce–triggered phase‐reversible CeO_2−x·Fe·CaO ↔ CeO₂·Ca₂Fe₂O₅ oxygen carrier with strong electron‐donating ability, which activates CO₂ at low temperatures and promotes oxygen transformation. Results reveal that the maximum CO₂ conversion and CO yield obtained with 50 mol% CeO_2−x·Fe·CaO are, respectively, 426% and 53.6 times higher than those of Fe·CaO at 700°C. This unique multiphase material also retains exceptional redox durability, with no obvious deactivation after 100 splitting cycles. The addition of Ce promotes the formation of the Fe–O_v–Ce structure, which acts as an activator, triggers CO₂ splitting, and lowers the energy barrier of C═O dissociation. The metallic Fe plays a role in consuming O²⁻_lattice transformed from Fe–O_v–Ce, whereas CaO acts as a structure promoter that enables phase‐reversible Fe⁰ ↔ Fe³⁺ looping.