Tuning the Support Properties toward Higher CO₂ Conversion during a Chemical Looping Scheme

The chemical looping process is promising for CO₂ conversion because of the much higher CO₂ conversion efficiency than the photocatalytic and electrocatalytic processes. Conventional oxygen carriers have to include a high content of inert support, typically Al₂O₃, to avoid sintering, thus leading to a trade-off between reactivity and stability. Here, we propose the use of ion-conductive GdCe_2-O_2-δ (GDC) to prepare the supported oxygen carriers. The resulting Fe₂O₃/GDC materials achieve both high reactivity and stability. Fe₂O₃/Gd_0.3Ce_1.7O_2-δ shows high CO productivity (∼10.79 mmol·g^-1) and CO production rate (∼0.77 mmol·g^-1·min^-1), which are twofold higher than that of Fe₂O₃/Al₂O₃. The performance remains stable even after 30 cycles. The mechanism study confirmed the rate-limiting role of the oxygen-ion conductivity, and the GDC support enhanced the oxygen-ion conductivity of oxygen carriers during the redox reactions, thus leading to improved CO₂ splitting performance. A roughly linear relationship between the oxygen-ion conductivity and CO₂ yield is also obtained and verified in our testing conditions. This relation can be used to predict and select oxygen carriers with high CO₂ splitting performance.