Differences in the Nature of Reaction Process for Thermochemical CO 2 Splitting over NiFe 2 O 4 ‐Based Materials

Perspectives concerning the two‐step thermochemical CO 2 splitting via NiFe 2 O 4 ‐based materials are given for CO production. The thermochemical reactivity of these materials is investigated, and the nature of reaction process is discussed. NiFe 2 O 4 /MgO exhibits universally better performance, giving 3–10 times higher CO production than that of two other materials, NiFe 2 O 4 /SiO 2 and NiFe 2 O 4 /ZrO 2 . A comprehensive analysis indicates that the spinel ferrites in NiFe 2 O 4 /MgO can dissolve in and exsolve out of the wüstite matrix in synchronization with the temperature swing, leading to the self‐regeneration of spinel ferrites, which alleviates the sintering of NiFe 2 O 4 /MgO. Meanwhile, a similar dynamic transition between spinel and wüstite occurs under the periodic variation between reductive and oxidative atmospheres, associated with the internal reaction that promotes the interior iron diffusion, which plays a critical role in enhancing the reactivity of NiFe 2 O 4 /MgO.