100% CO2 selectivity Fe2O3/Fe3O4 redox pair of Ba‐hexaferrite for CO2 capture via relay oxygen donation

Abstract Engineering an iron‐based oxygen carrier with high oxygen transport capacity (O t ) surpassing Fe 2 O 3 /Fe 3 O 4 redox pair without decreasing CO 2 selectivity and recyclability remains a substantial obstacle for CO 2 capture via chemical looping combustion (CLC) technology. Herein, we propose a novel strategy by confining iron‐cations into the matrix of BaFe 12 O 19 hexaferrite, which exhibited both superior O t of 3.0 mmol/g with 100% CO 2 selectivity (exceeding the maximal limit of 2.08 mmol/g for pure Fe 2 O 3 → Fe 3 O 4 ), and a unique increased trend in O t with good recyclability during 50 redox cycles, different from most reported Fe‐based OCs. The high O t and recyclability were closely related to the “relay oxygen supply” involving the preferential diffusion route of the mirror plane in Ba‐hexaferrite and in situ formation of nanosized Ba‐modified Fe 3 O 4 /FeO. The cyclic redox treatment induced more Ba 2+ into Fe oxides and the surface enrichment of Ba 2+ , thus ensuring high recyclability with increased O t during the later redox cycles.