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

Engineering an iron‐based oxygen carrier with high oxygen transport capacity (Ot) surpassing Fe2O3/Fe3O4 redox pair without decreasing CO2 selectivity and recyclability remains a substantial obstacle for CO2 capture via chemical looping combustion (CLC) technology. Herein, we propose a novel strategy by confining iron‐cations into the matrix of BaFe12O19 hexaferrite, which exhibited both superior Ot of 3.0 mmol/g with 100% CO2 selectivity (exceeding the maximal limit of 2.08 mmol/g for pure Fe2O3 → Fe3O4), and a unique increased trend in Ot with good recyclability during 50 redox cycles, different from most reported Fe‐based OCs. The high Ot 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 Fe3O4/FeO. The cyclic redox treatment induced more Ba2+ into Fe oxides and the surface enrichment of Ba2+, thus ensuring high recyclability with increased Ot during the later redox cycles.