Self-generated Ni nanoparticles/LaFeO₃ heterogeneous oxygen carrier for robust CO₂ utilization under a cyclic redox scheme

High reaction temperature and low impurity-tolerance of traditional oxides challenges the application of CO ₂ reduction via chemical looping. Here, we report a robust and stable cyclic redox scheme with a self-generated Ni nanoparticles/LaFeO ₃ heterogeneous structure to efficiently utilize CO ₂. At a low temperature of 800 ℃, the LaNi _0.05Fe _0.95O _3−δ exhibited stable and superior performance: 98% CO selectivity during the half cycle of methane oxidation; 98.5% CO ₂ conversion in another cycle of CO ₂ reduction even with other oxidative impurities, which were maintained for 100 redox cycles. Through a combination of catalyst characterizations, the existence of exsolved Ni metal nanoparticles from the bulk lattice was confirmed on the perovskite surface. The CO productivity only decreased by 1.5% when feeding the gas mixture (O ₂/CO ₂ = 25 at%) over the LaNi _0.05Fe _0.95O _3−δ sample for CO ₂ reduction, much better than that in pure LaFeO ₃. It was verified that exsolved metal Ni served as catalytically active sites for both methane conversion and the activation of C–O bonds during CO ₂ reduction via the density functional theory calculation. The stable performance tolerant to oxygen gas enables Ni-modified LaFeO ₃ to effectively reduce cheap CO ₂ with impure oxidative gases. The proposed cyclic redox scheme offers an economic pathway of utilizing directly carbon sources from air capture without energy-costing purifications.