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 CO₂ reduction via chemical looping. Here, we report a robust and stable cyclic redox scheme with a self-generated Ni nanoparticles/LaFeO₃ heterogeneous structure to efficiently utilize CO₂. 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% CO₂ conversion in another cycle of CO₂ 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 (O₂/CO₂ = 25 at%) over the LaNi_0.05Fe_0.95O_3−δ sample for CO₂ reduction, much better than that in pure LaFeO3. It was verified that exsolved metal Ni served as catalytically active sites for both methane conversion and the activation of C–O bonds during CO₂ reduction via the density functional theory calculation. The stable performance tolerant to oxygen gas enables Ni-modified LaFeO₃ to effectively reduce cheap CO₂ 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. © 2021 Elsevier Ltd