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 La Ni 0.05 Fe 0.95 O 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 La Ni 0.05 Fe 0.95 O 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. In the present work, we report a durable Ni-doped LaFeO 3 perovskite for CLCS via optimizing the doping ratio of Ni cations and activating the exsolution effect of Ni particles. Ni nanoparticles segregating out of the perovskite lattice play critical catalytic roles for facilitating CO 2 splitting and activating methane into syngas. Consequently, the 5 at% Ni-doped perovskite ( La Ni 0.05 Fe 0.95 O 3 − δ ) exhibited synergic enhancements at a relatively low temperature (~800 ℃ ): 98.5% CO 2 conversion was maintained with 25% molar content of O 2 , and the 5.5 mol/kg syngas productivity with a H 2 /CO ratio of 2.0 was simultaneously achieved. • Ni promoted LaFeO 3 oxygen carriers were developed for highly effective thermochemical CO 2 splitting. • Ni nanoparticles in La Ni 0.05 Fe 0.95 O 3 − δ can precipitate the crystal lattice rapidly during methane partial oxidation, while partially re-oxidized Ni/NiO nanoparticles are conductive to split CO 2. • La Ni 0.05 Fe 0.95 O 3 − δ exhibit excellent robustness against strongly oxidative impurities.