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 LaNi0.05Fe0.95O3−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 LaNi0.05Fe0.95O3−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
Bibliographical noteThe work of X.B.L. and X.C. was supported by the Center for Advanced Materials for Energy and Environment. This work was supported by the National Key Research and Development Program of China (2018YFB0605401), National Natural Science Foundation of China (Nos. 51774159 and 21706108), the Qinglan Project of Kunming University of Science and Technology, and Youth Top Talent Program of Yunnan Province.
- Chemical looping
- CO2 reduction
- Exsolved Ni nanoparticles
- Oxygen tolerance