Highly efficient photo-thermal synergistic catalysis of CO2 methanation over La1−xCexNiO3 perovskite-catalyst

Solar-driven photo-thermal catalytic CO 2 methanation reaction is a promising technology to alleviate the problems posed by greenhouse gases emissions. However, designing advanced photo-thermal catalysts remains a research challenge for CO 2 methanation reaction. In this work, a series of ABO 3 (A = lanthanide, B = transition metal) perovskite catalysts with Ce-substituted LaNiO 3 (La 1− x Ce x NiO 3 , x = 0, 0.2, 0.5, 0.8, 1) were synthesized for CO 2 methanation. The La 0.2 Ce 0.8 NiO 3 exhibited the highest CH 4 formation rate of 258.9 mmol·g −1 ·h cat −1 , CO 2 conversion of 55.4% and 97.2% CH 4 selectivity at 300 °C with the light intensity of 2.9 W·cm −2 . Then the catalysts were thoroughly analyzed by physicochemical structure and optical properties characterizations. The partial substitution of the A-site provided more active sites for the adsorption and activation of CO 2 /H 2 . The sources of the active sites were considered to be the oxygen vacancies (O v ) created by lattice distortions due to different species of ions (La 3+ , Ce 4+ , Ce 3+ ) and exsolved Ni 0 by H 2 reduction. The catalysts have excellent light absorption absorbance and low electron–hole (e − /h + ) recombination rate, which greatly contribute to the excellent performance in photo-thermal synergistic catalysis (PTC) CO 2 methanation. The results of in situ irradiated electron paramagnetic resonance spectrometer (ISI-EPR) and ISI-X-ray photoelectron spectroscopy (XPS) indicated that the aggregation of unpaired electrons near the defects and Ni metal (from La and Ce ions to O v and Ni 0 ) accelerated adsorption and activation of CO 2 /H 2 . At last, the catalyst properties and structure were correlated with the proposed reaction mechanism from the in situ diffuse reflection infrared Fourier transform spectrum (DRIFTS) measurements. The in situ precipitation of the B-site enhanced the dispersion of Ni, while its enriched photoelectrons upon illumination further promote hydrogen dissociation. More H* spillover accelerated the rate-determining step (RDS) of HCOO* hydrogenation. This work provides the theoretical basis for the development of catalysts and industrial application.