Examination of the influence of La promotion on Ni state in hydrotalcite-derived catalysts under CO2 methanation reaction conditions: Operando X-ray absorption and emission spectroscopy investigation

Hydrotalcite-derived Ni-containing and Ni-La promoted catalysts showed very high activity in CO2 methanation, which is an efficient way of carbon dioxide conversion into methane - a valuable product. The catalysts were obtained by co-precipitation method followed by thermal decomposition and characterized by elemental analysis, low temperature nitrogen sorption, XRD, H-2-TPR, CO2-TPD and TEM. The obtained results confirmed the formation of periclase-like structure materials, with nickel present as NiO nanoparticles and suggested successful incorporation of lanthanum into the catalytic system. The addition of lanthanum changed the interaction between nickel and periclase matrix (H-2-TPR) and changed the distribution of basic sites, especially medium strength ones (CO2-TPD). Moreover, the catalysts were studied by complementary HERFD-XANES and XES spectroscopy under model operando conditions. The results uncovered that the presence of lanthanum strongly influenced the chemical nature and oxidation state of nickel species and its crucial role in catalyst activity enhancement in CO2 methanation reaction.