Alkaline-assisted Ni nanocatalysts with largely enhanced low-temperature activity toward CO2 methanation

Abstract

The CO₂ methanation reaction is a promising approach for the chemical transformation of carbon dioxide into useful fuels or products. The key challenge at present relies on the design and exploration of non-noble metal catalysts so as to achieve high activity at a low reaction temperature. In this work, we have obtained alkaline-assisted Ni nanocatalysts supported on Mg/Al mixed metal oxides (denoted as Ni_x/Mg_2−xAl-MMO) derived from Ni-Mg-Al hydrotalcite precursors. The catalytic performance toward CO₂ methanation was studied in detail, and the best low-temperature reaction activity was obtained over Ni/MgAl-MMO (CO₂ conversion: 97.9%; selectivity: 97.5%; 250 °C). By establishing the correlation between the catalytic performance and the alkaline site structure, it is found that the Ni nanoparticles and MgO base sites at the interface serve as dual active centers to cooperatively catalyze CO₂ methanation, resulting in low-temperature reaction activity. Moreover, in situ diffuse reflectance Fourier transform infrared spectroscopy (in situ DRIFTS) demonstrates that MgO acts as the active site for CO₂ activation to give carbonate/hydrocarbonate species, while Ni provides H-species for further hydrogenation of intermediates. Therefore, this work rationalizes the significant influence of alkaline-assisted Ni nanoparticles on CO₂ methanation, which provides a promising heterogeneous catalyst for this reaction.