Enhanced CO₂ Methanation over Ni/Na-HNTs: Effect of Pretreatment with NaOH

Hydrogenation of CO2 into high value-added methane has received increasing attention as one of the most effective ways to reduce CO2 emissions in the atmosphere and alleviate the energy crisis. However, improving the catalytic performance of Ni-based catalysts at low temperatures is still the focus of research at the present. Herein, a series of Ni-based catalysts supported on halloysite nanotubes (HNTs) pretreated with NaOH solution were prepared through a simple impregnation method. The optimized catalyst Ni/1.0Na-HNTs demonstrate exceptional catalytic activity, achieving CO2 conversion of 82.3% and CH4 selectivity of 97.3% at a low temperature of 300 °C. The characterization results show that NaOH pretreatment can increase the defective sites on the support surface and successfully introduce the alkali metal (sodium), resulting in highly dispersed metal nanoparticles and increased capacity for H2 dissociation and CO2 activation, which is critical in CO2 methanation. Additionally, in situ DRIFTS analysis reveals that the reaction path for CO2 methanation in this work follows both the formate route and the CO route.