An efficient Ni-Mg/HNTs catalyst for CO2 methanation prepared by sol-gel method assisted with citric acid

Developing a stable and effective Ni-based catalyst for low-temperature CO₂ methanation remains a significant challenge. This study presents the synthesis of a range of MgO-promoted Ni-based catalysts supported on natural halloysite nanotubes (HNTs) through a sol-gel method assisted by citric acid. At 275°C, Ni-Mg/HNTs-1.0 CA exhibits the highest CO₂ conversion (88.5%) and CH₄ selectivity (98.4%). The sufficient basic sites and Ni⁰ sites of Ni-Mg/HNTs-1.0CA are beneficial for CO₂ activation and H₂ dissociation, leading to high activity at low temperatures. Additionally, Ni-Mg/HNTs-1.0 CA exhibits better anti-sintering ability during 100 h reaction, attributed to the increased interaction between metal and support. The in-situ DRIFTS results show that Ni-Mg/HNTs-1.0 CA mainly follows both formate and CO pathways, and the rapid transformation of intermediates causes superior catalytic performance. This work offers a rational design of stable and active catalysts for low-temperature CO₂ methanation.