Heteroatom-Mediated Structural Modulation in Ni–Mg–Al Hydrotalcite for Enhanced CO2 Methanation

The development of high-activity Ni-based catalysts for efficient CO2 methanation remains challenging, primarily due to Ni particle aggregation under high loading conditions, which limits their long-term stability at low temperature. To address this issue, this work evaluates the effect of doping with typical metals M (i.e., Co, La, Fe, and Ce) on the properties of Ni–Mg–Al layered double oxides (LDOs). The Ni–Co LDO (Ni/Co = 18:2, wt%), with the lowest activation energy (i.e., 54.5 kJ/mol), achieved 80% CO2 conversion and 99.9% CH4 selectivity at 350 °C, while Ni–La LDO only showed 73% CO2 conversion. The catalytic performance of optimized Ni–Co LDO is also quite stable under a 140 h time-on-stream thermal shock evaluation. Comprehensive characterization reveals that Co doping is particularly effective in generating abundant oxygen vacancies, creating numerous interfacial basic sites and stabilizing small Ni particles. In situ DRIFTS analysis further elucidates the resulting differences in reaction intermediates, pathways, and coordination environments, linking the enhanced structural properties to superior catalytic performance.