Mesoporous CeO₂-Supported Ni Catalysts: Tuning Nickel Dispersion for CO₂ Methanation

Due to the growing concern over global warming, significant efforts are being directed toward the production of green fuels obtained via the hydrogenation of captured CO₂ using hydrogen from renewable sources. Methane represents one of the most relevant e-fuels and can be produced through the Sabatier reaction. Among the various catalytic systems, Ni-based catalysts are widely investigated due to their high activity, good selectivity at relatively low temperatures, and lower cost compared to noble metal-based alternatives. Their performance is often enhanced by the presence of supports or promoters such as CeO₂.

In this work, composite catalysts consisting of a NiO active phase dispersed on mesoporous CeO₂ were developed. The mesoporous structure enables a high dispersion of NiO as ultra-small nanoparticles, improving catalytic efficiency while minimizing the amount of active phase.

NiO was deposited on the support using both impregnation and self-combustion methods, yielding catalysts with Ni loadings of 5, 10, and 15 wt%. XRD analysis indicates that NiO is highly dispersed, particularly at low loading, where no distinct crystalline phases are detected. This is supported by HR-TEM, EDX/EELS mapping, H₂-TPR, and H₂ chemisorption, confirming increased dispersion at lower Ni content.

Catalytic tests reveal high CO₂ conversion (80–85 mol%) for CeO₂-supported samples with near-complete CH₄ selectivity. Notably, catalytic activity is only weakly dependent on Ni loading, highlighting that a low Ni content (5 wt%) is sufficient to achieve high performance due to an improved dispersion. This is particularly relevant for reducing the use of Ni, a critical and potentially hazardous material, without compromising efficiency.