Carbon Reduction Strategy for the Growth of Ni Nanoparticles on Binary TiO₂–Al₂O₃ for CO₂ Methanation

Achieving targeted activity and stability in heterogeneous catalysts by concurrently increasing the number of metal active sites and reducing particle size remains a significant challenge. Herein, we effectively design a robust Ni catalyst through a reduction–oxidation–reduction (ROR) strategy, involving an initial carbon reduction, followed by oxidation and a final H2 reduction. The structural evolution of different Ni features was monitored at each stage. Strong metal–support interaction and encapsulated structure on the initially carbon-reduced Ni catalyst were formed and presented inferior CO2 methanation activity. Notably, a high Ni loading of 14.8 wt % on the binary TiO2–Al2O3 support, obtained by the ROR approach, possessed a small particle size of 12.3 ± 3.4 nm and tailored interactions between Ni and the support. Compared to a low-loading Ni/TiO2–Al2O3, the high-loading Ni catalyst exhibited superior activity and stability as well as low active energy for CO2 methanation. The origin for the enhanced catalytic performance was discussed based on the available Ni active sites and metal–support interaction.