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

Abstract

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.