Boosting CO₂methanation over Ni-based catalysts via La–Al mixed oxide synergy

LaAlO₃ demonstrated a pronounced mixed-oxide synergistic effect as a support for Ni-based catalysts in the CO₂ methanation reaction. Catalysts supported on LaAlO₃ exhibited higher CH₄ yields and turnover frequency (TOF) values than those supported on the individual oxides, La₂O₃ and Al₂O₃. This enhanced performance was attributed to the higher density of intermediate-strength basic sites and the lower apparent activation energies associated with the LaAlO₃-supported catalysts. Among the tested formulations, the 15 wt% Ni catalyst on LaAlO₃ (15Ni/LaAlO₃) showed the best performance, achieving 91% CO₂ conversion and 99% CH₄ selectivity at 350 °C under high space velocity conditions [10 000 mL (g cat·h⁻¹)]. A comprehensive characterization using SEM-TEM, TPR, and H₂-chemisorption, combined with a mechanistic assessment via time-resolved operando FT-IR spectroscopy, revealed that the catalyst's activity stems from a well-balanced distribution of moderate basic sites and high Ni⁰ surface availability. This combination favors the complete reduction of carbonated intermediates through a hydrogen-assisted associative pathway, with monodentate carbonate and Ni⁰–CO identified as key intermediates. Additionally, 15Ni/LaAlO₃ was evaluated for the first time in biogas upgrading. Using a model sweetened biogas mixture (60% CH₄–40% CO₂), the catalyst produced biomethane with 90.2% CH₄ content after 24 hours of continuous operation, confirming its potential for sustainable energy applications.