Modification of Ni catalysts via La-induced Ce-O frustrated Lewis-pair sites on CeO2 for enhancing CO2 methanation

Catalytic CO 2 methanation enables the conversion of captured CO 2 and renewable H 2 into synthetic methane, a crucial process for sustainable energy cycles. The Ni/La-CeO 2 catalyst was prepared by introducing La species into the CeO 2 support via the coprecipitation-hydrothermal method followed by Ni loading. The catalytic performance in the CO 2 methanation reaction was investigated by experimental characterizations and density functional theory (DFT) calculations. The results demonstrate that La species is dissolved in the CeO 2 matrix to form a La-Ce composite oxide solid solution. La 3+ substitution induces lattice distortion and charge-compensated oxygen-vacancy formation, constructing La-induced Ce-O frustrated Lewis-pair sites: under-coordinated Ce 3+ adjacent to oxygen vacancies acts as Lewis-acid site, while nearby intact lattice-oxygen serves as Lewis-base site. The Ce–O–La interactions in La-CeO 2 facilitate the formation of oxygen vacancies. These vacancies enhance the acid-base properties of Ce–O pairs adjacent to the La–Ov sites thus promoting the adsorption and activation of CO 2 , showing a large uphill thermodynamic energy change for the HCOO*-to-CHO* transformation, which suggests this step is kinetically challenging. The CO 2 reaction rate over Ni/La-CeO 2 is 8.69 × 10 –6 mol CO2 g –1 s –1 at 180°C, considerably higher than 4.93 × 10 –6 mol CO2 g –1 s –1 obtained over Ni/CeO 2 . The improved catalytic performance mainly originates from synergistic coupling between optimized Ni nanoparticles and FLP sites, providing a facile strategy for improving the catalytic activity of metal oxides in CO 2 methanation.