Synthesis, CO₂ methanation performance and surface dynamics of high surface area LaNiO₃-derived catalysts

The development of highly active and durable CO₂ methanation catalysts remains a major challenge, particularly because catalyst restructuring and sintering of the active particles can progressively reduce catalytic performance. Exsolved perovskite-derived catalysts have therefore attracted growing interest due to their ability to generate strongly anchored metallic nanoparticles with enhanced metal–support interactions and stability. However, conventional perovskite synthesis methods generally produce low-surface-area materials, limiting the accessibility of active sites and their catalytic performance. Here, a high-surface-area LaNiO₃ perovskite was synthesized by a nanocasting approach using SBA-15 as a hard template and investigated as a precursor for exsolved Ni/LaOₓ catalysts for CO₂ methanation. Reduction under H₂ led to the exsolution of metallic Ni nanoparticles with average sizes below 6 nm and a narrow particle-size distribution. The reduction temperature has a clear influence on the CO 2 methanation performance, with the catalyst reduced at 600 °C exhibiting the highest activity, nearly complete CH₄ selectivity, and good medium-term stability over 65 h on stream, after a slight initial deactivation. In situ surface-sensitive spectroscopy measurements revealed that H₂ reduction induces partial encapsulation of Ni nanoparticles by lanthanum oxide species within the outermost few nanometers of the catalyst surface. Under CO₂ methanation conditions, however, the catalyst dynamically restructures, leading to a progressive enrichment of Ni within the outermost surface layers. This reversible change in surface Ni concentration correlates with the formation of surface carbonate species, suggesting that adsorbate-induced restructuring governs the active interfacial state. These findings demonstrate that the active phase for CO₂ methanation over LaNiO₃-derived catalysts is a dynamically reconstructed Ni–LaOₓ interface controlled by the gas-phase environment, highlighting the central role of surface restructuring in the performance of exsolved perovskite-derived catalysts.