Tuning Ru/Ni sites in the perovskite-based precursor synthesis to make more efficient and durable dual-function materials for integrated CO2 capture and methanation

Abstract

A new generation of Dual Function Materials (DFMs) were obtained after the controlled reduction of 20 % La_0.6Ca_0.4Ni_0.95Ru_0.05O₃/CeO₂ synthesized combining citric acid-wetness impregnation methods. Different parameters such as pH of the starting solution, calcination protocol were modified in order to synthesize materials with variable nanostructure, surface chemistry and textural properties, thereby effectively tuning the material activity and stability for the integrated CO₂ adsorption and in situ methanation operation. The samples were extensively characterized before and after catalytic tests by XRD, Raman, STEM-EDS, XPS, N₂ adsorption-desorption, H₂-TPR, H₂-TPD, CO₂-TPD, and H₂-TPSR. It was found that the DFM obtained from the precursor prepared in absence of NH₃ promoted Ru accommodation within the perovskite structure. The corresponding DFM showed enhanced textural properties, Ru/Ni actives sites accessibility and weak/medium basic sites concentration and, consequently, displayed the highest CH₄ yield (312 µmol g⁻¹) and fastest CH₄ production kinetics under cycles of CO₂ adsorption and in situ hydrogenation to CH₄. Furthermore, this sample showed higher stability than conventional Ru-based DFMs, with CH₄ production decreasing by less than 6 % compared to 25 % observed for conventional ones, due to a lower tendency for metal sintering, emerging as a promising alternative for long-term operation under realistic industrial conditions.