Precipitate Washing Level as a Key Parameter of Ni‐Al‐LDH Catalyst Properties for CO ₂ Methanation

Abstract This study investigates the influence of the washing step on the physicochemical properties and catalytic performance of Ni–Al layered double hydroxide (LDH)‐derived catalysts for CO 2 methanation. Catalysts were synthesized via co‐precipitation and subjected to different washing levels, resulting in final conductivities ranging from 21000 µS/cm (0 W) to < 50 µS/cm (10 W). Nitrogen physisorption and X‐ray diffraction analyses revealed that lower conductivity values led to increased surface area, reduced crystallite size, and improved structural homogeneity. H 2 ‐TPR and CO 2 ‐TPD profiles demonstrated that efficient washing enhances metal–support interactions and promotes the formation of stronger basic sites, both of which are critical for CO 2 activation. Catalytic tests showed that the 2 W sample washed to an intermediary level exhibited the highest CO 2 conversion at low temperatures (200–300 °C), whereas more thoroughly washed samples (10 W and 5 W) performed better at higher temperatures (>300 °C), likely due to their superior thermal stability and resistance to sintering. Post‐reaction XRD and XPS characterization confirmed the structural integrity of the catalysts, with minimal crystallite growth. Furthermore, the 2 W catalyst maintained structural integrity, showed no coke formation, and experienced less than 3% mass loss in TPO after 51 h of reaction, confirming its excellent long‐term stability. These findings highlight the importance of controlling washing conditions during synthesis to optimize the redox behavior, basicity, and overall catalytic efficiency of Ni–Al LDH‐derived materials for CO 2 methanation.