Insights into surface chemistry of Silica-based Dual Function Materials.

Dual function materials (DFMs) are capable of simultaneous CO₂ capture and catalytic conversion, thus offering a suitable pathway in decarbonization processes through in-situ CO₂ conversion to valuable chemicals such as methane. Common surface features are the presence of basic sites (alkali or alkaline-earth oxides) to promote CO₂ capture, together with metallic centres to activate Hydrogen and drive methanation reaction. Several formulations have been proposed for this application, typically based on alumina support. In this presentation, a ternary Ru/Ba/SiO₂ system is investigated, synthesized via sequential impregnation of commercial silica powders and of new mesoporous and macroporous silicas. These latter materials have been obtained starting from hexafluorosilicic acid (as example of hazardous industrial by-product), using a precipitation method through ammonia solution addition and the use of organic templates. For both silica supports, Infrared (FTIR) spectroscopy of the functionalized catalysts revealed complex surface functionalities: basic sites, weakly acidic silanol groups, dispersed Ru particles. CO₂ adsorption/desorption spectroscopic studies point out the formation of diverse surface carbonated species having different thermal stability. Although less performant than reference Al₂O₃-based materials, these new silicas have been successfully functionalized (Ru-Ba) to obtain DFMs to activate CO₂, and exhibit surface properties and morphologies comparable to commercial materials, highlighting their potential as sustainable support for methanation catalysts.