Tuning Cu–Zn–Mg catalysts by flame spray pyrolysis for CO$_2$-to-methanol synthesis

CO$_2$-hydrogenation is a key route for producing renewable methanol, a carbon-neutral chemical and energy carrier. As this reaction is highly structure-sensitive, many studies have focussed on understanding the structure–activity relationships in typical Cu/ZnO based catalysts. In addition to ZnO, MgO has been identified as a basic support that can further promote methanol synthesis activity. Flame spray pyrolysis (FSP) is a versatile synthesis technique that enables to prepare nanocrystallne materials and to tune the interaction and structure in multicompoenent systems by varying the flame spray configurations. In this study, we explore the direct interaction of Cu, ZnO and MgO through variations of single and double flame FSP configurations for Cu/MgO/ZnO model catalysts. The catalysts were characterized by ICP-OES, XRD, STEM, N$_2$ physisorption, N$_2$O titration, Raman spectroscopy, H$_2$-TPR and operando XAS. The results elucidate that varition of the flames in FSP allows tuning the metal–metal oxide interactions, as reflected by differences in reduction behavior, surface area, phase composition, crystallite size and catalytic performance during CO$_2$ hydrogenation to methanol. ... mehrNotably, the single-flame catalyst exhibited the highest methanol space–time yield despite its lower surface area and larger crystallites, indicating a particularly strong metal–metal oxide interaction. In contrast, the double-flame catalyst, with Zn introduced separately from Cu–Mg, showed enhanced Zn reducibility and improved Cu stability under transient H2-dropout conditions. These findings highlight the potential of FSP to tailor metal–support interactions and suggest that separate Zn deposition can enhance catalyst stability while maintaining high methanol productivity.