Gallium: A Universal Promoter Switching CO2 Methanation Catalysts to Produce Methanol

Hydrogenation of CO2 to methanol is foreseen as a key step to close the carbon cycle and enable sustainable development. In this study, we show that introducing Ga into silica-supported nanoparticles based on group 8-9 transition noble metals (M = Ru, Os, Rh, and Ir – MGa@SiO2) switches their reactivity from producing methane (sel. >97%) to producing methanol (50% CH3OH/DME sel.) alongside CO as the only byproduct. These silica-supported catalysts, prepared via a surface organometallic chemistry approach, consist of small, alloyed and narrowly distributed MGa nanoparticles, as evidenced by X-Ray absorption spectroscopy (XAS) and CO adsorption studies. Notably, detailed in-situ XAS and diffuse reflectance FT-IR spectroscopy (DRIFTS) studies complemented with density functional theory (DFT) calculations indicate that Ga generates stable MGa alloys, which persist during CO2 hydrogenation and favor the formation of methoxyl species, thus driving the overall reaction to methanol formation while suppressing methanation.