Gallium Switches the Selectivity of Classical Methanation Catalysts to Produce Methanol from CO2

Carbon dioxide is a major contributor to global climate change and ocean acidification, making efficient capture and utilization a required step for sustainable development. A pivotal aspect of sustainable development is to close the carbon cycle by converting CO2 with “green” H2 to value-added product or fuel, such as methanol. In this context, supported metal catalysts have been extensively investigated, focusing on the role of promoters and/or supports to drive catalytic performance. In particular, besides classical promoters like zinc, gallium has emerged as an alternative, to change properties from classical Cu-based methanol synthesis catalysts to Ni-, Pd- and Pt-based systems. Here, we show that upon addition of Ga, the selectivity of group 8 and 9 transition-metal elements (Ru, Rh, Os and Ir), is switched from their widely-observed methanation behavior to methanol synthesis catalysts, highlighting the universal propensity of Ga in promoting methanol formation. Detailed studies on the series of tailored silica-supported catalysts, amenable to in situ spectroscopy, complemented with density functional theory (DFT) calculations indicate that Ga is particularly prone to generate stable MGa alloyed nanoparticles, that persist during CO2 hydrogenation, driving methanol formation while suppressing the methanation reaction.