| Summary: | The thermo-catalytic synthesis of hydrocarbons from CO<sub>2</sub> and H<sub>2</sub> is of great interest for the conversion of CO<sub>2</sub> into valuable chemicals and fuels. In this work, we aim to contribute to the fundamental understanding of the effect of alloying on the reaction yield and selectivity to a specific product. For this purpose, Fe-Co alloy nanoparticles (nanoalloys) with 30, 50 and 76 wt% Co content are synthesized via the Inert Gas Condensation method. The nanoalloys show a uniform composition and a size distribution between 10 and 25 nm, determined by means of X-ray diffraction and electron microscopy. The catalytic activity for CO<sub>2</sub> hydrogenation is investigated in a plug flow reactor coupled with a mass spectrometer, carrying out the reaction as a function of temperature (393–823 K) at ambient pressure. The Fe-Co nanoalloys prove to be more active and more selective to CO than elemental Fe and Co nanoparticles prepared by the same method. Furthermore, the Fe-Co nanoalloys catalyze the formation of C<sub>2</sub>-C<sub>5</sub> hydrocarbon products, while Co and Fe nanoparticles yield only CH<sub>4</sub> and CO, respectively. We explain this synergistic effect by the simultaneous variation in CO<sub>2</sub> binding energy and decomposition barrier as the Fe/Co ratio in the nanoalloy changes. With increasing Fe content, increased activation temperatures for the formation of CH<sub>4</sub> (from 440 K to 560 K) and C<sub>2</sub>-C<sub>5</sub> hydrocarbons (from 460 K to 560 K) are observed.
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