Robust Iron-based Fischer-Tropsch Catalysts by Direct Joule Synthesis

Abstract Converting CO2 into gasoline- and jet-fuel-range hydrocarbons offers an elegant approach to sustainable fuels compatible with existing infrastructure. However, widely applied iron-based syngas Fischer-Tropsch catalysts deactivate in CO2-rich feeds due to oxidation of active carbides in oxidising CO2 environments and the doubled H2O byproduct. Herein, we demonstrate Direct Joule Synthesis (DJS) coupled with mechanochemical treatment as an effective method to prepare metal-rich Fe-Co-Na precursors, which reconstruct during CO2 hydrogenation into carbide-containing active structures. The optimised FeCoNa sample attains 57.3% CO2 conversion, 24.1% C5+ yield, 43.7% C2+ yield, and space-time-yields of 0.40 gC₅₊ h−1 gcat−1 and 0.68 gC2₊ h−1 gcat−1 at 350°C and 30 bar, exceeding reported systems. Even more intriguing, stable operation for at least 500 h on stream is achieved due to retention of Fe5C2 as a dominant phase, stabilised by residual metallic FeCo acting as a reduction promoter, limiting carbide re-oxidation, in addition to enhancing olefin release and supply of adsorbed intermediates. These findings demonstrate the activity and stability advantages of metal-derived Fe-based CO2 hydrogenation catalysts, establishing DJS as a rapid non-equilibrium synthesis method for versatile multimetallic catalysts.