Constructing FeCx Active Sites Confined within F-Doped Mesoporous Carbon to Enhance Activity and Stability for CO2 Hydrogenation to Light Olefins.

The hydrogenation of CO2 to light olefins is a key route for converting waste carbon into value-added chemicals, and FeCx catalysts exhibit high activity and promising application potential. However, FeCx or Fe0 active sites can be oxidized by H2O generated during the reaction, severely compromising the activity and stability of Fe-based catalysts. Herein, FeCx active species confined within F-doped mesoporous carbon were prepared using a F-functionalized carbon source, constructing a H2O-resistant interface to protect FeCx from oxidation. Under the reaction conditions of 320 °C, 3.0 MPa, H2/CO2 = 3, and GHSV = 6000 mL/gcat/h, the 0.8Fe-0.1K@NMC-0.2F catalyst exhibited a CO2 conversion of 47.24% and a light-olefin selectivity of 52.43%. A light-olefin space-time yield of 36.5 mmol/gcat/h was achieved over 100 h at a high GHSV of 24,000 mL/gcat/h, surpassing the performance of most reported catalysts. The structure-performance relationship and stability enhancement mechanism were investigated using various characterization techniques, revealing that F incorporation enhances the graphitization degree and H2O resistance of the carbon layer, regulates the electron distribution, and promotes the formation of unsaturatedly coordinated Fe5C2 active sites. The F-doped graphene interface modulated the electronic structure of FeCx active sites to enhance CO2 adsorption-dissociation while weakening H2 activation, increasing the surface C/H ratio, and promoting the C-C coupling reaction. Furthermore, the F-functionalized graphene layer suppressed the overcarbonization and H2O-induced oxidation of Fe0 species, boosting the catalytic stability. This work provides a new strategy for the design of high-performance and long-lifetime FeCx catalysts for the cost-effective conversion of CO2 to high-value chemicals and new insights into the stability enhancement mechanism of Fe active sites against H2O generated during the hydrogenation reaction.