Structure-Induced Iron Carbides for CO2 Hydrogenation into Liquid Fuels

Abstract

Coal resources, due to their cheapness and high-energy density, are widely used in large quantities, causing greenhouse gas emissions in turn, and thus need to be utilized in a resourceful way to reduce carbon emissions. Herein, we designed an alternative route of value-added utilization using coal-based activated carbon support loaded with Fe nanoparticles for CO₂ hydrogenation to liquid fuels. The coal-based derived carbon support with tunable structure, elemental composition, defects, and special surface area controlled by a proposed two-step coking-activation strategy, in which special scale-like or alveolate structures were obtained. It was demonstrated by characterization that the structure and defect of the carbon support affect the carburization behavior of iron species, and then the highest Fe₅C₂ content was found on FeK@AC-2.0-750 catalyst. The high level of exposure of active χ-Fe₅C₂ sites presents benign liquid fuel selectivity. In situ diffuse reflectance infrared Fourier transform spectroscopy and DFT calculation further support the improved carbon chain propagation over χ-Fe₅C₂ rather than θ-Fe₃C. Compared with commercial carbon supports, its loaded Fe-based catalyst has a better performance with 29.3% CO₂ conversion and 58.8% C₅₊ selectivity, respectively. These results provide new insights into the development of novel nanocarbons and the efficient utilization of coal-based resources as well as broaden the design of efficient iron-based catalysts for C1 chemistry.