Carbon-Supported Fe-Based Catalyst for Thermal-Catalytic CO₂ Hydrogenation into C₂₊ Alcohols: The Effect of Carbon Support Porosity on Catalytic Performance

Carbon materials supported Fe-based catalysts possess great potential for the thermal-catalytic hydrogenation of CO₂ into valuable chemicals, such as alkenes and oxygenates, due to the excellent active sites' accessibility, appropriate interaction between the active site and carbon support, as well as the excellent capacities in C-O bond activation and C-C bond coupling. Even though tremendous progress has been made to boost the CO₂ hydrogenation performance of carbon-supported Fe-based catalysts, e.g., additives modification, the choice of different carbon materials (graphene or carbon nanotubes), electronic property tailoring, etc., the effect of carbon support porosity on the evolution of Fe-based active sites and the corresponding catalytic performance has been rarely investigated. Herein, a series of porous carbon samples with different porosities are obtained by the K₂CO₃ activation of petroleum pitch under different temperatures. Fe-based active sites and the alkali promoter Na are anchored on the porous carbon to study the effect of carbon support porosity on the physicochemical properties of Fe-based active sites and CO₂ hydrogenation performance. Multiple characterizations clarify that the bigger meso/macro-pores in the carbon support are beneficial for the formation of the Fe₅C₂ crystal phase for C-C bond coupling, therefore boosting the synthesis of C₂₊ chemicals, especially C₂₊ alcohols (C₂₊OH), while the limited micro-pores are unfavorable for C₂₊ chemicals synthesis owing to the sluggish crystal phase evolution and reactants' inaccessibility. We wish our work could enrich the horizon for the rational design of highly efficient carbon-supported Fe-based catalysts.