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[Display omitted] • Mixed Na-Fe 3 O 4 and Fe 5 C 2 can enhance the performance of CO 2 hydrogenation to C 5+. • An optimal oxide/carbide ratio is crucial for achieving high yields of C 2 -C 4 olefins and C 5+ hydrocarbons. • Closer proximity of oxide and carbide hindered CH 4 formation and olefin hydrogenation. • Oxide/carbide reduction can enhance carbon shell graphitization and C 5+ formation. CO 2 hydrogenation into sustainable chemical feedstocks and fuels is a pivotal focus of energy research. Fe-based catalysts have emerged as promising candidates due to their high efficiency in the CO 2 hydrogenation toward C 2 –C 4 olefins and C 5+ hydrocarbons. Fe 5 C 2 is known as the active phase of the CO 2 hydrogenation. Therefore, it is imperative to discern the roles of active phases in product distribution. Accordingly, in the present study, Fe 5 C 2 is synthesized separately and physically mixed with Na-Fe 3 O 4. The effects of oxide/carbide ratio, the proximity of active phases, and reduction treatment are investigated. The results show that adding carbide to oxide in an appropriate ratio significantly increases CO 2 conversion due to the controlled reduction of the oxide phase and enhanced CO 2 adsorption. Additionally, a closer distance (mixed-powder pellets) between Na-Fe 3 O 4 and Fe 5 C 2 results in higher selectivity for C 2 -C 4 olefins and C 5+ hydrocarbons and less CH 4. Furthermore, the graphitized layers of reduced catalyst (R-Na-Fe 3 O 4 /Fe 5 C 2 (70/30 wt%)) enhance the selectivity to C 2 -C 4 olefins (40 %) and C 5+ hydrocarbons (35 %) at around 40 % CO 2 conversion. In contrast, amorphous carbon in the non-reduced catalyst (NR-Na-Fe 3 O 4 /Fe 5 C 2 (70/30 wt%)) favors more C 2 -C 4 paraffins and CH 4. Therefore, the interplay between the influential factors, i.e., oxide/carbide ratio, spatial distance, and reduction treatment, can result in tailoring an efficient CO 2 hydrogenation catalyst toward the formation of valuable hydrocarbons. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of 5 wt% NiO-xP-Al 2 O 3 with different phosphorus loading contents (x = 0, 5, 15 and 20 wt%) were prepared by a modified sol-gel method. • All the catalysts reach the highest conversion at 600 °C with 61.54 %, 62.89 %, 63.88 % and 66.13 % respectively for 5 wt% NiO-Al 2 O 3 , 5 wt% NiO-5P-Al 2 O 3 , 5 wt% NiO-15P-Al 2 O 3 and 5 wt% NiO-20P-Al 2 O 3 catalysts. • Ni/NiO/Ni 2 P/Ni 5 P 12 /AlPO 4 interfacial species were detected on the surface as active species on the used catalysts by X-ray photoelectron spectroscopy. • The formation ratio of the metal-phosphide is relatively low ∼3−5 %, and this atomic concentration is decreasing with the rising of the phosphate content. However, the nickel enrichment in the surface layer presumable in Ni 2 P/Ni 5 P 12 form is very likely according to the P 2p spectra and the authors assume that could be responsible for the enhanced catalytic activity. A series of 5 wt% NiO-xP-Al 2 O 3 with different phosphorus loading contents (x = 0, 5, 15 and 20 wt%) were prepared by a modified sol-gel method. A significant promotional effect of phosphorus on NiO-Al 2 O 3 in CO 2 hydrogenation is observed. All the catalysts reach the highest conversion at 600 °C with 61.54 %, 62.89 %, 63.88 % and 66.13 % respectively for 5 wt% NiO-Al 2 O 3 , 5 wt% NiO-5P-Al 2 O 3 , 5 wt% NiO-15P-Al 2 O 3 and 5 wt% NiO-20P-Al 2 O 3 catalysts. Ni/NiO/Ni 2 P/Ni 5 P 12 /AlPO 4 interfacial species were detected on the surface as active species on the used catalysts by X-ray photoelectron spectroscopy. The formation ratio of the metal-phosphide is relatively low ∼3−5 %, and this atomic concentration is decreasing with the rising of the phosphate content. However, the nickel enrichment in the surface layer presumable in Ni 2 P/Ni 5 P 12 form is very likely according to the P 2p spectra and the authors assume that could be responsible for the enhanced catalytic activity. [ABSTRACT FROM AUTHOR]