Nickel–Zinc Catalysts Favor CO Production via Carbide Formation in CO2 Hydrogenation

Abstract Achieving high CO selectivity in CO2 hydrogenation with non-noble metal catalysts remains challenging. Here, we report a simple and cost-effective in situ synthesis of nickel–zinc carbide (Ni3ZnC) from Ni species supported on ZnO under reaction conditions. A higher amount of Ni3ZnC forms in the calcined NiO/ZnO catalyst compared to the prereduced Ni/ZnO system. Thermodynamic analysis reveals a strong driving force for Ni3ZnC formation via NiO/ZnO coreduction (ΔE ≈ −455 kJ mol–1), which is more exothermic than the metallic Ni pathway due to favorable H2O stoichiometry. Density functional theory calculations show that the carbide phase moderates surface reactivity. CO becomes geometrically trapped and isolated from hydrogen due to site blocking by Zn and C atoms. This combination of weakened adsorption and site confinement suppresses deep hydrogenation, leading to high CO selectivity over methanation. This strategy provides a practical route for designing selective reverse water–gas shift catalysts for tandem reaction pathways to liquid fuel synthesis.