Elucidating the role of ZrO2 in a cobalt catalyst in the direct hydrogenation of CO2 to C5+ hydrocarbons

Abstract

Transforming CO₂ into long-chain hydrocarbons that can be used in the current energy and chemical sectors is a promising pathway toward a circular carbon economy. However, the direct conversion of CO₂ into C₅₊ hydrocarbons over Co-based catalysts is significantly challenging owing to the inherent high methanation activities of these catalysts. Herein, the incorporation of oxygen vacancy-containing ZrO₂ into a Co-based catalyst is demonstrated to increase C₅₊ yields up to 26.9% by suppressing the CH₄ selectivity at 270 °C. The Na- and ZrO₂-promoted Co catalyst (Na-CoZrO_x-8) exhibited highly stable CO₂ hydrogenation performance during a 2100 h on-stream reaction. In situ-formed Co⁰ core and ZrO₂ shell structure inhibited Co particle agglomeration and maintained the structural integrity of the catalyst during CO₂ hydrogenation. Preferential adsorption of CO at the ZrO₂-Co interfacial site facilitated CO dissociation, ultimately increasing the C₅₊ selectivity. Reaction mechanism analysis by an operando in situ study revealed a carbonate pathway for the reverse water gas shift reaction and H-assisted CO dissociation for the Fischer-Tropsch synthesis to produce C₅₊ over Na-CoZrO_x-8.