CoFe alloy carbide catalysts for higher alcohols synthesis from syngas: Evolution of active sites and Na promoting effect

• A preparation method of CoFe alloy carbide catalyst was proposed. • Co-Fe interdiffusion happened in reduction and affect the alloy carbide formation. • ε'-(Co x Fe 1-x ) 2.2 C facilitated the synergy between CO insertion and dissociation. • 0.25 wt% Na promoted ε'-(Co x Fe 1-x ) 2.2 C formation and enhanced STY of higher alcohols. Higher alcohols synthesis (HAS) from syngas is quite attractive but still challenging due to the unsatisfied product selectivity and stability. Here, we prepared a series of CoFe bimetallic carbide catalysts and investigated the evolution of active species. The catalysts reduced above 300 °C could ensure an adequate interdiffusion between Co and Fe species to form CoFe alloy and then achieved a high fraction of ε'-(Co x Fe 1-x ) 2.2 C species during HAS reaction, which exhibited excellent catalytic performance and stability over 200 h. The ε'-(Co x Fe 1-x ) 2.2 C, acting as uniformly atomic neighboring Co x C-Fe x C dual sites, facilitated the synergy between CO nondissociative adsorption and CO dissociation, thus boosting the selective production of higher alcohols. It is also demonstrated that adding proper content of Na (0.25 wt%) can enhance the formation of ε'-(Co x Fe 1-x ) 2.2 C as well as modulate the surface concentration of intermediates. These results may provide new idea for the design of high-performance catalysts for HAS.