Strategic assembly of active phases on Co-Fe bimetallic catalysts for efficient Fischer-Tropsch synthesis

Abstract

In the realm of Fischer-Tropsch synthesis (FTS), the escalating cost of cobalt has spurred interest in Co-Fe bimetallic catalysts as substitutes for monometallic Co catalysts. Unfortunately, it is difficult to clarify specific functions and interactions of the two phases, as investigating catalysts in a unified dimension of both metal and support is still a challenge. Herein, we realize precise control over synthesizing nitrogen-doped carbon materials supported bimetallic catalysts containing CoFe alloy and Co + Fe2C dual active phases. The catalysts are comprehensively characterized to address the above problem by excluding the influence of metal sizes and support properties. Our findings reveal that compared to metallic Co alone and Co + Fe2C dual active phases, the Co-Fe interaction in CoFe alloy with electron transfer from Fe to Co optimizes reactant adsorption behaviors through achieving a larger number of strongly adsorbed CO per active site to increase the density of C* adsorbates and a higher surface CO/H2 ratio to inhibit the hydrogenation of CHx* intermediates for chain termination, as well as an appropriate ability for CO adsorption/ dissociation. These advantages collectively enhance both CO activation and C-C coupling, and consequently, the CoFe/NC (CoFe alloy) catalyst exhibits the superior catalytic performance in the cobalt space–time yield in C5+ products (3011.2 gC5+ kgCo−1h−1), which surpasses the Co/NC (monometallic Co) and Co + Fe/NC (Co + Fe2C dual active phases) by 2.2 times and 2.4 times, respectively. This study serves as a promising route for the development of efficient and low-cost bimetallic catalysts through the strategic arrangement of multiple active phases for various reactions.