Atomic Scale Investigation of the Structural and Electronic Properties of Cobalt-Iron Bimetallic Fischer-Tropsch Catalysts

Supported cobalt and iron catalysts are important for many catalytic processes. It is believed that combining both elements in a bimetallic catalyst would result in a synergetic catalytic activity during Fischer-Tropsch Synthesis. However, the nature of the interaction between the two elements and its effect on their catalytic properties are not well understood. In the present work, we report the synthesis of carbon-nanotube-supported Co-Fe alloy catalysts using colloidal chemistry methods. The ratios of Co-Fe and their homogeneous distribution in the supported nanoparticles were confirmed using local and bulk characterization techniques. We observed the formation of Co-Fe Janus-like alloy structure and a change of their elemental distribution at the nanoparticle scale upon reduction. The bimetallic catalyst showed reasonable Fischer-Tropsch catalytic activity and selectivity to C5+ hydrocarbons when compared with monometallic iron and cobalt catalysts. Finally, we found that the active phase of the Co-Fe bimetallic species during catalysis depends on the catalytic conditions.