Insights into the Fischer–Tropsch mechanism on χ-Fe5C2(510) based on the hydrogen coverage effect

Abstract

Investigating the mechanism of the Fischer–Tropsch synthesis is beneficial for modifying catalysts, which would result in an improved catalyst performance. However, theoretical calculations have mainly focused on several key elementary reactions and have thus provided fragmented information. Here, we select χ-Fe5C2(510) as representative facet and consider the elementary reactions on as comprehensively as possible via the density-functional theory (DFT)-based kinetic Monte Carlo (kMC) method to generate the fine structure of the Fischer–Tropsch mechanism. The results reveal that the CO activation mechanism is divided into cyclical pathways and termination pathways. The chain growth process and chain dissociation process coexist in the Fischer-Tropsch synthesis while the former follows the CO insertion mechanism, and the latter follows the carbide mechanism. The product methane and ethylene are produced major from the intermediates which are generated in the chain dissociation process rather than the chain grown process as the article reported before. The deep interpretation of the Fischer–Tropsch mechanism from the fine structure could be the guidance to experimentalists in mechanism verification or catalyst design.