Toward understanding Fischer − Tropsch synthesis on cobalt carbides from first principles and microkinetic analysis

Abstract

Cobalt carbides (Co2C) have been recognized as crucial active phases in emerging applications for direct producing high-value chemicals including oxygenates and olefins from syngas. A mechanistic understanding of the complex nature of the surface reactions on Co2C is vital but remains incompletely investigated. In this work, a comprehensive reaction network analysis on Co2C(111) facet by first-principles-based microkinetics modeling reveals pathways for generating methane, ethane, ethylene, acetaldehyde, ethanol and C3 + products, and the model-predicted product distribution as a function of temperature can reflect experimental observations. The competition between the formation of hydrocarbon and oxygenates was analyzed in detail, on both an energetic and microkinetic basis. The elementary reaction steps that control the selectivity of desired products were quantitatively determined using the concept of degree of selectivity control (DSC). Underlying mechanisms for chain growth and product formation were discussed, altogether to provide a better understanding of Fischer − Tropsch synthesis on cobalt carbides.