In heterogeneous catalysis, the strong adsorption of reaction intermediates can introduce massive structural changes to the surface of catalyst particles under reaction conditions. Often the catalytically active sites form only under those reaction conditions. Fischer-Tropsch synthesis converts synthesis gas, a mixture of CO and H2, to long-chain hydrocarbons and water over supported cobalt catalysts. Under this high CO pressure, cobalt single crystals are found to undergo a massive reconstruction, leading to the spontaneous formation of sub-2 nm Co islands. [1] The driving force for this reconstruction and its kinetic consequences remain poorly understood. Using DFT, we show that the unusual stability of square planar-carbon at the B5 step edges [2], and the attractive interactions between this square-planar carbon and CO at the neighboring edge site lead to a negative  edge creation energy under reaction conditions, driving the formation of nano-scale islands of well-defined shapes. The newly created island sites are not fully covered under FT conditions and the available vacancies provide possible active sites for rapid CO activation. References [1] Wilson, de Groot, J. Phys. Chem., 99, 7860, 1995 [2] Alexandrova, Trinh, Saeys, submitted

Spontaneous formation of nano-islands on Co catalysts under reaction conditions: Driving force and kinetic consequences

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.