Geometric effects of cobalt B5 sites on CO activation
BFP CS MFPInvestigate how the geometry of cobalt B5 sites influences CO adsorption, bond activation, and dissociation barriers in Fischer-Tropsch catalysis.
Cobalt-based catalysts are widely used in Fischer-Tropsch synthesis (FTS) for the conversion of synthesis gas (CO + H2) into hydrocarbons and fuels. A key elementary step in this process is the activation and dissociation of carbon monoxide on the catalyst surface. Step-edge motifs known as B5 sites are commonly proposed as highly active sites for CO dissociation on cobalt surfaces and are therefore frequently studied using atomistic simulations.
Most computational studies investigate idealized and fully optimized stepped cobalt surfaces in which the B5 geometry is fixed. In realistic catalyst systems, however, the local structure of these sites can vary substantially due to strain, nanoparticle morphology, or interactions with the catalyst support. As a result, the geometry of the B5 ensemble may become more open or closed, due to altered local bond lengths and angles. In supported catalysts, these geometric changes are often accompanied by charge transfer between the support and the metal, making it difficult to disentangle purely geometric effects from electronic effects.
This project aims to isolate and investigate the influence of geometry on CO activation at cobalt B5 sites. Rather than introducing supports explicitly, the project focuses on extended cobalt surfaces in which the local B5 geometry is systematically modified through controlled lattice distortions. By stretching or compressing one lattice direction, differently shaped B5 sites can be generated while minimizing additional electronic perturbations from support interactions.
The project will investigate how geometric descriptors such as bond lengths, coordination environments, and local site angles correlate with adsorption energies and CO dissociation barriers. Bonding analysis methods will be used to understand how geometric changes modify the electronic structure of adsorbed CO and the occupation of bonding and antibonding states. In this way, the project connects geometric structure, electronic structure, and catalytic reactivity.
A report describing how variations in cobalt B5 site geometry influence CO adsorption and dissociation energetics. The project will provide insight into the relationship between active-site structure and catalytic activity by combining plane-wave DFT calculations with transition-state searching, COHP bonding analysis, and charge analysis methods. The final report should identify geometric trends governing CO activation and discuss the extent to which lattice distortions influence the electronic structure and reactivity of cobalt B5 sites.