(558j) A Density Functional Study of Transition Metal Fischer Tropsch Catalysts

Fischer–Tropsch synthesis is a well-known method to convert syngas into valuable hydrocarbons. The chemical reactions are catalyzed more commonly by transition metals including Fe, Co and Ru. Although, only Fe and Co catalysts are commonly employed in industry because of their lower cost. The catalytic activity of metal nanoparticles is greatly shape and size dependent and even just an additional atom can entirely change the reactivity and stability. Also, it is possible to improve the activity and selectivity of pure catalysts by alloying them with additional metals.

All Fischer-Tropsch mechanisms known to date begin with the adsorption of carbon monoxide followed by its dissociation on a given catalyst surface. Understanding how catalyst materials modify reactivity descriptors, such as CO adsorption and dissociation energies, is key for nano-engineering materials for this type of applications.

By obtaining encouraging results with our prior studies on 13-atom cluster models of Co, Fe, Ni, Pd, Pt, and Ru, we are now investigating 55-atom cluster models of the same metals using Density Functional Theory (DFT) calculations. These cluster models have shown to retain the accuracy of the periodic slab models at a lower computational cost. Since experimental information at the atomic level is difficult to obtain, we carried out systematic DFT calculations for evaluating reactivity descriptors of larger models.

These cluster-based models offer a platform for the study of the adsorption and desorption of CO and H₂ at the preliminary steps of the FT synthesis.