Modulation of Fischer-Tropsch product selectivity via various substrates supported rhodium nanoclusters – A DFT study

CO and H₂ have been used to synthesize hydrocarbons efficiently via Rh-based nanocatalysts in Fischer-Tropsch synthesis (FTS). Unfortunately, the conformations of the small nanoclusters (N ≦ 20) would be difficult to define if the clusters were not supported on a substrate. However, the catalytic activity of the Rh nanocluster on appropriate supports would differ appreciably because of the varied interactions between cluster and support, depending on whether the interactions induced a positive or negative effect. Therefore, we investigate the stability of Rh₄ nanocluster on different supports and further discuss the influence of the support on the catalytic effect. The reaction mechanism of *CH_x formation in Fischer-Tropsch synthesis on Rh₄@supports (Supports = Graphene, ZSM-5 and MCM-41) is studied by DFT calculations. We systematically investigate the selectivity of the hydrogen-assisted dissociation of *CH_xO (x = 1, 2, 3) on Rh₄@Graphene, Rh₄@ZSM-5 and Rh₄@MCM-41 to generate specific *CH_x fragments. In addition, we further analyze how the *CH_x fragment is selectively stabilized by different Rh₄@supports through natural bond orbital (NBO) analysis. Finally, we hope that an optimal barrier may be achieved by carefully screening the appropriate support to alter the activity of the Rh₄ nanocluster to assist in developing a high selectivity FTS catalyst.