A new insight into the initial step in the Fischer-Tropsch synthesis: CO dissociation on Ru surfaces.

In the present work, we have investigated the CO dissociation on corrugated Ru(1121) and the stepped Ru(0001) surfaces by means of density functional theory with slab models. Our results show that, while the direct CO dissociation is preferred on the six-fold site of Ru(1121), the H-assisted CO dissociation is found to be favored on the B5 site of the stepped Ru(0001) surface. Furthermore, we have studied the effects of co-adsorbed spectator species on the CO dissociation mechanisms. Our results demonstrate that spectators can change the potential energy landscape dramatically, such that different reaction mechanisms can be favored in the presence of different spectators. Neither the H-assisted CO dissociation mechanism nor the CO direct dissociation mechanism should be overlooked at authentic ambient conditions. This work emphasizes a dynamic picture of the reaction mechanisms due to the inherent structural and compositional inhomogeneity on surfaces. Different mechanisms can work together as different active sites will co-exist on a real catalyst surface, and the reaction preferences on an active site can vary as the adsorbate compositions on surfaces are varying during the course of the reactions.