| AVS 55th International Symposium & Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS-ThP |
| Session: | Poster Session |
| Presenter: | B. Wang, University of St Andrews, UK |
| Authors: | B. Wang, University of St Andrews, UK A. Purdie, University of St Andrews, UK M. Caffio, University of St Andrews, UK R. Schaub, University of St Andrews, UK |
| Correspondent: | Click to Email |
Fischer-Tropsch synthesis, discovered in the 1920s, is one of the most researched topics within heterogeneous catalysis. Fe and Rh are two widely studied Fischer-Tropsch catalysts. The former strongly dissociates CO and catalyzes the preferential formation of methane and higher hydrocarbons, while the latter exhibits a unique catalytic activity on syngas reactions to form carbon-two oxygenates.1 It has been demonstrated that additive Fe species to silica-supported Rh catalysts exert a significant promotion in CO hydrogenation by enhancing the yields and unexpectedly increasing the selectivities toward oxygen-containing products such as alcohols2 In this work, we investigated the FeRh catalyst system within a surface science approach, aiming to get atomic level information on the structure, composition and chemical state of different bimetallic catalysts, and hence an understanding of the Fe promotional role. The nucleation and growth of Fe deposited at room temperature on single-crystalline Rh(111) surfaces (flat and stepped) was investigated as function of Fe coverage. Upon annealing at high temperatures (>600K), STM data confirm the formation of a near surface alloy. By a thorough and systematic comparison of STM images following CO exposure on Rh(111) and on Fe/Rh(111), we investigated the promotional role played by Fe (site specific versus local electronic structure alteration). In an attempt to address more realistic systems, we also performed STM measurements on Rh and Fe physically vapour deposited onto SiO2 thin films. The morphology of the resulting nano-particles, their dispersion and sintering, were studied as function of the Fe:Rh molar ratio. We observed that the addition of Fe dramatically enhances the dispersion of the active Rh loading, concomitant with a significant decrease in average particles size. The implications of our findings are discussed in light of the selective catalysis reported for FeRh systems.
1M. Ichikawa, Polyhedron, 7 (1988) 2351.
2M. M. Bhasin, et al., Journal of Catalysis, 54 (1978) 120.