Operando STM of Fischer-Tropsch model catalysts

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The industrial Fischer-Tropsch synthesis of long-chain hydrocarbons is currently seeing an enormous upturn, in particular in form of the Co-catalyzed low-temperature process. The catalytic mechanism is not fully understood, despite of intensive research. Unclear points, in particular, are the initial dissociation of the CO molecules and the lacking structure sensitivity of the reaction. Often a hypothesis is put forward according to which the surface of the Co catalyst restructures, so that the active sites are only formed under the conditions of the reaction. However, there is currently no direct evidence for this hypothesis. We propose a project in which we will use scanning tunneling microscopy to investigate single-crystal Co surfaces as catalyst models under pressure and temperature conditions that come close to those applied in the industrial Fischer-Tropsch synthesis. The project is based on extensive preliminary work performed under methanation conditions at lower pressures and higher H2:CO ratios than used in the industrial Fischer-Tropsch process. Applying Fischer-Tropsch conditions we expect to resolve the assumed restructuring phenomena under "operando" conditions, i.e., while activity and selectivity are measured at the same time. The project opens the possibility of monitoring the formation of the active sites of a catalytic reaction with atomic resolution.