Reactivity of a model SCILL: Influence of co-adsorbed [C2C1Im][OTf] on the dehydrogenation of dimethylamine on Pt(111)

Solid catalysts with ionic liquid layers (SCILLs) are heterogeneous catalysts whose selectivity is significantly improved by the application of a thin coating of an ionic liquid (IL). In this work, we studied the influence of the IL 1-ethyl-3-methyl-imidazolium-trifluormethansulfonate ([C2C1Im][OTf]) on the dehydrogenation of dimethylamine (DMA) on Pt(111) by surface science experiments under ultrahigh vacuum (UHV) conditions. We investigated the growth, thermal stability, and the dehydrogenation reaction of DMA on Pt(111) both in the presence and absence of [C2C1Im][OTf] by time-resolved and temperature-programmed infrared reflection absorption spectroscopy (IRAS) and density functional theory (DFT). We found that pre-adsorbed DMA has a strong influence on the interaction of [C2C1Im][OTf] with the Pt surface. The competition for the same adsorption sites leads to changes in the binding motif and binding angles of the IL. In the presence of the IL, the reaction temperature of DMA is shifted to higher temperature due to the same competition and blocking effects. Thus, the IL leads to an enhanced stability of DMA on the surface and influences the product spectrum of the dehydrogenation reaction at higher temperature.