Dynamic CO Adsorption and Desorption Through the Ionic Liquid Layer of a Pt Model SCILL

Solid catalysts with ionic liquid layers (SCILLs) have recently attracted a lot of attention, since the ionic liquid (IL) coating can give rise to drastically improved selectivity. Here, we studied the interaction of the IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)-imide [C4C1Pyr][NTf2] with Pt(111) and Pt nanoparticles (NPs) on highly oriented pyrolytic graphite (HOPG) under ultrahigh vacuum (UHV) conditions. The IL film on Pt(111) and on the Pt NPs consists of a strongly bound monolayer and a weakly bound bulk phase. In the monolayer, [NTf2]- adopts cis conformation and binds via the SO2 groups. Adsorption of [NTf2]- at Pt defect sites is preferred to adsorption at terraces, while pre-adsorbed CO blocks the adsorption at defects. Further, IL co-adsorption leads to desorption and displacement of on-top CO on terraces while CO resides in bridging position. IL multilayers desorb at 380 K, while the strongly adsorbed monolayer on Pt resides and gradually desorbs and decomposes between 400 a...