Reactivity of Graphene-Supported Pt Nanocluster Arrays

Abstract

Nanocluster arrays on graphene (Gr) are intriguing model systems for catalysis. We studied the adsorption and oxidation of CO on Pt/Gr/Rh(111) with synchrotron-based high-resolution X-ray photoelectron spectroscopy. On the nanoclusters, CO is found to adsorb at three different sites: namely, on-top, bridge, and step. The C 1s spectra exhibit remarkable similarities to those on the stepped Pt(355) surface. Similar to the case for stepped Pt surfaces, a clear preference for the adsorption on the step sites is found, while the preference for the adsorption on the on-top site over the bridge site on the terraces is much less pronounced in comparison to that on Pt single crystals. Temperatureprogrammed X-ray photoelectron spectroscopy revealed an enhanced binding energy for the cluster step sites, similar to the situation on stepped Pt surfaces. The oxidation of CO on graphene-supported Pt nanoclusters follows a pseudo-first-order rate law. Applying an Arrhenius analysis, we found an activation energy of 13 ± 4 kJ/mol, which is much smaller than that on Pt(111), due to the more reactive step and kink sites on the nanoclusters.

Adsorption and Reaction of SO2 on Graphene-Supported Pt Nanoclusters

“…However, the presence of SO 2 ly , which was only observed on Pt(355) and not Pt(322), indicates that also (111) steps are occupied to some extent. It is interesting to note that we find the opposite behavior for CO on the Pt nanoclusters [8]. In the case of CO, we found the highest similarity with the Pt(355) surface, indicating a significant role of (111) steps.…”

“…On the Pt nanoclusters the highest amount of sulfur-more than half of the original amount of SO 2 -was observed, in comparison to the investigated single crystal surfaces (see Table 1). This finding is attributed to the high reactivity of step and kink sites on the Pt nanoclusters [8].…”

“…Graphene (Gr) was prepared by chemical vapor deposition (CVD) of ethene at 920 K [12,13]. Platinum nanoclusters were deposited at 150 K by electron beam evaporation [8], and the Pt amount was calibrated with the QCM. SO 2 was dosed with the capillary array doser.…”

“…These nanocluster arrays are intriguing model systems for catalysis due to the small size distribution of the metal particles, on a chemically innocent support. [8] In this study, we report on the detailed investigation of the adsorption and reaction of SO 2 on graphene-supported Pt nanoclusters by high resolution synchrotron-based XPS (HR-XPS). Further insight is gained from the comparison of our results to earlier results on different Pt single crystal surfaces [31,39].…”

Effect of Gold on the Adsorption Properties of Acetaldehyde on Clean and h-BN Covered Rh(111) Surface

“…At present, two non-oxide supports are studied where the metal support interaction could be minimized. Graphene is in the focus of research and it is suitable to control the growth of metal including gold [25][26][27]. The other inert support is the boron-nitride prepared on single crystal surfaces.…”