A site-selective in situ study of CO adsorption and desorption on Pt(355)

Abstract

Using time-dependent high-resolution x-ray photoelectron spectroscopy at BESSY II, the adsorption and desorption processes of CO on stepped Pt(355) = Pt[5(111) x (111)] were investigated. From a quantitative analysis of C 1s data, the distribution of CO on the various adsorption sites can be determined continuously during adsorption and desorption. These unique data show that the terrace sites are only occupied when the step sites are almost saturated, even at temperatures as low as 130 K. The coverage-dependent occupation of on-top and bridge adsorption sites on the (111) terraces of Pt(355) is found to differ from that on Pt(111), which is attributed to the finite width of the terraces and changes in adsorbate-adsorbate interactions. In particular, no long-range order of the adsorbate layer could be observed by low-energy electron diffraction. Further details are derived from sticking coefficient measurements using the method devised by King and Wells [Proc. R. Soc. London, Ser. A 339, 245 (1974)] and temperature-programmed desorption. The CO saturation coverage is found to be slightly smaller on the stepped surface as compared to that on Pt(111). The initial sticking coefficient has the same high value of 0.91 for both surfaces.

Promotion Effect of Platinum on Gold’s Reactivity: A High-Resolution Photoelectron Spectroscopy Study

“…However, they reported that a critical temperature is needed in order to promote the cracking of the pre-adsorbed molecule, the temperature being dependent on the density of defects on the surface. On the other hand, results regarding CO adsorption on stepped Pt(hkl) surfaces indicate that the process is molecular rather than dissociative 38 . In this sense, our results indicate that the Pt@Au/Au(332) surface has an inherent ability for the dissociation of CO since this process is observed at room temperature.…”

The dissimilar twins – a comparative, site-selective in situ study of CO adsorption and desorption on Pt(322) and Pt(355)

“…1a and b the C 1s spectra taken during CO adsorption on Pt(3 2 2) at 150 K and for comparison on Pt(3 5 5) at 130 K [4], respectively, are shown. The total time of the experiment was 1560 s at a pressure of 1.8 · 10 À9 mbar, corresponding to an exposure of 2.81 L.…”

“…[3] and references therein) but also, to a lesser extend, on stepped surfaces (Ref. [4] and references therein, Refs. [5,6]).…”

“…By high-resolution X-ray photoelectron spectroscopy (HR-XPS), the occupation of different adsorption sites can be quantitatively monitored in situ during adsorption and desorption [3]. In order to study the influence of the step orientation on adsorption and desorption processes in detail, we have investigated the interaction of CO with Pt(3 2 2) (also denoted as Pt(S)-[5(1 1 1) · (1 0 0)]) and compare the results to those obtained on Pt(3 5 5) (also denoted as Pt(S)-[5(1 1 1) · (1 1 1)]) [4] and also Pt(1 1 1) [17], which were obtained previously in our group. Both stepped surfaces have (1 1 1) terraces that are five atomic rows wide, but differ in the orientation of their monatomic steps, being (1 1 1) and (1 0 0), respectively.…”

Mobility and Oxidation of Adsorbed CO on Shape-Controlled Pt Nanoparticles in Acidic Medium

“…Also, the diffusion can be 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 influenced by the lateral interaction present in the adsorbate layer. In fact, as examined for stepped Pt surfaces, CO adsorbs more strongly in under-coordinated sites than in terrace sites [39][40][41][42] , and the rate of CO filling on under-coordinated is higher as higher is the overall CO coverage. 35 The argument above can be employed, at least in part, to justify why the CO ads does behave like an immobile species during its oxidation.…”