CO Chemisorption on Vicinal Rh(111) Surfaces Studied with a Curved Crystal

Abstract

Curved crystal surfaces enable the systematic and accurate comparison of physical and chemical processes for a full set of vicinal crystal planes, which are probed in the very same environment. Here, we examine the early stages of the CO chemisorption on vicinal Rh(111) surfaces using a curved Rh crystal that exposes a smoothly variable density of {100} (A-type) and {111} (B-type) steps. We readily identify and quantify step and terrace species by resolving their respective core-level lines using X-ray photoelectron spectroscopy at different locations on the curved surface. Uptake experiments show similar sticking probabilities at all surface planes, subtle asymmetries between A- and B-type steps, and significantly lower saturation coverage at densely stepped surfaces as compared to the (111) plane. The analysis of the C 1s intensity variation across the curved sample allows us to discuss the adsorption geometry around the step edge.

Catalytic Oxidation of CO on a Curved Pt(111) Surface: Simultaneous Ignition at All Facets through a Transient CO‐O Complex**

“…ac onstant terrace-CO density at all a angles. [19] In contrast, the terrace-CO in NAP, particularly at 550 K, exhibits breaks of slope at a c < À98 8 and a c > 78 8 in the B-and the A-side of the crystal, respectively,asmarked in Figure 2b.Assuming again constant CO density at terraces,s lope discontinuities in Figure 2c could arise due to oxygen-induced step-doubling beyond a c , [23] as also revealed in O1ss pectra below,a nd discussed in detail in the Supporting Information.…”

“…Straight lines for Terrace and Step panels fit the data assumingasimple CO adsorptionm odel. [19] Changes in the slope in NAP curves occur at a C (dotted lines).…”

Catalytic Oxidation of CO on a Curved Pt(111) Surface: Simultaneous Ignition at All Facets through a Transient CO‐O Complex**

“…Forschungsartikel 20214 www.angewandte.de ac onstant terrace-CO density at all a angles. [19] In contrast, the terrace-CO in NAP, particularly at 550 K, exhibits breaks of slope at a c < À98 8 and a c > 78 8 in the B-and the A-side of the crystal, respectively,asmarked in Figure 2b.Assuming again constant CO density at terraces,s lope discontinuities in Figure 2c could arise due to oxygen-induced step-doubling beyond a c , [23] as also revealed in O1ss pectra below,a nd discussed in detail in the Supporting Information.…”

Catalytic Oxidation of CO on a Curved Pt(111) Surface: Simultaneous Ignition at All Facets Through a Transient CO-O Complex

“…In UHV at 300 K, the terrace-CO coverage decreases linearly away from the (111) center, as expected on simple grounds, that is, for a constant terrace-CO density at all vicinal angles. 65 In contrast, the terrace-CO in NAP, particularly at 550 K, exhibits changes in the decreasing rate at α c >-9 • and α c >7 • in the B-and the A-side of the crystal, respectively, which are also mirrored in the Total-CO-coverage curve of the bottom panel.…”

“…64 Straight lines for Terrace and Step panels are fits to the data assuming a simple CO adsorption model with steps having a finite width W S . 65 The breaks in the slope in NAP are explained by adsorption-induced step-doubling occurring at critical α C (see the text).…”