Electrocatalytic Activity of Ru-Modified Pt(111) Electrodes toward CO Oxidation

Abstract

The electrochemical deposition of Ru on Pt(111) electrodes has been investigated by electron diffraction, Auger spectroscopy, and cyclic voltammetry in a closed UHV transfer system. At small coverages Ru formed a monatomic commensurate layer, at higher coverage mostly small islands with a bilayer height were detected. When the Pt was almost completely covered by Ru, three-dimensional clusters developed. The island structure of Ru changed upon electrooxidation of CO, reflecting an enhanced mobility of Ru. Adsorption and electrooxidation of CO have been studied on such Ru-modified Pt(111) electrodes using cyclic voltammetry and in situ FTIR spectroscopy. Compared to the pure metals, the Ru−CO bond is weakened, the Pt−CO bond strengthened on the modified electrodes. The catalytic activity of the Ru/Pt(111) electrode toward CO adlayer oxidation is higher than that of pure Ru and a PtRu alloy (50:50). It is concluded that the electrooxidation of CO takes place preferentially at the Ru islands, while CO adsorbed on Pt migrates to them.

Epitaxial Growth of Ruthenium Dioxides on Ru(0001) Surface

“…Few (100) Ru surface atoms of the nano-clusters are not perfectly scattered in phase and contribute too weak scattering intensity to "light up" the LEED reflection spots in line with that previously observed for Ru(0001) electroxoidation at +1.11 V for 2 min in 0.1 M HClO 4 , for that LEED also shows a (1 x 1) [24]. An analogous result has been demonstrated by the Pd UPD onto Au(100), where a monolayer Pd shows a c (2 x 2) LEED pattern shown in Figure 10A, however, after partial dissolution of bulk Pd the roughened Pd layers on Au(100) give a (1 x 1) LEED pattern as seen Figure 10B [28].…”

“…, where N 3 is the number of layers, s and c are the RL-and the lattice-vector perpendicular to the surface, respectively [24].…”

Disentangling Catalytic Activity at Terrace and Step Sites on Selectively Ru-Modified Well-Ordered Pt Surfaces Probed by CO Electro-oxidation

“…appears at ~1833 cm -1 which is attributed to CO B on Pt sites. 14 The potential at which CO2 formation starts is ~0.30 V (Figure 8A), that is ~0.1 V lower in comparison to the experiment depicted in Figure 7A.…”

“…13,14 Accordingly, Ru produces perturbations in the energy of the surface d-band of Pt, 13,15 which can result in modifications on both the strength of Pt-(CO) bond and the activation energy of reaction, in such a way that on Pt surfaces modified by Ru, Pt-(CO) might be easily oxidized to CO2 at potentials lower than those required in Pt alone. 14 Besides electronic effects, it is well known that the attachment of foreign atoms to a substrate can also induce changes in the catalytic properties of the substrate, once different equilibrium positions are attained due to strains in lattice constant provoked by these foreign atoms, [16][17][18] in which both electronic and strain effects are expected to operate simultaneously. 19 The combined action of bifunctional mechanism and electronic effect has been proposed to explain the role of Pt-Ru during CO electro-oxidation, 13 but the bifunctional mechanism is still the predominant model to explain the behavior of such systems.…”

Spontaneous and Electrodeposition of Pt on Ru(0001)

“…The spontaneous technique has e.g. be used for preparing Ru-modified Pt(111) [4,5] as well as Pt/Ru(0001) surfaces [6]. Remarkable enhancements of the electrocatalytic activity towards methanol and formic acid oxidation has been found with both Ru- [7,8] and Pd-modified [9,10] Pt electrodes.…”