Synergetic Effects of the Cu/Pt{110} Surface Alloy:  Enhanced Reactivity of Water and Carbon Monoxide

Abstract

We have used synchrotron-based high-resolution X-ray photoelectron spectroscopy in combination with ab initio density functional theory calculations to investigate the characteristics of water and CO adsorption on the bimetallic Cu/Pt{110}-(2 × 1) surface at a Cu coverage near 0.5 ML. Cu fills the troughs of the reconstructed clean surface forming nanowires, which are stable up to 830 K. Their presence dramatically influences the adsorption of water and CO. Water adsorption changes from intact to partially dissociated while the desorption temperature of CO on this surface increases by up to 27 K with respect to the clean Pt{110} surface. Ab initio calculations and experimental valence band spectra reveal that the Cu 3d-band is narrowed and shifted upward with respect to bulk Cu surfaces. This and electron donation to surface Pt atoms cause the increase in the bond strength between CO and the Pt surface atoms. The pathway for water dissociation occurs via Cu surface atoms. The heat of adsorption of water bonding to Cu surface atoms was calculated to be 0.82 eV, which is significantly higher than on the clean Pt{110} surface; the activation energy for partial dissociation is 0.53 eV (not corrected for zero point energy).

Coverage-dependent molecular tilt of carbon monoxide chemisorbed on Pt{110}: A combined LEED and DFT structural analysis

“…By comparing the areas under the TPD spectra for saturation coverage and the so-prepared disordered layer the coverage was determined to be 0.54 ML. Additional information from XPS [15,29,32] and IR spectroscopy [27] indicates that only one type of adsorption site, most likely atop, is occupied. As shown earlier by Held et al [35,36], a LEED IV analysis of a simple adsorption system can be performed reliably by only using integral order LEED beams.…”

“…in the automotive three-way catalyst where it catalyzes the oxidation of uncombusted hydrocarbons and carbon monoxide [1]. In particular, adsorption on the Pt{110} surface has been the subject of various theoretical and experimental investigations in the modern surface science era because it represents a prototype for adsorbate-induced structure transformations in an ultrahigh vacuum environment (UHV) with dramatically changing reactivities depending on the structure of the substrate [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]. The clean Pt{110} surface exhibits a p(1 × 2) "missing row" reconstructed phase, where every second row in the [001] direction is missing [4,18,26].…”

“…In addition, there is evidence from XPS and IR spectroscopy that the molecules adsorb on atop sites [15,29,16,21,27]. Other structural parameters for CO adsorption have been studied theoretically using density functional theory (DFT) [28,30,32], but there is no quantitative experimental data for structural parameters such as bond lengths and substrate reconstruction in this adsorption system.…”

Establishing Relationships Between the Geometric Structure and Chemical Reactivity of Alloy Catalysts Based on Their Measured Electronic Structure

“…As such, alloys show promise for many applications including heterogeneous catalysis [3][4][5][6][7][8]. While the potential for the utilization of alloys in heterogeneous catalysis is significant, predictive models relating the geometric structure of alloys to their chemical reactivity are lacking.…”

Communications: Developing relationships between the local chemical reactivity of alloy catalysts and physical characteristics of constituent metal elements

“…2 As such, alloys show promise for many applications including heterogeneous catalysis [3][4][5][6][7] and electrocatalysis. [8][9][10][11] While the potential for the utilization of alloys in heterogeneous catalysis and electrocatalysis is significant, predictive models relating the geometric structure of alloys to their chemical reactivity are lacking and desirable alloy catalysts are typically identified through trial-and-error experimental approaches.…”