Field-Dependent Chemisorption of Carbon Monoxide on Platinum-Group (111) Surfaces: Relationships between Binding Energetics, Geometries, and Vibrational Properties as Assessed by Density Functional Theory

Abstract

The field-dependent frequency behavior of the metal−adsorbate (νM-CO) as well as the intramolecular (νCO) vibration of carbon monoxide chemisorbed in atop and threefold-hollow sites on three platinum-group (111) metal surfacesPt, Ir, and Pdis explored in relation to the metal−chemisorbate (M−CO) binding energetics and geometries by means of Density Functional Theory (DFT) calculations for finite clusters. This overall objectivehaving particular importance in electrochemical systemsof linking field-dependent vibrational, energetic, and geometric properties of the M−CO bond, prompted by the availability of potential-dependent νM-CO data at Pt-group electrodes from Raman spectroscopy, provides an opportunity to assess in quantum-chemical terms these surface−adsorbate binding parameters in relation to the extensively studied intramolecular CO vibration. The binding energies (−Eb) tend to increase toward negative fields (F), especially for hollow-site binding. An energy decomposition into specific orbital and ...