Room Temperature CO_ad Desorption/Exchange Kinetics on Pt Electrodes—A Combined In Situ IR and Mass Spectrometry Study

Abstract

The room temperature desorption and exchange of CO in a saturated CO adlayer on a Pt electrode, at potentials far below the onset of oxidation, was investigated by isotope labeling experiments, using a novel spectroelectrochemical setup, which allows the simultaneous detection of adsorbed species by in situ IR spectroscopy and of volatile (side) products and reactants by online mass spectrometry under controlled electrolyte flow conditions. Time-resolved IR spectra show a rapid, statistical exchange of pre-adsorbed (13)CO(ad) by (12)CO(ad) in (12)CO containing electrolyte; mass spectrometric data reveal first-order exchange kinetics, with the rate increasing with CO partial pressure. The increasing CO(ad) desorption rate in equilibrium with a CO containing electrolyte is explained by a combination of an increasing CO(ad) coverage upon increasing the CO pressure, and a decrease of the CO adsorption energy with coverage, due to repulsive CO(ad)-CO(ad) interactions.

Molecular Adsorbates at Single‐Crystal Platinum‐Group Metals and Bimetallic Surfaces

“…[28]) on the partial pressure of CO. [24] In CO-saturated solution, this transition occurs within some tens of a millisecond. [29,30] In COfree solution, a maximum coverage of 0.68 was found with a transition to about 0.63 at 0.3 V versus RHE, while hydrogen adsorption was still completely blocked.…”

Mass transport effects in CO adsorption and continuous CO electrooxidation over regular arrays of Pt nanostructures on planar glassy carbon supports

“…Employing combined ATR-FTIRS/DEMS measurements, the CO adlayer build-up [20,28] and CO bulk oxidation on thin-film Pt electrodes [29] were investigated recently in an electrochemical environment under controlled transport conditions. CO adsorption/oxidation on a polycrystalline Pt microelectrode was studied recently employing time-resolved reflectance spectroscopy for probing the adlayer build-up and the resulting steady-state CO ad coverage upon continuous CO oxidation [30].…”

“…The CO adsorption kinetics under well-defined mass transport conditions can either be monitored via the loss of CO in the electrolyte, e.g., by on-line differential electrochemical mass spectrometry (DEMS) in a thin-layer flow cell [18], or via the build-up of the CO adlayer by in situ spectroscopy under continuous flow conditions, e.g., by in situ FTIR spectroscopy in an attenuated total reflection (ATR) configuration [28,29]. Employing combined ATR-FTIRS/DEMS measurements, the CO adlayer build-up [20,28] and CO bulk oxidation on thin-film Pt electrodes [29] were investigated recently in an electrochemical environment under controlled transport conditions.…”

The Effect of Structurally Well‐Defined Pt Modification on the Electrochemical and Electrocatalytic Properties of Ru(0001) Electrodes

“…The empty Ru site, A(Ru), must result from fluctuations in the CO adlayer and/or from displacement of CO ad at the high coverage (low adsorption energy), similar to exchange of CO ad in a CO adlayer at room temperature [Heinen et al, 2006]. …”