Quantifying Oxidation Rates of Carbon Monoxide on a Pt/C Electrode

TL;DR

This study investigates the oxidation mechanisms of CO adsorbed on Pt/C electrodes, revealing how weakly and strongly bound CO species behave under different potentials and temperatures using voltammetry and kinetic modeling.

Contribution

It introduces a methodology combining voltammetry and a nucleation-growth model to quantify and analyze the oxidation rates of different COad species on Pt/C electrodes.

Findings

Weakly bound COad decreases exponentially over time.

Strongly bound COad transitions from nucleation to exponential decay with increasing potential.

Oxidation rate parameters depend on potential and temperature.

Abstract

The electrochemical oxidation of carbon monoxide adsorbed (COad) on platinum-on-carbon electrodes was studied via a methodology in which pre-adsorbed CO was partially oxidized by applying potentiostatic pulses for certain durations. The residual COad was analyzed using stripping voltammetry that involved the deconvolution of COad oxidation peaks of voltammograms to quantify the weakly and strongly bound species of COad. The data obtained for various potentials and temperatures were fit to a model based on a nucleation and growth mechanism. The resulting fit produced potential- and temperature-dependent rate parameters that provided insight into the oxidation mechanism of the two COad species. Irrespective of the applied potential or temperature, the concentration of weakly bound COad species decreased exponentially with time. In contrast, the strongly bound COad species showed a gradual transition of mechanisms, from progressive nucleation at relatively low potentials to exponential decay at high potentials.