Methanol, Formaldehyde, and Formic Acid Adsorption/Oxidation on a Carbon-Supported Pt Nanoparticle Fuel Cell Catalyst: A Comparative Quantitative DEMS Study - Fuel Cell Catalysis: A Surface Science Approach - page 411

Figure 13.1 Electrooxidation of CO ad and C 1 adsorbate layers pre-adsorbed on a Pt/Vulcan
thin-film electrode (7 mg Pt cm 22 , geometric area 0.28 cm 2 ) in 0.5 M H 2 SO 4 solution during a
first positive-going potential scan, and subsequent response of the faradaic (a) and m/z ¼ 44
ion current (b) to the electrode potential in the thin-layer DEMS flow cell. The potential scan
rate was 10 mV s 21 and the electrolyte flow rate was 5 mLs 21 , at room temperature. The respect-
ive adsorbates were adsorbed at 0.11 V for 10 minutes from CO-saturated solution (solid line),
0.1 M HCHO solution (dashed line), 0.1 M HCOOH solution (dash - dotted line), and 0.1 M
CH 3 OH solution (dash - double-dotted line).
much as that for hydrogen monolayer adsorption (one-electron reaction) in the sub-
sequent base CV (Fig. 13.1a, dotted line), the coverage of the saturated CO adlayer
on Pt/Vulcan is about 0.75 monolayers (ML) [Jusys and Behm, 2001], assuming
an H upd coverage of 0.77 ML at the onset of bulk hydrogen evolution and an H upd
monolayer charge of 0.21 mC cm 22 for polycrystalline Pt [Biegler et al., 1971].
This value agrees well with results reported previously [Jusys et al., 2001, 2003].
Oxidation of the adsorbed species resulting from interaction with formaldehyde,
formic acid, and methanol, respectively, leads to stripping peaks that are downshifted
to more negative potentials. Furthermore, the adsorbate coverage is significantly lower