Surface cyclic voltammogram electrooxidation

For Pt catalyst, the surface cyclic voltammogram shows that the electrooxidation starts to occur when the electrode potential is more positive than 0.6 V vs RHE to form Pt oxides such as PtO. In the presence of O2, the electrode potential is more positive than 1.0 V, at which Pt will be definitely electrochemically oxidized to form PtO. In an acidic environment, the formed PtO will be dissolved according to Reaction (3-1) ... 

The formation of carbon surface oxides, phenols, quinones, lactones, and car-boxyhc acids upon the electrooxidation of carbon has been detected by physical methods such as infrared spectroscopy [262], ellipsometry [263], x-ray photoelectron spectroscopy [262,264,265], thermal desorption, and electrochemistry (see refs. [8, 96, 248, and 261] and references therein). Cyclic voltammograms of oxidized carbons exhibit increased charge in the potential interval from 0.4 to... 

Formic acid electrooxidation has been studied on both Pt [39-41] and Pd [42] singlecrystal surfaces. Herein we compare the work of Iwasita et al. [41] and Hoshi et al. [42] on Pt and Pd single crystals, respectively. The cyclic voltammograms were... 

Fig. 3.3 Single-crystal cyclic voltammograms of (A) Ft [41] and (B) Pd [42] for (110), (111), and (100) facets. The electrooxidation of 0.1 M formic acid is evaluated on the various faceted surfaces in 0.1 M HCIO4 supporting electrolyte at scan rates of 50 mV s and 20 mV s respectively. In (A) the dashed lines are for the background cyclic voltammograms of the different faceted Pd single crystals in 0.1 M HCIO4 alone, as are the designated (b) plots in (B) forPt (reprinted with permission from [41] and [42], respectively)...

Park et al. compared methanol versus formic acid electrooxidation on polycrystalline Pt and on two sizes of carbon-supported Pt (2.0 nm vs. 8.8 nm) (Fig. 3.5) [44]. The potentials were referenced to a saturated calomel electrode (SCE) (RHE, 0.242 V) in 0.05 M H2SO4 at a scan rate of 50 mV s The cyclic voltammograms were normalized to a 1 cm Pt effective area. They observed a reduction in methanol activity for particles smaller that 4 nm and an opposite effect for formic acid see Fig. 3.5. The disparity between methanol and formic acid size-dependent performance trends is due to methanol preferentially adsorbing onto three adjacent Pt atoms found on Pt(lll)-faceted surfaces during the C-H bond dissociation step... 

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