Mobility and Oxidation of Adsorbed CO on Shape-Controlled Pt Nanoparticles in Acidic Medium

Abstract

The knowledge about how CO occupies and detaches from specific surface sites on well-structured Pt surfaces provides outstanding information on both dynamics/mobility of CO ads and oxidation of this molecule under electrochemical conditions. This work reports how the potentiostatic growth of different coverage CO adlayers evolves with time on both cubic and octahedral Pt nanoparticles in acidic medium. Data suggest that during the growth of the CO adlayer, CO ads molecules slightly shift towards low coordination sites only on octahedral Pt nanoparticles, so that these under coordinated sites are the first filled on octahedral Pt nanoparticles. Conversely, on cubic Pt nanoparticles, adsorbed CO behaves as an immobile species, and low coordinated sites, as well as (100) terraces are apparently filled uniformly and simultaneously. However, once the adlayer is complete, irrespectively of whether the CO is oxidized in a single 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 step or in a sequence of different potential steps, results suggest that CO ads behaves as an immobile species during its oxidation on both octahedral and cubic Pt nanoparticles.

Electrochemical CO stripping on nanosized Pt surfaces in acid media: A review on the issue of peak multiplicity

“…Further knowledge of the issue of the CO surface diffusion was obtained in the works of Maillard et al [10], Koper et al [49], Savinova et al [50], Wieckowski et al [51,52], Feliu et al [53], and others. In general, it was found that the diffusion coefficient of CO (D CO ) on Pt surfaces depends on the coverage of CO and particle size.…”

Electrochemical CO Oxidation at Platinum on Carbon Studied through Analysis of Anomalous in Situ IR Spectra

“… 16 , 20 The NG model is also supported by recent work, which suggests that surface diffusion of CO is not as fast as previously thought. 18 , 21 , 22 …”

In Situ Raman Study of CO Electrooxidation on Pt(hkl) Single‐Crystal Surfaces in Acidic Solution

“…[3] Based on the results of previous electrochemical studies, it is currently considered that the CO electrooxidation reaction is facilitated according to the "reaction pair mechanism", that is, the Langmuir-Hinshelwood mechanism (L-H mechanism). [4] The premise of the L-H mechanism is that there are both adsorbed OH* (originating from H 2 O dissociation at free sites) and adsorbed CO* molecules on adjacent sites undergoing a surface bimolecular reaction. [5] The adsorption and migration of surface species, such as CO*, OH* and COOH* on the Pt surface plays a decisive role in the electrooxidation process and controls the kinetics of the CO electrooxidation.…”