Evidence of an Eley–Rideal Mechanism in the Stripping of a Saturation Layer of Chemisorbed CO on Platinum Nanoparticles

Abstract

The oxidative stripping of a saturation layer of CO(chem) was studied on platinum nanoparticles of high shape selectivity and narrow size distribution. Nanospheres, nanocubes, and nano-octahedrons were synthesized using the water-in-oil microemulsion or polyacrylate methods. The three shapes allowed examination of the CO(chem) stripping in relation to the geometry of the nanoparticles and presence of specific nanoscopic surface domains. Electrochemical quartz crystal nanobalance (EQCN) measurements provided evidence for the existence of more than one mechanism in the CO(chem) stripping. This was corroborated by chronoamperometry transient for a CO(chem) saturation layer at stripping potentials of E(strip) = 0.40, 0.50, 0.60, and 0.70 V. The first mechanism is operational in the case of CO(chem) stripping at lower E(strip) values; it proceeds without adsorption of anions or H(2)O molecules and corresponds to desorption of a fraction of CO(chem) in the form of a prepeak in voltammograms or in the form of an exponential decay in chrono-amperometry (CA) transients. The second mechanism is operational in the desorption of the remaining CO(chem) at higher E(strip) values and gives rise to at least two voltammetric peaks or two CA peaks. Analysis of the experimental data and modeling of the CA transients lead to the conclusion that the stripping of a saturation layer of CO(chem) first follows an Eley-Rideal mechanism in the early stage of the process and then a Langmuir-Hinshelwood mechanism.

The Effect of Substrates at Cathodes in Low‐temperature Fuel Cells

“…2 nm, with a high dispersion; see Figures 5 a and 5 c. Pt NPs supported or unsupported generated via the carbonyl chemical route have been reviewed by one of us 44. 47, 48 The identical CO electro‐oxidation position of Pt to CO stripping curves for Pt supported onto carbon black catalysts,49, 50 rules out the possible contribution of Pt crystallographic orientation to the observed difference in CO stripping curves for Pt/C, Pt/MWCNT and Pt/MWCNT‐m catalysts.…”

CO electro-oxidation reaction on Pt nanoparticles: Understanding peak multiplicity through thiol derivative molecule adsorption

“…First, CO electro-oxidation is generally considered to follow the LangmuirHinshelwood mechanism [9,10] in which CO electro-oxidation is controlled by the reaction of the OH adsorbed on Pt. However several other possibilities (such as the Eley-Rideal mechanism) have been proposed at low potential [11]. Second, in Pt and Pt-based systems, multiple peaks are often observed [12][13][14] the reason for which is still under debate.…”

Coverage-dependent formic acid oxidation reaction kinetics determined by oscillating potentials

“…Hence, excessive θ CO values prevent the adsorption of co-reactant while the co-adsorption of water was also observed to favor the formation of bridged CO species further enhancing reactivity. 28,37 Although contributions of alternative mechanisms like the Eley-Rideal mechanism can be assumed to be negligible under our reaction conditions, 38 variations for the LH mechanism have been reported before. Island versus random oxidation mechanisms are commonly discussed, the former of which comprises the formation of adsorbed CO islands which tend to react on the rim while the latter indicates the reaction of a CO molecule homogeneously located on the electrode surface.…”