The adsorption of methylamine on Pt single crystal surfaces

Electro-Oxidation of CO Saturated in 0.1 M HClO4 on Basal and Stepped Pt Single-Crystal Electrodes at Room Temperature Accompanied by Surface Reconstruction

The electro-oxidation of CO on Pt surface is not only fundamentally important in electrochemistry, but also practically important in residential fuel cells for avoiding the poisoning of Pt catalysts by CO. We carried out cyclic voltammetry on Pt(111), (110), (100), (10 10 9), (10 9 8), (10 2 1), (432), and (431) single-crystal surfaces using a three compartment cell to understand the activity and durability towards the electro-oxidation of CO saturated in 0.1 M HClO4. During the potential cycles between 0.07 and 0.95 V vs. the reversible hydrogen electrode, the current for the electro-oxidation of CO at potentials lower than 0.5 V disappeared, accompanied by surface reconstruction. Among the electrodes, the Pt(100) electrode showed the lowest onset potential of 0.29 V, but the activity abruptly disappeared after one potential cycle; the active sites were extremely unstable. In order to investigate the processes of the deactivation, potential-step measurements were also conducted on Pt(111) in a CO-saturated solution. Repeated cycles of the formations of Pt oxides at a high potential and Pt carbonyl species at a low potential on the surface were proposed as the deactivation process.

In situ STM observation of the CO adlayer on a Pt(110) electrode in 0.1 M HClO4 solution

We have obtained the first in situ STM molecular image of a CO adlayer on a Pt(110)-(1 x 1) electrode surface in 0.1 M HClO(4) solution. The observed CO adlayer formed an ordered (2 x 1)-2CO structure at saturated coverage. The CO molecules were found to adsorb on top of each Pt surface atom; however, they were tilted with a zigzag configuration along the atomic rows because of the dipole-dipole repulsion of neighboring CO molecules. The high activity of the Pt(110) electrode for surface CO oxidation can be attributed to the low packing density of the adsorbed CO molecules as well as their tilted orientation.

A Comparative Study of Adsorption of Aliphatic Amines at a Gold Electrode

Adsorption of aliphatic amines (C1-C4) at the gold electrode was studied by tensammetry. It has been established that the experimental dependence between the gold surface coverage (Θ) and the bulk amine concentration (cA) fits satisfactorily both by the Frumkin and Flory-Huggins isotherms. The standard Gibbs energy of adsorption, ∆G°ad at Emax for Θ < 0.8 has been found to increase in the order methylamine < ethylamine < propylamine < butylamine. This is rationalised in terms of surface-adsorbate, adsorbate-adsorbate and adsorbate-solvent interactions.