Transients of the Open-Circuit Potential Observed during the Interaction of Formic Acid with Preliminarily Adsorbed Oxygen on a Platinized Platinum Electrode

Transients of the open-circuit potential, which are observed during the interaction of formic acid with preliminarily adsorbed oxygen (O_ads) on a Pt/Pt electrode in 0.5 M H₂SO₄, are measured. It is established, by means of the method of cathodic potentiodynamic pulses, that the slowest interaction of formic acid with O_ads occurs in the region of large coverages of the electrode surface by oxygen (θ_O ∼1–0.8). A presumption is put forward that the process rate in this region is defined by a direct reaction of O_ads with molecules of formic acid from the bulk solution. It is shown that the interaction of formic acid with O_ads in the region of intermediate coverages (θ_O ∼ 0.8–0.2) proceeds via a mechanism of “conjugated reactions.” Transients of the open-circuit potential for formic acid are compared to transients for carbon monoxide obtained in analogous conditions. The substantially shorter overall time of potential decay in the case of CO (at the same concentrations) is caused by a faster reaction of CO with adsorbed oxygen in the region of large θ_O. The difference is explained by assuming that the HCOOH adsorption as opposed to CO bears a dissociative character.__________Translated from Elektrokhimiya, Vol. 41, No. 8, 2005, pp. 936–942.Original Russian Text Copyright © 2005 by Manzhos, Maksimov, Podlovchenko.     

Specific features of interaction between formic acid and oxygen adsorbed on smooth polycrystalline platinum: Transients of the open-circuit potential

Transients of the open-circuit potential, which are observed when formic acid is interacting wit adsorbed oxygen (O_ads) preliminarily accumulated on polycrystalline “smooth” platinum (pcPt), are measure in an aqueous solution of sulfuric acid. It is shown that, as with platinized platinum (Pt/Pt), at large coverage by adsorbed oxygen (θ_O = 1?0.8), adsorbed oxygen interacts directly with molecules of formic acid from solution. In the region of medium coverages (θ_O = 0.8?0.2), on the other hand, a mechanism of “conjugated reactions” is realized. It is established that, in the case of pcPt, the direct interaction of O_ads with molecules of HCOOH from solution proceeds slower by nearly three times and the interaction via the mechanism of “conjugated reactions,” faster by about three times, as compared with Pt/Pt.     

Superexcited state reconstruction of HCl using photoelectron and photoion imaging

The velocity-map imaging technique was used to record photoelectron and photofragment ion images of HCl following two-photon excitation of the E Sigma(+)(0+), V 1Sigma(+)(0+) (nu=9,10,11) states and subsequent ionization. The images allowed us to determine the branching ratios between autoionization and dissociation channels for the different intermediate states. These branching ratios can be explained on the basis of intermediate state electron configurations, since the configuration largely prohibits direct ionization in a one-electron process, and competition between autoionization and dissociation into H* (n=2)+Cl and H+Cl*(4s,4p,3d) is observed. From a fit to the vibrationally resolved photoelectron spectrum of HCl+ it is apparent that a single superexcited state acts as a gateway to autoionization and dissociation into H+Cl*(4s). Potential reconstruction of the superexcited state to autoionization was undertaken and from a comparison of different autoionization models it appears most likely that the gateway state is a purely repulsive and low-n Rydberg state with a (4Pi) ion core.     

Effect of Plasma-Assisted Electrochemical Treatment of Boron-Doped Diamond on the Kinetic Characteristics of Reversible Electrode Reactions

Russian Journal of Electrochemistry - Surface of boron-doped diamond film electrode was subjected to plasma-assisted electrochemical treatment by anodic plasma pulses, and a change in the rate...     

Special features of methanol interaction with adsorbed oxygen at platinized platinum electrode: Transients of the open-circuit potential

Open-circuit potential transients are measured under the conditions of methanol interaction with the pre-adsorbed oxygen at platinized platinum electrode. The time necessary for complete removal of the adsorbed oxygen monolayer appeared being shorter by a factor of ～1.5 as compared with smooth polycrystalline platinum. The dependence of platinum surface coverage with adsorbed oxygen on the potential during its decay is found. It was shown that the reaction of methanol with the adsorbed oxygen is most slow at a high coverage (1–0.8). It is suggested that at these coverages, like the case of polycrystalline platinum, the adsorbed oxygen directly interacts with the methanol molecules from the solution. At moderate coverages (0.8–0.2), the reaction of the adsorbed oxygen with methanol at the platinized platinum is better described by the “conjugated reactions” mechanism. The specific rates of the methanol dissociative adsorption at the platinized platinum turned out to be close to those observed earlier for the polycrystalline platinum.     

A model for the dissociative adsorption of N2O on Cu(1 0 0) using a continuous potential energy surface

For the first time, a continuous ab initio potential energy surface (PES) taking into account all molecular degrees of freedom is built and used to model the reaction of a polyatomic molecule with a surface. DFT slab calculations are used to sample the configuration space of the system N₂O/Cu(1 0 0), and the PES function is built with a method of Manzhos and Carrington [J. Chem. Phys. 127 (2007) 014103] using dimensionality reduction from only 4300 single-point energies. Molecular dynamics simulations are performed on the PES to calculate the probability of dissociative adsorption.     

One-Stage Plasma-Assisted Electrochemical Synthesis of Cobalt-Containing Catalysts for Oxygen Reduction

Russian Journal of Electrochemistry - t—The potentialities of single-stage plasma-assisted electrochemical synthesis of few-layer graphene structures with high electrocatalytic...     

Using neural networks to represent potential surfaces as sums of products

By using exponential activation functions with a neural network (NN) method we show that it is possible to fit potentials to a sum-of-products form. The sum-of-products form is desirable because it reduces the cost of doing the quadratures required for quantum dynamics calculations. It also greatly facilitates the use of the multiconfiguration time dependent Hartree method. Unlike potfit product representation algorithm, the new NN approach does not require using a grid of points. It also produces sum-of-products potentials with fewer terms. As the number of dimensions is increased, we expect the advantages of the exponential NN idea to become more significant.     

Comparative Study of Graphite and the Products of Its Electrochemical Exfoliation

Russian Journal of Electrochemistry - A comparative study of electrochemical characteristics of graphite electrodes and precipitates of suspensions produced by the graphite exfoliation is carried...