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The influence of nitrate concentration and acidity on the electrocatalytic reduction of nitrate on platinum
No full textCombining experiment and theory for understanding electocatalysis
No full textAn overview is given of different methods of modern computational chemistry, with emphasis on how, in combination with experiment, the results of such simulations may enhance our understanding of electrochemical and electrocatalytic processes on the molecular level. Recent developments in modeling electrode reactions using Marcus theory and molecular dynamics simulations include treatment of electrode reactions in which bonds with the surface or within the reacting molecule are broken or formed. First-principles electronic structure calculations based on density-functional theory allow the accurate calculation of binding energies and vibrational properties, which are of much interest in comparison with experiment. Inclusion of electric field effects and water in these state-of-the-art simulations also yield unique insight into the properties of the electrochemical interface on the molecular level, and this is certainly a field in which there will be much progress in the not too distant future. Finally, kinetic modeling using mean-field equations or Monte Carlo simulations, preferably combined with input or insight from first-principles calculations, produce voltammetric and chronoamperometric responses, which may be compared to experiment
De Thermodynamica voorbij in de Elektrochemie
No full textComputersimulaties geven de elektrochemie een moleculaire basis. Moderne inzichten in het gedrag van moleculen, oppervlakken en elektronen toegepast op het klassieke vakgebied van de elektrochemie
Electrocatalysis on bimetallic and alloy surfaces
No full textBimetallic surfaces and alloys are well known to have unique catalytic properties for many important chemical transformations [1]. In electrocatalysis, bimetallic and alloy catalysts have been a particularly active area of research in relation to low-temperature fuel cells [2]. On the anode side, bi- or even tri-metallic electrodes are used to improve the CO tolerance of the hydrogen oxidation or to enhance methanol oxidation activity [3], whereas on the cathode side it has recently been established that for oxygen reduction certain bimetallic surfaces have superior activity compared to pure platinum [4 and 5]. The enhanced catalytic activity of bimetallic surfaces in comparison to pure metal surfaces is usually ascribed to two effects, or a combination thereof: the bifunctional effect in which the unique catalytic properties of each of the elements in the alloy combine in a synergetic fashion to yield a surface which is more active than each of the elements alone, and the ligand or electronic effect, in which one of the elements alters the electronic properties of the other so as to yield a more active catalytic surface.
In relation to the issue of CO tolerance and the electrochemical oxidation of CO, bimetallic surfaces have been studied since the early work of Bockris and Wroblowa [6], Janssen and Moolhuysen [7], and, most notably, Watanabe and Motoo [8]. These issues have become more important recently, with the increased emphasis on fuel cells for our energy future. It is now well established that for the electrochemical oxidation of CO on bimetallic surfaces such as PtRu, PtSn and PtMo, the bifunctional effect is the most dominant mechanism. The more oxophylic element Ru or Sn provides the oxygen donor, usually believed to be adsorbed hydroxyl, by activating water at reduced overpotential
Stripping voltammetry and chronoamperometry of an adsorbed species with repulsive lateral interactions
No full textIn this paper a simple model is considered for the stripping voltammetry and chronoamperometry of an adsorbed species with repulsive lateral interactions. In the limit of
strongly repulsive lateral interactions, the chronoamperometric transient is predicted to
be hyperbolic, i.e. to have a t-1 dependence. This dependence is confirmed by both
the numerical simulation of the mean-field equations and by the Dynamic Monte Carlo
simulations. However, in the analysis of the Dynamic Monte Carlo simulations, inflexion
points are found in a log-log plot of the data, corresponding to the formation of ordered
configurations on the surface. The stripping voltammetry exhibits broader stripping peaks
with increasingly repulsive lateral interactions. An analysis of the peak potential versus
the logarithm of the scan rate yields the Tafel slope, irrespective of the strength of the
lateral interactions. In the Dynamic Monte Carlo simulations, strong repulsive interactions
lead to multiple stripping peaks, the peaks becoming more pronounced with a faster
surface diffusion of the adsorbed species. These peaks are related to the existence of
ordered configurations on the electrode, whose long-range order is enhanced at faster
diffusion rates
Electrooxidation of small organic molecules on single crystal and bi-metallic electrodes
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