NEW APPROACHES TO THE STUDY OF ELECTROCHEMICAL DECARBOXYLATION AND THE KOLBE REACTION: PART III. QUANTITATIVE ANALYSIS OF DECAY AND DISCHARGE TRANSIENTS AND THE ROLE OF ADSORBED INTERMEDIATES

1963 ◽  
Vol 41 (1) ◽  
pp. 55-67 ◽  
Author(s):  
B. E. Conway ◽  
M. Dzieciuch
Keyword(s):  
Reaction Mechanism ◽  
Anodic Polarization ◽  
Film Growth ◽  
Open Circuit ◽  
Gas Evolution ◽  
Autocatalytic Decomposition ◽  
Kolbe Reaction ◽  
Current Potential ◽  
Potential Curves

Galvanostatic cathodic discharge and open-circuit decay transients have been obtained for the decarboxylation of formate in formic acid and interpreted quantitatively in terms of the adsorption of intermediates in the reaction. These intermediates are identified with HCOO• radicals. Extended anodic polarization at platinum and particularly at palladium leads to the formation of films of an anodic product which are considerably thicker than a monolayer. After relatively long times (> 100 seconds) of anodic polarization, the film growth obeys the inverse logarithmic rate law deduced by Mott and Cabrera. The thick films which are formed at palladium are believed to be responsible, upon autocatalytic decomposition, for the delayed gas evolution phenomenon observed at this metal.A new method for deduction of adsorption pseudocapacitance and charge associated with the ad-layer from open-circuit decay curves and Tafel parameters is used to obtain the pseudo-capacitance and charge associated with the transition region in the current–potential curves for the formate decarboxylation. It is shown that this region corresponds to filling of the surface with adsorbed intermediates formed in the reaction. These observations are shown to support the reaction mechanism proposed in Part I.

NEW APPROACHES TO THE STUDY OF ELECTROCHEMICAL DECARBOXYLATION AND THE KOLBE REACTION: PART I. THE MODEL REACTION WITH FORMATE

1963 ◽  
Vol 41 (1) ◽  
pp. 21-37 ◽  
Author(s):  
B. E. Conway ◽  
M. Dzieciuch
Keyword(s):  
Reaction Mechanisms ◽  
Film Formation ◽  
Open Circuit ◽  
Model Reaction ◽  
Radical Coupling ◽  
Diffusion Controlled ◽  
Reverse Pulse ◽  
Kolbe Reaction ◽  
Current Potential ◽  
Potential Curves

The kinetics of electrochemical decarboxylation of formate ions has been studied in detail for the first time as a model reaction for examination of the decarboxylation and radical coupling that occurs with higher aliphatic acids. Current–potential curves have been obtained which show a sharp transition region, not diffusion controlled, which is characteristic of passivation phenomena. The behavior is observed with gold, palladium, platinum, and gold–palladium alloys. Tafel slopes and exchange currents have been evaluated for the reaction and possible reaction mechanisms are examined in relation to the experimental results.Galvanostatic charging, reverse pulse discharging, and open-circuit decay transients have been obtained which indicate formation of films of adsorbed intermediates on the surface. The transition regions in the current–potential curves are associated with formation of this ad-layer. The galvanostatic results enable distinctions to be made between some of the possible reaction mechanisms proposed and estimates to be made of the extent of film formation by adsorbed intermediates formed in the reaction.

scholarly journals Dynamics of Oxidation of Reduced Forms of CO2 under Electrochemical and Open-Сircuit Conditions on Polycrystalline Pt in H2CO3

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 274
Author(s):  
Alexander V. Smolin ◽  
Мikhail N. Mikhailov ◽  
Aleksey F. Gadzaov ◽  
Leonid M. Kustov
Keyword(s):  
Quantum Chemical ◽  
Preliminary Analysis ◽  
Oxidation Reaction ◽  
Density Functional ◽  
Oxidation Process ◽  
Open Circuit ◽  
Organic Substances ◽  
Oxidation Of Co ◽  
Reduced Forms

The problem of identifying correlations between catalytic and electrocatalytic processes is one of the fundamental problems of catalysis among “simple” organic substances, and the oxidation of CO and rCO2 is of great interest, since CO and CO2 are considered in pairs both during catalytic and electrocatalytic transformations. In the case of electrocatalysis, this analysis is important in the study of fuel cells. In this paper, we studied the correlation between the oxidation of reduced forms of CO2 (rCO2) under potentiodynamic-galvanoctatic electrochemical and open-circuit conditions of measurements on polycrystalline (pc)Pt in H2CO3. Periodic oscillations are revealed at the oxidation of Had and rCO2 on (pc)Pt. Quantum chemical calculations were carried out on the Pt13 cluster in order to identify the mechanisms of the rCO2 oxidation reaction. The correspondence in the energy parameters of the oxidation process of rCO2 under open-circuit conditions and electrochemical conditions is shown. The preliminary analysis of the system using density functional (DFT) calculations is carried out and the most stable systems that are based on Pt13 are found, namely rOH-Pt13-(CO)n, rOH-Pt13-(COH) and rOH-Pt13-(rCOOH). OH• species was chosen as the most likely candidate for the role of the oxidant for rCO2. Preliminary calculations for the expected reactions were carried out, and the optimal PES is revealed.

Enhancement of the performance of CdS/CdTe heterojunction solar cell using TiO2/ZnO bi-layer ARC and V2O5 BSF layers: A simulation approach

2020 ◽  
Vol 92 (2) ◽  
pp. 20901
Author(s):  
Abdul Kuddus ◽  
Md. Ferdous Rahman ◽  
Jaker Hossain ◽  
Abu Bakar Md. Ismail
Keyword(s):  
Solar Cell ◽  
Short Circuit ◽  
Photovoltaic Performance ◽  
Short Circuit Current ◽  
Short Circuit Current Density ◽  
Open Circuit ◽  
Heterojunction Solar Cell ◽  
Back Surface ◽  
Heterojunction Solar Cells

This article presents the role of Bi-layer anti-reflection coating (ARC) of TiO2/ZnO and back surface field (BSF) of V2O5 for improving the photovoltaic performance of Cadmium Sulfide (CdS) and Cadmium Telluride (CdTe) based heterojunction solar cells (HJSCs). The simulation was performed at different concentrations, thickness, defect densities of each active materials and working temperatures to optimize the most excellent structure and working conditions for achieving the highest cell performance using obtained optical and electrical parameters value from the experimental investigation on spin-coated CdS, CdTe, ZnO, TiO2 and V2O5 thin films deposited on the glass substrate. The simulation results reveal that the designed CdS/CdTe based heterojunction cell offers the highest efficiency, η of ∼25% with an enhanced open-circuit voltage, Voc of 0.811 V, short circuit current density, Jsc of 38.51 mA cm−2, fill factor, FF of 80% with bi-layer ARC and BSF. Moreover, it appears that the TiO2/ZnO bi-layer ARC, as well as ETL and V2O5 as BSF, could be highly promising materials of choice for CdS/CdTe based heterojunction solar cell.

Oxidations ofNω-Hydroxyarginine Analogues and VariousN-Hydroxyguanidines by NO Synthase II: Key Role of Tetrahydrobiopterin in the Reaction Mechanism and Substrate Selectivity

2001 ◽  
Vol 14 (2) ◽  
pp. 202-210 ◽  
Author(s):  
Catherine Moali ◽  
Jean-Luc Boucher ◽  
Axelle Renodon-Corniere ◽  
Dennis J. Stuehr ◽  
Daniel Mansuy
Keyword(s):  
Reaction Mechanism ◽  
No Synthase ◽  
Substrate Selectivity

scholarly journals Redox mediation at poly(o-aminophenol) coated electrodes: Mechanistic diagnosis from steady state polarization curves

2018 ◽  
Author(s):  
Gabriel Ybarra ◽  
Carlos Moina ◽  
María Inés Florit ◽  
Dionisio Posadas
Keyword(s):  
Steady State ◽  
Polarization Curve ◽  
Experimental Measurements ◽  
Steady State Current ◽  
Thermodynamical Parameters ◽  
Reduction And Oxidation ◽  
Mediated Reduction ◽  
Coated Electrodes ◽  
Current Potential ◽  
Potential Curves

<p class="PaperAbstract"><span lang="EN-US">In this work, the mediated reduction and oxidation of Fe(CN)<sub>6</sub><sup>3-/4-</sup> and Fe<sup>3+ </sup>in poly(o-aminophenol) coated electrodes is analyzed by means of diagnosis diagram based on the features of steady state current-potential curves. This analysis allows to identify the current determining process and to reproduce the experimental characteristics of the polarization curve from the relevant kinetic and thermodynamical parameters with a minimum amount of experimental measurements. </span></p>

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