Search results for "Electrode"
showing 10 items of 950 documents
Tetrathiafulvalene-based molecular nanowires.
2008
A new molecular wire suitably functionalized with sulfur atoms at terminal positions and endowed with a central redox active TTF unit has been synthesized and inserted within two atomic-sized Au electrodes; electrical transport measurements have been performed in STM and MCBJ set-ups in a liquid environment and reveal conductance values around 10(-2) G0 for a single molecule.
Spontaneous periodic and bursting current oscillations in iron corrosion by dichromate: a useful study for simulating biological systems
1995
Abstract Studies on chemical and electrochemical oscillating systems are very useful in understanding more complex biological systems. Spontaneous periodic and bursting current oscillations were found in iron/dichromate systems coupled with graphite or zinc electrodes. In this paper, we study some phenomenological features of the two systems: their typical oscillation profiles and the influence of external resistance. The results are explained by the Franck-Fitzhugh model using the mixed potential theory.
Alternating current electrogravimetry of copper electrodissolution in a sulfuric acid solution
2017
Abstract Copper electrodissolution processes have been studied by means of electrochemical impedance spectroscopy and ac-electrogravimetry (mass impedance). During ac-electrogravimetry acquisition, mass decreases or increases due to the electrodissolution or the electrodeposition of copper, respectively. As a result, this continuous mass drift makes impossible obtaining a true ac-electrogravimetry response unless a numerical correction was applied. It has been compared the electrochemical behavior of copper layers previously treated and other freshly deposited on the gold electrode of the quartz crystal microbalance. The simultaneous analysis of both impedance functions has allowed separati…
Ion motion in salt water flowing under a transverse magnetic field
2012
The problem of ion motion in an electrolyte solution flowing in a thin rectangular duct with velocity VE in the presence of a transverse magnetic field B0 is studied by means of classical mechanics and electrodynamics. Because of Lorentz force on the ions in the electrolyte solution, a so called Faraday voltage appears at the electrodes orthogonal to both the field B0 and the velocity VE. The dynamics of positive and negative ions (cations and anions, respectively) in this classical system is studied by taking into account the viscosity of the fluid and the process of charge accumulation on the opposite walls of the duct. Hydrogen production is seen to take place at one of the electrodes wh…
Molecular scale structure and dynamics at an ionic liquid/electrode interface.
2017
After a century of research, the potential-dependent ion distribution at electrode/electrolyte interfaces is still under debate. In particular for solvent-free electrolytes such as room-temperature ionic liquids, classical theories for the electrical double layer are not applicable. Using a combination of in situ high-energy X-ray reflectivity and impedance spectroscopy measurements, we determined this distribution with sub-molecular resolution. We find oscillatory charge density profiles consisting of alternating anion- and cation-enriched layers at both cathodic and anodic potentials. This structure is shown to arise from the same ion-ion correlations dominating the liquid bulk structure.…
Bipolar membranes under forward and reverse bias conditions. Theory vs. experiment
1994
Abstract Bipolar membranes are layered structures composed of one cation-and one anion-exchange membrane joined together in series. The current—voltage curves of two recently developed bipolar membranes have been analysed theoretically and experimentally under both forward and reverse bias conditions. The experimental trends observed are high conductivity under forward bias conditions and high impedance first, and then electric field enhanced (EFE) water dissociation for high enough applied voltages, under reverse bias conditions. The forward bias measurements can contribute to a better knowledge of some of the transport parameters entering also in the reverse biased membrane. Comparison of…
ELECTROCHEMICAL CONVERSION OF DICHLOROACETIC ACID TO CHLOROACETIC ACID IN A MICROFLUIDIC STACK AND IN A SERIES OF MICROFLUIDIC REACTORS
2015
The electrochemical conversion of dichloroacetic acid to chloracetic acid was performed in three different micro devices: a simple micro fluidic cell; a microfluidic stack equipped with various electrode chambers in series and three micro fluidic cells in series. The electrochemical synthesis of chloracetic acid was performed successfully with high yields and selectivity under a single-pass mode without supporting electrolyte at low cell voltages. An increase of the productivity and of the final concentration of the target product was achieved by using a stack with two or three electrode chambers in series. The utilization of three micro reactors in series open interesting new perspectives,…
Direct observation of the electroadsorptive effect on ultrathin films for microsensor and catalytic-surface control.
2013
Microchemical sensors and catalytic reactors make use of gases during adsorption in specific ways on selected materials. Fine-tuning is normally achieved by morphological control and material doping. The latter relates surface properties to the electronic structure of the bulk, and this suggests the possibility of electronic control. Although unusual for catalytic surfaces, such phenomena are sometimes reported for microsensors, but with little understanding of the underlying mechanisms. Herein, direct observation of the electroadsorptive effect by a combination of X-ray photoelectron spectroscopy and conductivity analysis on nanometre-thick semiconductor films on buried control electrodes …
Combined theoretical and experimental analysis of processes determining cathode performance in solid oxide fuel cells
2013
Solid oxide fuel cells (SOFC) are under intensive investigation since the 1980's as these devices open the way for ecologically clean direct conversion of the chemical energy into electricity, avoiding the efficiency limitation by Carnot's cycle for thermochemical conversion. However, the practical development of SOFC faces a number of unresolved fundamental problems, in particular concerning the kinetics of the electrode reactions, especially oxygen reduction reaction. We review recent experimental and theoretical achievements in the current understanding of the cathode performance by exploring and comparing mostly three materials: (La,Sr)MnO3 (LSM), (La,Sr)(Co,Fe)O3 (LSCF) and (Ba,Sr)(Co,…
Atomistic Modeling of a New Storage
2008
It was observed that Me/Li2O and Me/LiF nanocomposites (Me is a metal that does not alloy with lithium) are able to exhibit an extra Li storage typically beyond the uptake of stoichiometric Li in the potential window 1.2 0.02 V, with pseudo-capacitive behavior and high-rate performance. Among the composites, the Ru/Li2O exhibits a high extra Li storage at this low potential. Moreover, the Li2O matrix allows one a higher storage in contact with transition metal than the LiF matrix [1,2]. To clarify the mechanism of the Li interfacial storage anomaly, we have performed comparative first principles calculations on the atomic and electronic structure of polar Ti/Li2O(111) and nonpolar Cu/LiF(00…