Search results for "Electrode"
showing 10 items of 950 documents
Redox potentials and acidity constants from density functional theory based molecular dynamics.
2014
CONSPECTUS: All-atom methods treat solute and solvent at the same level of electronic structure theory and statistical mechanics. All-atom computation of acidity constants (pKa) and redox potentials is still a challenge. In this Account, we review such a method combining density functional theory based molecular dynamics (DFTMD) and free energy perturbation (FEP) methods. The key computational tool is a FEP based method for reversible insertion of a proton or electron in a periodic DFTMD model system. The free energy of insertion (work function) is computed by thermodynamic integration of vertical energy gaps obtained from total energy differences. The problem of the loss of a physical refe…
Electrodeposition of CeO2 and Co-Doped CeO2 Nanotubes by Cyclic Anodization in Porous Alumina Membranes
2013
An anodic electrodeposition process is proposed to prepare CeO2 and Co-doped CeO2 nanotubes. Anodic alumina membrane is used as template and linear sweep voltammetry is employed to allow the formation of nanotubes without alumina dissolution. SEM micrographs showed large arrays of well defined and aligned NTs, which resulted to be crystalline soon after deposition according to XRD diffraction patterns and Raman Spectroscopy.
Interface engineering in efficient vacuum deposited perovskite solar cells
2016
Abstract We studied the effect of the charge transport layers in p-i-n perovskite solar cells using vacuum deposited methylammonium lead iodide thin-film absorbers. While solution-processed perovskite films are frequently deposited directly on PEDOT:PSS leading to good solar cell performances, in some cases even to very good Voc values, we show that in devices employing vacuum deposited MAPbI3 perovskites, the removal of the polyTPD electron blocker substantially reduces the photovoltaic behavior. This is indicative of rather different charge transport properties in the vacuum deposited MAPbI3 perovskites compared to those prepared from solution. On the other hand, we investigated the use o…
Growth of large liquid crystalline domains of phospholipids at air-water interfaces
1990
Abstract The fusion of condensed phase domains in a fluid environment in monolayers is studied. A system of electrodes permits the non-invasive and predetermined movement of single domains while the film is observed by fluorescence microscopy. Two domains fuse when they are brought into contact with special positions of their borderlines. The experiment yields information about the molecular structure of the domains and allows us to fabricate very large domains. The equilibrium size is estimated and verified.
Chloride, carboxylate and carbonate transport by ortho-phenylenediamine-based bisureas
2013
Highly potent but structurally simple transmembrane anion transporters are reported that function at receptor to lipid ratios as low as 1 : 1 000 000. The compounds, based on the simple ortho-phenylenediamine-based bisurea scaffold, have been studied for their ability to facilitate chloride/nitrate and chloride/bicarbonate antiport, and HCl symport processes using a combination of ion selective electrode and fluorescence techniques. In addition, the transmembrane transport of dicarboxylate anions (maleate and fumarate) by the compounds was examined. Molecular dynamics simulations showed that these compounds permeate the membrane more easily than other promising receptors corroborating the e…
Synthesis of Silver Gallium Selenide (AgGaSe2) Nanotubes and Nanowires by Template-Based Electrodeposition
2020
In this work, a systematic investigation of the different parameters that control the electrodeposition processes was carried out at the aim to synthetizing AgGaSe₂ nanostructures. We found that pH is a key parameter to control both the morphology and composition of the nanostructures. Low pH favours mainly the formation of Ag2Se nanotubes with a scarce mechanical stability, while multi-phase nanowires well anchored to the substrate were obtained at higher pH. We also found that it was necessary to increase dramatically the concentration of the gallium precursor into the deposition bath in order to obtain AgGaSe₂ owing to lower redox potential of the Ga3+/Ga couple than Ag2+/Ag and Se4+/Se.…
Electroactive polymeric material with condensed structure on the basis of magnesium(II) polyporphine
2011
International audience; Previous publication of the authors presented evidences that electroch emical oxidation of Mg(II) porphine (fully unsubstituted porphyrin, MgP) in acetonitrile (AN) at a very low potential leads to deposition of films at electrode surface corresponding to typical electroactive polymers, with their reversible transition betwee n the electronconducting and insulating states depending on the electrode potential/oxidation level ("film of type I"). It is demonstrated in the actual publication that these films in contact with a monomer-free solution are subject to an irreversible transformation to quite a different material ("film of type II") under the influence of a high…
An electrochemical quartz crystal microbalance study of lithium insertion into thin films of tungsten trioxide II. Experimental results and compariso…
1995
Abstract Lithium insertion into amorphous thin films of tungsten trioxide (a-WO 3 ) prepared by thermal vacuum evaporation of WO 3 powder has been studied experimentally by chronoamperometry, cyclic voltammetry and ac impedance spectroscopy associated with electrochemical quartz crystal microbalance (EQCM). During cathodic polarization of the electrode and at short times two antagonistic processes occur. One is a non faradaic process and is associated with the expulsion of anions from the electrode surface under the effect of the electric field built in the electrolyte when a potential difference is imposed between the electrodes. The other one is the faradaic insertion of non-solvated lith…
The pseudostationary mercury electrode
1998
Abstract A detailed study of the pseudostationary mercury electrode is presented, based on its use in LSV. Delay times ( t 1 ) as short as 20 ms can be employed; the drop area is still given by its classical expression, and minimization of the ohmic drop allows sweep rates of a few thousands of volts per second to be used. The conditions for pseudostationarity are given; the lower sweep rates utilizable are of the order of few tenths of volt per second. Reactant adsorption is considered, and zones where rehomogenization near the electrode surface is practically either 100 or 0% are defined in a plane log t 1 /log b O ( b O is the adsorption coefficient); the diffusional or surface character…
Ohmic drop effect on the voltammetric behaviour of graphite + polyethylene composite electrodes
1997
Graphite + polyethylene composites can be used as electrodes in electrochemical experiments because of their low charging current in contrast with other composite electrodes. However, the results reveal that the ohmic drop must always be considered in the data analysis. The peak potential and the peak current are related through an expression deduced for a Nernstian process where the mass transport is controlled by diffusion. The determination of the uncompensated resistance implies also the calculation of the convolution of the current.