The Experts below are selected from a list of 9498 Experts worldwide ranked by ideXlab platform
Nicholas Leventis - One of the best experts on this subject based on the ideXlab platform.
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magnetohydrodynamic electrochemistry in the field of nd fe b magnets theory experiment and application in self powered flow delivery systems
Analytical Chemistry, 2001Co-Authors: Nicholas Leventis, Xuerong GaoAbstract:Nd−Fe−B permanent magnets are easily available, powerful, and inexpensive and generate strong quantifiable convective effects during electrolysis, similar to those obtained with rotating electrodes or large electromagnets. The magnetic field of Nd−Fe−B magnets has been simulated numerically and mapped. Its most characteristic difference from the field of most commercial electromagnets is the presence of magnetic field gradients, which introduce additional body forces in the Electrolytic Solution and create new modes of mass transfer due to the attraction of electrogenerated radicals into areas of stronger field. The effect of those new forces on the radial distribution of the flow profile in the vicinity of the electrode has been monitored with generation−collection experiments and optical photography. The emerging utility of Nd−Fe−B magnets in systems of chemical interest is demonstrated with flow control and delivery devices, based on galvanic cells configured as self-powered magnetohydrodynamic pumps.
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steady state voltammetry with stationary disk millielectrodes in magnetic fields nonlinear dependence of the mass transfer limited current on the electron balance of the faradaic process
Journal of Physical Chemistry B, 1999Co-Authors: Nicholas LeventisAbstract:Generally, faradaic current passing through an Electrolytic cell placed in a magnetic field causes stirring of the Electrolytic Solution and current−voltage characteristics similar to those obtained with rotating disk electrodes. It is reported herein that the intensity of the hydrodynamic convection generated by conventional disk millielectrodes in magnetic fields is intimately related to the nature of the faradaic process, and that the mass-transfer limited current, il, is proportional to n3/2 where n is the number of electrons involved in the heterogeneous electron transfer. That finding has been justified on the basis of a feedback mechanism that relies on the dependence of the faradaic current on the hydrodynamic velocity profile within the Electrolytic conductor, and of the hydrodynamic velocity profile on the current. The implications of the nonlinear dependence of il on n have been discussed in terms of a moving-boundary diffusion-layer model which is introduced into digital simulations and reprod...
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steady state voltammetry with stationary disk millielectrodes in magnetic fields nonlinear dependence of the mass transfer limited current on the electron balance of the faradaic process
Journal of Physical Chemistry B, 1999Co-Authors: Nicholas Leventis, Xuerong GaoAbstract:Generally, faradaic current passing through an Electrolytic cell placed in a magnetic field causes stirring of the Electrolytic Solution and current−voltage characteristics similar to those obtaine...
Anders Hagfeldt - One of the best experts on this subject based on the ideXlab platform.
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new approach for preparation of efficient solid state dye sensitized solar cells by photoelectrochemical polymerization in aqueous micellar Solution
Journal of Physical Chemistry Letters, 2013Co-Authors: Lei Yang, Jinbao Zhang, Yang Shen, Byungwook Park, Leif Haggman, Erik M J Johansson, Gerrit Boschloo, Anders HagfeldtAbstract:Hereby, we present a new, cost-effective, and environmentally friendly method of preparing an efficient solid-state dye-sensitized solar cell (sDSC) using a PEDOT conducting polymer as the hole conductor and a recently developed organic sensitizer. PEDOT is generated and deposited on the dye-sensitized TiO2 electrode by in situ photoelectropolymerization of bis-EDOT in aqueous micellar Solution. The advantages of this approach are the use of water as the solvent and the obtainment of a sDSC simply by adding a silver layer on the as-obtained polymer film deposited on dye/TiO2 without the need for Electrolytic Solution. The sDSC containing the film prepared as above is compared to those where the organic dye is used to generate the same polymer film but in organic solvent. The energy conversion efficiency values of the two cells appear comparable, 4.8% for sDSC prepared in the aqueous-phase polymerized PEDOT and 6% for the sDSC prepared with in organic-phase polymerized PEDOT.
Xuerong Gao - One of the best experts on this subject based on the ideXlab platform.
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magnetohydrodynamic electrochemistry in the field of nd fe b magnets theory experiment and application in self powered flow delivery systems
Analytical Chemistry, 2001Co-Authors: Nicholas Leventis, Xuerong GaoAbstract:Nd−Fe−B permanent magnets are easily available, powerful, and inexpensive and generate strong quantifiable convective effects during electrolysis, similar to those obtained with rotating electrodes or large electromagnets. The magnetic field of Nd−Fe−B magnets has been simulated numerically and mapped. Its most characteristic difference from the field of most commercial electromagnets is the presence of magnetic field gradients, which introduce additional body forces in the Electrolytic Solution and create new modes of mass transfer due to the attraction of electrogenerated radicals into areas of stronger field. The effect of those new forces on the radial distribution of the flow profile in the vicinity of the electrode has been monitored with generation−collection experiments and optical photography. The emerging utility of Nd−Fe−B magnets in systems of chemical interest is demonstrated with flow control and delivery devices, based on galvanic cells configured as self-powered magnetohydrodynamic pumps.
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steady state voltammetry with stationary disk millielectrodes in magnetic fields nonlinear dependence of the mass transfer limited current on the electron balance of the faradaic process
Journal of Physical Chemistry B, 1999Co-Authors: Nicholas Leventis, Xuerong GaoAbstract:Generally, faradaic current passing through an Electrolytic cell placed in a magnetic field causes stirring of the Electrolytic Solution and current−voltage characteristics similar to those obtaine...
L R Evangelista - One of the best experts on this subject based on the ideXlab platform.
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a connection between anomalous poisson nernst planck model and equivalent circuits with constant phase elements
Journal of Physical Chemistry C, 2013Co-Authors: E K Lenzi, J L De Paula, Fernanda R G B Silva, L R EvangelistaAbstract:A connection between the impedance spectroscopy response of an anomalous Poisson–Nernst–Planck (PNPA) diffusional model and of equivalent circuits containing constant phase elements (CPEs) is established for a typical Electrolytic cell. The analysis is carried out in the limit of low frequency in order to highlight the surface effects and to explore how they can be connected to the presence of CPEs in the circuit. It is shown that, depending on the choice of the equivalent circuit, the action of these elements can be the same as the one obtained using integro–differential boundary conditions to describe anomalous diffusive processes in the framework of PNPA models. The predictions are also compared with experimental data obtained from an Electrolytic Solution.
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a framework to investigate the immittance responses for finite length situations fractional diffusion equation reaction term and boundary conditions
arXiv: Other Condensed Matter, 2013Co-Authors: E K Lenzi, Fernanda R G B Silva, M K Lenzi, G Goncalves, R Rossato, R S Zola, L R EvangelistaAbstract:The Poisson-Nernst-Planck (PNP) diffusional model for the immittance or impedance spectroscopy response of an Electrolytic cell in a finite-length situation is extended to a general framework. In this new formalism, the bulk behavior of the mobile charges is governed by a fractional diffusion equation in the presence of a reaction term. The Solutions have to satisfy a general boundary condition embodying, in a single expression, most of the surface effects commonly encountered in experimental situations. Among these effects, we specifically consider the charge transfer process from an Electrolytic cell to the external circuit and the adsorption-desorption phenomenon at the interfaces. The equations are exactly solved in the small AC signal approximation and are used to obtain an exact expression for the electrical impedance as a funcion of the frequency. The predictions of the model are compared to and found to be in good agreement with the experimental data obtained for an Electrolytic Solution of CdCl2H20.
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a connection between anomalous poisson nernst planck models and equivalent circuits with constant phase elements
arXiv: Other Condensed Matter, 2013Co-Authors: E K Lenzi, J L De Paula, Fernanda R G B Silva, L R EvangelistaAbstract:A connection between the impedance spectroscopy response of anomalous Poisson-Nernst-Planck (PNPA) diffusional models and of equivalent circuits containing constant phase elements (CPE) is established for a typical Electrolytic cell. The analysis is carried out in the limit of low frequency in order to highlight the surface effects and to explore how they can be connected to the presence of CPE in the circuit. It is shown that, depending on the choice of the equivalent circuit, the action of these elements can be the same as the one obtained by using integro-differential boundary conditions to describe anomalous diffusive processes in the framework of PNPA models. The predictions are also compared with an experimental data obtained from an Electrolytic Solution.
Richard G. Compton - One of the best experts on this subject based on the ideXlab platform.
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on the estimation of the diffuse double layer of carbon nanotubes using classical theory curvature effects on the gouy chapman limit
Chemical Physics Letters, 2010Co-Authors: Martin C Henstridge, Edmund J F Dickinson, Richard G. ComptonAbstract:The Poisson-Boltzmann equation is solved numerically in cylindrical space to examine the effects of curvature upon the properties of the diffuse double layer at a charged nanotube in Electrolytic Solution. Simulations reveal increased double layer capacitance, especially for cylinders with radius less than 20 nm. The potential drop from the nanotube surface to the maximum tunnelling distance is therefore expected to be greater than for larger cylinders, providing a possibly enhanced electrochemical driving force for electron transfer and a possible partial cause for altered electrode kinetics at carbon nanotube modified electrodes. This effect is also predicted for cylinders of radius larger than 20 nm in Solutions of low supporting electrolyte concentration. However, the effects on the observed electrode kinetics are predicted to be small.
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theoretical and experimental study of differential pulse voltammetry at spherical electrodes measuring diffusion coefficients and formal potentials
Journal of Electroanalytical Chemistry, 2009Co-Authors: Angela Molina, Carmen Serna, Eduardo Laborda, Francisco Martinezortiz, Emma I Rogers, Juan G Limonpetersen, Neil V Rees, Richard G. ComptonAbstract:Rigorous and approximate analytical expressions are deduced for Differential Pulse Voltammetry at spherical electrodes of any size, including microelectrodes, when the electrogenerated species is soluble in the Electrolytic Solution. From these, we examine the utility of DPV for the determination of diffusion coefficients and formal potentials, establishing the optimum conditions for this purpose. The experimental validation of the theoretical results is reported for mercury microelectrodes of ca. 50 and 10 μm diameters both in aqueous and ionic liquid media.
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theory for double potential step chronoamperometry for any potential values at spherical electrodes simultaneous determination of the diffusion coefficients of the electroactive species
Electrochimica Acta, 2009Co-Authors: Angela Molina, Carmen Serna, Francisco Martinezortiz, Richard G. Compton, Eduardo LabordaAbstract:Abstract We present a general and explicit analytical Solution for double potential step chronoamperometry with any applied potential values ( E 1 , E 2 ) corresponding to a reversible charge transfer process at spherical electrode. This Solution is essential to analyze double pulse electrochemical techniques such as RPV and DPV. We consider unequal diffusion coefficients, initial presence of both electroactive species and that the reaction product can dissolve in the Electrolytic Solution or in the electrode. From the analytical equation obtained it is possible to deduce interesting simplified expressions for some particular cases: both species soluble in the Electrolytic Solution with equal diffusion coefficients, planar electrodes, ultramicroelectrodes when both species are soluble in the Electrolytic Solution, and double potential step chronoamperometry with limit current potentials ( E 1 − E ° ′ → − ∞ , E 2 − E ° ′ → + ∞ ). In this last case, when reaction product is not initially present it is pointed that planar electrodes and ultramicroelectrodes cannot be used for determining both diffusion coefficients. This interesting practical consequence can be demonstrated by means of the analytical expression deduced here, which represents a notable advantage in front of numerical results.