Search results for "Electrode potential"
showing 6 items of 36 documents
Ohmic drop of Prussian-blue/graphite+epoxy electrodes
1999
Abstract Ohmic drop effects on the voltammogram shape of the Prussian-blue⇌Everitt’s salt system have been studied by considering the electroactive film model. As the uncompensated resistance varies, the experimental characteristic curve parameters also varies. A dependence of the voltammograms with the graphite proportion was found related with the ohmic drop due to the composite electrodes. The optimal graphite proportion to obtain a good faradaic-to-charge current ratio was 62% in weight which coincides with the second percolation threshold. The ohmic overpotential, which relates the ohmic drop with the electrochemical magnitudes, is also minimum at this proportion.
Grand-canonical approach to density functional theory of electrocatalytic systems: Thermodynamics of solid-liquid interfaces at constant ion and elec…
2018
Properties of solid-liquid interfaces are of immense importance for electrocatalytic and electrochemical systems, but modeling such interfaces at the atomic level presents a serious challenge and approaches beyond standard methodologies are needed. An atomistic computational scheme needs to treat at least part of the system quantum mechanically to describe adsorption and reactions, while the entire system is in thermal equilibrium. The experimentally relevant macroscopic control variables are temperature, electrode potential, and the choice of the solvent and ions, and these need to be explicitly included in the computational model as well; this calls for a thermodynamic ensemble with fixed…
An electrochemical impedance and ac-electrogravimetry study of PNR films in aqueous salt media
2002
Electrochemical impedance spectra and ac-eletrogravimetry of poly(neutral red) films are studied in different aqueous media. The dependence of these experimental data on the nature of alkaline cation and monovalent anion present in the solution and on the pH is analysed. During the electrochemical processes, it is observed that all three species—the salt cation, the salt anion and the hydronium ion—participate to balance the electrical charge within the film. It is also possible to conclude that the participation of anions takes place faster than hydronium ions participation. Besides, the relative participation of these species is related to the pH of the solution. Keywords: Poly (neutral r…
Surface modification of graphite+polymer composite and ITO electrodes by Nafion®+cupromeronic phthalocyanine films
1999
Abstract The surface of indium tin oxide (ITO) and graphite+polymer composite electrodes can be modified by Nafion ® films containing a little amount of dispersed electroactive substances, such as phthalocyanines. This procedure allows the recovery of electroanalytical information on the electroactive deposited substance. The preparation methods for these types of modified electrodes are discussed from the voltammetric results obtained in this work. The Nafion ® net acts as a permeable membrane to the hydrogen ions. Furthermore, the presence of methylviologen within the Nafion ® film makes the electron transport throughout this membrane easy.
Electrocatalytic rate constants from DFT simulations and theoretical models: Learning from each other
2022
Electrochemical interfaces present an extraordinarily complex reaction environment and several, often counter-acting, interactions contribute to rate constants of electrocatalytic reactions. We compile a short review on how electrode potential, solvent, electrolyte, and pH effects on electrocatalytic rates can be understood and modelled using computational and theoretical methods. We address the connections between computational models based on DFT and (semi)analytical model Hamiltonians to extract physical or chemical insights, identify some omissions in present DFT simulation approaches and analytic models, and discuss what and how simulations and models could learn from each other. peerR…
Constant inner potential DFT for modelling electrochemical systems under constant potential and bias
2021
Electrochemical interfaces and reactions play a decisive role in e.g. clean energy conversion but understanding their complex chemistry remains an outstanding challenge. Constant potential or grand canonical ensemble (GCE) simulations are indispensable for unraveling the properties of electrochemical processes as a function of the electrode potential. Currently, constant electrode potential calculations at the density functional theory (DFT) level are carried out by fixing the Fermi level of the simulation cell. However, the Fermi level from DFT calculations does does not always reflect the experimentally controlled electrode potential or describe the thermodynamic independent variable in G…