Diffuse-charge dynamics in electrochemical systems.

By Martin Z. Bazant, K. Thornton, A. Ajdari. Physical review. E, Statistical, nonlinear, and soft matter physics, 2004

914 citations recorded by the source corpus.

The response of a model microelectrochemical system to a time-dependent applied voltage is analyzed. The article begins with a fresh historical review including electrochemistry, colloidal science, and microfluidics. The model problem consists of a symmetric binary electrolyte between parallel-plate blocking electrodes, which suddenly apply a voltage. Compact Stern layers on the electrodes are also taken into account. The Nernst-Planck-Poisson equations are first linearized and solved by Laplace transforms for small voltages, and numerical solutions are obtained for large voltages. The "weakly nonlinear" limit of thin double layers is then analyzed by matched asymptotic expansions in the small parameter epsilon= lambdaD/L, where lambdaD is the screening length and L the electrode separation. At leading order, the system initially behaves like an RC circuit with a response time of lambdaDL/D (not lambdaD2/D), where D is the ionic diffusivity, but nonlinearity violates this common picture and introduces multiple time scales. The charging process slows down, and neutral-salt adsorption by the diffuse part of the double layer couples to bulk diffusion at the time scale, L2/D. In the "strongly nonlinear" regime (controlled by a dimensionless parameter resembling the Dukhin number), this effect produces bulk concentration gradients, and, at very large voltages, transient space charge. The article concludes with an overview of more general situations involving surface conduction, multicomponent electrolytes, and Faradaic processes.

Subfields: Biomedical Engineering, Electrochemistry, Physical and Theoretical Chemistry

View Paper: https://www.semanticscholar.org/paper/0ca959297381160728ae44dedfb82ab71d21e689

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Citations in the corpus

AN ASYMPTOTIC DERIVATION OF THE THIN-DEBYE-LAYER LIMIT FOR ELECTROKINETIC PHENOMENA (2009, background): “This choice accounts for possible time dependence that may arise from resulting flow (e.g., through electrophoretic rotation of nonspherical particles) but is not appropriate to describe unsteady charging processes (Bazant et al., 2004)), which are not discussed here.”
A new approach to the Lennard-Jones potential and a new model: PNP-steric equations (2014, neutral): “[2, 3, 6, 7, 10, 12, 14, 15, 30, 32, 40, 41, 42, 45, 48, 52, 53, 59, 60]).”
Breaking symmetries in induced-charge electro-osmosis and electrophoresis (2005, methodology): “In such large electric fields, the double layer on the conducting body in regions of large zeta potential adsorbs enough neutral salt to perturb the bulk concentration (Bazant et al. 2004), which we neglect here in order to make the problem analytically tractable.”
A mathematical model for the hard sphere repulsion in ionic solutions (2011, methodology): “The PNP equations have been applied to solve charge transport problems in semiconductor and ion dynamics in biological phenomena [13, 14, 8, 45, 46, 47, 48, 49, 50, 51, 61, 62, 63, 64].”
ANALYSIS OF THE NAVIER–STOKES–NERNST–PLANCK–POISSON SYSTEM (2009, background): “In [3, 7, 15, 19, 25], for example, such phenomena are considered.”
Induced-charge electrokinetic phenomena (2003, methodology): “Although this model can be rigorously justified only for very small voltages, ΨD≪kT /e, in a dilute solution [12,19,70,71], it manages to describe many features of ICEO flows at much larger voltages.”
Review on the science and technology of water desalination by capacitive deionization (2013, background): “[81], but the main reason is simply the very short (nm-scale) typical thickness of the EDL across which equilibration will be very fast, relative to the time-scale of seconds and minutes in a full CDI-cell with typical dimensions of the electrode layers of more than 100 μm and full cell dimensions o”
Experimental observation of induced-charge electro-osmosis around a metal wire in a microchannel (2005, background): “At higher voltages bubbles form at the electrodes at low frequency and at smaller voltages velocities are too small to measure accurately with our -”