Potential and current density distributions along a bipolar electrode

Abstract

Potential and current density distributions were modelled and measured for an electrochemical cell with a bipolar electrode. The dimension of the bipolar electrode in the direction of current flow was extended, to enable experimental determination of the electrode potential and the local current densities at various positions inside the electrolyte and in the electrode body. The experimental results showed that the most active regions of the bipolar electrode are located at the ends of the bipolar electrode facing the terminal electrodes. The equations corresponding to the mathematical model of the experimental cell were solved using the finite volume method and gave very good qualitative agreement with the experimental data. However, some discrepancies between model predictions and experimental data were evident in the active parts of the bipolar electrode and in the variation of the terminal voltage with the total current. This was explained in terms of the active electrolyte cross-section and the electrode surface area being diminished due to the presence of gas bubbles in the system.Keywords Bipolar electrode Á Mathematical modelling Á Parasitic current Á Local potential and current density distribution Nomenclature A F Cross-sectional area of the free electrolyte space beside the bipolar electrode (m 2 ) d G Inter-electrode distance (m) d E Bipolar electrode thickness (m) E Electrode potential (V) f E Current utilisation in a bipolar cell (-) I Current (A) I E Current flowing through bipolar electrode (A) I P Parasitic current (A) I T Total current (A) j Current density (A m -2 ) n Vector normal to the boundary (m) N Number of electrolytic cells (-) r Radius (m) RResistivity (X) R F Electrolyte resistivity in the fictitious electrolyser (X) R G Average resistivity of the inter-electrode gap (X) R S Short-circuit resistivity (X) S Electrode surface (m 2 ) U Voltage (V) U r Open-circuit cell voltage (V)xPosition along the cell (m)Greek letters u Galvani potential (V) r Conductivity (S m -1 ) j F Electrolyte conductivity (S m -1 ) g Overpotential (V)

Oscillatory motion of water droplets in kerosene above co-planar electrodes in microfluidic chips

“…In the 8e arrangement, the two outer electrodes served as the forcing electrodes and the six inner electrodes behaved as bipolar electrodes. 30 The bipolar electrodes are not connected to the electric source and form highly conductive stripes on the microchannel wall with opposite electric charges localized at the stripe ends.…”

“…One being that all six internal electrodes behave like bipolar electrodes with the electrochemical charge transfer localized predominantly at the edges. 30 Above each bipolar electrode, the droplet can lose a part of its original charge. The bipolar electrode becomes itself charged.…”

“…Electric fields of low intensities are then observed at the electrodes and the main potential drop is concentrated among the electrodes. 30 This suggests that between the charging electrode and the adjacent bipolar electrode is more intensive electric field than that in the 2e arrangement. Thus the 8e arrangement facilitates the release of the droplet from the charging electrode even if the averaged electric field strength is equal in both the arrangements.…”

Microstructured reactor for electroorganic synthesis

“…As is known, however, a significant risk of this approach is a decrease in process efficiency. This is caused by the existence of by-pass or shunt currents [43] which are influenced by the system geometry, number of bipolar electrodes, electrolyte conductivity, electrode reaction kinetics and the conductivity of the electrode material. Careful optimization of the cell parameters was, therefore, ensured by means of mathematical modeling of the local potential and current density distribution.…”

Effect of leakage currents on the secondary current distribution in bipolar electrochemical reactors

“…The presence of gases in the outlet manifolds was considered, Tafelian kinetics was adopted at the electrodes and uniform current distributions along the electrodes were assumed. Furthermore, Kodým et al [4] reported experimental and theoretical results of potential and current distribution in a bipolar system. The special configuration of the electrochemical reactor allowed for the simulation of the current distribution along the electrode thickness and the identification of the electrode ends as the most active regions of the bipolar electrode.…”