Compact and General Strategy for Solving Current and Potential Distribution in Electrochemical Cells Composed of Massive Monopolar and Bipolar Electrodes

A. N. Colli,H. H. Girault

doi:10.1149/2.0471711jes

Abstract

A compact, fast and general algorithm based on Dirichlet boundary conditions for the potential field is derived to enable the calculation of local current distribution, shunt currents and the local potential distribution on massive electrodes in electrochemical cells of any type of geometry in three dimensions, composed of bipolar electrodes at an unknown floating potential and/or terminal monopolar electrodes. The algorithm allows performing the calculation of current-potential distributions and bypass currents for a fixed cell potential (potentiostatic) or a fixed cell current (galvanostatic) enforced to the cell. The proposed approach can be extended to take into account concentration variations of one or several species inside the cell or electrical conductivity variations due to the presence of separators or liquid-gas-solid phases. In order to validate the algorithm, a detailed comparison, between the suggested strategy with experimental results is made in the case of secondary current distribution for i) a segmented one bipolar electrode ii) a cell stack composed of 14 bipolar electrodes in the industrial process of alkaline water electrolysis. The proposed tool can help designers to develop more efficient electrochemical reactors by comparing results using different electrode materials, electrolytes and cell designs.

Highlights

Bipolar electrolyzer design is attractive for industrial processes due to the simplified design and construction where no busbars are required inside the stack, and the ability to operate the cell at much higher voltages and much lower currents than in monopolar cells
The goal of this paper is to provide a general, compact and fast strategy based on Dirichlet boundary conditions (BC) for the potential field in order to design and/or evaluate electrochemical reactors composed of monopolar or bipolar electrodes, not to discuss the already well-known interpretation of the potential-current distribution in bipolar or monopolar reactors
Validation with experimental results from Henquın and Bisang21,44.—The proposed model was validated with the experimental results obtained with two undivided reactors electrically connected in series, resulting in a two-cell stack with one bipolar electrode

Summary

Introduction

Current-potential distributions are among the most significant parameters influencing the operation of monopolar or bipolar electrochemical reactors.[1] Non-uniform current-potential distribution due to the electrolyte inlet and outlet channels can result in several problems. The power required for operating an electrochemical cell and the ohmic loss are dependent on the current distribution. The current distribution is largely determined by geometric factors such as the shape of the cell, the location of the cathodes relative to the anodes and the placement of bipolar electrodes.[3,4,5] current distribution will be affected by hydrodynamic conditions,[6] composition and conductivity of the electrolyte, conductivities of the electrode and catalyst material, electrode kinetics and on the mass transfer rates of reactants and products to and from reaction sites. Simulations allow sensitivity analysis of different parameters to direct research efforts to obtain most significant improvements

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Results

Conclusion