Numerical simulation of the distribution of reverse currents in a practical alkaline water electrolysis stack immediately after electrolysis

In alkaline water electrolysis, reverse currents are reported to occur after rapid cell voltage change due to the electrodes oxidation state difference and such currents lead to electrodes degradation. The reverse current problems can be more severe in practical applications with larger electrode sizes and larger numbers of cells. In this study, reverse current with changes in the oxidation state of electrodes and potential distribution after sudden shutdown were analyzed based on a multi-physical simulation considering an electronic and ionic conduction in practical-scale. The effects of stack height, number of cells, and ionic resistance through the manifold on the reverse current distribution were investigated. The numerical results reveal that, especially under the condition of low manifold resistance and higher stack height, the discharge current extremely concentrated near the bottom of the edge electrode. This information is important for future stack development because this current concentration can cause severe stack degradation.