Ohmic resistance in zero gap alkaline electrolysis with a Zirfon diaphragm

Alkaline water electrolyzers are traditionally operated at low current densities, due to high internal ohmic resistance. Modern diaphragms with low internal resistance such as the Zirfon diaphragm combined with a zero gap configuration potentially open the way to operation at higher current densities. Data for the Zirfon diaphragm show that the resistance is only 0.1-0.15 Omega cm(2) in 30% KOH at 80 degrees C, in line with estimations based on the porosity. Nevertheless, an analysis of data on zero gap alkaline electrolyzers with Zirfon reveals that the area resistances are significantly higher, ranging from 0.23 to 0.76 Omega cm(2). A numerical simulation of the secondary current distribution in the zero gap configuration shows that an uneven current distribution, imperfect zero gap and the presence of bubbles can probably only partly explain the increased resistance. Therefore, other factors such as the presence of nanobubbles could play a role. (C) 2021 The Authors. Published by Elsevier Ltd.

Automated summary

Traditional alkaline water electrolyzers operate at low current densities due to high internal ohmic resistance. Using modern diaphragms like Zirfon and a zero gap configuration could potentially allow for operation at higher current densities. However, data analysis reveals that the area resistances are significantly higher in zero gap alkaline electrolyzers, suggesting factors like uneven current distribution and the presence of nanobubbles may contribute to the increased resistance.