Effects of operation and shutdown parameters and electrode materials on the reverse current phenomenon in alkaline water analyzers

One of the major challenges facing the coupling of alkaline water electrolyzers (AWE) and inherently intermittent renewable energy sources (RES) is the reverse current phenomenon that takes place after shutdown and adversely affects the service life of the electrocatalysts. Herein, this phenomenon was studied experimentally and theoretically. The study showed that the potential of the electrodes on either side of the bipolar plate (BP) changes according to the amount of the reverse charge flowing through the BP during shutdown. In addition, the potential of the electrodes of the middle BP changed relatively faster than that of the other BPs due to the increased reverse current of the middle BP. Moreover, effects of the operating parameters and electrode materials on the reverse current phenomenon are uncovered. The electrolyte circulation during shutdown as well as the high operating temperature increased the reverse current. However, the electrolysis current did not significantly affect the reverse current. Additionally, the origin of the reverse current is mainly the redox reactions of the electrodes during shutdown. Furthermore, the cathode that attached to a robust anode, on the same BP, is subject to more stressors. This study is useful for adapting the AWE to the dynamic operation.

Automated summary

This study experimentally and theoretically investigated the reverse current phenomenon that occurs after shutdown in alkaline water electrolyzers coupled with intermittent renewable energy sources. It was found that the potential of the electrodes on either side of the bipolar plate changes according to the amount of reverse charge flowing through the plate during shutdown. The study also uncovered the effects of operating parameters and electrode materials on the reverse current phenomenon. The findings have implications for adapting alkaline water electrolyzers to dynamic operation.