Investigating Reverse Current Phenomena Induced by Start/Stop Cycling in Lab-Scale Single-Cell Liquid Alkaline Water Electrolyzers

Liquid alkaline water electrolyzers (LAWEs) represent one of the most mature hydrogen production technologies. Large-scale alkaline electrolysis plants have already been deployed at the 100MW scale. Developments advancing LAWEs are crucial in meeting the soaring demand for hydrogen, driven by efforts to combat carbon emissions and transition to cleaner energy sources. Integrating LAWEs with renewable energy sources like wind and solar holds the potential to facilitate the production of green hydrogen at a low cost. However, a significant challenge arises when coupling LAWE with inherently intermittent renewable energy sources. This challenge comes from the reverse current phenomenon following shutdown, which accelerates the degradation of electrolyzer components, including bipolar plates and electrodes. Typically, when an electrolyzer is shutdown, the anode and cathode on the bipolar plate of neighboring cells discharge rapidly. This causes current to flow through the bipolar plates in the opposite direction to normal electrolysis operation. This results in the oxidation of the cathode and the reduction of the anode. While this phenomenon is observed in industrial-scale electrolyzers and multi-cell stacks, it is relatively difficult to replicate in lab-scale single-cell LAWE setups, where bipolar plates are not typically utilized. Many researchers have proposed various start/stop cycling protocols aimed at mimicking the reverse current phenomenon to study the degradation of electrocatalysts or electrodes in lab-scale LAWE setups. These protocols often involve voltage or current cycling. However, despite these efforts, the reverse current phenomenon and start/stop cycling protocols are not yet fully understood. Additionally, there remains uncertainty on how these findings can be confidently extrapolated to industry-scale LAWE components. In this study, we have systematically examined several start/stop strategies and their impacts on LAWE performance and component durability. Furthermore, we have applied these start/stop cycling protocols to various anode and cathode catalysts to determine whether these protocols are exclusively applicable to conventional nickel electrodes or universal in nature. The authors would like to acknowledge the support of the U.S. Department of Energy, and the Hydrogen from Next-Generation Electrolysis of Water (H2NEW) Consortium for their support.