Current bunching effect of large-scale alkaline hydrogen evolution driven by renewable energy sources

Alkaline water electrolyzers (AWEs) are suitable for industrial hydrogen production driven by renewable energy sources. However, there are still gaps in understanding underlying the operating principles of AWEs. Here, we report on the current bunching effect and its related phenomena in large-scale AWEs. It is generally thought that the electrolysis current is distributed uniformly on the surface of bipolar plates in AWEs, but these findings demonstrate that current is not uniform and is located within narrow areas, especially for low-load states. The mechanism of the current bunching effect is revealed. The results indicate that the physical structures and electrical characteristics, instead of the chemical properties, are strongly related to the current bunching effect. Consequently, the inefficiency and anomalous efficiency-temperature relationship of low-load AWEs can be explained effectively. This work sheds light on the further development of industrial hydrogen production from fluctuating renewable energy sources based on low-cost AWEs.