Current Bunching Effect of Large-Scale Alkaline Hydrogen Evolution

Abstract Alkaline water electrolysers (AWEs) are suitable for the industrial hydrogen production driven by renewable energy sources. However, the understanding about the operating principle of large-scale AWEs is not profound and enough. Here, we report the current bunching effect and its related phenomena for large-scale AWEs, namely low-load inefficiency and anomalous efficiency-temperature relationship. It is generally thought that the electrolysis or ionic current is distributed uniformly on the surface of bipolar plates in AWEs, but in fact, the current is not consistent and locates within narrow areas especially for low-load states. Through the detailed electric field calculation, the mechanism of current bunching effect is revealed. It is pointed out that the physical structures and electrical characteristics instead of the chemical properties of AWEs are strongly related to the current bunching effect. Based on the found current bunching effect, the inefficiency and anomalous efficiency-temperature relationship of low-load AWEs can be explained effectively. This work sheds new light on and provides inspiration for the further development of the industrial hydrogen production from fluctuating renewable energy sources based on low-cost AWEs.