Strategies and Countermeasures Against Reverse Current for Enhanced Durability in Water Electrolysis Systems

Reverse current, a detrimental phenomenon arising during shutdown or fluctuating input from renewable energy sources in water electrolysis, poses a critical threat to the longevity and efficiency of green hydrogen production systems. This current flows in the opposite direction to the normal operational current, instigating severe degradation of electrode materials, particularly at the cathode, and thereby diminishing hydrogen generation rates. Herein, the underlying electrochemical mechanisms of reverse current are comprehensively elucidated and critically assess its influence on electrode integrity and overall electrolyzer performance. Furthermore, state-of-the-art mitigation strategies are being explored and analyzed to counteract this damage, encompassing innovations from materials-level approaches (e.g., electrode modification via dopants and protective coatings) to system-level external regulation and control. This review bridges fundamental insights with practical engineering strategies (e.g., multifunctional dynamic protective layers and in situ and operando techniques) to guide the designs of electrolyzer to reduce damage from reverse current.