Reverse-Current Tolerance for Hydrogen Evolution Reaction Activity of Lead-Decorated Nickel Catalysts in Zero-Gap Alkaline Water Electrolysis Systems

Alkaline water electrolysis (AWE) systems offer a cost-effective and scalable approach for large-scale hydrogen production using renewable energy sources. However, their susceptibility to load fluctuations, particularly the reverse-current (RC) phenomenon during shutdown events, poses a significant challenge to the long-term stability and scalability of these systems. Herein, a catalytic approach for enhancing the RC tolerance in AWE systems by using Pb-decorated Ni cathode catalysts (Pb/Ni) is introduced. The oxidation of Pb/Ni by repeated RC lowers the electromotive force for the reverse current operation, and consequently, imparts RC tolerance. Intriguingly, contrary to the expectation that the decoration with lead, an inert material for the hydrogen evolution reaction (HER), will interfere with the hydrogen generation of the Ni catalyst, the presence of Pb on the Ni cathode after the RC flow promotes both the proton desorption and water-dissociation steps, improving the HER activity. Furthermore, the AWE stack testing with Pb/Ni catalysts is perfectly operated, demonstrating remarkably enhanced RC tolerance during startup/shut-down (SU/SD) testing protocol. This paper presents a new strategy for mitigating the AWE performance degradation induced by RC flow and for achieving Pb/Ni catalysts with improved operational durability against RC flow in AWE systems. The transient stability of the catalyst caused by the reverse-current phenomenon during the shutdown of the AWE system by load fluctuations is one of the most challenging limitations to address. This study introduces a catalytic approach for enhancing the RC by decorating lead on Ni catalysts. The surface decoration of the Ni catalyst with Pb (Pb/Ni) catalyst exhibits improved HER activity as well as remarkable RC-flow resistance. image