Platinum Clumping Fix Boosts Water Electrolyzer Life

Abstract

Understanding early stage degradation in anion exchange membrane water electrolyzers (AEMWEs) is critical, as the majority of the long-term performance loss arises during the initial phase of operation. In this study, we employed a membrane-extended three-electrode system to investigate the origins of initial degradation under dual electrolyte feeding and dry cathode configurations. Contrary to the commonly held assumption that the anode is the bottleneck, electrochemical analysis revealed that the cathode was the dominant contributor to early performance loss, primarily due to pronounced increases in both kinetic and residual overpotentials. Notably, the degradation rate under dual electrolyte feeding conditions was nearly twice that observed under dry cathode operation, primarily due to accelerated Pt agglomeration, which led to increased overpotentials and loss of active sites, emphasizing the impact of cathodic environments. These findings underscore the central role of cathode stability and highlight that tailoring the cathodic environment is an effective strategy to mitigate initial degradation in AEMWEs.

A recent breakthrough has identified that the primary cause of early-stage performance decline in water electrolyzers is due to the agglomeration of platinum (Pt) catalyst particles on the cathode. By implementing a dry cathode operation-which prevents liquid electrolyte from directly contacting the cathode-the research team achieved a reduction in performance degradation by nearly 50%, accelerating the path toward more reliable and commercially viable green hydrogen production technologies.

Professor Youngkook Kwon and his research team in the School of Energy Chemical Engineering at UNIST has uncovered that, contrary to previous assumptions, the initial performance deterioration predominantly originates from the cathode side. Their findings demonstrate that operating under dry cathode conditions effectively mitigates this early degradation.

Water electrolysis, a process that splits water into hydrogen and oxygen using electricity, is a promising clean energy technology. Among various types, anion exchange membrane (AEM) water electrolyzers are particularly advantageous due to their corrosion resistance and lightweight design. However, a persistent challenge has been 'initial degradation,' characterized by rapid voltage increases within the first few hours of operation, which drastically reduces efficiency-since higher voltage demands more energy for the same hydrogen output.

The research revealed that over 90% of this early degradation stems from the cathode, where hydrogen evolution occurs. Specifically, the agglomeration of platinum catalyst particles-primarily caused by moisture present at the cathode-leads to decreased reactivity and performance.

Utilizing a novel three-electrode analysis method developed by the team, as opposed to conventional two-electrode setups, they precisely identified the origin of performance loss. Traditional two-electrode measurements often obscure which electrode is responsible, typically attributing issues to the anode. In contrast, the new approach allowed for targeted analysis, revealing that dry cathode operation significantly reduces voltage increases: during the first 40 hours, voltage rise was nearly halved-from approximately 163 mV to 96 mV-indicating prolonged stable hydrogen production.

Tae-Hoon Kong, the first author of the study, explained, "While the anode side typically employs well-established wet operation conditions, the cathode has been operated under mixed wet and dry conditions. Our study experimentally demonstrates that moisture trapped at the cathode facilitates platinum particle clumping, leading to initial degradation. This insight paves the way for new operational standards."

Professor Kwon emphasized, "Although AEM water electrolysis is a highly promising green hydrogen production method, its commercialization has been hindered by rapid early-stage performance decline," adding "Our findings show that simple operational adjustments, such as adopting dry cathode conditions, can significantly enhance the long-term stability of these systems, offering a practical pathway toward commercial deployment."

He added, "Furthermore, this innovative analysis method can be applied to electrode material development, durability assessments, and electrode design optimization, contributing broadly to the advancement of electrochemical energy technologies."

This research was published online in ACS Energy Letters on July 3, 2025. The study was supported by the National Research Foundation of Korea (NRF) through the mid-career researcher grants and STEAM research programs, funded by the Ministry of Science and ICT (MSIT).

Journal Reference

Tae-Hoon Kong, Jihoo Cha, Hojeong Lee, et al., "A Cathode Is the Key Contributor to the Initial Degradation of Anion Exchange Membrane Water Electrolyzers," (2025).