Time-Resolved Performance and Stability of Different Gas Recombination Catalysts in PEM Water Electrolysis

Abstract

Proton exchange membrane (PEM) water electrolysis is a key technology for large-scale green hydrogen production. However, operation at elevated cathode pressure is increasingly limited by safety-critical gas crossover. While membrane-integrated gas recombination catalysts (GRCs) are widely proposed to master this challenge, their time-dependent performance and stability under realistic operating conditions remain poorly understood. Here, we report a 1,500 hour time-resolved comparative study of three platinum-based GRC configurations (Pt supported on carbon, Pt black, and Pt nanoparticles) operated under identical high-pressure conditions. Despite identical Pt loadings, the investigated systems exhibit markedly different \textcolor{black}{measurable hydrogen in oxygen values}, demonstrating that GRC effectiveness is governed by the catalyst configuration rather than Pt loading alone. Post-mortem cross-section analyses reveal pronounced changes in the Pt spatial distribution for the Pt/C system, characterized by an apparent depletion of Pt at the original GRC layer position and the occurrence of a band-like Pt-enriched region within the membrane. Across all GRC systems, \textcolor{black}{measurable hydrogen in oxygen values} increase predominantly during the first 250 h of operation, accounting for the majority of the total rise and defining a pronounced run-in period. The evolution of open-circuit voltage decay closely correlates with this behavior, indicating its potential as a non-invasive diagnostic marker. Overall, the results highlight that material-dependent performance evolution, rather than Pt loading alone, governs the long-term effectiveness of membrane-integrated GRC layers. These findings provide indications relevant to the design of resource-efficient and durable GRC concepts for safe high-pressure PEM water electrolysis.