(358i) Elucidating Dynamics of Ni-Fe Based Catalyst for the Development of Zero-Gap Anion Exchange Membrane Water Electrolyzers

Zero-gap water electrolyzers utilizing anion exchange membrane (AEM) technology hold promise for efficient and sustainable hydrogen production. Due to the kinetically slow oxygen evolution reaction (OER), optimizing OER catalysts is central for optimal operation within the membrane electrode assembly (MEA). In this study, we focus on exploring varying compositions of Ni, Fe, and Co due to their promising potential as high-performance OER catalysts. Our investigation encompasses a comprehensive approach involving both fundamental catalyst characterization and device performance evaluations. Synthesizing and evaluating the performance of NiFe-based catalysts, our goal is to understand the conversion dynamics of catalyst activation to oxyhydroxide and material degradation during electrolysis. Uncovering the catalyst behavior under realistic operational conditions will provide crucial insights into the catalyst's performance under high current densities, similar to industrial conditions.

A series of metallic Ni:Fe:Co thin films were fabricated through a controlled process of electron beam physical vapor deposition and deposited onto Glassy Carbon and Porous Transport Layer substrates. This enabled precise tuning of the composition ratios to evaluate the impact on OER catalysis for a rotating disk electrode configuration and membrane electrode assembly electrolyzer. Using cyclic voltammetry in an RDE, we studied various dynamic features, such as the size and position of the Ni redox peaks. We observed that the introduction of Co inhibited the conversion of metal to oxyhydroxides, thus affecting the current density. Additionally, we found that cycling across a potential range and oxidizing and reducing the surface of the metal catalysts drove conversion, and increasing the electrolyte concentration enhanced the conversion rate of the catalyst. Furthermore, we used the same thin film deposition technique to assess the catalysts' performance in an MEA and found that while in an RDE the cobalt incorporation decreased the catalyst performance, translation to MEA configuration revealed that cobalt enhances the catalyst performance. Through this comprehensive research effort, we strive to contribute to the advancement of efficient and durable catalyst materials for next-generation AEM water electrolyzers.