Limitations and Opportunities of Self-Supported Co-Based Anodes for Pure Water-Fed Anion Exchange Membrane Water Electrolyzers

Hydrogen has been regarded as an energy source with a potential to be used in various sectors, including transportation, power generation and industrial processes 1-3 . Producing hydrogen via water electrolysis using green electricity will be necessary for a sustainable future. Proton exchange membrane water electrolysis (PEMWE) is one of mature and leading electrolysis technologies, while anion exchange membrane water electrolysis (AEMWE) is regarded as a new, emerging technology 4 . However, PEMWE system suffers from their expensive cost and scarcity of iridium-based oxygen evolution reaction (OER) catalysts, having no alternative OER catalysts. Compared to PEMWE, AEMWE can be pursued with non-platinum group metal (non-PGM) thanks to its alkaline environment 4,5 . Here, non-PGM Co-based catalyst coated anodes were prepared using a simple hydrothermal reaction followed by heat treatment. Different phases and crystallinity of cobalt-based anodes were prepared and tested in pure water-fed AEMWE devices. To investigate the catalyst-ionomer/membrane interfaces at the anodes, the loadings of Co 3 O 4 catalyst and ionomer topcoats were controlled. The cell performance in polarization curves was correlated with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements. The comparison of anodes operated with pure water feed and with supporting electrolyte was made to highlight the importance of catalyst-ionomer interface in pure water-fed AEMWE. Lastly, our self-supported Co 3 O 4 anode outperformed a commercial Co 3 O 4 NP ink-based anode, projecting a potential of direct growth of catalyst materials on PTLs in pure water-fed AEMWE. Reference (1) Agyekum, E. B.; Nutakor, C.; Agwa, A. M.; Kamel, S. A Critical Review of Renewable Hydrogen Production Methods: Factors Affecting Their Scale-Up and Its Role in Future Energy Generation. Membranes 2022 , 12 (2). (2) Qusay, H.; Sameer, A.; Aws Zuhair, S.; Hayder, M. S.; Marek, J. Green hydrogen: A pathway to a sustainable energy future. Int. J. Hydrogen Energy 2024 , 50 , 310-333. (3) Joonsik, H.; Krisha, M.; HeeJin, C. A review of hydrogen utilization in power generation and transportation sectors: Achievements and future challenges. Int. J. Hydrogen Energy 2023 , 48 (74), 28629-28648. (4) Lee, S. A.; Kim, J.; Kwon, K. C.; Park, S. H.; Jang, H. W. Anion exchange membrane water electrolysis for sustainable large-scale hydrogen production. Carbon Neutralization 2022 , 1 (1), 26-48. (5) Juchan, Y.; Myeong Je, J.; Xiaojun, Z.; Yoo Sei, P.; Jooyoung, L.; Sung Mook, C.; Yadong, Y. Non-precious electrocatalysts for oxygen evolution reaction in anion exchange membrane water electrolysis: A mini review. Electrochem. Commun. 2021 , 131 , 107118.