Highly Porous Ir-Based Catalyst-Integrated Electrode for Efficient Proton Exchange Membrane Water Electrolyzer
Authors: Kim Hoyoung , Yeo Kyeong-Rim , Kim Soo Kil , Lee Jinwoo 
Published: December 2024

Proton exchange membrane water electrolyzer (PEMWE) is the most promising green hydrogen production device suitable for responding to the intermittency of renewable energy sources [1]. However, anodes in acidic and oxidizing environments require the use of noble Ir that is resistant to harsh conditions. Although many efforts have been made to develop efficient and robust Ir-based catalysts, most have focused on developing catalysts in powder form and evaluating half-cells based on aqueous model systems consisting of three-electrode using rotating disk electrode (RDE). The membrane electrode assembly (MEA)-based PEMWE system has significant differences in operating conditions (temperature, electrolyte, catalyst loading, substrate type, etc.) from the half-cell system, and therefore, the high performance and durability in the half-cell system do not ensure the same results within the PEMWE system [2]. This means that the developed catalysts should be applied to a single cell and its compatibility assessed.

In this study, a catalyst-integrated electrode was fabricated by forming an Ir-based catalyst on a Ti fiber felt used as an anode PTL in the PEMWE system, and applied directly to the anode without using a binder. The application of a powder-type catalyst to MEA is complicated through many steps such as powder production, ink preparation, and catalyst layer coating, requiring a lot of time and cost. In addition, when coating the catalyst layer, it is physically deposited together with a polymer binder, which not only blocks the active sites of the catalyst but also causes the problem of lowering the electrical conductivity of the catalyst layer [3]. On the other hand, the catalyst-integrated electrode is a simple method of growing on PTL, providing good electrical conductivity and excellent mechanical stability, and can be directly applied to the PEMWE system without using a binder. Our Ir-based catalyst-integrated electrode prepared through electrochemical reaction showed excellent OER activity (248 mV at 10 mA cm−
2) and durability (50 h at 200 mA cm−
2) in a half-cell system based on excellent physicochemical/electrochemical properties, and also showed the similar results when applied to a single-cell (performance of 6.5 A cm−
2 @ 2.0 Vcell with a degradation rate of only 1.58 mV h−
1 for 100 h stability test at 2 A cm−
2), showing feasibility for industrial use.

[1] S. Shiva Kumar, V. Himabindu, Hydrogen Production by PEM water electrolysis – A review, Materials Science for Energy Technologies, 2 (2019) 442-454.

[2] K. Ehelebe, D. Escalera-Lopez, S. Cherevko, Limitations of aqueous model systems in the stability assessment of electrocatalysts for oxygen reactions in fuel cell and electrolyzers, Current Opinion in Electrochemistry, 29 (2021) 100832.

[3] W. Wang, L. Ding, J. Li, Z. Xie, M.M. Mench, F.-Y. Zhang, An ink-free integrated dual electrode assembly for economical proton exchange membrane water electrolysis at ultrahigh current densities, Chemical Engineering Journal, 494 (2024) 153015.