Abstract
Proton exchange membrane water electrolyzers (PEMWEs) are promising zero-emission technologies. However, their high cost remains a barrier to widespread adoption. Iridium oxide is commonly used as an oxygen evolution reaction (OER) catalyst, and its cost and scarcity make it essential to reduce its loading while increasing its activity. Evaluation of iridium oxide activity should be carried out in the membrane electrode assembly (MEA) configuration to replicate realistic operating conditions. Herein, we present a comprehensive benchmarking framework to accurately evaluate the amorphous and crystalline iridium oxides at the MEA level. By systematically varying the catalyst loading, this study confirmed that each MEA was utilized uniformly, presenting intrinsic electrochemical properties independent of the loading. Through intrinsic charge density determined by voltammetry, we established two electrochemical descriptors to evaluate catalyst redox reactions. The mass activity was evaluated by correlating current vs. loading, and the slope provides loading-independent mass activity. The effect of the porous transport layer on OER activity was discussed, identifying a ‘background’ current at zero-loading. This study highlights potential pitfalls in MEA-level catalyst screening and underscores the importance of the loading study for reliable results.
| Original language | English |
|---|---|
| Pages (from-to) | 3342-3353 |
| Number of pages | 12 |
| Journal | Journal of Materials Chemistry A |
| Volume | 14 |
| Issue number | 6 |
| DOIs | |
| State | Published - Jan 22 2026 |
Funding
The (S)TEM, EELS, and EDS portions of this research were supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors acknowledge funding from the DOE Energy Earthshot Initiative as part of the Center for Ionomer-Based Water Electrolysis, award DE-AC02-05CH11231. We thank Dr Valerie Brogden for carrying out FIB-SEM measurements at the University of Oregon. The authors acknowledge the use of facilities and instrumentation at the University of California, Irvine (UC, Irvine) Irvine Materials Research Institute (IMRI), which is supported in part by the National Science Foundation through the UC Irvine Materials Research Science and Engineering Center (DMR-2011967). The XPS work was performed using instrumentation funded in part by the National Science Foundation Major Research Instrumentation Program under Grant CHE-1338173, and used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. Ishifuku Metal Industry Co. is acknowledged for providing two types of Ishifuku catalyst materials.