TY - JOUR
T1 - X-ray photoelectron spectroscopy investigation of iridium oxide catalyst layers
T2 - Insights into the catalyst-ionomer interface
AU - Foster, Jayson
AU - Lyu, Xiang
AU - Serov, Alexey
AU - Mauger, Scott
AU - Padgett, Elliot
AU - Pylypenko, Svitlana
N1 - Publisher Copyright:
© 2025
PY - 2025/3/20
Y1 - 2025/3/20
N2 - X-ray photoelectron spectroscopy (XPS) is a commonly used technique for investigating the surface properties and composition of catalysts used in polymer electrolyte membrane fuel cells and electrolyzers. XPS analysis of catalyst layers (CLs) is becoming increasingly utilized to provide greater understanding of CL properties and relationships between catalyst and support composition and structure, catalyst ink composition, CL fabrication methods and parameters, and their performance and durability. Characterization of Ir-based CLs is challenging due to several factors including interpretation of Ir 4f spectra, deconvolution of catalyst and ionomer species in O 1s spectra, and ionomer susceptibility to X-ray damage that leads to changes at the catalyst-ionomer interface often more significant than differences between samples. This study reports an approach for detailed XPS characterization of Ir-based CLs, establishes quantitative metrics, and provides insights into the catalyst-ionomer interface that can be correlated to wide variety of processing and performance metrics. Specifically, we have evaluated surface compositional differences in CLs prepared with several common CL coating methods. We also investigated CLs prepared with different catalyst loadings and selected samples after electrochemical testing. In general, we found good agreements in trends observed from elemental ratios and those derived from detailed analysis of the O 1s spectra. Additionally, O 1s analysis revealed differences in the catalyst composition, addressing some of the challenges and limitations related to the interpretation of the Ir 4f spectra.
AB - X-ray photoelectron spectroscopy (XPS) is a commonly used technique for investigating the surface properties and composition of catalysts used in polymer electrolyte membrane fuel cells and electrolyzers. XPS analysis of catalyst layers (CLs) is becoming increasingly utilized to provide greater understanding of CL properties and relationships between catalyst and support composition and structure, catalyst ink composition, CL fabrication methods and parameters, and their performance and durability. Characterization of Ir-based CLs is challenging due to several factors including interpretation of Ir 4f spectra, deconvolution of catalyst and ionomer species in O 1s spectra, and ionomer susceptibility to X-ray damage that leads to changes at the catalyst-ionomer interface often more significant than differences between samples. This study reports an approach for detailed XPS characterization of Ir-based CLs, establishes quantitative metrics, and provides insights into the catalyst-ionomer interface that can be correlated to wide variety of processing and performance metrics. Specifically, we have evaluated surface compositional differences in CLs prepared with several common CL coating methods. We also investigated CLs prepared with different catalyst loadings and selected samples after electrochemical testing. In general, we found good agreements in trends observed from elemental ratios and those derived from detailed analysis of the O 1s spectra. Additionally, O 1s analysis revealed differences in the catalyst composition, addressing some of the challenges and limitations related to the interpretation of the Ir 4f spectra.
KW - Ionomer
KW - Iridium oxide catalysts
KW - Surface composition
KW - Water electrolyzers
KW - X-ray photoelectron spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=85216320898&partnerID=8YFLogxK
U2 - 10.1016/j.electacta.2025.145705
DO - 10.1016/j.electacta.2025.145705
M3 - Article
AN - SCOPUS:85216320898
SN - 0013-4686
VL - 517
JO - Electrochimica Acta
JF - Electrochimica Acta
M1 - 145705
ER -