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Understanding compositionally complex electrocatalysts using epitaxial films and correlative multi-scale
Satyakam Kar1, Alejandro E Perez-Mendoza2, Huixin Xiu3,4
1Chair for Materials Discovery and Interfaces, Institute for Materials, Ruhr University Bochum, Universitätsstraße 150, 44801 Bochum, Germany. alfred.ludwig@rub.de.
Materials Horizons
|July 24, 2026
Summary
Epitaxial films offer a new model for studying high entropy alloys as electrocatalysts. This platform enables nanoscale structure-activity mapping for rational catalyst design.
Area of Science:
- Materials Science
- Electrochemistry
- Nanotechnology
Background:
- High entropy alloys (compositionally complex solid solutions) are promising for high-performance electrocatalysts due to tunable surface properties.
- Limited mechanistic understanding of these alloys is due to the lack of model systems with crystallographically defined surfaces for multi-scale characterization.
Purpose of the Study:
- To establish epitaxial films as a model platform for fundamental studies of compositionally complex electrocatalysts.
- To enable scale-bridging characterization and facilitate the rational design of advanced electrocatalysts.
Main Methods:
- Fabrication of (111) epitaxial Ir-Pd-Pt-Rh-Ru films on sapphire substrates using magnetron sputtering and a Pt buffer layer.
- Characterization using X-ray diffraction (XRD) and transmission electron microscopy (TEM) to confirm film epitaxy and structure.
- Nanoscale structure-activity mapping via correlative atomic force microscopy (AFM), electron backscatter diffraction (EBSD), and scanning electrochemical cell microscopy (SECCM).
Main Results:
- Successfully synthesized smooth, epitaxial Ir-Pd-Pt-Rh-Ru films with controlled crystallographic orientation and micrometer-sized grains.
- Demonstrated the capability for precise co-localization of nanoscale features using micro-indents for correlative characterization.
- Achieved direct structure-activity mapping at the nanoscale, linking material structure to catalytic performance.
Conclusions:
- Epitaxial films provide a viable model system for investigating compositionally complex electrocatalysts.
- The developed platform supports fundamental, scale-bridging characterization essential for understanding structure-property relationships.
- This approach paves the way for the rational design of next-generation high-performance electrocatalysts.
