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arXiv · 2602.20784

Epitaxial Films as Model Platform for Understanding Compositionally Complex Electrocatalysts

Satyakam Kar·Alejandro E. Perez-Mendoza·Huixin Xiu·Miran Joo·Kirill V. Yusenko·Ulrich Hagemann·Christoph Somsen·Janine Pfetzing-Micklich·Christina Scheu·Corina Andronescu·Alfred Ludwig
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Abstract

Compositionally complex solid solutions provide a unique route for engineering high-performance electrocatalysts, where the polyelemental surface composition can be seamlessly tuned to optimize activity, selectivity, and stability. However, the mechanistic understanding of these electrocatalysts remains limited by the lack of a model system with a crystallographically-defined surface that is compatible with correlative, multi-scale characterization. Here, we present epitaxial films as a model platform for studying compositionally complex electrocatalysts. Using magnetron sputtering, we realize (111) epitaxial Ir-Pd-Pt-Rh-Ru films on (0001) sapphire substrate via a (111) Pt buffer layer, confirmed by X-ray diffraction and transmission electron microscopy. The growth approach is applicable across a broad composition range and produces smooth surfaces (root mean square roughness < 1 nm) with micrometer-sized grains in the nanoscale films. With these films, we demonstrate direct structure-activity mapping at the nanoscale through precise co-localization using micro-indents and performing correlative atomic force microscopy, electron backscatter diffraction, and scanning electrochemical cell microscopy. Our work establishes a model platform for fundamental scalebridging characterization and paves the way for rational design of compositionally complex electrocatalysts.

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Satyakam Kar, Alejandro E. Perez-Mendoza, Huixin Xiu, Miran Joo, Kirill V. Yusenko, Ulrich Hagemann, Christoph Somsen, Janine Pfetzing-Micklich, Christina Scheu, Corina Andronescu, Alfred Ludwig. 2026-02-24. Epitaxial Films as Model Platform for Understanding Compositionally Complex Electrocatalysts. https://doi.org/10.1039/d6mh00852f

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