Complex-Solid-Solution Electrocatalyst Screening and Characterization via Electrochemical Microscopy.

Emmanuel Batsa Tetteh, Ruhr University Bochum, Bochum, Germany
Lars Banko, Ruhr University Bochum, Bochum,
Olga Krysiak, Ruhr University Bochum, Bochum,
Alfred Ludwig, Ruhr University Bochum, Bochum,
Wolfgang Schuhmann, Ruhr University Bochum, Bochum,

Electrochemical energy conversion devices such as fuel cells and electrolyzers are ca¬pable of providing cleaner energy platforms with negligible carbon footprint. However, these devices require efficient electrocatalyst as electrode materials to be economically feasible. [1] Complex solid solutions (CSS) also known as high-entropy alloys cover complex compo¬sitional spaces providing the opportunity to realize high performance electrocatalysts because of their nearly unlimited number of different active sites exposed at the surface. It has been shown by theoretical studies that multiple arrangements of different elements directly neighbouring a binding site create millions of differently active catalytic sites. [2] Here we use a thin-film material library in tandem with a scanning droplet cell (SDC) and Scanning electrochemical cell microscopy (SECCM) to provide a view on the activity of CSS electrocatalysts. The choice of elements (Ag-Ir-Pd-Pt-Ru) and the composition space covered were previously predicted theoretically to be active for ORR. [2] We zoomed in to areas of a supposedly homogeneous composition by taking advantage of the availability of different SECCM capillary sizes and the large statistical data sets, and we attempted to visualize experimentally for the first-time statistical heterogeneity of active sites on the model CSS catalyst. [3] References [1] T. Quast, S. Varhade, S. Saddeler, Y.-T. Chen, C. Andronescu, S. Schulz, W. Schuhmann, Angew Chem Int. Ed. 2021. 2021, 60, 23444. [2] T. A. A. Batchelor, T. Löffler, B. Xiao, O. A. Krysiak, V. Strotkötter, J. K. Pedersen, C. M. Clausen, A. Savan, Y. Li, W. Schuhmann et al., Angew. Chem. Int. Ed. 2021, 60, 6932. [3] E. B. Tetteh, L. Banko, O. A. Krysiak, T. Löffler, B. Xiao, S. Varhade, S. Schumacher, A. Savan, C. Andronescu, A. Ludwig, W. Schuhmann, Electrochem. Sci. Adv. 2021. DOI: 10.1002/elsa.202100105. Acknowledgements This project was supported by SENTINEL. SENTINEL has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 812398.

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