Operando X-Ray Scattering for Electrocatalysis and Beyond

The energy transition stands as one of the greatest challenges of today’s society. In this context, electrocatalyst materials at the heart of electrochemical energy conversion devices such as fuel cells and water electrolyzers are expected to play an increasing crucial role in the near future. The urgent bottleneck to be overcome in electrocatalyst materials development to allow the widespread deployment of electrochemical systems is thus reaching combined high activity and long-term stability at low cost. Despite the diversity in electrocatalyst materials, the latter being largely imposed by the various types of electrochemical systems (noble vs. non-noble metals in acidic vs. alkaline media for example) and the prerequisites of the different electrochemical processes (oxidation or reduction reactions of various species at different electrode potential ranges), most activity and stability properties of electrocatalysts directly derive from their (surface) chemistry and structure 1. Such properties (and their temporal evolution) can thus be directly investigated by means of in situ or operando high energy X-ray scattering (XRD) technique 2. In this presentation, the versatility of in situ and operando XRD technique in addressing key bottlenecks in electrocatalyst materials development, notably by probing adsorption and oxidation trends 3, will be showcased. After an overview of previous contributions from the literature, the talk will focus on our ongoing works which encompass the study of Pt-based nanocatalysts for the oxygen reduction reaction (ORR) at proton-exchange membrane fuel cells (PEMFCs) anode, carbon-capped Ni@C catalyst for the hydrogen oxidation reaction (HOR) at anion-exchange membrane fuel cells (AEMFCs) anode and IrCu unsupported aerogel catalyst for the oxygen evolution reaction (OER) at proton-exchange membrane water electrolyzers (PEMWEs) anode. Finally, the ability of operando XRD to provide device-relevant insights at the macroscale (such as ionomer hydration in PEMFCs or water distribution in AEMFCs) beyond electrocatalysts microstructural properties will be presented. References 1 Z. W. Seh, J. Kibsgaard, C. F. Dickens, I. Chorkendorff, J. K. Nørskov, and T. F. Jaramillo. Combining theory and experiment in electrocatalysis: Insights into materials design. Science, 355(6321): eaad4998, 2017. 2 Magnussen, O. M., Qiu, C., Drnec, J., Martens, I., Jared Huang, J., Chattot, R., & Singer, A. (2023). In situ and operando X-ray scattering methods in electrochemistry and electrocatalysis. Chemical Reviews , Accepted. 3 Chattot, R., Martens, I., Mirolo, M., Ronovsky, M., Russello, F., Isern, H., Braesch, G., Hornberge, E., Strasser, P., Sibert, E., Chatenet, M., Honkimäki, V., Drnec, J. (2021). Journal of the American Chemical Society, 1, 17068-17078.