<em>(Invited)</em> In-Situ/Operando X-Ray Absorption Spectroscopy: Methods and Challenges in Electrocatalysts Characterization

Zitolo, Andrea

During the last decades X-ray absorption spectroscopy (XAS) has proved to be a fundamental tool for understanding the nature of active catalytic species, especially in the form of highly dispersed, amorphous phases, and in the case of single atom catalysts. [1-4] The efforts in developing this technique under working conditions are justified by the extraordinary information that can be obtained on the identity of active species, reaction intermediates and activation/degradation phenomena. Clearly, the challenges embrace many fields: 1) catalysts can be very complex materials, comprising different, even disordered, phases; 2) it is a technique that uses synchrotron radiation, and the design of an appropriate experimental set-up requires know-how, but also synergy with a beamline team; 3) a rigorous interpretation of the XAS data requires high level of expertise to avoid easy misinterpretations, and the continuous development of new data analysis methods.

This talk aims to discuss in-situ/operando XAS studies to investigate the activity and stability of novel catalysts during electrochemical reactions in proton exchange membrane fuel cell (PEMFC) devices and during CO₂ reduction. In most studies with operando XAS, electrochemical studies have been performed in liquid electrolyte cells. While instructive, the performance and stability observed in liquid electrolyte at room temperature is however never directly transferable to the performance in a PEMFC device, operating at high temperature, high current density, and with a solid-polymer electrolyte interface. This current limitation can be overcome by the design of an appropriate cell able to isolate and extract the signal coming from the area where the reactions take place.

Part of the talk will also be devoted to some time-resolved structural probing techniques to follow a reaction pathway under high temperature or pressure conditions.

M. Elmaalouf,M. Odziomek, S. Duran, M. Gayrard, M. Bahri, C. Tard, A. Zitolo, B. Lassalle-Kaiser, J.Y. Piquemal, O. Ersen, C. Boissière, C. Sanchez, M. Giraud, M. Faustini and J. Peron Nat Commun2021, 12, 3935
D. Karapinar, N.H. Tran, N.R. Sahraie, J. Li, D. Wakerley, N. Touati, S. Zanna, D. Taverna, L.H. Galvão Tizei, A. Zitolo, F. Jaouen, V. Mougel, M. Fontecave, Angewandte Chemie International Edition 2019, 58(42), 15098-15103
Zitolo, A.; Ranjbar-Sahraie, N.; Mineva, T.; Li, J.; Jia, Q.; Stamatin, S.; Harrington, G. F.; Lyth, S. M.; Krtil, P.; Mukerjee, S.; Fonda, E.; Jaouen, F., Nat Commun 2017, 8 (1), 957
A. Zitolo, V. Goellner, V. Armel, M. T. Sougrati, T. Mineva, L. Stievano, E. Fonda, F. Jaouen, Nature Materials 2015, 14, 937-942

(Invited) In-Situ/Operando X-Ray Absorption Spectroscopy: Methods and Challenges in Electrocatalysts Characterization