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The role of experimental thermodynamics in deciphering complex solvated interfaces – insights into the enthalpy of a ion exchange reaction

Séminaire Chimie ED459

Dr. Nadine Kabengi (Georgia State University, USA)

Le Jeudi 06 Juillet 2023 à 14h

CNRS, Amphithéâtre Balard (bâtiment Balard RdC, 1919 route de Mende)

Date de début : 2023-07-06 14:00:00

Date de fin : 2023-07-06 15:30:00

Lieu : CNRS amphi Balard

Intervenant : Dr. Nadine Kabengi

Georgia State University, USA

Chemical reactions at interfaces between solids and fluids play a fundamental role in environmental, geological, industrial and technological settings, and have significant global and economic repercussions. The complexity of these interfaces is not yet fully understood, and their structure-reactivity relationships still not fully unlocked. Our ability to harness the potential of solvated interfaces in technological and environmental applications hinges on our ability to adequately understand and model interfacial chemical reactions – protonation, exchange, adsorption, desorption, precipitation, redox, etc. in situ and under realistic operating conditions. A host of experimental and computational techniques have been applied to this task, yet very few studies deal with the thermodynamics of interfacial reactions and even fewer have been directly supported by experimental data. Understandably, these data do not resolve molecular configurations and interactions that underpin them. These details can be provided by other in-depth spectroscopic and molecular simulations. Yet, the significance of connecting fundamental thermodynamic parameters of exchange with molecular-level structure of the interface lies in the ability to develop a quantitative mechanistic understanding of the relationship between a surface structure and its chemical reactivity, and hence predict macroscopic behavior based on surface reactivity. Then, equilibrium and kinetic information at the molecular scale can be used to model macroscopic environmental reactive transport.

This contribution will present illustrative examples on how insights from thermodynamic data obtained through operando and in situ flow microcalorimetry have helped advance our understanding of interfacial reactions. Operando and in situ flow microcalorimetry provides a direct, quantitative measure of the heat evolved during a reaction. Besides providing information of thermodynamic significance, i.e., heats of reactions (Q in–1) and enthalpy changes (∆H in kJ.mol–1), flow microcalorimetry can also provide information about changes that occur in the properties of a surface or a mineral-water interface, e.g., chemical bonding, heterogeneity of surface functional groups and most importantly charging behavior with varying experimental conditions. These measured energetics data have provided a framework to rationalize the drivers of elementary interfacial reactions, connect them to molecular-level modeling and computational frameworks, and eventually predict their enthalpy.

Contact local ICGM : Dr. Bénédicte Prélot, D.R. CNRS (Dépt. D3)