(Invited) Operando Approaches for Observing Reactions at Buried Electrochemical Interfaces

Abstract

The performance of materials for electrochemical energy storage and conversion depends critically on reactions taking place at the interfaces between these materials and their operating environment: from the reversible incorporation of ions at electrode−electrolyte interfaces in rechargeable batteries, to the conversion of the waste carbon dioxide into liquid fuels. As the reaction conditions change so these interfaces change, with often dramatic effects on their structure and chemical state. Understanding the evolution of these interfaces under realistic conditions is critical to the selection and design of improved electrochemical materials. However, it is extremely challenging to extract this information during operation, due to interference from the bulk phases either side of these buried interfaces, which disturb most interface-sensitive probes.1,2 I will give an overview of our recent efforts to develop operando approaches for resolving the structural and chemical evolution of electrochemical interfaces.3-8 This includes enclosed reaction cells sealed with X-ray/electron-transparent membranes such as thin (<100 nm) silicon nitride or graphene membranes that remain impermeable liquids. We thereby use soft X-ray absorption spectroscopy (sXAS) to observe solid-electrolyte interphase (SEI) formation on Li-ion battery anodes,4 and changes in the chemical state of transition metal electrocatalysts under electrochemical control. I will further discuss our recent progress in depositing thin lithium layers onto solid electrolytes,5,6 and using hard X-ray Photoelectron Spectroscopy (XPS) to study electrode-electrolyte interfaces in all-solid-state batteries.7,8 The development of these interface-sensitive operando approaches is expected to provide valuable tools for revealing a wide range of interfacial reactions. Collaboration across European and international partners has been critical to this work, and I will highlight how European funding has helped make this possible and the benefits associated with this. References Wu et al. Phys. Chem. Chem. Phys. 2015, 17, 30229.Weatherup et al. Top. Catal. 2018, 61, 2085.Velasco-Velez et al. Angew. Chemie 2015, 54, 14554.Swallow et al. Nature Commun. 2022, 13, 6070Weatherup et al. J. Phys. Chem. B 2018, 122, 737.Khatun et al. Electrochimica Acta 2022, 431, 141145Narayanan et al. Nature Commun. 2022, 13, 7237Gibson et al. Faraday Discuss., 2022 , 236, 267