Electrochemical liquid phase TEM in aqueous electrolytes for energy applications: the role of liquid flow configuration

Abstract Electrochemical Liquid Phase Transmission Electron Microscopy (EC-LPTEM) is envisioned as an invaluable tool for the investigation of structural and morphological properties of functional materials in electrochemical systems for energy transition applications, especially in aqueous-based electrolytes. However, one major issue in accessing electrochemical conditions (e.g. overpotential, current density) relevant for energy applications (e.g. heterogeneous catalysis, batteries) is the saturation of the liquid cell by gaseous products resulting both from the reaction of interest and from water decomposition at the Working electrode (WE) and Counter electrode (CE). In this work, the performance of an optimized liquid cell geometry is investigated, with the aim of fine tuning the experimental set-up and optimizing the functional activity of the active materials under investigation. Ex situ and in situ comparative flow experiments are carried out in order to understand the role of the optimized liquid flow configuration for electrochemical experiments in aqueous electrolytes. The key role of the optimized flow geometry in reducing the formation of gas bubbles at both the WE and CE is highlighted, coupled with an improvement in the removal of gaseous products at the WE/CE. Finally, the validation of the optimized microfluidic set-up, through the electrodeposition of Zn nanostructures in aqueous electrolyte, is presented as a proof-of-concept experiment showing that the optimized geometry provides access to experimental conditions which have not been available with the standard liquid cell configuration.