Understanding the intrinsic properties of the electroactive species at electrode-electrolyte interfaces (EEIs) is essential for the rational design of high-performance solid-state systems for energy production and storage. In situ infrared spectroscopic characterization provides insights into structural changes of adsorbed species at interfaces. Ion soft-landing enables precisely-controlled deposition of mass- and charge-selected ions onto surfaces. In this work, we describe a unique approach for the simultaneous electrochemical and spectroscopic characterization of precisely-selected ions soft-landed at EEIs. The approach involves a specially-designed three-electrode cell compatible with in situ infrared reflection absorption spectroscopy (IRRAS) characterization of the soft-landed ions at interfaces. In this cell, a surface prepared using ion soft-landing is used as the working electrode (WE) while the counter electrode and reference electrode are wired around the WE. The entire three-electrode assembly is covered with a thin nanoporous ionic liquid membrane. Keggin polyoxometalate (POM) anions were selected as a model system for ion soft-landing experiments due to their multielectron redox activity, structural stability and a well-characterized IR spectrum. In situ cyclic voltammetry (CV) studies reveal sequential multielectron transfer processes of the soft-landed PW12O403- anions in the potential range of 0.3 V to -2.1 V. A distinct shift in the wavenumber of the terminal W=O band in the IRRAS spectra was observed during the multielectron reduction process. The experimental results demonstrate the feasibility of the in situ spectroelectrochemical approach for examining structural changes of well-defined electroactive species during electron transfer processes at solid-state EEI.

In situ infrared and electrochemistry approach for studying the structural evolution of soft-landed ions at electrochemical interfaces

256th National Meeting (2018)

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