Lab-based operando x-ray photoelectron spectroscopy for probing low-volatile liquids and their interfaces across a variety of electrosystems

Göktürk, Pınar Aydoğan; Camcı, Merve Taner; Süzer, Şefik

doi:10.1116/6.0000273

Cited by 9 publications

(5 citation statements)

References 85 publications

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“…That experimental setup enabled the formation of a liquid film thin enough to probe the IL/electrode interface such that the authors were able to follow the EDL processes by tracing the shifts in the core-level binding energies under bias. While the application of direct current (DC) bias during XPS data acquisition provides steady-state information, demonstrated by us and others as well, − our group has previously shown that alternating current (AC) excitation is indispensable for investigation of the dynamics of electrical potential developments. − Use of scanning electron microscopy (SEM) for detecting similar changes due to potential induced intensity modulations was also recently reported by us . Both our XPS and SEM investigations revealed that the effects of time-resolved polarization of the metal electrodes can be followed locally up to extremely long-distance (centimeters) and long-time (hundreds of seconds) ranges, in a chemically specific fashion.…”

Section: Introductionsupporting

confidence: 58%

Assessing Local Electrical Properties of Ionic Liquid/Metal Interfaces with Operando-XPS and by Incorporating Additional Circuit Elements

Karaoglu,

Kutbay,

Ince

et al. 2023

Anal. Chem.

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X-ray photoelectron spectroscopy (XPS) has been utilized to record binding energy changes upon applying direct current (DC) and/or alternating current (AC) (square-wave) bias with different frequencies on a coplanar capacitor, having an ionic liquid (IL) film as the electrolyte. Electrical potential developments in numerous locations on the device are extracted from the variations in binding energy positions of the atomic core levels, which together with electrochemical measurements are used to extract local information before and after insertion of additional resistors in series. The presence of the IL introduces complex charging/discharging processes with a direct influence on the electrical double layer (EDL) formation, some of which can be untangled from each other via AC modulation by choosing appropriate time windows of observation. Accordingly, under 10 kHz modulation, fast processes are sampled, which are associated with electronic currents, and effects of slow migratory currents can be measured using 0.1 Hz. The addition of serial resistors allows us to quantify AC currents passing through, which reveals the magnitude of the system's impedance under different conditions. This process surprisingly reverses differences(s) in the voltage developments between the low and high frequencies over the electrified electrodes compared to those over the porous membrane in between. Our approach turns XPS into a powerful electrical and surface-sensitive tool for extracting localized electrochemical properties in a noninvasive and direct way. We expect that a wider utilization of the technique will lead to better identification of the obstacles for developing the next-generation sensing, energy harvesting, and storage systems as well as devices for iontronic/neuromorphic applications.

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Section: Introductionsupporting

confidence: 58%

Assessing Local Electrical Properties of Ionic Liquid/Metal Interfaces with Operando-XPS and by Incorporating Additional Circuit Elements

Karaoglu,

Kutbay,

Ince

et al. 2023

Anal. Chem.

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“…This experimental setup allowed the formation of a liquid film thin enough to probe the IL/electrode interface, so that the authors were able to follow the EDL processes by tracing the shifts in binding energy under an external potential . While applying such DC potential during XPS data acquisition provides vital steady-state information, our group has previously shown that AC excitation is helpful for understanding the dynamics of electrical potential developments. − …”

Section: Introductionmentioning

confidence: 99%

Probing the Dynamics of Non-Faradaic Processes in Ionic Liquids at Extended Time and Length Scales Using XPS with AC Modulation

Göktürk

Süzer

2021

J. Phys. Chem. C

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Charging dynamics of ionic liquid (IL) electrolytes play important roles in various aspects of electrochemical processes. However, the precise understanding of such processes at extended time and length scales is incomplete due to the experimental difficulties in probing the electrochemical potential and other relevant parameters. In principle, such shortcomings should not apply to theoretical/computational approaches; however, existing works have mostly concentrated on or around electrode/electrolyte interfaces and short timescales due mostly to prohibitive demands on computational efforts. To fill this gap, we have utilized X-ray photoelectron spectroscopy to study the charging dynamics of ILs in contact with two wire electrodes under AC square wave excitation, with frequencies ranging from hundreds of kHz down to the mHz region. Using the changes in the binding energy position of the IL-related core-level peaks, electrical potential profiles along the lines in between the electrodes and on the entire surface of the electrolyte have been investigated in situ. From these results, we identify two widely different time constants. The timescale of the fast process was shown to be on the order of RC time constant, while the slow process takes place on a timescale of seconds. Our method in the present study is expected to open up a new way for extracting novel dynamic information for gaining a better understanding of such processes and designing efficient IL-based electrochemical devices with a novel perspective on the charging.

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“…Facilitated by their high vacuum compatibility, over the past decade ILs have been fairly well characterized in‐vacuo by X‐ray photoelectron spectroscopy (XPS) as a function of electrochemical potential [34–58] . XPS allows for the determination of surface composition of an IL while also probing the binding energy shifts in the ions ( U XPS ; units of eV) as a function of an external electrochemical potential ( U ; units of V).…”

Section: Introductionmentioning

confidence: 99%

The Influence of Water Vapor on the Electrochemical Shift of an Ionic Liquid Measured by Ambient Pressure X‐ray Photoelectron Spectroscopy

2021

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Ionic liquids (ILs) are considered to be one of the steppingstones to fabricate next generation electrochemical devices given their unique physical and chemical properties. The addition of water to ILs significantly impact electrochemical related properties including viscosity, density, conductivity, and electrochemical window. Herein we utilize ambient pressure X‐ray photoelectron spectroscopy (APXPS) to examine the impact of water on values of the electrochemical shift (S), which is determined by measuring changes in binding energy shifts as a function of an external bias. APXPS spectra of C 1s, O 1s and N 1s regions are examined for the IL 1‐butyl‐3‐methylimidazolium acetate, [C4mim][OAc], at the IL/gas interface as a function of both water vapor pressure and external bias. Results reveal that in the absence of water vapor there is an IL ohmic drop between the working electrode and quasi reference electrode, giving rise to chemical specific S values of less than one. Upon introducing water vapor, S values approach one as a function of increasing water vapor pressure, indicating a decrease in the IL ohmic drop as the IL/water mixture becomes more conductive and the potential drop is driven by the electric double layer at the electrode/IL interface.

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Lab-based operando x-ray photoelectron spectroscopy for probing low-volatile liquids and their interfaces across a variety of electrosystems

Cited by 9 publications

References 85 publications

Assessing Local Electrical Properties of Ionic Liquid/Metal Interfaces with Operando-XPS and by Incorporating Additional Circuit Elements

Assessing Local Electrical Properties of Ionic Liquid/Metal Interfaces with Operando-XPS and by Incorporating Additional Circuit Elements

Probing the Dynamics of Non-Faradaic Processes in Ionic Liquids at Extended Time and Length Scales Using XPS with AC Modulation

The Influence of Water Vapor on the Electrochemical Shift of an Ionic Liquid Measured by Ambient Pressure X‐ray Photoelectron Spectroscopy

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