XPS enables visualization of electrode potential screening in an ionic liquid medium with temporal- and lateral-resolution. Issue 41 (26th August 2016)

• Record Type: Journal Article
• Authors: Camci, M. T.; Aydogan, P.; Ulgut, B.; Kocabas, C.; Suzer, S.
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 41(2016)
• Page Start: 28434
• Page End: 28440
• Publication Date: 2016-08-26
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp04933h
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Potential screening of metal electrodes is followed non-invasively by time- and position-dependent F1s signals of an ionic liquid. Abstract : We present an X-ray photoelectron spectroscopic (XPS) investigation of potential screening across two gold electrodes fabricated on a porous polymer surface which is impregnated with the ionic liquid (IL) N-N -diethyl- N -methyl- N -(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide [DEME-TFSI]. The IL provides a sheet of conducting layers to the insulating polymer film, and allows monitoring charging and screening dynamics at the polymer + IL/vacuum interface in a laterally resolved fashion across the electrodes. Time-resolved measurements are also implemented by recording F1s peaks of the IL, while imposing 10 mHz square-wave (SQW) pulses across the two electrodes in a source–drain geometry. Variations in the F1s binding energy reflect directly the transient local electrical potential, and allow us to visualize screening of the otherwise built-in local voltage drop on and across the metal electrodes in the range of millimeters. Accordingly, the device is partitioned into two oppositely polarized regions, each following polarization of one electrode through the IL medium. On the other extreme, upon imposing relatively fast 1 kHz SQW pulses the charge screening is prevented and the device is brought to assume a simple resistor role. A simple equivalent circuit model also reproduces the observed voltage transients qualitatively. The presented structure and variants of XPS measurements, enabling us to record voltage transients in unexpectedly large lateral distances away from the electrodes, can impact the understanding of various electrochemical concepts.