Spectroelectrochemical Investigation of an Electrogenerated Graphitic Oxide Solid–Electrolyte Interphase

Abstract

This study investigates electrogenerated graphitic oxides (EGO) on the surface of carbon optically transparent electrodes (C-OTEs) using a combined UV-vis spectroelectrochemical approach. By monitoring the π-π* aromatic carbon transition for reduced GO (270 nm) and GO (230 nm), we observe the growth of GO in KCl upon applying oxidizing potentials. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS) are used to confirm sample composition and location of salt ions within the electrode. Formation of EGO stable enough to be observed by UV-vis is found to be unique to alkali chloride supporting electrolytes due to formation of a solid-electrolyte interphase (SEI) which incorporates the alkali cation to stabilize the negatively charged oxygen functional groups while the presence of chloride anion acts as a passivation agent that protects the electrode surface from dissolution. The spectroelectrochemical approach highlights the detection and study of EGO that cannot be detected by electrochemical measurements. Specifically, the amount of EGO observed by UV-vis scales with increasing cation size (Li(+), Na(+), K(+)) despite all the cations showing identical electrochemical response.

Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

“…22,42 However, the surface oxidation process is slow and would not be expected to change the surface significantly and promote electrowetting, as we show with further measurements below. 46 Rather extreme conditions of potential, time and electrolyte are needed to produce significant changes to the graphite surface, such as exfoliation, 47,48 and these processes can be ruled out.…”

“…With the positive potential limit increased further to +1.6 V, the anodic peak was seen even more clearly, followed by an anodic process, likely due to the onset of water oxidation. The corresponding reduction peak on the reverse scan became more pronounced and shifted positively to +0.34 The oxidation-reduction process observed as the pair of peaks identified could be due to the intercalation/de-intercalation of anions, 42 or related to surface quinone-hydroquinone redox conversion (or other surface oxidation/reduction processes). 43 As we demonstrate below, the former process is most likely and is responsible for the electrowetting seen for the aqueous droplet.…”

Identification of Li-Ion Battery SEI Compounds through 7Li and 13C Solid-State MAS NMR Spectroscopy and MALDI-TOF Mass Spectrometry

“…AFM, STM, and other microscopy studies indicate that the SEI consists of large deposits of compounds rather than consisting of thin films. ,− It has also been suggested in previous work that oligomerized species make up a portion of SEI material. Techniques including thermal gravimetric mass spectrometry (TG-MS) on Cr 2 O 3 anodes and graphite electrodes, X-ray photoelectron spectroscopy, gel permeation chromatography, IR analysis indicate that oligomerized species are involved in the formation of the SEI. − ,− Additionally, a study using time-of-flight (TOF) secondary ion mass spectroscopy (SIMS) determined that long chain oligomer species are formed in the SEI on highly ordered pyrolytic graphite (HOPG) electrodes .…”

Surface Coating‐Dependent Cytotoxicity and Degradation of Graphene Derivatives: Towards the Design of Non‐Toxic, Degradable Nano‐Graphene

“…Materials Characterization : The concentrations of GO, GO‐PEG, and GO‐BSA were calculated by the absorbance of those solutions at 230 nm recorded by a 750 UV‐Vis spectrophotometer (PerkinElmer) with a mass extinction coefficient of 65 mL mg –1 cm –1 . The concentrations of RGO‐PEG and RGO‐BSA were based on the absorbance peak at 270 nm with a mass extinction coefficient of 70 mL mg –1 cm –1 . AFM images of graphene derivatives were captured by a Multi‐Mode V AFM (Veeco).…”

“…[ 12 ] The concentrations of RGO-PEG and RGO-BSA were based on the absorbance peak at 270 nm with a mass extinction coeffi cient of 70 mL mg -1 cm -1 . [ 37 ] AFM images of graphene derivatives were captured by a Multi-Mode V AFM (Veeco). Their sizes were calculated by (length × width) 1/2 while their thickness were measured based on sheet heights in AFM images.…”