Monitoring SEIRAS on a Graphitic Electrode for Surface-Sensitive Electrochemistry: Real-Time Electrografting

• Published in: Analytical chemistry (Washington) 2024-02, Vol.96 (6), p.2435-2444
• Main Authors: Siddiqui, Abdur-Rahman, N’Diaye, Jeanne, Martin, Kristin, Baby, Aravind, Dawlaty, Jahan, Augustyn, Veronica, Rodríguez-López, Joaquín
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Carbon; Electrochemistry; Electrodes; Electrolytes; Energy storage; Gold; Grafting; Graphene; Heavy metals; Infrared absorption; Infrared spectroscopy; Nanoribbons; Nitrobenzene; Nitrogen dioxide; Piperidine; Real time; Substrates
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/acs.analchem.3c04407

The ubiquity of graphitic materials in electrochemistry makes it highly desirable to probe their interfacial behavior under electrochemical control. Probing the dynamics of molecules at the electrode/electrolyte interface is possible through spectroelectrochemical approaches involving surface-enhanced infrared absorption spectroscopy (SEIRAS). Usually, this technique can only be done on plasmonic metals such as gold or carbon nanoribbons, but a more convenient substrate for carbon electrochemical studies is needed. Here, we expanded the scope of SEIRAS by introducing a robust hybrid graphene-on-gold substrate, where we monitored electrografting processes occurring at the graphene/electrolyte interface. These electrodes consist of graphene deposited onto a roughened gold-sputtered internal reflection element (IRE) for attenuated total reflectance (ATR) SEIRAS. The capabilities of the graphene-gold IRE were demonstrated by successfully monitoring the electrografting of 4-amino-2,2,6,6-tetramethyl-1-piperidine N-oxyl (4-amino-TEMPO) and 4-nitrobenzene diazonium (4-NBD) in real time. These grafts were characterized using cyclic voltammetry and ATR-SEIRAS, clearly showing the 1520 and 1350 cm–1 NO2 stretches for 4-NBD and the 1240 cm–1 C–C, C–C–H, and N–Ȯ stretch for 4-amino-TEMPO. Successful grafts on graphene did not show the SEIRAS effect, while grafting on gold was not stable for TEMPO and had poorer resolution than on graphene-gold for 4-NBD, highlighting the uniqueness of our approach. The graphene-gold IRE is proficient at resolving the spectral responses of redox transformations, unambiguously demonstrating the real-time detection of surface processes on a graphitic electrode. This work provides ample future directions for real-time spectroelectrochemical investigations of carbon electrodes used for sensing, energy storage, electrocatalysis, and environmental applications.