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.