Carbon-based materials are highly diverse in terms of their mechanical,
electronic, and thermodynamic properties, and as such can be used in a vast array of
applications in numerous industries. These materials contain various types of carbon
and oxygen radicals. Oxidation processes that influence the composition of these
radical populations can have substantial effects on the materials’ electronic properties.
Therefore, it is important to gain a systematic understanding of oxidation processes in
carbonaceous materials at various temperatures and pressures. Electron paramagnetic
resonance (EPR) spectroscopy is routinely used to characterize defects in carbon-based
materials and the nature of the radicals they contain. Specifically, spin concentrations
and the composition and distribution of radicals can be correlated to the electronic
properties of carbon-based materials. Accordingly, over the last few years, our group
has been using EPR spectroscopy to develop methodologies to explore the oxidation
properties of carbon-based materials. Our overarching goal is to produce a toolkit that
can correlate between the physical properties of specific carbon-based materials and
these materials’ sensitivity to oxidation processes. In this chapter, we will describe our
findings regarding the oxidation processes of coal and graphene oxide materials. Our
data are derived from in-situ EPR experiments in which carbon-based materials were
exposed to various atmospheric environments. Our findings have clear practical
implications with regard to identifying appropriate storage conditions for carbon-based
materials.
Keywords: Bituminous coals, Carbon-centered radicals, Coal, Graphene oxide
(GO), EPR, EPR linewidth, Free radicals, In-situ gas-flow EPR, Lorentzian
lineshape, Lignites, Low temperature oxidation, NMR, Oxidation process,
Oxidation time, Oxygen-centered radicals, Radical concentration, Reduced
graphene oxide (rGO), Reduction temperature, Sub-bituminous coals, Surface
radicals.
