Nonthermal plasma activation of light alkanes is an encouraging
decarbonization strategy to produce chemicals or fuels from abundant
and/or flared carbon sources. However, prolific carbon growth on both
the catalyst and electrode has limited its practicality, requiring
additional knowledge of the carbon structure and growth mechanism
before breakthroughs are realized. Here, visual evidence is provided
for nonuniform diamond-like carbon (DLC) microstructures that materialize
in a coaxial dielectric barrier discharge (DBD) reactor flowing ethane
and He at 278 K. Through a connection to known behaviors of DBD microdischarge
patterns, the microstructure spacing was controlled by altering the
applied voltage (ΔV) of the plasma or the burning voltage (Ub). Additionally, carbon valorization through nitrogen incorporation
from N2 was explored as an orthogonal solution to carbon
mitigation, with N/C values >0.25 achieved and both sp2 and sp3 C–N bonding observed in the microstructures.
Plasma-surface coupling has emerged as a promising approach
to
perform chemical transformations under mild conditions that are otherwise
difficult or impossible thermally. However, a few examples of inexpensive
and accessible in situ/operando techniques
exist for observing plasma-solid interactions, which has prevented
a thorough understanding of underlying surface mechanisms. Here, we
provide a simple and adaptable design for a dielectric barrier discharge
(DBD) plasma cell capable of interfacing with Fourier transform infrared
spectroscopy (FTIR), optical emission spectroscopy (OES), and mass
spectrometry (MS) to simultaneously characterize the surface, the
plasma phase, and the gas phase, respectively. The system was demonstrated
using two example applications: (1) plasma oxidation of primary amine
functionalized SBA-15 and (2) catalytic low temperature nitrogen oxidation.
The results from application (1) provided direct evidence of a 1%
O2/He plasma interacting with the aminosilica surface by
selective oxidation of the amino groups to nitro groups without altering
the alkyl tether. Application (2) was used to detect the evolution
of NOX species bound to both platinum and silica surfaces
under plasma stimulation. Together, the experimental results showcase
the breadth of possible applications for this device and confirm its
potential as an essential tool for conducting research on plasma-surface
coupling.
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