Primary questions common to Thermo-Catalytic Decomposition (TCD)/regeneration and soot
growth/oxidation are its rate dependence on active sites, its rate relation to nanostructure and
the similarity of active sites in carbon deposition/regeneration to those associated with soot
growth/oxidation. The abundance of natural gas prompts these questions as natural gas is
increasingly used for power generation while it holds a high potential for transition to the H2
economy by decarbonization using TCD. This study combines experimental measurements of reaction
rates, active sites, nanostructure characterization with atomistic simulations for carbon surface
reactions to address knowledge gaps in soot models and TCD.

Reaction rates will be correlated to active sites during TCD and regeneration as a function of
reaction extent. Carbons with different nanostructures will serve as initial catalysts to establish
active site dependence (number and type) on nanostructure. Curvature in carbon lamellae formed
under TCD will be comparatively tested against “flat” lamellae for hypothesized increase in
regeneration rate with increasing reaction progress as signaling a corresponding increase in active
sites. Critically these active sites formed during regeneration will be tested for their
equivalency as active sites under TCD by comparative rate measurements. Temperatures and reactants
will include those relevant to soot formation by combustion of present-day fuels, since the active
sites, nanostructure and rates related to TCD are also central to understanding soot growth and
oxidation reactions. These same factors also define the connections between experiments and
modeling.
Experimental tools include an integrated fixed-bed reactor and coupled GC for reaction rates,
product speciation, reactant conversion and in situ temperature programmed oxidation (TPO) for
active site measurement to inform atomistic scale simulation. High resolution transmission electron
microscopy (HRTEM) coupled with custom image analysis algorithms will be applied for nanostructure.
Chemistry of the depositing carbon and post-regeneration action will be probed by electron energy
loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS) to validate and inform
simulation predictions for carbon hybridization, sp2/sp3  and C/H ratio.
Atomistic simulations, using reactive molecular dynamics, will be compared to the experimental
metrics of active sites, reaction rates and apparent activation energies. Simulations will be used
to identify the nature of active sites and to test the hypothesized mechanisms whereby curvature
enables multiplication and regeneration of active sites. Unifying experimental carbon
characterization and reaction simulations will provide a predictive model for TCD activity based on
active sites and identified dependencies upon nanostructure and reaction conditions. The
cyclability of deposition and regeneration will be tested for congruity between rates, active sites
and control through nanostructure curvature. The role of active sites, loss during TCD, gain during
regeneration, their equivalency, rate dependence and relation to nanostructure will also allow us
to advance soot growth and oxidation models.
As goal, the outcome of this study will be predictive model for TCD grounded in active sites and
benchmarked against comparative nanostructures. Furthermore, definition of TCD-relevant parameters
and mechanistic insights by simulations will advance our understanding of soot growth and oxidation
towards
integrated soot models.