Carbon
Allotropes Accelerate Hydrogenation via Spillover Mechanism
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Abstract
Solid-phase hydrogenation kinetics
can be substantially increased by utilizing hydrogen spillover phenomenon.
Carbonaceous allotropes are considered as promising spillover agents
(SOAs) for improved hydrogen transport rate. We studied the effect
of carbon-based SOA properties on irreversible hydrogenation. We divided
the reaction into two major stages, near- and far-field hydrogenation
(with respect to a catalyst), and determined their rate-limiting steps.
The hydrogenation kinetics was analyzed for hydrogen originating from
either catalyst on activated carbon or catalyst-decorated carbon nanotubes.
The far-field hydrogenation is investigated for three types of loaded
nanocarbons: 1D (nanotubes), 2D (graphene), and 3D (activated carbon).
We found that the kinetics acceleration is strongly correlated with
the nanocarbon dimension, 1D > 2D > 3D, and could reach almost
2 orders of magnitude. These findings are useful for the study of
reversible hydrogen storage applications