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Straightforward Synthesis of Hierarchically Porous Nitrogen-Doped Carbon via Pyrolysis of Chitosan/Urea/KOH Mixtures and Its Application as a Support for Formic Acid Dehydrogenation Catalysts
journal contribution
posted on 2017-09-27, 00:00 authored by Dong-Wook Lee, Min-Ho Jin, Duckkyu Oh, Sung-Wook Lee, Jong-Soo ParkThe
development of cheap, simple, and green synthetic methods for
hierarchically porous nitrogen-doped carbon, especially derived from
renewable biomass, such as chitosan, remains a challenging topic.
Here, we first synthesized hierarchically porous nitrogen-doped carbon
(KIE-8) having graphene-like structure via simple pyrolysis of a chitosan/urea/KOH
mixture without any conventional sophisticated treatments, such as
freeze-drying, hydrothermal carbonization, and soft or hard templating.
On the basis of various analyses of KIE-8, we demonstrated that effect
of urea on mesopore formation was insignificant; however, when KOH
is used as an activating agent in the presence of urea, a large amount
of mesopores can be created along with conventional KOH-derived micropores.
In addition, it was revealed that chitosan-derived carbon nanosheets
directed by urea are torn into chitosan-derived carbon nanoflakes
via KOH activation, and mesopores originate from interstitial voids
in aggregates of the carbon nanoflakes, and micropores are derived
from in-plane pores in each nanoflake. KIE-8 was used as a catalyst
support for formic acid dehydrogenation at room-temperature. Pd(6
wt %)/KIE-8 catalysts provided excellent catalytic activity (TOF =
280.7 mol H2 mol metal–1 h–1), and we demonstrated that the pore structure and nitrogen structure
of KIE-8 are crucial factors to determine the catalytic activity.