Nitrogen-containing, Emulsion-templated Porous Carbons with Hierarchical Porosities

תמונה_סמינרים
03.07.2016
14:30
David Wang Auditorium, 3rd floor Dalia Maydan Bldg.
Prof. Michael S. Silverstein

Adi Horowitz

The Grand Technion Energy Program
Department of Materials Science and Engineering
Technion – Israel Institute of Technology, Haifa 32000, Israel

Porous carbons are being developed for a range of energy-storage applications including
super capacitors, batteries, fuel cells, and hydrogen storage. This research has focused on the
generation of nitrogen-containing monolithic carbons with hierarchical porosities through the
pyrolysis of emulsion-templated porous polymers termed polyHIPEs. PolyHIPEs are macroporous
monoliths that are usually synthesized within surfactant-stabilized water-in-oil (w/o) high internal
phase emulsions (HIPEs). It should be possible to introduce microporosity and/or mesoporosity
into polyHIPE-based carbons using porogens and/or carbon activation.

The objectives of this research were to generate monolithic porous carbons with macro-,
meso-, and microporous architectures, to characterize the resulting polymers and carbons, and to
describe the effects of the synthesis and pyrolysis parameters on the resulting materials. Two
different polyHIPE systems were investigated. One system was based on polyacrylonitrile (PAN)
crosslinked with divinylbenzene synthesized in w/o HIPEs. Different porogens were evaluated
including solvents, nanoparticles, degradable comonomers, and degradable oligomers. The other
system was based on the hydro-thermal carbonisation (HTC) of a renewable resource material
(e.g. glucose) in the presence of hydrophilic monomers (e.g. hydroxyl ethyl methacrylate (HEMA)
crosslinked with N,N'-methylenebisacrylamide) within oil-in-water HIPEs. The resulting
macroporous structures, atomic compositions, macromolecular structures, specific surface areas
(ASP), microporosities, and thermal properties were characterized.

Generally, the PAN-based polyHIPEs exhibited relatively closed-cell structures, before and
after pyrolysis. The as-synthesized PAN-based polyHIPEs had densities of around 0.07 g/cc,
relatively low ASP, around 11 m2/g and N/C ratios of 0.22. Microporous carbons with ASP of 500
m2/g were produced by introducing porogens into these polyHIPEs, with micropores of around 0.71
nm and micropore volumes of around 0.21 cc/g. HTC generated open-cell polyHIPEs with densities
of around 0.06 g/cc. Carbons with ASP of 100 m2/g were produced through pyrolysis of these
polyHIPEs. N/C ratios were enhanced, increasing from 0.04 to 0.10, through the addition of
nitrogen-containing monomers. Carbons with ASP of 1500 m2/g were produced through chemical
activation of the HTC polyHIPEs, with micropores of around 0.74 nm and micropore volumes of
around 0.62 cc/g. While, carbon activation did not enhance the ASP in the PAN-based carbons, it
did generate a more open-cell structure.

Supervisor: Prof. Michael S. Silverstein