2020 Fiscal Year Annual Research Report
High-Performance Gas Separation Membranes by Guided-Assembly of Graphene-based Nanocomposites
| Project/Area Number |
19F19367
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
KARAHAN HUSEYIN 京都大学, 高等研究院, 外国人特別研究員
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| Project Period (FY) |
2019-11-08 – 2022-03-31
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| Keywords | Nanosheet synthesis / Charge compensation / Nanolaminate fabrication |
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| Outline of Annual Research Achievements |
Our original research plan was divided into four main tasks: (1) preparation and characterization of graphene-based nanosheets, (2) preparation and characterization of electrostatically complexed nanosheet-crosslinker slurries, (3) fabrication and vacuum-assisted compaction of laminated membranes, and (4) physical characterization and performance testing of resulting membranes for gas separation. For the first task, we have optimized the synthesis and purification of graphene oxide (GO) nanosheets prepared based on a modified-Hummers method (starting with natural graphite) followed by ultrasonic exfoliation. For the second task, we initially tested several cationic polymers (such as polyethyleneimine, polyallylamine, poly(diallyldimethylammonium chloride)) to compensate the negative charge of GO nanosheets and obtained gel-like slurries. Nevertheless, due to aggregate formations, the resulting membranes were found to be unsuitable for separating hydrogen from its mixture with carbon dioxide. To overcome this obstacle, we have also utilized an alternative crosslinker, cationic nanodiamonds, which provided defect-free membranes.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
Our research was a little behind the initial plan for two main reasons. The first reason is the occasional limitations in laboratory access due to the coronavirus outbreak. However, the main reason is the addition of experimental work on developing stable GO membranes to keep up with the recent progress made in the field. Several groups have recently shown that GO-polymer films exhibit low stability under humid conditions, which is critical for industrial operations. So, we decided to test beyond originally planned polyethyleneimine and polyallylamine crosslinkers, both of which are weak polyelectrolytes. To obtain stronger complexes, we first tested the utility of a strong polycation, poly(diallyldimethylammonium chloride). Poly(diallyldimethylammonium chloride) gave stable films but caused even faster coagulation, and hence more defects. As an alternative system, we also tested a poorly water-soluble polymer (a polyamide-poly(ethylene glycol) block copolymer) but failed at preparing conformal GO-polymer films (when the solvent system was kept water-dominant). Thus finally, we have switched back to electrostatic stabilization and tested positively charged nanodiamonds instead of polycations, which provided more uniform yet stable composite membranes.
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| Strategy for Future Research Activity |
We plan to work on three major angles: (1) optimization of GO-polycation mixture preparation conditions to prepare defect-free membranes, (2) characterization of GO-nanodiamond membranes, and (3) testing the role of vacuum compaction in laminate membranes. The first future plan aims at troubleshooting our initial primary materials design. The second future plan aims at exploring the utility of nanoparticles instead of polymers as a promising approach. The third plan aims at exploring the role of vacuum-aided membrane development better, which is among the main components of the project. Besides, since our ultimate goal is to develop high-performance gas separation membranes with high stability, we will also test using graphene nanoplatelets instead of GO.
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