Anion Exchange Membranes with Improved Chemical Stability Chulsung Bae Department of Chemistry & Chemical Biology Rensselaer Polytechnic Institute CFES Symposium (02/26//2015, 25 min) Contact: [email protected]Collaborators: Yu Seung Kim (Los Alamos National Laboratory) Chang Y. Ryu (Rensselaer Polytechnic Institute) Michael Hickner (Pennsylvania State University) 1
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Anion Exchange Membranes with Improved Chemical Stability
Collaborators: Yu Seung Kim (Los Alamos National Laboratory) Chang Y. Ryu (Rensselaer Polytechnic Institute) Michael Hickner (Pennsylvania State University)
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Clean Energy Ion-conducting (H+, OH-) polymer electrolytes for fuel cells
Functional Polymer Synthesis Polymerization of functional monomers Controlled polymer modifications
Overview of Bae Group Research
Clean Environment • Water purification
• CO2 capture
• Polymer-supported
recyclable catalysts
Functional Organic/Polymeric
Materials forEnvironment &
Energy
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Fuel Cells: PEMFC and AEMFC
• Highest power density • PEM: insufficient conductivity at low RH high cost of Nafion • Catalyst: expensive Pt
• Lower power density than PEMFC • AEM: insufficient conductivity poor stability against OH-
Reaction at Cathode: ½ O2 + 2 H+ + 2 e- H2O ½ O2 + H2O + 2 e- 2 OH-
Overall Reaction: H2 + ½ O2 electricity + H2O H2 + ½ O2 electricity + H2O
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Synthetic Methods Toward Functional Polymers
Specific Applications: Electronic, Biomedical, Energy-generation, etc
Light-weight Flexible Shape Mechanical Stability
Reduced reactivity Low molecular weight Distribution of FG
Side reactions (degradation, XL) Molecular weight control
Low Cost
High Value
Direct Borylation of Aromatic C–H Bonds
• Iridium-catalyzed aromatic C-H bond activation/borylation • Boron substitutes only aromatic C–H bonds selectively • Mixture of meta and para-borylated products
– No C–O bonds, high molecular weights 3. Incorporate stable QA structures to non-degradable polymer
Cations Polymer Backbone
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NMR Study of QA Model Compounds (1) Ion exchange & isolate QA in OH- form (2) Transfer to NMR tube
& immerse in preheated oil bath for 1 mo.
(3) Record NMR spectrum periodically
0 h 1 d 6 d
11 d 18 d
28 d
D2O
a b c
d a b c d
18-crown-6
Degradation product
Angela Mohanty
A. Mohanty & C. Bae J. Mater. Chem. A. 2014, 2, 17314
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Quantitative Stability Comparison of Small Molecule QAs
Angela Mohanty 14
Summary Ion-conducting aromatic polymers with different cation/anion structures
synthesized by combination of C-H borylation & Suzuki coupling Convenient controls of structure & concentration of ionic groups
QA Model Compounds Stability • Systematic quantitative stability study of QAs • Sterically hindered QAs (-CH2N+R3) are more stable • Long alkyl-tethered QAs are more stable than benzyl-tethered QAs
Anion Exchange Membrane • Polymer chains made of C–C bonds: no backbone degradation • PF-, SEBS-QA (where QA = -CH2N+R3) • Good chemical stability with high OH– conductivity • Excellent fuel cell performance
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Acknowledgment
Current and Past Group Members • Postdoc: Ying Chang, Woo-Hyung Lee Dongwon Shin • Graduate student: Angela Mohanty,
Bhagyashree Date, Sarah Park, Stefan Turan, Jihoon Shin, Se Hye Kim
Collaborators
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• Molecular Dynamics: Seung Soon Jang (Georgia Tech)
• AFM, Mechanical Property, MEAs: Yu Seung Kim (Los Alamos National Laboratory)
• Water Absorption, SAXS: Michael A. Hickner (Penn State)
• SAXS: Joel Morgan, Chang Y. Ryu (RPI)
• Ir and Pd catalysts: Sino Chemicals • B2pin2: Frontier Scientific