Discipline: Chemistry and Chemical Sciences
Subcategory: Chemical/Bimolecular/Process Engineering
Session: 4
Room: Coolidge
Shejla Pollozi - City University of New York, The Graduate Center & Lehman College
Co-Author(s): Hossam Elshendidi, Department of Chemistry, Lehman College of the City University of New York, Bronx, NY 10468 ; , Adlai Katzenberg, Department of Chemical and Biomolecular Engineering, New York University Tandon School of Engineering, Brooklyn, NY 11201 ; Dr. Miguel Modestino, Department of Chemical and Biomolecular Engineering, New York University Tandon School of Engineering, Brooklyn, NY 11201 ; Dr. Gustavo Lopez, Department of Chemistry, Lehman College of the City University of New York, Bronx, NY 10468 & Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10016 ; Dr. Donna McGregor, Department of Chemistry, Lehman College of the City University of New York, Bronx, NY 10468 & Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10016
Proton Exchange Membrane Fuel Cells (PEMFC) convert chemical energy into electricity. Given the depleting amounts of fossil fuels today, hydrogen-powered PEMFCs can be crucial in reducing carbon emissions, eliminating greenhouse gases and reducing climate change effects. Nonetheless, their membranes are generally comprised of perfluorosulphonic acid polymers, such as Nafion. This polymer consists of a polytetrafluoroethylene (PTFE) backbone, attached to a sulfonic acid sidechain. Nafion has been shown to be susceptible to thermal degradation and prone to impurities, thus reducing a cell?s performance and longevity. Peptides can serve as more sustainable, greener alternatives to Nafion. When self-assembled into gels via hydrogen bonds between N-accepting and N-donating moieties (imidazole rings in histidine and similar moieties in aspartic acid/glutamic acid), these small biological molecules result in a myriad of cross-linked secondary nanostructures (imaged via Atomic Force Microscopy) and exhibit comparable proton transfer rates to Nafion. Therefore, they can potentially serve as proton transfer membranes for PEMFCs. Specifically, this work focuses on the synthesis (via Solid State Peptide Synthesis), self-assembly (incremental pH increases of acidic peptide solutions that yield gel formation) and characterization (Infrared, UV-Visible and Circular Dichroism) of fluorenylmethyloxycarbonyl (Fmoc)-protected tripeptides containing histidine (His) and aspartic acid (Asp). In addition to their structural properties we have also been measuring their proton transfer properties and conductivity through Electrochemical Impedance Spectroscopy (EIS) as a function of amino acid arrangement. Preliminary data shows higher conductivity rates when the negatively charged Asp occupies the N-terminus of the tripeptide. In the future, we will be measuring proton transfer rates as a function of film thickness, humidity, temperature and solvent.
Funder Acknowledgement(s): Centers of Research Excellence in Science and Technology (CREST)
Faculty Advisor: Donna McGregor, donna.mcgregor@lehman.cuny.edu
Role: I have been focusing on the synthesis, self-assembly and characterization of tripeptides containing histidine and aspartic acid at various arrangements. I have chosen specific sequences that exhibit the formation of beta sheet fibers via hydrogen bonds, apparent in Atomic Force Microscopy as well. I have also performed preliminary Impedance Spectroscopy measurements to identify sequences with higher conductivity potentials. Alongside our collaborators at NYU, I will be investigating the preparation of interdigitated array (IDA) chips and thin film casting to perfect the impedance analysis and perform thickness, temperature, humidity and solvent dependent studies. Alongside Dr. Gustavo Lopez I have investigated the theoretical kinetic barrier values between histidine-containing peptides and Nafion membranes.