Date(s) - 02/13/2018
4:00 pm - 5:00 pm
Postdoctoral Research Associate
Oak Ridge National Laboratory
Dr. Jan-Patrick Melchior recently joined the Neutron Sciences Division at the Oak Ridge National Laboratory. His research interests include the structure property relations in ion conducting membranes for electrochemical applications. More specifically, he works to combine the use of neutron scattering, NMR, and more widely available techniques in membrane science.
Jan Melchior moved to neutron sciences following a post-doc and Ph.D. in material chemistry with K.D. Kreuer in the department of Joachim Maier at the Max Planck Institute for Solid State Research in Stuttgart, Germany. He received his bachelor’s and master’s degree in physics from the Technical University Darmstadt, Germany.
“Studying Proton Transport on Multiple Time and Length Scales:
Why Do Proton Conducting Poly- Benzimidazole Phosphoric Acid Membranes Perform Well in High-Temperature PEM Fuel Cells?”
High-temperature PEM fuel cells operating at temperatures above 120 °C are used in auxiliary power units (APU) or micro combined heat and power (m-CHP) generators. Such fuel cells employ phosphoric acid soaked polymer membranes as electrolyte.  Despite efforts to develop new membrane chemistries over the last 20 years, the combination of phosphoric acid and different poly-benzimidazole polymers remains the prevailing choice for application.  In this talk we discuss in how far the proton conduction properties of phosphoric acid in general and the combination of this particular acid with the Brønsted base benzimidazole are indeed very special.
Based on ab-initio molecular dynamics simulations [3,4] we discuss the unique hydrogen bond network topology and proton conduction mechanism of neat phosphoric acid. The fundamental results obtained through simulation work provide a guide for experimental design and choice of model systems as to relate theoretical findings to actual proton conducting membranes. For that purpose, we explore the specific merits of a series of experimental techniques for the investigation of proton dynamics spanning from the sub-nanosecond to the microsecond timescale. [5-7] Discussed techniques include quasi-elastic neutron scattering (QENS), dipolar and quadrupolar NMR relaxation, pulsed field gradient (PFG-) NMR, impedance spectroscopy, and classical electrochemical transference measurements.
Through this multiscale and multimethod approach a detailed picture emerges about the role of phosphoric acid’s unique conduction mechanism and the role of benzimidazole and water for the performance of hygroscopic HT-PEM fuel cell membranes.
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 Q. Li, D. Aili, H. A. Hjuler and J. O. Jensen, High Temperature Polymer Electrolyte Membrane Fuel Cells – Approaches, Status, and Perspectives, Springer International Publishing, Cham, Heidelberg, New York, Dordrecht, London, 2016
 L. Vilčiauskas, M. E. Tuckerman, G. Bester, S. J. Paddison, K. D. Kreuer, Nat. Chem., 2012, 4, 461–466
 L. Vilčiauskas, M. E. Tuckerman, J.-P. Melchior, G. Bester, K. D. Kreuer, Solid State Ionics, 2013, 252, 34–39
 J.-P. Melchior, K. D. Kreuer, J. Maier, Phys. Chem. Chem. Phys., 2017, 19, 587–600
 J.-P. Melchior, G. Majer, K. D. Kreuer, Phys. Chem. Chem. Phys., 2017, 19, 601–612
 J.-P. Melchior, B. Frick, Phys. Chem. Chem. Phys., 2017, 19, 28540-28554