Anion Exchange Membranes for Electrochemical Energy Storage (Herring - Colorado School of Mines)
“Anion Exchange Membranes for Electrochemical Energy Conversion and Storage”
Prof. Andrew M. Herring
Dept. of Chemical & Biological Engineering
Colorado School of Mines
The potential of anion exchange membrane (AEM) fuel cells/electrolyzers and other devices to provide inexpensive compact power from a wider variety of fuels than is possible with a proton exchange membrane (PEM) fuel cell, has continued to drive the research interest in this area. Alkaline catalysis in fuel cells has been demonstrated with non-precious metal catalysts, and with a variety of fuels beyond H2 and methanol. Alkaline fuel cells (AFCs), based on aqueous solutions of KOH, have serious drawbacks associated with system complexity and carbonate formation. AEM fuel cells have a number of advantages over both PEM fuel cells and traditional AFCs; however, although anionic conductivity in AEMs can be comparable to PEMs the chemical stability of membrane attached cations in hydroxide is still not always sufficient for practical applications. The real issue though, is water transport; water is both a product and a reactant in these systems, and wet cations are much more stable than dry. So an understanding of water in these membranes is essential.
Here we discuss water and anion transport in a series of thin mechanically robust state-of-the-art experimental AEMs. The membranes are generally constructed from an isoprene or ethylene block and a vinyl benzyl bromide block, either randomly or in di-, tri- or penta- block configurations. Quaternization with various amines leads to functionalized AEMs. We use electrochemical impedance spectroscopy to measure anion conductivity, multi-nuclear pulse field gradient spin echo NMR to measure self-diffusion, and broadband electric spectroscopy to measure the relaxation processes in these polymers. This information is coupled with microscopy and SAXS to explore the polymer morphology. Putting transport and morphology together allows us to describe a complete picture of water and anion transport in these systems.
We have begun to build direct fueled AEM fuel cells and electrolyzers for hydrogen or ammonia production from these membranes and their related ionomers. A few examples of the AEMs practical uses in single cell devices will be discussed in this talk.
Prof. Herring’s interests are generally in materials or catalysis to enable renewable energy, energy efficiency, or energy storage. He has been studying ion conduction for low and intermediate temperature fuel cells for the last 20 years. Studies are on-going on understanding fundamental properties of fuel cell catalysts, ionomers, fuel cell characterization, and manufacturing for a future renewable energy economy. The Herring group has extensive experience in the fabrication of inorganic/organic nano-composites and polymers for ion conduction and the development of novel new hybrid polymeric proton conducting systems that show superior proton conduction under relatively hot and dry conditions. Prof. Herring is an expert in advanced techniques for the characterization of transport and morphology in these systems. Extensive use is made of advanced NMR techniques to probe transport in a complementary manner to electrochemical measurements, and his group has developed in-situ techniques to probe polymer morphology/chemistry by SAXS using synchrotron radiation, and FTIR. Currently, Dr Herring leads a MURI that is developing next generation anion exchange membranes and has complimentary projects in elecrocatalysis and membrane electrode assembly testing for both anion and proton exchange membrane fuel cells. Smaller efforts are underway in photo catalysis for water splitting, and hydrocarbon conversion both for new heavy oil resources and for biomass.
Andy Herring has a B.Sc. Hons in Chemistry and a Ph.D. in Inorganic Chemistry from the University of Leeds. After postdoctoral appointments at Caltech and NREL he joined the Colorado School of Mines where he is now an Associate Professor of Chemical and Biological Engineering.
Tuesday, April 14
Michael's Restaurant at Shoreline Park
2960 N. Shoreline Park
Mountain View, CA 94043
6 PM social hour
7 PM dinner
8 PM lecture
Employed/postdoc Student/unemployed/retired Early Registration $30 $15 Registration $35 $20 Walk-in (not guaranteed) $40 $25
Lecture-only is free.
We accept cash or checks at the door, or online payment via credit card. No-shows are responsible for full payment of registration fee.
Please register on the web page http://www.ggpf.org/ or contact:
Deadline for registration:
11:59PM, Monday, April 6 for early registration discount.
5PM, Monady, April 13 for regular registration.
Seafood - Broiled salmon with lemon beurre blanc
Chicken - Chicken Marsala
Vegetarian - Eggplant parmagiana
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