Research Focus
Fuel cells are being considered one of the promising candidates for automotive propulsion, residential, and portable power generation applications. Fuel cells have high energy conversion efficiency and no polluting products. However, large enhancements in the performance of fuel cell components are essential to make fuel cell an economically viable option. Research in the group focuses on the issues that affect these performance limitations.
The difficulties involved in storing and using hydrogen in an automobile has led to generation of hydrogen on-board by reforming carbon based fuels. The reformed fuels have trace amounts of carbon monoxide, which reduces the performance of the fuel cell.
The UConn Chemical Engineering Fuel Cell Research Group is investigating new catalytic materials for the fuel electrode and developing new membranes to enable efficient cell operation using either hydrogen with residual CO or methanol directly as the fuels.
Fuel processing catalysts for CO clean-up and sulfur removal are also being
investigated. Many of the catalysts that are being investigated have been
synthesized with the help of faculty in UConn’s Chemistry Department (Suib,
McGrath, and Bailey).
Hydrogen is a very good fuel for use in a fuel cell, but with even small
amounts of CO, the performance of the anode deteriorates due to poisoning of Pt
(anode catalyst) by chemisorbed CO. The anode catalyst research involves
development of improved anode catalysts that can tolerate moderate levels of CO
without much loss in performance. Research was carried out to develop anode
catalysts for methanol oxidation in phosphoric acid and polymer electrolytes.
Methanol is a very practical alternative for hydrogen, but methanol oxidation
involves CO as an intermediate and suffers poor performance. Investigations
were performed to study the activity of ternary alloy catalysts based on Pt-Ru,
for methanol oxidation in phosphoric acid electrolyte. Organic metal-macrocycle
complexes were investigated as co-catalysts with Pt for methanol oxidation in
proton exchange membrane electrolyte. Research is underway to develop new CO
tolerant anode electrocatalysts that are better than the currently best Pt-Ru
catalysts. New ternary catalysts with improved CO tolerance has been developed.
The proton exchange membrane which functions as the electrolyte must satisfy several requirements and addresses some of these research issues. In a direct methanol fuel cell, methanol diffuses across the proton exchange membrane, depolarizes the cathode and lowers the performance of the fuel cell. Reducing the methanol diffusion, while retaining the ionic conductivity of the membrane would enhance the performance. Research was carried out to develop membranes that would reduce the methanol diffusion. Investigations are underway to develop high temperature proton exchange membranes in a Department of Energy sponsored project through a sub-contract from Energy Research Corporation, CT. Raising the operating temperature will enhance the electrode reactions and also reduce methanol crossover due to lower solubility of methanol vapor than liquid methanol. High temperature operation also reduces CO poisoning problems when using reformed fuels. Research involves development of membranes with high conductivity at temperatures of 120oC or higher.
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Improvement of Oxygen Transport Characteristics in Proton
Exchange Membrane Fuel Cells
The
research is involved with understanding and improvement of oxygen transport characteristics in a hydrogen/air proton
exchange membrane fuel cell, especially for high temperature/low relative
humidity operation. The focus of the research is on several oxygen transport
mechanisms in the gas diffusion layer, its interaction with the flow field design,
and the cathode catalyst layer. The research scope covers both experimental and
modeling aspects with extensive diagnostics for polarization sources in a
membrane electrode assembly.
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Stabilized Membranes and Membrane Electrode Assemblies
for High Temperature Low Relative Humidity PEM Fuel Cell Operation
The research is
focused on the development of stabilized proton exchange membranes (PEMs) for
high temperature / low relative humidity (atmospheric pressure) operation.
Since conductivity generally increases with temperature (following either an
Arrhenius or a VTF relationship), the key feature of the research is low
relative humidity operation. The proposed approach involves the preparation and
characterization (by spectroscopy, microscopy and testing in an operating fuel
cell environment) of organic / inorganic composite (or hybrid) materials that
facilitate proton conductivity by the Grotthuss mechanism, thereby alleviating
the dependence on membrane hydration. Typical organic materials studied include
Nafion® and sulfonated hydrocarbons. The inorganic materials
considered include heteropolyacids, layered phosphates, metal oxides and
combinations therein. The stability of the inorganic phase in the organic
matrix, the incorporation of improved PEMs in the electrode layers, and the
ionic form of the PEM during MEA preparation and heat treatment (for better
interfacial stability and endurance) are key issues that will be addressed.
Nafion®
membranes were modified with different ionically conductive inorganic additives
such as SiO2, ZrO2 using Sol-Gel techniques.
Electrochemical characterization of these membranes was performed to investigate
their feasibility for DMFC applications. Using Nafion®-Teflon®-Zr(HPO4)2
membranes, carbon monoxide tolerance properties of hydrogen PEMFC was studied
at elevated temperature (>100°C). Also, membranes based on a much cheaper
material, sufonated Poly (Ether Ether Ketone) (SPEEK), was prepared and
characterized for both hydrogen PEMFC and DMFC applications.
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Evaluation and Improvement of Oxygen Reduction Reaction in
Proton Exchange Membrane Fuel Cells
The goal of this study is to understand and improve oxygen reduction reaction (ORR) kinetics in proton exchange membrane fuel cells (PEMFCs), especially at elevated temperatures (>100oC). The influences of pressures, temperatures and relative humidity on ORR kinetics at platinum/ionomer interface will be evaluated, and appropriate physical models will be developed to explain these influences. Based on the above information, the structure of the cathode electrode will be further optimized to improve the performance of PEMFCs.
The study of PEM fuel cells under the affect of carbon monoxide fed to the anode, the work involves investigating the role of temperature, oxygen partial pressure, and relative humidity in reducing the CO polarization. The work also involves investigating different catalyst materials best suited for anode feed containing CO.
The development
of a micro-scale high temperature PEM fuel cell for portable applications. The main scope of this work is to study
and optimize the operating conditions of miniature PEMFC’s operation in
junction with a micro-fuel reformer capable of producing flows as low as 1 cm3/min.
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Optimization of Microscale Proton-Exchange Membrane Fuel
Cells for Portable Applications
Research areas would involve a complete study and understanding of the sources of losses in such fuel cells. It would then be optimized for the performance and endurance with respect to the working conditions with the portable Applications in view. It would also involve improving the CO tolerance of the micro fuel cell to enable it to work on fuels other than pure Hydrogen.
Another interesting area would be the design of the fuel cell along with its integration with the other components in a complete fuel cell unit.
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Characterization and Optimization of a CO Tolerant
Microscale Proton-Exchange Membrane Fuel Cell
The research is involved with Nafion® based PEM. The
structure and morphological information of Nafion® based Polyelectrolyte
Membranes with their high temperature performance is to be investigated. A main
objective is to develop a micro size fuel cell operated under high temperature
with low relative humidity so as to demonstrate good CO tolerance. The research
will be carried out with the aid of X-ray, SEM, TEM and DSC