Vijay K. Ramani

Hybrid Membranes for DMFC and Low Relative Humidity PEFC Operation

Work in this area is focused on identifying fundamental structure - processing -property relationships that relate novel polymeric and organic / inorganic hybrid microstructures to relevant properties such as proton conductivity, permeability, film forming ability, modulus etc. The insight gained is used to design polymeric and hybrid materials that possess high proton conductivities at lower relative humidities (RH), low methanol permeabilities and high mechanical and chemical stabilities for application in PEFCs operating at low RH and in DMFCs.

Electrodes with low ionic and transport resistances for PEMFCs and DMFCs

The electrodes on either side of the proton conducting membrane must have a structure that aids proton conduction from the reaction sites to the membrane interface. Such a structure is currently induced by incorporating a small amount of electrolyte material into the electrode. Since the electrolyte material has very low gas (H 2 and O 2) permeability, its introduction into the electrode leads to significant mass transport (MT) losses, especially at the oxygen reduction electrode. Research is focused on exploring strategies to design novel electrode structures that possess high electrochemical activity and low ionic and electronic resistances, while simultaneously yielding a high limiting current (corresponding to low MT losses).

Membrane Electrode Interfacial Stability

The proton conducting material in the membrane and electrode have different optimal properties (as indicated in the previous paragraph) and hence will have different composition and / or structure. The stability of the membrane electrode interface thereby assumes great significance, especially given that any interfacial mismatch and delamination will lead to catastrophic fuel cell failure.

Research in this area is focused on investigating the interfacial stability of dissimilar materials as a function of materials structure and processing. This information is used to enhance the stability of the membrane electrode interface in PEMFCs and DMFCs.

Degradation Mechanisms and Mitigation Strategies

Polymeric and hybrid materials are susceptible to mechanical and chemical degradation, often with a detrimental effect on the properties and durability. The degradation of polymeric and hybrid materials is explored in real and simulated fuel cell environments by in-situ electrochemical / chemical analyses and ex-situ accelerated tests such as thermally accelerated aging and exposure to selected degradation agents.

This information is used to identify degradation pathways and to develop appropriate mitigation strategies and design electrolyte and electrode materials (with these strategies built –in) that demonstrate enhanced durability and lifetime.