featuring Yanghua He and Thien Tran
Wednesday, December 4, 2019
Wu Lab Group
High-performance and inexpensive platinum-group-metal (PGM)-free catalysts for the oxygen reduction reaction (ORR) in challenging acidic media are crucial for proton-exchange-membrane fuel cells (PEMFCs). Catalysts based on Fe and N codoped carbon (Fe-N-C) have demonstrated promising activity and stability. However, a serious concern is the Fenton reactions between Fe2+ and H2O2 generating active free radicals, which likely cause degradation of the catalysts, organic ionomers within electrodes, and polymer membranes used in PEMFCs. Alternatively, Co-N-C catalysts with mitigated Fenton reactions have been explored as promising replacements for Fe and PGM catalysts. In this presentation, recent progress of developing atomically dispersed and nitrogen coordinated Co single site catalysts will be introduced for the ORR in PEMFC applications. Catalyst synthesis, structure/morphology, activity and stability improvement, and reaction mechanisms will be discussed in detail. Combining experimental and theoretical understanding, the aim is to elucidate the structure-property correlations and provide guidance for rational design of advanced Co catalysts with a special emphasis on the fuel cell MEA performance and durability.
Lin Research Group
Membrane technology has been widely practiced for water purification and wastewater treatment because of its high energy-efficiency and small footprint. However, polymeric membranes for water purification are faced with with fouling by the aggregation of contaminants on the surface, decreasing water permeance. The conventional approach to mitigate fouling is to increase membrane surface hydrophilicity or surface energy to be as close to water (72 mJ/m2) as possible. On the other hand, surfaces with low energy (≈20 mJ/m2) such as Teflon and silicon rubber have demonstrated excellent antifouling properties due to their non-stick nature. Herein, we demonstrate a facile method to reduce the surface energy of UF membranes by the grafting of an amine-functionalized tetramethyldisiloxane (Si-NH2) via polydopamine (PDA). The surface modification significantly reduces the surface energy and adhesion of a model foulant of bovine serum albumin (BSA), resulting in better antifouling properties. On the other hand, a fundamental study on the effect of water state in hydrophilic polymers, commonly used for surface modifcation, on salt transport properties will also be discussed.