Nanomaterials development in membrane electrode assembly for proton exchange membrane fuel cell

Polymer exchange membrane fuel cells (PEMFCs), fueled by hydrogen or methanol, have been considered promising for powering vehicles, residential applications, and portable electronic devices. Widespread commercialization of fuel cells hinges, however, on further reduction in materials cost, improvements of component durability, and increase in overall PEMFCs efficiency. At the heart of the PEMFC are the anode catalyst layer, the cathode catalyst layer, and the polymer electrolyte membrane. For the catalysts, the longstanding goals have been low cost, high catalytic activity for oxygen reduction reaction (ORR) and viable durability. For the membrane, the most desirable properties are the ability to operate at high temperatures in the case of the hydrogen-air fuel cell and low methanol crossover in the case of the direct methanol fuel cell.;The dissertation will address some main challenges of the PEMFCs technology by focusing on the following three dependent topics: (I) Precious metal electrocatalysts: Carbon nanotubes (CNTs) and platinum nanotubes (PtNT), used as potential replacement of amorphous carbon nanoparticles as catalyst support or as a part of the catalyst. DWNT demonstrated to be an ideal catalyst supports because it has higher electronic conductivity and higher thermal and chemical stability than SWNT, and much higher surface area than MWNT. MWNTs with different functional groups have been used as catalyst support to check the anchor group effect on the catalytic activity. MWNT with -NH- group exhibited the best performance. The new class of supportless Pt nanotubes (PtNTs) have been synthesized and worked as the cathode catalyst, capable of combining remarkable durability with high catalytic activity. (II) Non-precious metal electrocatalysts: Novel nanostructured (non-precious metal)/(conductive polymer) nanocomposite catalysts, such as FeCo-PPy-C and Co-PPy-C, developed as electrocatalysts for the PEMFC cathode, capable of combining high oxygen-reduction activity with good performance durability. (III) NafionRTM/zeolite nanocomposite membranes: The use of acid-functionalized zeolite nanoparticles for polymer-zeolite nanocomposite membranes will be discussed as a way of increasing the operating temperature of the hydrogen-air fuel cell and reducing methanol crossover in the direct methanol fuel cell.;These improvements on catalyst and membrane could potentially revolutionize the fuel cell and provide cheap fuel cells with higher volumetric power densities for use in automotive applications.