1441
(Invited) Controlling Fuel Crossover and Hydration in Ultra-Thin Proton Exchange Membrane Based Fuel Cells Using Pt-Nanosheet Catalysts

Monday, 29 May 2017: 14:40
Grand Salon B - Section 7 (Hilton New Orleans Riverside)
P. Gao (Hong Kong University of Science and Technology)
An ultra-thin proton exchange membrane (PEM) with Pt-nanosheet catalysts was designed for a self-humidifying fuel cell running on hydrogen and oxygen with 0% relative humidity. In this design, an ultra-thin Nafion membrane was used to reduce ohmic resistance. Pt nanocatalysts were uniformly anchored on exfoliated layered double hydroxide (LDH) nanosheets by chemical vapor deposition (CVD). After embedding Pt-LDHs nanocatalysts in 9 µm thick Nafion membranes, exfoliated LDH nanosheets effectively captured crossovered hydrogen and oxygen through membranes. Meanwhile, Pt nanocatalysts on LDH nanosheets catalyzed reactions between captured hydrogen and oxygen and provided in-situ hydration inside Nafion membranes to maintain theirs proton conductivity level. Furthermore, LDH nanosheets reinforced Nafion membranes with 162% improvement in tensile modulus and 126% improvement in yield strength. In a hydrogen fuel cell running with dry fuels, the MEA employing Pt-LDHs/Nafion membrane showed an improvement of 250 % in maximum power density, an increase of 300 % in current density at 0.3V and an improvement of 900 % in current density at 0.5V as compared to those of the MEA with a commercial Nafion 112 membrane. Furthermore, fuel cell tests were conducted on the PEMs with the thickness of 25 μm to observe the synergic effects of self-humidification and the suppression of fuel crossover. Compared to the commercial Nafion 211 membrane, Pt-LDHs/Nafion membrane with a thickness of 25 μm exhibited a combination of desirable properties for the development of affordable and durable hydrogen fuel cell technology, including better mechanical properties, higher open-circuit voltage (OCV), lower ohmic resistance and enhanced water management in a hydrogen fuel cell without external humidification.