Huamin Zhang

Nafion/PTFE composite membranes for fuel cell applications

The composite membranes were prepared by impregnation of porous poly(tetrafluoroethylene) membranes with a 5 wt% Nafion solution. Scanning electron microscope micrographs of composite membranes show the surface and cross section of poly(tetrafluoroethylene) membranes were covered and filled with Nafion resin. Comparison of physical properties and fuel cell performance of composite membranes with those of Nafion membranes (DuPont Co) is presented. The composite membrane has better thermal stability and gas barrier property but worse ionic conductivity than Nafion membrane. Though the composite membrane has a lower conductivity than Nafion membrane, however, owing to the thinner thickness of composite membrane (in thickness of 20±5 µm) than Nafion-115 (in thickness of 125 µm) and Nafion-117 (in thickness of 175 µm) membranes, the composite membrane has a shorter H+ ion transporting pathway and thus a higher conductance (conductance = conductivity/membrane thickness) than Nafion-115 and Nafion-117 membranes. Thus the composite membrane has a better fuel cell performance than Nafion-117 and Nafion-115 membranes. In this report, we show that our composite membrane has a fuel cell performance similar to Nafion-112 membrane (in thickness of 50 µm).

Characteristics of Polyethersulfone/Sulfonated Polyimide Blend Membrane for Proton Exchange Membrane Fuel Cell

Solution-cast membranes from sulfonated polyimide (SPI) and its blend were prepared from polyethersulfone (PES) and SPI. The water uptake and swelling were tested and compared between the SPI membrane and the four kinds of blend membranes. Through comparison of the stability of the membranes, we concluded that the PES could greatly increase the stability of the whole membrane and restrict the swelling. However, the PES did not decrease the water uptake very much. We also compared the fuel cell performance with different membranes. The performance was decreased when the content of the PES in the blend membrane increased. The loss of the fuel cell performance with the blend membranes did not decrease very much before the content of the PES was exceeded 20%. It was prospected that the blend membrane could increase the stability of the SPI and, more importantly, even replace the commercial Nafion membranes.

PTFE based composite anion exchange membranes: thermally induced in situ polymerization and direct hydrazine hydrate fuel cell application

Anion exchange membrane fuel cells (AEMFCs) are advantageous over proton exchange membrane fuel cells in terms of electrode reaction kinetics and electrocatalyst versatility. As one of the key materials for this type of fuel cell, AEM transports anions from cathode to anode during cell operation and governs the performance of AEMFC. In this work, we report on the fabrication of a novel type of PTFE based composite anion exchange membrane and its application in direct hydrazine hydrate fuel cells (DHFC). The membrane was prepared viain situ thermal polymerization of chloromethyl monomer in pre-treated PTFE matrix followed by quaternary amination and alkalization. Attributed to a high chloromethyl monomer uptake and a membrane structure featuring “hydrophobic matrix confined hydrophilic domain”, the fabricated membrane showed hydroxide conductivity up to 0.049 S cm−1 at room temperature and a maximum DHFC power density of 110 mW cm−2 at a voltage of 0.7 V. Such membranes are promising candidates for application in AEMFC.