Volume 1, Issue 3 (December 2023) – 1 articles

Cover Story (View full-size image):
Polymer electrolyte membrane fuel cells are one of the promising energy conversion devices for realization of carbon neutral society. In particular, anion exchange membrane fuel cells are advantageous over proton exchange membrane fuel cells for lowering cost of the total devices because of possible use of abundant transition metals as electrocatalysts. One of the technical issues associated with anion exchange membrane fuel cells is the durability of the membranes, mechanical and chemical instability under the fuel cell operating conditions. We in this study approach this issue by reinforcing our previously developed anion exchange membranes (partially fluorinated, ether free polymers with pendent ammonium head groups) with porous polyethylene substrate. The reinforced membranes exhibit improved mechanical properties, and accordingly better fuel cell performance and durability. The membranes are expected to be applicable to other related energy devices such as electrolyzers and batteries.  View this manuscript

Article

25 September 2023

Anion Exchange Membrane Reinforced with Polyethylene Substrate for Alkaline Fuel Cell Applications

To enhance mechanical robustness of our in-house anion exchange membrane (QPAF-4), the reinforcement technique was applied using ozone-treated, porous polyethylene (PE) thin film (Toray SETELA) as a substrate. Homogenous and flexible reinforced membranes (QPAF-4-PE, 15–20 µm thick) were obtained by bar-coating method. The cross-sectional SEM image and EDS analysis revealed triple-layered (sandwich-like) structure without detectable pinholes. The QPAF-4-PE with ion exchange capacity (IEC) of 1.48 meq·g−1 exhibited lower water uptake (15 wt% at 90% relative humidity) and slightly lower hydroxide ion conductivity (71 mS·cm−1 at 80 ℃) than those of the pristine QPAF-4 (IEC = 1.84 meq·g−1, 25 wt% water uptake and 82 mS·cm−1 of the conductivity). The reinforced QPAF-4-PE exhibited slightly higher viscoelasticity (particularly, in MD direction) due to the suppressed water absorbability. Furthermore, the elongation at break increased by 9.8% in TD direction and 6.3% in MD direction. An H2/O2 fuel cell using QPAF-4-PE as membrane was investigated at different back-pressure, in which the cell with 100 kPa back-pressure onto the cathode side only achieved the maximum performance (176 mW·cm−2 at current density of 364 mA·cm−2) and the longest durability for (>200 h) at a constant current density of 100 mA·cm−2 maintaining 0.43 V of the cell voltage (67% remaining). The durability was eight times longer than that with ambient pressure and two times longer than that with back-pressure on both sides.

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