Fuel cells are crucial energy conversion units that have the potential to revolutionize clean energy production. However, in the case of proton exchange membrane fuel cells (PEMFCs), the ion-conductive membranes used face a challenge of balancing durability with ion conductivity, impacting the performance and lifespan of the fuel cells. In recent years, chemically and physically modified proton-conductive membranes have been synthesized in an attempt to improve durability. Unfortunately, none of these membranes have passed the rigorous accelerated durability tests set by the U.S. Department of Energy (DOE) for use in automobile fuel cells by 2025. In a significant breakthrough, a group of researchers from Japan has developed novel proton-conductive membranes that meet the DOE’s targets. Their findings have been published in the journal Science Advances.
Led by Professor Kenji Miyatake from Waseda University and the University of Yamanashi, the researchers synthesized proton-conductive membranes using a partially fluorinated aromatic ionomer called SPP-TFP-4.0. To strengthen the ionomer, they utilized the push-coating method and reinforced it with either electrospun nanofibers of poly(vinylidene fluoride) (PVDF) or porous expanded polytetrafluoroethylene (ePTFE). This led to the creation of two composite membranes, SPP-TFP-4.0-PVDF and SPP-TFP-4.0-ePTFE, with thicknesses of 14µm and 16µm, respectively.
Superior Performance of SPP-TFP-4.0-PVDF Membrane
The researchers conducted a series of tests on the proton-conductive membranes to evaluate their performance. The SPP-TFP-4.0-PVDF membrane emerged as the clear winner, outperforming the state-of-the-art Nafion XL membrane, which is chemically stabilized and physically reinforced. The SPP-TFP-4.0-PVDF membrane displayed excellent fuel-cell operation and in situ chemical stability at a high temperature of 120°C and a low relative humidity of 30%.
Impressive Durability and Stability
One of the most remarkable aspects of the SPP-TFP-4.0-PVDF membrane is its durability. In the accelerated durability test with frequent wet-dry cycling under open-circuit-voltage conditions, the membrane exhibited a lifespan of 148,870 cycles or 703 hours, surpassing the DOE target by over seven times. Furthermore, the membrane demonstrated high chemical stability with minimal degradation, maintained stable rupture energy at various humidity levels, and exhibited excellent mechanical properties from zero to 60% relative humidity at 80°C. Notably, it delivered outstanding fuel-cell performance even at high temperatures ranging from 100°C to 120°C.
A Promising Future for Fuel Cells
The development of the aromatic polymer-based reinforced proton-conductive membrane represents a significant achievement in fuel cell technology. By meeting the U.S. DOE’s ambitious targets for future automobile fuel cells, this membrane offers a lucrative alternative with high-temperature operability and exceptional durability. The successful application of these membranes in fuel cell-based electric vehicles has the potential to enhance their power and affordability. Moreover, it contributes to the realization of a hydrogen-based, carbon-free society, providing a sustainable solution to energy and environmental challenges.
The synthesis of highly durable and efficient proton-conductive membranes is a game-changer for fuel cell technology. The breakthrough achieved by the Japanese researchers brings us closer to a future powered by clean energy. With continued advancements and further research, fuel cell-based electric vehicles may soon become the norm, driving us towards a more sustainable and eco-friendly world.