Novel proton-conductive membranes for automobile fuel cells

August 3, 2023 This article has been reviewed according to Science X’s editorial process and policies . Editors have highlighted the following attributes while ensuring the content’s credibility: fact-checked peer-reviewed publication trusted source proofread by Waseda University Fuel cells are compact energy conversion units that utilize clean energy sources like hydrogen and convert them into electricity through a series of oxidation–reduction reactions. Specifically, proton exchange membrane fuel cells (PEMFCs), an integral part of electric vehicles, utilize proton-conductive membranes for operation.

Unfortunately, these membranes suffer from a trade-off between high durability and high ion conductivity, affecting the lifetime and performance of PEMFCs. googletag. cmd.

push(function() { googletag. display(‘div-gpt-ad-1449240174198-2’); }); To overcome this issue, scientists have synthesized chemically and physically modified perfluorosulfonic acid polymer membranes, such as Nafion HP, Nafion XL, and Gore-Select, which have proven to be much more durable than unmodified membranes conventionally employed in fuel-cell operations. Unfortunately, none of the existing proton-conductive membranes have fulfilled the highly challenging technical target—passing an accelerated durability test or a combined chemical and mechanical test—set by the U.

S. Department of Energy (DOE) to facilitate their use in automobile fuel cells by 2025. Now, a group of researchers from Japan, led by Professor Kenji Miyatake from Waseda University and the University of Yamanashi, has synthesized novel proton-conductive membranes for PEMFCs.

Their work, published in the journal Science Advances , is co-authored by Dr. Liu Fanghua from Waseda University and the University of Yamanashi and Dr. Ick Soo Kim from Shinshu University.

The researchers synthesized proton-conductive membranes using a partially fluorinated aromatic ionomer (polymer material consisting of thermoplastic resins stabilized by ionic cross-linkages) called SPP–TFP-4. 0 (SPP: sulfonated polyphenylene, TFP: bis(trifluoromethyl) terphenylene). They then utilized the push-coating method to reinforce the ionomer either with electrospun, nonwoven, and isotropic poly(vinylidene fluoride) (PVDF) nanofibers with high porosity (78%) or using porous expanded polytetrafluoroethylene (ePTFE).

This resulted in composite membranes, SPP–TFP-4. 0–PVDF and SPP–TFP-4. 0–ePTFE, of thicknesses 14 and 16 µm, respectively.

The researchers performed a wide variety of tests on these proton-conductive membranes and demonstrated the one reinforced with PVDF to be superior. “It outperformed the state-of-the-art chemically stabilized and physically reinforced perfluorinated Nafion XL membrane in terms of fuel-cell operation and in situ chemical stability at a high temperature of 120 o C and a low relative humidity of 30%,” said Miyatake. The SPP–TFP-4.

0–PVDF membrane demonstrated a long lifetime of 148,870 cycles or 703 hours—over seven times longer than that of the DOE target—in the accelerated durability test with frequent wet-dry cycling under open-circuit-voltage conditions. In addition, it exhibited high chemical stability with little degradation, stable rupture energy at various humidity levels, highly stable mechanical properties from zero to 60% relative humidity at 80 o C, and excellent fuel-cell performance at high temperatures (100–120 o C). In effect, the proposed aromatic polymer-based reinforced proton-conductive membrane meets the U.

S. DOE’s target for future automobile fuel cells, providing a lucrative alternative. Thus, this study could pave the way for PEMFCs with high-temperature operability and durability.

“As a result, fuel cell-based electric vehicles may become more powerful and affordable. This would also contribute towards realizing a hydrogen-based, carbon-free society,” concludes Miyatake. More information: Fanghua Liu et al, Proton-conductive aromatic membranes reinforced with poly(vinylidene fluoride) nanofibers for high-performance durable fuel cells, Science Advances (2023).

DOI: 10. 1126/sciadv. adg9057 Journal information: Science Advances Provided by Waseda University.