Journal
ACS ENERGY LETTERS
Volume -, Issue -, Pages 529-536Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsenergylett.2c02367
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Funding
- US Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell technologies Office
- ARPA-E [DE-AR0001003]
- Triad National Security, LLC under US Department of Energy [89233218CNA000001]
- US Department of Energy National Nuclear Security Administration [89233218CNA000001]
- Office of Science of the US Department of Energy [DE-AC02-05CH11231]
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This article reports quaternary ammonium-biphosphate ion-pair high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) that do not lose phosphoric acids under normal and accelerated stress conditions. Energetics and computational studies show that the proposed ion-pair system has higher interaction energy and allows for containing all phosphoric acids in the membrane electrode assemblies. In addition, polar interactions between the phosphonic acid ionomer and phosphoric acid explain acid retention in the electrodes of the ion-pair HT-PEMFCs.
Phosphoric acid loss poses immense hurdles for the durability of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Here we report quaternary ammonium-biphosphate ion-pair HT-PEMFCs that do not lose phosphoric acids under normal and accelerated stress conditions. Our energetics study explains the acid loss behavior of the conventional phosphoric acid-polybenzimidazole (PA-PBI) system by two mechanisms. If PA loss occurs via acid evaporation, the acid loss is constant over time. On the other hand, when water activity in the PA-PBI system is high, exponential decay of PA loss occurs via the water replacement mechanism. Combined 31P NMR and computational studies show that the proposed ion-pair system has six times higher interaction energy, which allows for containing all PAs in the membrane electrode assemblies under a broad range of operating conditions. In addition, polar interactions between the phosphonic acid ionomer and phosphoric acid explain acid retention in the electrodes of the ion-pair HT-PEMFCs.
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