(390b) PFAS-Free Proton-Conducting Membranes for Sustainable Hydrogen Production
AIChE Annual Meeting
2024
2024 AIChE Annual Meeting
Catalysis and Reaction Engineering Division
Electrochemical Engineering and Reactor Design III: Engineering the Reactor for Electrochemical CO2 Conversion - Experimental Demonstrations
Tuesday, October 29, 2024 - 3:48pm to 4:06pm
Per- and Polyfluorinated Substances (PFAS)-containing ion-exchange membranes such as Nafion have been a critical component in proton-exchange membrane water electrolyzers due to their high proton conductivity and the low hydrogen crossover rate necessary for safe operation. Nonetheless, PFAS materials are very difficult to decompose and have significant environmental impacts.1 Many countries in the world have been pushing for stricter regulation and the phase-out of PFAS.1 Significant research efforts have been put into PFAS remediation.2 On the other hand, it is also imperative to develop PFAS-free proton exchange membranes in the first place. In this work, we developed a class of phosphorous-doped silicon dioxide (SiO2)-based proton exchange membranes using atomic layer deposition. Surface-enhanced Raman spectroscopy (SERS) and X-ray photoelectron spectroscopy (XPS) characterization results provide evidence for the incorporation of phosphate groups in the SiO2 matrix. The best performing membrane demonstrated a proton conductivity of 2.2±0.7x10-3 S cm-1 as measured by electrochemical impedance spectroscopy (EIS), which was an order of magnitude higher than previously reported phosphorus-doped SiO2 membranes3 and within an order of magnitude of that of Nafion-117 (~10-2 S cm-1)4. In the meantime, the dense SiO2 layer also helped to keep the hydrogen permeability under 1.3±0.1x10-10 cm2 s-1, which is crucial to ensure safe operation with thin membranes. Fourier-transform infrared spectroscopy (FTIR) characterization results further revealed the structural difference between POx-doped SiO2 and undoped SiO2, providing insights into the structure-performance relationship for further optimization. Overall, this work demonstrates a novel method for fabricating PFAS-free ion exchange membranes for sustainable hydrogen production using water electrolysis.
References
1. Brunn et al. Environmental Sciences Europe 2023, 35 (1), 20.
2. Li et al. Chemical Engineering Journal 2023, 452, 139202.
3. Prakash et al. Journal of Power Sources 2008, 175 (1), 91-97.
4. Sone et al. Journal of The Electrochemical Society 1996, 143 (4), 1254.