Probing membrane hydration in microfluidic polymer electrolyte membrane electrolyzers via operando synchrotron Fourier-transform infrared spectroscopy

Polymer electrolyte membrane (PEM) electrolyzers are renewable energy storage systems that produce high purity hydrogen fuel from electrochemical water splitting. The PEM in particular is a key component that acts as a solid electrolyte between electrodes and separates the reactants, but despite these benefits, its internal ion transport mechanisms are not fully understood. Here, the first microfluidic PEM electrolyzer that is semi-transparent in the infrared (IR) spectrum is developed as a platform for characterizing the PEM hydration during operation. The electrochemical performance of the chip is compared to its PEM hydration, which is measured via synchrotron Fourier-transform infrared (FTIR) spectroscopy. The PEM water content is directly probed in the operating electrolyzer by measuring the transmitted light intensity at wavelengths around 10 & mu;m. By supplying the electrolyzer with reactant starving flow rates, mass transport driven cell failure is provoked, which coincides with membrane dehydration. Furthermore, higher operating temperatures are observed to improve the stability in membrane hydration through increasing the membrane water uptake. The methods presented here prove the viability of IR techniques for characterizing membrane hydration, and future extension towards imaging and thermography would enable further quantitative studies of internal membrane transport behaviors.

Automated summary

Polymer electrolyte membrane (PEM) electrolyzers are developed as a renewable energy storage system for producing high purity hydrogen fuel through electrochemical water splitting. However, the internal ion transport mechanisms of PEM are not fully understood. This study presents a semi-transparent microfluidic PEM electrolyzer that allows characterization of PEM hydration during operation using synchrotron Fourier-transform infrared (FTIR) spectroscopy. The results show that mass transport driven cell failure and membrane dehydration can be provoked by reactant starving flow rates, while higher operating temperatures improve membrane hydration stability by increasing water uptake. These findings prove the feasibility of using IR techniques for studying membrane hydration.