(Invited) Membranes with Recombination Catalyst for Hydrogen Crossover Reduction: Water Electrolysis

Hydrogen and oxygen crossover phenomena through a solid polyelectrolyte membrane constitute one of the important safety concerns in PEM electrolysis. Hydrogen gas crossover in PFSA membranes during water electrolysis is a dynamic variable, characterised by complex functional relationships between the membrane water content, nature of the membrane, and operational conditions. Mitigation strategies to reduce gas crossover may include various approaches, based on the mechanism of interaction of hydrogen and the membrane matrix. These approaches may include passive solutions, reactive solutions, and combinations thereof. The most straightforward solution to reduce crossover is to increase membrane thickness; however, this leads to higher resistance to proton transport. Another rather straightforward approach includes developing mixed-matrix membranes, by adding fillers into the membrane matrix. By selecting a membrane material with a low diffusion coefficient and low water content, one can also reduce gas crossover. It is known that sulfonated hydrocarbon PEMs have significantly lower gas permeability than PSFA membranes (Bessarabov and Millet, 2018). The reactive approach includes promoting the process of hydrogen consumption by introducing Pt into either the CL and/or the current collector. The first membranes with Pt were fabricated for the purpose of self-humidification, for fuel cell applications (Watanabe et al., 1998). According to Ito et al. (2016) and Abdalla et al. (2017), it is critical for safe PEM electrolysis. The very well understood mechanism of hydrogen consumption involves recombination of hydrogen and oxygen on a Pt catalyst. This paper will describe morphology of Pt catalyst that was developed for the recombination purposes and embedded in the PFSA membranes. Experimental data for hydrogen reduction permeation will be presented. Catalyst was characterized by HR TEM. References. Abdalla, S., Al-Marzouki, F., Obaid, A., 2017. Safety considerations during production and consumption of hydrogen using proton exchange membrane electrolysis. J. Renew. Sustain. Energy 9, 013101 Bessarbov, D. and Millet, P. PEM Water Electrolysis, Elsevier, 2018 (in press) Ito, H., Miyazaki, N., Ishida, M., Nakano, A., 2016. Cross-permeation and consumption of hydrogen during proton exchange membrane electrolysis. Int. J. Hydrogen Energy, 41 (45), 20439–20446 Watanabe, M., Uchida, H., Emori, M., 1998. Analyses of self-humidification and suppression of gas crossover in Pt-dispersed polymer electrolyte membranes for fuel cells. J. Electrochem. Soc. 145 (4), 1137–1141