Polymer electrolyte water electrolyzers (PEMWEs) are a promising technology for the storage of energy from intermittent renewable sources such as wind and solar. PEMWEs split water into hydrogen and oxygen electrochemically. Under typical operating conditions, the hydrogen evolution reaction (HER) in the cathode is not limited by reactant transport, since it is supplied by the rapid transport of protons from the polymer electrolyte and electrons from the external circuit. There are very limited studies on the role of the cathode gas diffusion layer (GDL), typically a carbon-paper based layer. In this study, we investigated the effect of thickness, presence of a microporous layer, and wettability of the cathode GDL. Results show that cathode GDL properties have a significant effect on the performance of the PEMWE cells. Figure 1a shows the importance of the GDL thickness with the optimized GDL compression. The thickest GDL, MGL370 (i.e. 370µm thick ) has the best performance compared to MGL280 (280µm thick) and MGL190 (190µm thick). Compression of the GDL also affects the performance: when the compression is increased from 12% to 25% of the thickness, a performance loss is observed possibly due to damaged carbon fiber network and collapse the pores of the GDL (Figure 1b).

Acknowledgment: Financial support from the US Department of Energy through the Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cells Technology Office is gratefully acknowledged.