Clean hydrogen, produced by splitting water into H₂ and O₂ using renewable electricity, will play a crucial role as a renewable energy carrier and in decarbonizing industrial and hard-to-decarbonize transport sectors in the future.¹ Hydroxide-exchange-membrane water electrolyzers (HEMWEs) have the potential to be more cost effective compared to the incumbent technology, proton-exchange-membrane water electrolyzers (PEMWEs) through the use of cheaper and more abundant catalysts and cell components.² However, compared to PEMWEs, HEM systems have been studied significantly less and generally have much lower performance. Here, we systematically investigated a series of pivotal parameters that are related to catalyst inks, catalyst-layer structures, and porous-transport layer/catalyst-layer interfaces for HEMWEs. An integrated reference electrode is utilized to differentiate each individual effects on the cathode and anode when studying cell performance and durability. Catalyst-ink formulations are studied by varying ionomer‑to‑catalyst ratios, solid concentration, and solvent compositions. Additionally, parameters around the ink coating process are explored to study their impacts on catalyst-layer structures and provide guidance on key considerations for manufacturing robust catalyst layers. Finally, the impacts of porous-transport-layer architecture and cell configuration on the cell performance are probed. The findings elucidate critical properties and highlight urgently needed experimental practices towards high-performing HEMWEs.

Acknowledgements

This work was funded under the HydroGEN Consortium by the Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231.

References

1. B. Pivovar, N. Rustagi and S. Satyapal, The Electrochemical Society Interface, 27, 47 (2018).

2. K. Ayers, N. Danilovic, R. Ouimet, M. Carmo, B. Pivovar and M. Bornstein, Annual Review of Chemical and Biomolecular Engineering, 10, 219 (2019).