Green hydrogen production holds promise within the energy transition landscape, especially for its potential to generate clean energy without greenhouse gas emissions. In this field, alkaline exchange membrane water electrolysers (AEMWEs) –the type of electrolysers we develop at ANEMEL– have gained considerable attention due to their capability to produce hydrogen under environmentally friendly conditions.
Typically, AEMWEs operate at current densities below 3 A/cm², a range that has provided a stable output. This measure refers to the electric current flowing across a certain area. But what would happen if we pushed current density to higher values? This could achieve a higher hydrogen production rate, thereby reducing the stack footprint, volume, and material usage. As a result, it could improve efficiency and lower the cost of hydrogen production.
In a pioneering study, published in Angewandte Chemie, ANEMEL researchers at the École Polytechnique Fédérale de Lausanne (EPFL), in Switzerland, successfully pushed the limits of AEMWEs to operate at an ultrahigh current density of 10 A/cm² for an impressive 800 hours. By comparison, a state-of-the-art benchmark AEMWE can only operate for a few seconds at such current densities. This means we achieved a 500,000-fold increase! As ANEMEL researcher Ariana Serban says: “The results are very, very good… Operating at 10 A/cm² for that amount of time is quite amazing. I’ve never seen such a paper.” Serban is a member of the team behind the research, led by Professor Xile Hu.
benchmark. Credit: Yiwei Zheng et. al
At the heart of the team’s success is their strategic selection of materials and design choices. This is the ‘’backbone of this work’, in Serban’s words. The main innovation lays in optimising the gas diffusion layer (GDL)—a porous layer where deposited catalysts build up the electrodes—and in using a unique combination of an improved ion exchange ionomer and Nafion, a classic cation exchange ionomer. “This improved ionomer served both as a binding and stabilising agent for the catalyst,” explains Serban. Additionally, the membrane used in this study was developed by the EPFL team and outperformed commercially available alternatives.
This unique blend of materials addresses the main issues faced by AEMWEs at high current densities: degradation and a severe increase of mass transport resistance. The study observed that these issues, especially membrane degradation, were among the primary reasons for failure under ultrahigh current density operation. Using standard materials, the AEMWE could only operate for 6 seconds at 10 A/cm² current density. With the optimised material setup, the team were able to overcome these challenges, achieving an impressive operational lifetime of 800 hours for the ANEMEL device.
Operating at higher current densities could help reducing the total cost of hydrogen production. It also provides a way to confirm that we are using the right materials. The increased stress during high current operations can serve as a rapid assessment tool for the device’s robustness, without the need for lengthy tests spanning thousands of hours.
Although challenges remain—particularly in further reducing charge and mass transfer resistances—this study paves the way for future research, bringing us closer to the goal of affordable, sustainable hydrogen production on an industrial scale. At ANEMEL we’ll continue working to refine our electrolyser designs to move in this direction.