Currently the most popular system used for water electrolysis for hydrogen production relies on precious metals as catalysts. A collaborative research team, including scientists from Los Alamos National Laboratory (LANL) and Washington State University (WSU), has developed a nickel-iron (NiFe)-based catalyst, which is much less expensive, but which delivers comparable performance. They describe the advance in a paper published in Nature Energy.

Alkaline anion exchange membrane (AEM) electrolysers to produce hydrogen from water are still at an early stage of development, and their performance is far lower than that of systems based on proton exchange membranes. Here, we report an ammonium-enriched anion exchange ionomer that improves the performance of an AEM electrolyser to levels approaching that of state-of-the-art proton exchange membrane electrolysers.

Using rotating-disk electrode experiments, we show that a high pH (>13) in the electrode binder is the critical factor for improving the activity of the hydrogen- and oxygen-evolution reactions in AEM electrolysers. Based on this observation, we prepared and tested several quaternized polystyrene electrode binders in an AEM electrolyser. Using the binder with the highest ionic concentration and a NiFe oxygen evolution catalyst, we demonstrated performance of 2.7 A cm⁻² at 1.8 V without a corrosive circulating alkaline solution. The limited durability of the AEM electrolyser remains a challenge to be addressed in the future.

—Li et al.

Most water splitting is conducted using a proton exchange membrane electrolyzer, which generates hydrogen at a high production rate but works under very acidic conditions, requiring precious metal catalysts such as platinum and iridium as well as corrosion-resistant metal plates made of titanium.

The research team worked to solve this problem by splitting water under alkaline, or basic, conditions with an anion exchange membrane electrolyzer. This type of electrolyzer does not need a catalyst based on precious metals.

A team led by Yuehe Lin, professor at WSU’s School of Mechanical and Materials Engineering, created a catalyst based on nickel and iron. Lin’s team shared their development with Yu Seung Kim, a research scientist at Los Alamos National Laboratory and corresponding author on the paper.

Kim’s team, in turn, developed the electrode binder to use with the catalyst. The electrode binder is a hydroxide-conducting polymer that binds catalysts and provides a high pH environment for fast electrochemical reactions.

The combination of the Los Alamos-developed electrode binder and WSU’s catalyst boosted the hydrogen production rate to nearly ten times the rate of previous anion exchange membrane electrolyzers, making it comparable with the more expensive proton exchange membrane electrolyzer.

In addition to Los Alamos and WSU, researchers at Pajarito Powder and Sandia National Laboratories also contributed to this work. This research was supported by the HydroGen Advanced Water Splitting Materials Consortium established under the US Department of Energy and Washington state’s JCDREAM program.

Resources

• Li, D., Park, E.J., Zhu, W. et al. (2020) “Highly quaternized polystyrene ionomers for high performance anion exchange membrane water electrolysers.” Nat Energy doi: 10.1038/s41560-020-0577-x