Better Hydrogen Production Catalyst For Handling Oxygen

Gwangju Institute of Science and Technology (GIST) researchers have developed a new tantalum oxide-supported iridium catalyst that significantly boosts the oxygen evolution reaction speed.

The study paper was published in the Journal of Power Sources. The study was co-authored by Dr. Chaekyung Baik, a post-doctoral researcher at Korea Institute of Science and Technology (KIST).

Proton exchange membrane water electrolyzers converts surplus electric energy into transportable hydrogen energy as a clean energy solution. However, slow oxygen evolution reaction rates and high loading levels of expensive metal oxide catalysts limit its practical feasibility. The GIST catalyst also shows high catalytic activity and long-term stability in prolonged single cell operation.

The energy demands of the world are ever increasing. In the quest for clean and eco-friendly energy solutions, transportable hydrogen energy offers considerable promise. In this regard, proton exchange membrane water electrolyzers (PEMWEs) that convert excess electric energy into transportable hydrogen energy through water electrolysis have garnered remarkable interest.

However, their wide scale deployment for hydrogen production remains limited due to slow rates of oxygen evolution reaction (OER) – an important component of electrolysis – and high loading levels of expensive metal oxide catalysts, such as iridium (Ir) and ruthenium oxides, in electrodes. Therefore, developing cost-effective and high-performance OER catalysts is necessary for the widespread application of PEMWEs.

Recently, a team of researchers from Korea and USA, led by Professor Chanho Pak from Gwangju Institute of Science and Technology in Korea, has developed a novel mesoporous tantalum oxide (Ta₂O₅)-supported iridium nanostructure catalyst via a modified formic acid reduction method that achieves efficient PEM water electrolysis.

Prof. Pak explained, “The electron-rich Ir nanostructure was uniformly dispersed on the stable mesoporous Ta₂O₅ support prepared via a soft-template method combined with an ethylenediamine encircling process, which effectively decreased the amount of Ir in a single PEMWE cell to 0.3 mg cm^-2. Importantly, the innovative Ir/Ta₂O₅ catalyst design not only improved the utilization of Ir but also facilitated higher electrical conductivity and a large electrochemically active surface area.

Additionally, X-ray photoelectron and X-ray absorption spectroscopies revealed strong metal-support interaction between Ir and Ta, while density functional theory calculations indicated a charge transfer from Ta to Ir, which induced the strong binding of adsorbates, such as O and OH, and maintained Ir (III) ratio in the oxidative OER process. This, in turn, led to the enhanced activity of Ir/Ta₂O₅, with a lower overpotential of 0.385 V compared to a 0.48 V for IrO₂.

The team also demonstrated high OER activity of the catalyst experimentally, observing an overpotential of 288 ± 3.9 mV at 10 mA cm^-2 and a mass activity of 876.1 ± 125.1 A g^-1 of Ir at 1.55 V, significantly higher than the corresponding values for Ir Black. In effect, Ir/Ta₂O₅ exhibited excellent OER activity and stability, as further confirmed through membrane electrode assembly single cell operation of over 120 hours.

The proposed technology offers the dual benefit of reduced Ir loading levels and an enhanced OER efficiency. “The improved OER efficiency complements the cost-effectiveness of the PEMWE process, enhancing its overall performance. This advancement has the potential to revolutionize the commercialization of PEMWEs, accelerating its adoption as a primary method for hydrogen production,” speculated an optimistic Prof. Pak.

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This looks like real progress on the water splitting effort. And by any means a 120 hour run without a productivity drop off is worthwhile news by itself.

But still, this work is on producing pure hydrogen.

One day someone will write a post about just what a straight hydrogen economy might be actually like. Something in gaseous form that ignites at 4% to 96% and is nearly impossible to keep stored for transport without it simply slipping out of the container. Sounds like quite a challenge.

Widely observant folks do understand the mechanics of the positioning. To the hysterics and the media carbon is evil. One wonders how long they would last if the was no carbon in their lives at all.

Perhaps the realization that hydrogen is best hooked up to some carbon for practical use will gain traction one day. Which means this team’s work is useful, important, and a step into a better future.

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