Researchers design efficient iridium catalyst for hydrogen generation

The energy demands of the world are constantly increasing as we seek clean and eco-friendly energy solutions. One promising solution is transportable hydrogen energy. Proton exchange membrane water electrolyzers (PEMWEs) have gained significant attention for their ability to convert excess electric energy into transportable hydrogen energy through water electrolysis.

However, the widespread use of PEMWEs for hydrogen production is limited due to slow rates of oxygen evolution reaction (OER) and the high loading of expensive metal oxide catalysts, such as iridium and ruthenium oxides, in electrodes. Therefore, it is crucial to develop cost-effective and high-performance OER catalysts to promote the widespread application of PEMWEs.

In a recent study published in the Journal of Power Sources, a team of researchers from Korea and the United States, led by Professor Chanho Pak from the Gwangju Institute of Science and Technology in Korea, has made significant progress in this area. They have developed a novel mesoporous tantalum oxide-supported iridium nanostructure catalyst using a modified formic acid reduction method, which enables efficient PEM water electrolysis.

This study was co-authored by Dr. Chaekyung Baik, a post-doctoral researcher at the Korea Institute of Science and Technology (KIST).

“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,” explains Prof. Pak. The innovative Ir/Ta₂O₅ catalyst design not only improves the utilization of Ir but also enhances electrical conductivity and provides a large electrochemically active surface area.

Additionally, advanced spectroscopic techniques revealed a strong metal-support interaction between Ir and Ta, and theoretical calculations showed a charge transfer from Ta to Ir, resulting in a strong binding of adsorbates during the oxidative OER process. This leads to the enhanced activity of Ir/Ta₂O₅ compared to traditional IrO₂ catalysts.

The team conducted experimental tests on the catalyst and observed high OER activity with 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 surpassing Ir Black catalysts. Furthermore, the Ir/Ta₂O₅ catalyst exhibited excellent stability over 120 hours of membrane electrode assembly single cell operation.

This technology offers the dual benefit of reducing the loading levels of expensive iridium catalysts and improving 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 their adoption as a primary method for hydrogen production,” speculates Professor Pak enthusiastically.

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