Researchers design iridium catalyst for hydrogen generation

Researchers from Korea and the U.S. have developed a novel mesoporous tantalum oxide (Ta2O5)-supported iridium (Ir) nanostructure catalyst via a modified formic acid reduction method that achieves efficient PEM water electrolysis.

According to the researchers, this iridium catalyst significantly boosts the oxygen evolution reaction speed and shows high catalytic activity and long-term stability in prolonged single-cell operation.

The energy demands of the world are ever-increasing, and in the quest for clean and eco-friendly energy solutions, transportable hydrogen energy offers considerable promise, researchers said, adding that 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, they pointed out that PEMWEs widescale deployment for hydrogen production remains limited due to slow rates of oxygen evolution reaction (OER) and high loading levels of expensive metal oxide catalysts, such as iridium and ruthenium oxides, in electrodes.

Therefore, the development of cost-effective and high-performance OER catalysts is necessary for the widespread application of PEMWEs, researchers noted.

Chanho Pak from Gwangju Institute of Science and Technology in Korea, who led the study, said: “The electron-rich iridium 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 iridium in a single PEMWE cell to 0.3 mg cm–2.”

Importantly, the research team found that 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 ratio in the oxidative OER process, the team said, noting that 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 said it demonstrated high OER activity of the catalyst experimentally.

Pak speculated: “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.”

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