A new catalyst enabling increased production of ecological hydrogen

Scientists from the RIKEN Center for Sustainable Resource Science (CSRS) in Japan, led by Ryuhei Nakamura, have proposed an innovative technique that allows to reduce the amount of iridium needed to produce hydrogen by 95%.

A new catalyst enabling increased production of ecological hydrogen

Scanning electron microscope image of synthesized iridium oxide (D) and scanning transmission electron microscope images of iridium (light spots) scattered on manganese oxide electroplated on a corrosion-resistant platinum-coated titanium grid (E, F, G). Image source: RIKEN

As the global transition away from fossil fuels gathers pace, hydrogen is emerging as a leader towards a sustainable energy future. However, widespread adoption of “green” hydrogen, produced without the use of fossil fuels, is hampered by a shortage of iridium, a metal critical to the process.

In a groundbreaking study, scientists have demonstrated a novel approach that can reduce the amount of iridium required by 95% while maintaining the rate of hydrogen production. This breakthrough has the potential to transform our ability to produce hydrogen in an environmentally friendly manner, paving the way to a carbon-neutral hydrogen economy.

With 70% of the Earth’s surface covered by water, hydrogen stands out as a promising renewable energy source. However, extracting hydrogen from water on a scale that can compete with energy production from fossil fuels remains a challenge. Current global energy production is approaching 18 terawatts, which means that on average about 18 trillion watts of energy is produced worldwide at any given time. For green energy alternatives to replace fossil fuels, they must match energy production rates.

The environmentally friendly method of extracting hydrogen from water involves an electrochemical reaction using a catalyst. The most effective catalysts for this reaction, ensuring the highest speed and most stable hydrogen production, are rare metals, with iridium being the king. However, iridium deficiency is a serious obstacle.

Iridium is so rare that it is estimated that increasing global hydrogen production to the terawatt scale will require 40 years of iridium.

Shuang Kong, study co-author, RIKEN

The biofunctional catalysts research team at RIKEN CSRS is actively working to bypass the iridium bottleneck and explore alternative methods for high-efficiency, long-term hydrogen production. Their ultimate goal is to pioneer the development of new catalysts based on abundant earth metals, ensuring long-term sustainability. Recently, the team achieved a milestone by stabilizing green hydrogen production at relatively high levels using a form of manganese oxide as a catalyst.

However, transferring this success to industrial-scale production remains a future goal, requiring further research and development.

We need a way to bridge the gap between rare metal and common metal electrolysers so that we can gradually transition to fully sustainable green hydrogen over many years.

Ryuhei Nakamura, head of research, RIKEN

In the latest study, this was achieved by mixing manganese with iridium. Scientists have found that by dispersing individual iridium atoms onto a layer of manganese oxide, preventing them from accumulating, hydrogen production in a proton exchange membrane (PEM) electrolyzer remains at the same level as iridium alone, but with a remarkable 95% reduction in use iridium.

Using this innovative catalyst, continuous hydrogen production lasted over 3,000 hours (equivalent to approximately four months) with an impressive efficiency of 82% without any degradation.

The key to our success was the unexpected interaction between manganese oxide and iridium. This is because the iridium produced from this interaction was in the rare and highly active oxidation state +6.

Ailong Li, study co-author, RIKEN

According to Nakamura, there is a good chance that the amount of hydrogen produced by the new catalytic converter will be used immediately.

Nakamura said: “We expect our catalyst to be easily transferred to real-world applications,” He says, which will immediately increase the efficiency of current PEM electrolysers

The group has started cooperation with industry partners who have already perfected the first iridium-manganese catalyst. To further reduce the amount of iridium required, RIKEN CSRS researchers intend to conduct more research on the precise chemical interactions between iridium and manganese oxide. At the same time, they intend to test and implement the new catalyst on an industrial scale in the near future and continue cooperation with industrial partners.

Magazine number:

Li, A., et al. (2024) Atomically dispersed hexavalent iridium oxide from MnO2 reduction for catalysis of oxygen evolution. Science.