Moves are accelerating around the world to break free of fossil fuels, with the aim of achieving carbon neutrality by 2050. Hydrogen has garnered a great deal of attention as a clean energy source, but its large-scale implementation still faces challenges.
Currently, most industrial hydrogen is produced from fossil fuels, but this method will not lead to carbon neutrality because the production process involves CO2 emissions. The production of hydrogen via renewable energy-based water electrolysis, so-called "green hydrogen," is a promising solution in the fight against climate change. However, high costs are a major obstacle to its widespread use. In particular, the price of the water electrolysis equipment itself and the high cost of the rare metal catalysts used in the equipment are major factors impeding the large-scale production and spread of green hydrogen.
Proton exchange membrane (PEM) technology boasts the highest energy efficiency among water electrolysis systems, but its use of the expensive rare metal iridium as a catalyst has made it difficult to bring down costs. According to calculations by the International Association for Hydrogen Energy, achieving the carbon neutrality target of 2050 would require about a 1.5 TW of PEM water electrolysis systems, which would take about 500 tons of iridium. This is an enormous amount, equivalent to more than 60 years of annual global production.
This challenge has been taken on by Shuang Kong, a researcher in the Biofunctional Catalyst Research Team at the RIKEN Center for Sustainable Resource Science. Kong succeeded in developing an innovative catalyst for PEM water electrolysis systems that reduces the use of iridium to nearly zero.
First, Kong elucidated a mechanism that increases the stability of the catalyst, yielding a 40-fold improvement in the durability of Earth-abundant manganese oxide. Non-precious metal catalysts are low in durability and were previously thought to be unusable in PEM water electrolysis, but this result has dramatically expanded the applicability of non-precious metal materials to PEM water electrolysis.
Kong continued her research and developed a new iridium catalyst using manganese oxide as a support. High activity and stability were achieved while reducing the amount of iridium used by more than 95%. This groundbreaking result was published in the journal Science in 2024 and sparked significant interest from both academic and industrial circles.
Kong's research results have also accelerated moves toward practical implementation. Joint research with the diversified chemical manufacturer Tosoh has resulted in more than 10 patent applications (three of which are international patents). In 2022, a new research and development group was established within Tosoh to start scaling up Kong's research results. Since 2023, she has also been collaborating with equipment makers in a project under the national research and development agency NEDO, working on research and development into increasing the scale of water electrolysis systems with a view toward practical implementation.
Kong's research is a major step toward the implementation and propagation of green hydrogen and has raised the prospects for clearing a path toward carbon neutrality.
