KAIST develops 1-nanometer catalyst to replace costly platinum in green hydrogen production

Water electrolysis technology, which splits water electrochemically to produce hydrogen, has long been constrained by its reliance on costly platinum catalysts. South Korean researchers have now developed a new catalyst technology that can significantly boost hydrogen production efficiency in alkaline water electrolysis without using platinum.

The Korea Research Foundation announced that a research team led by Lee Jin-woo, a professor in the Department of Biological and Chemical Engineering at KAIST, collaborated with a team led by Professor Han Jeong-woo of Seoul National University, a team led by Professor Kim Woo-yeol of Korea Institute of Energy Technology, and a team led by Dr. Cho Seong-gi of the Korea Institute of Science and Technology. Together, they identified the surface state of ruthenium nanocluster catalysts during operation and the interfacial water structure at the electrode-electrolyte boundary, then used those findings to substantially improve hydrogen production performance in anion exchange membrane water electrolysis.

Anion exchange membrane water electrolysis — which splits water to obtain hydrogen and operates in an alkaline environment — has drawn attention as a core technology for green hydrogen production because it allows the use of inexpensive cell materials and non-precious-metal anode catalysts. However, the hydrogen evolution reaction at the cathode requires water molecules to be cleaved first to form hydrogen intermediates, making the reaction slower than under acidic conditions.

The research team deposited ruthenium on a carbon support and varied the heat treatment temperature to synthesize a series of catalysts of different sizes — single atoms, sub-nanometer clusters of about 1 nm and larger nanoclusters — then compared the surface oxidation states of each during actual reactions based on the size and atomic structure of the ruthenium clusters.

Operando X-ray absorption spectroscopy showed that the approximately 1 nm ruthenium nanoclusters stably maintained a partially oxidized surface containing ruthenium-oxygen (Ru-O) bonds even under the reductive conditions of hydrogen evolution. Operando infrared spectroscopy further revealed that this surface state influences the adsorption characteristics of reaction intermediates and the arrangement of water molecules around the catalyst, thereby promoting the alkaline hydrogen evolution reaction.

In half-cell tests measuring initial activity, the developed catalyst triggered a reaction at a very low overpotential of just 20 millivolts, and its mass activity per unit weight of precious metal reached 11.05 A/mgNM at 100 mV — an exceptionally high figure.

In single-cell tests simulating commercial operating conditions, the catalyst achieved a high current density of 5.34 A/cm², and operated stably for more than 400 hours at 1 A/cm² — a current density considered practical for real-world use — demonstrating its potential for application in actual devices.

"The role of the operando surface state confirmed in this study will serve as an important foundation for designing high-performance alkaline water electrolysis catalysts and advancing green hydrogen production technology," Lee said. He added that scaling up single-cell results to large-area electrodes and stack-level systems, and verifying durability under long-duration high-current operation and variable-load conditions linked to renewable energy sources, will be necessary before commercialization.

The research was supported by the Nano Future Materials Source Technology Development Project and the Green Hydrogen Technology Independence Project, both promoted by the Ministry of Science and ICT and the Korea Research Foundation. The findings were published online June 4 in the international energy journal Energy & Environmental Science.