KAIST

<(From Left) Ph.D candidate HyunWoo J Yang, Ph.D candidate SangJae Lee, Professor EunAe Cho, Ph.D candidate DongWon Shin>

Catalysts are the “invisible engines” of hydrogen energy, governing both hydrogen production and electricity generation. Conventional catalysts are typically fabricated in granular particle form, which is easy to synthesize but suffers from inefficient use of precious metals and limited durability. KAIST researchers have introduced a paper-thin sheet architecture in place of granules, demonstrating that a structural innovation—rather than new materials—can simultaneously reduce precious-metal usage while enhancing both hydrogen production and fuel-cell performance.

KAIST (President Kwang Hyung Lee) announced on the 21st of January that a research team led by Professor EunAe Cho of the Department of Materials Science and Engineering has developed a new catalyst architecture that dramatically reduces the amount of expensive precious metals required while simultaneously improving hydrogen production and fuel-cell performance.

The core of this research lies in the application of ultrathin nanosheet structures, with thicknesses tens of thousands of times thinner than a human hair, enabling the team to overcome both efficiency and durability limitations of conventional catalysts.

Water electrolyzers and fuel cells are key technologies for hydrogen energy production and utilization. However, their commercialization has been severely constrained by the scarcity and high cost of iridium (Ir) and platinum (Pt), which are commonly used as catalysts. In conventional particle-based catalysts, only a limited surface area participates in reactions, and long-term operation inevitably leads to performance degradation.

To address this, the research team transformed agglomerated catalyst particles into paper-like, ultrathin and laterally extended sheets. For water electrolysis, they developed ultrathin iridium nanosheets with lateral size of 1–3 micrometers and thicknesses below 2 nanometers. This structure dramatically increased the active surface area participating in reactions, enabling significantly higher hydrogen production with the same amount of iridium.

< Ultrafine Iridium Nanosheet (AI-generated image) >

In addition, the team discovered that these ultrathin nanosheets naturally formed interconnected conductive pathways on titanium oxide (TiO₂), a material previously considered unsuitable as a catalyst support due to its poor electrical conductivity. As a result, titanium oxide could be stably used as a catalyst support, further enhancing durability.

The resulting catalyst achieved a 38% higher hydrogen production rate than commercial catalysts and operated stably for over 1,000 hours under high-load, industry-relevant conditions (1 A/cm²*). Notably, even with approximately 65% less iridium, the catalyst delivered performance comparable to commercial benchmarks, demonstrating a major reduction in precious-metal usage.
 *1 A/cm²: a high-current condition corresponding to intensive operation of practical hydrogen-production systems

The team further applied the ultrathin nanosheet design strategy to fuel-cell catalysts, producing platinum–copper nanosheets with thicknesses again tens of thousands of times thinner than a human hair.

In fuel-cell evaluations, this catalyst exhibited a 13-fold improvement in mass activity per unit platinum compared with commercial catalysts, and delivered approximately 2.3 times higher performance in full fuel-cell tests. Even after 50,000 accelerated durability cycles, the catalyst retained about 65% of its initial performance, significantly outperforming conventional catalysts. Importantly, the same performance was achieved while reducing platinum usage by approximately 60%.

Professor EunAe Cho emphasized, “This study presents a new catalyst architecture that simultaneously enhances hydrogen production and fuel-cell performance while using far less expensive precious metals,” adding, “It represents a critical turning point for lowering the cost of hydrogen energy and accelerating its commercialization.”

<Schematic illustration of ultrathin nanosheet synthesis and transmission electron microscopy (TEM) images of the fabricated catalyst>

<Fabrication process of an ultrathin nanosheet catalyst and transmission electron microscopy (TEM) images of the fabricated catalyst>

The results of this work were published in two separate papers, both based on the shared core technology of ultrathin nanosheet architectures—one focused on hydrogen-production catalysts and the other on fuel-cell catalysts.

The iridium nanosheet study, with doctoral candidate Dongwon Shin as first author, was published online on December 10, 2025, in ACS Nano (IF 16.0).
 ※ Paper title: “Ultrathin Iridium Nanosheets on Titanium Oxide for High-Efficiency and Durable Proton Exchange Membrane Water Electrolysis,” DOI: 10.1021/acsnano.5c15659

The platinum–copper nanosheet study, with SangJae Lee and doctoral candidate HyunWoo Yang as co–first authors, was published online on December 11, 2025, in Nano Letters (IF 9.6).
 ※ Paper title: “Ultrathin PtCu Nanosheets: A New Frontier in Highly Efficient and Durable Catalysts for the Oxygen Reduction Reaction,” DOI: 10.1021/acs.nanolett.5c04848

This research was supported by the Energy Human Resource Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) under the Ministry of Trade, Industry and Energy, and by the Nano- and Materials-Technology Development Program of the National Research Foundation of Korea under the Ministry of Science and ICT.