"Hydrogen Production Efficiency Increased Sixfold"... KAIST Develops Nanomaterial Synthesis Platform

A platform technology has been developed that uses a flash of light to achieve ultra-high temperatures, thereby significantly enhancing the efficiency of catalysts for hydrogen production. By utilizing this platform, hydrogen production efficiency can be increased by up to six times while consuming only 1/1000 of the energy compared to conventional methods. This breakthrough is expected to accelerate the commercialization of future clean energy technologies.

KAIST announced on October 20 that a research team led by Professor Kim Il-Doo from the Department of Materials Science and Engineering and Professor Choi Sungyul from the School of Electrical and Electronic Engineering has developed a "direct-contact photothermal annealing" synthesis platform, which enables the synthesis of high-performance nanomaterials by exposing them to light for just 0.02 seconds.

(From left) Seo-Hak Park, PhD candidate; Jae-Wan Ahn, PhD; Do-Kyung Jeon, PhD candidate; Sung-Yul Choi, Professor; Il-Doo Kim, Professor; Choong-Sung Park, PhD; Ui-Cheol Shin, PhD candidate; (From top left) Ha-Min Shin, PhD; Jun-Hoe Choi, PhD. Provided by KAIST

This technology is a catalyst synthesis method that instantly reaches an ultra-high temperature of 3,000 degrees Celsius using a flash of light. The ultra-high temperature achieved through light can transform "nano diamond," a hard and chemically inert material, into "carbon nano onion," a high-performance carbon material that conducts electricity well and is suitable for use as a catalyst.

Through this approach, the research team reduced energy consumption to 1/1000 of that required by conventional filament-based thermal processing, while also shortening the processing time by several hundred times.

Notably, the team succeeded in attaching individual metal atoms to the surface of the converted carbon nano onion, thereby simultaneously imparting catalytic functionality. This means that simply exposing nano diamond to a flash of light not only transforms its structure into carbon nano onion but also endows the material with new functional properties, achieving a dual benefit.

Carbon nano onion is an ultra-fine spherical material in which carbon atoms are layered in multiple shells like an onion. It exhibits excellent electrical conductivity and chemical resistance, making it ideal for supporting catalysts.

However, until now, synthesizing carbon nano onion required a complex process of first creating the material and then attaching the catalyst. Conventional thermal processing using filament heating consumed large amounts of energy and took a long time, making commercialization difficult.

To address these challenges, the research team utilized the "photothermal effect," which converts light energy into heat.

The process involves mixing "carbon black," a black substance that absorbs light well, with nano diamond-the precursor to carbon nano onion-and then exposing the mixture to intense light from a xenon lamp.

As a result, nano diamond was converted into carbon nano onion in just 0.02 seconds. Molecular dynamics simulations also confirmed that this process is physically feasible.

This platform is particularly notable for its ability to simultaneously synthesize carbon nano onion and attach single-atom catalysts. When metal precursors such as platinum are included, the metals are decomposed at the atomic level and immediately adhere to the surface of the newly formed carbon nano onion as "single-atom catalysts."

During the rapid cooling process that follows, the atoms do not aggregate, resulting in a single-step process that perfectly integrates material synthesis and catalyst functionalization.

The research team successfully synthesized eight types of high-density single-atom catalysts, including platinum (Pt), cobalt (Co), and nickel (Ni), using this technology. They emphasized that the "platinum single-atom catalyst-carbon nano onion" produced with this method achieved six times higher hydrogen production efficiency compared to conventional methods, and maintained high efficiency even when the use of expensive metals was drastically reduced.

Professor Kim stated, "The technology developed by our team is an ultra-fast, integrated process for synthesis and single-atom catalyst functionalization that reduces energy consumption by more than 1,000 times compared to conventional thermal processing. We expect it will contribute to accelerating commercialization in various application fields such as hydrogen energy, gas sensors, and environmental catalysts."

Meanwhile, this research was conducted with Do-Kyung Jeon, PhD candidate, and Ha-Min Shin, PhD (currently a postdoctoral researcher at ETH Zurich) from the KAIST Department of Materials Science and Engineering, and Jun-Hoe Choi, PhD (currently a researcher at SK hynix) from the KAIST School of Electrical and Electronic Engineering, as co-first authors. Professors Choi Sungyul and Kim Il-Doo served as corresponding authors.

The research findings (paper) were published as a cover article in the September issue of "ACS Nano," a journal issued by the American Chemical Society (ACS) specializing in nanoscience and chemistry.

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