Producing Hydrogen with Only Sunlight and Water? Development of Doping Technology to Enhance 'Artificial Leaf' Efficiency

UNIST Professor Jang Ji-hyun's Team Maximizes Germanium Doping Effect on Iron Oxide Without Carbon Emissions

Schematic diagram of hydrogen production using artificial leaves based on iron oxide (Fe2O3).

[Asia Economy Yeongnam Reporting Headquarters Reporter Kim Yong-woo] A technology that produces hydrogen without carbon gas emissions using only sunlight and water has been developed.

This technology maximizes hydrogen production efficiency using an "artificial leaf."

The artificial leaf is a device that mimics the principle of plant photosynthesis to produce hydrogen by absorbing sunlight in water. Since it produces clean fuel hydrogen without emitting carbon gases, it is expected to accelerate the carbon-neutral era.

Ulsan National Institute of Science and Technology (UNIST) announced on the 29th that Professor Jang Ji-hyun’s team from the Department of Energy and Chemical Engineering developed a manufacturing technology that dopes germanium into the artificial leaf to increase hydrogen production efficiency.

Although germanium is theoretically an excellent dopant, it was less effective than other dopants in practice. The research team identified the reason and improved the efficiency by more than three times compared to before.

The core of the artificial leaf system is the photocatalyst. It plays the role of absorbing sunlight and generating electrons, similar to plant chlorophyll.

Iron oxide, a rust component of iron, is considered the main material for the photocatalyst. It is inexpensive and, above all, stable in water. However, iron oxide has low electrical conductivity, so an additive (dopant) is needed to enhance it.

Schematic diagram of the manufacturing method for porous iron oxide doped with germanium.

Germanium is also one of the main dopant candidates. However, there has been a question as to why its actual effect is not as great as the theoretical expectation, so it has not been widely studied.

The research team found the cause during the photocatalyst electrode manufacturing process. Tin (Sn) components penetrate into the photocatalyst during high-temperature heat treatment, damaging the internal structure.

Tin is a component contained in the transparent electrode (FTO) attached to the photocatalyst.

This study newly revealed that the presence of both germanium and tin inside the photocatalyst significantly damages the internal structure.

Professor Jang’s team developed a germanium oxide film coating method that prevents tin from being doped together during heat treatment.

This also solved the problem of the photocatalyst’s surface area decreasing after heat treatment, resulting in a threefold increase in hydrogen production efficiency.

(From left) Researcher Gwak Myung-jun, Professor Jang Ji-hyun, Researcher Yoon Ki-yong, Researcher Park Joo-hyung.

Yoon Ki-yong, first author and a doctoral researcher in the Department of Energy and Chemical Engineering at UNIST, stated, “With a simple surface treatment, we were able to instantly solve the problems of low electrical conductivity and surface area reduction after heat treatment, which were issues of iron oxide photocatalyst technology.”

Also, the developed coating method is so simple that it only requires dipping in a trace amount of germanium solution and then removing it, making it advantageous for commercialization.

Professor Jang Ji-hyun explained, “The existing artificial leaf technology composed of single iron oxide electrodes had a limitation where hydrogen production efficiency mostly remained between 1% and 3%. The 5% efficiency demonstrated in this study is the world’s highest level compared to existing technologies.”

Professor Jang added, “Iron oxide is a material that can theoretically achieve 15% hydrogen production efficiency, making it an excellent photocatalyst candidate not only in terms of cost but also technical potential. Our goal is to develop more sophisticated manufacturing technologies and achieve commercialization within a few years.”

This research was conducted in collaboration with Professor Seok Sang-il and Professor Lee Jun-hee from the Department of Energy and Chemical Engineering at UNIST. The research results were published in the July 14 issue of Nature Communications.

The research was supported by the National Research Foundation of Korea (NRF) through the ‘Mid-career Researcher Support Project,’ the ‘Development Project for Photoelectrochemical Hydrogen Production Technology and System for On-site Hydrogen Refueling Stations,’ and funding from S-Oil.

This content was produced with the assistance of AI translation services.