'Stepwise Charge Transfer' Inspired by Leaves... Producing Hydrogen Peroxide Using Only Sunlight [Reading Science]

UNIST Develops High-Efficiency, Highly Durable Artificial Photosynthesis Electrode

Mimics Plant Photosynthesis to Minimize Charge Loss... Achieves World-Class Efficiency

Korean researchers have developed an artificial photosynthesis electrode that mimics the principles of photosynthesis in plant leaves to produce hydrogen peroxide, a high value-added chemical, using only sunlight. The team implemented a "stepwise" charge transfer structure, effectively addressing both chronic issues of energy loss and low durability found in conventional technologies.

Comparison of Charge Transfer Structures and Operating Principles of Dye-Sensitized Photoelectrochemical Cells (DSPEC). a) The conventional structure where the dye is in direct contact with the electrolyte, resulting in significant electron loss. b) A structure with an added protective layer, but still experiencing potential losses during the charge transfer process. In contrast, c) is the embedded structure developed by the research team, which minimizes energy loss by stepwise separating the charge transfer paths with nickel foil in between. d) The actual operating schematic, illustrating the process where water is decomposed to generate oxygen at the electrode exposed to sunlight, while hydrogen or hydrogen peroxide is produced at the opposite electrode. Provided by UNIST

On May 7, UNIST (Ulsan National Institute of Science and Technology) announced that a research team led by Professor Tae-Hyuk Kwon of the Department of Chemistry and Professor Ji-Wook Jang of the Department of Energy and Chemical Engineering has developed a dye-sensitized artificial photosynthesis electrode with reduced charge transfer losses and enhanced durability.

The artificial photosynthesis electrode is a core component that uses sunlight to produce fuels and chemicals such as hydrogen or hydrogen peroxide from water. A key feature of this technology is its environmentally friendly system, which uses organic dyes that absorb light, similar to plant chlorophyll, but does not rely on harmful substances such as lead.

The research team designed a new structure in which the dye layer and redox mediator are embedded within a nickel foil. In this structure, charges generated in the dye upon exposure to light are transferred in a stepwise manner: from the dye, to the redox mediator, to the nickel foil, and finally to the catalyst.

Much like descending a staircase, the charges move sequentially, minimizing energy loss and back reactions along the way. This principle is inspired by the photosynthetic mechanism in plant leaves, where charges are stably transferred through multiple electron transport proteins.

"Reduced Charge Loss"... Achieves World-Class Efficiency

Traditional dye-sensitized photoelectrodes face problems where the dye, being in direct contact with the liquid electrolyte, is easily decomposed or where charges disappear midway. The research team significantly improved durability by using the nickel foil structure to prevent direct contact between the dye and the electrolyte.

The developed electrode achieved a Faradaic efficiency of 98% in water-splitting reactions. This means that out of 100 charges generated by the dye, approximately 98 were actually used in the chemical reaction.

Photo of the research team. (From left) Professor Taehyuk Kwon, Professor Jiuk Jang, Researcher Junhyuk Park, Researcher Kyunglim Kim, Researcher Jinyoung Lee. Provided by UNIST

Notably, when applied to a hydrogen peroxide production system, the electrode achieved a solar-to-fuel (STF) conversion efficiency of 4.15% using only sunlight, without any external voltage. According to the research team, this is a world-leading record. It was also confirmed that the system operated stably for over 150 hours without any performance degradation.

Hydrogen peroxide is a high value-added chemical widely used in the semiconductor, medical, sterilization, and eco-friendly chemical processing industries. The research team emphasized that the industrial potential is significant, especially since hydrogen peroxide has an economic value about 20 times higher than that of hydrogen.

Junhyuk Park, Ph.D. of UNIST, explained, "This technology applies the way plants transfer charges with almost no loss to the design of artificial devices."

Professor Tae-Hyuk Kwon stated, "Through interfacial design, we have simultaneously addressed both the efficiency and lifespan issues of dye-sensitized systems," adding, "We have established a technological foundation for producing high value-added chemical feedstocks with an eco-friendly system free of harmful substances."

The results of this research were published in the international journal Advanced Functional Materials in the field of materials science on April 13.

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