SDGs

Kyungpook National University, Investigating the Principle of Hydrogen Generation by Dissolving Water in Photocatalysis

A Korean research team has found out the principle of hydrogen generation by dissolving water in photocatalysis. It is assessed that it has provided a short-term for improving the efficiency of hydrogen production.

Kyungpook National University said that it has found out the principle of hydrogen fission from photocatalytic water in cooperation with Pohang University of Science and Technology, Institut fuer Technische Chemie, Institut Químic de Sarrià (IQS)—School of Engineering, Universitat Ra-mon Llull, etc

It revised the principle of photo-catalyst water decomposition hydrogen generation, which had been taken for granted in related fields of research, and presented new possibilities to increase hydrogen production efficiency.

Water decomposition using photocatalysts is a phenomenon in which sunlight-induced photocatalysts produce both oxygen and hydrogen from water. Over the past 50 years, hundreds of optical catalysts have been developed for water degradation, and academic circles have compared and evaluated the water-dissolving performance of optical catalysts simply in terms of oxygen and hydrogen generation.

The problem is that when water breaks down into oxygen and hydrogen, interference occurs with each other, and the speed of one reaction determines the speed of the other. Until now, the government has adopted a method that inhibits one of the two responses and causes only other reactions, separating the individual reactions of oxygen and hydrogen, rather than a comprehensive evaluation, and separately assessing them.

The most representative example is the use of Ag(I), which has been used to measure the performance of photo-catalyst water decomposition reactions by inhibiting hydrogen generation only in the process of changing the Ag(I) into silver.

Using photoelectrochemical techniques and electro-spin resonance, the research team found that  Ag(I) turns into Ag(II), which suppresses some of the oxygen as well as hydrogen generation.

This means that existing photocatalysts' ability to generate oxygen has been undervalued than it is, and the production efficiency of photo-catalyst water-dissolving hydrogen that is currently in a state of return can be higher.

"Most research on photocatalytic hydrogen generation is focused only on improving the fragmented performance of photocatalytic materials, and understanding of the photocatalytic water decomposition itself is greatly overlooked," Professor Hyun Woong Park said. "We hope that the new knowledge of photocatalytic materials and water decomposition will contribute to the research on the generation of highly efficient photocatalytic hydrogen."

"The ultimate goal of developing artificial photosynthetic photocatalytic materials that exceed the limit of photosynthesis is to synthesize gasoline consisting of eight carbons using only sunlight, water, and carbon dioxide. If this goal comes true, a car running on carbon dioxide will no longer be a dream."

A research team led by Professor Hyun Woong Park of the Department of Energy Engineering at Kyungpook National University and Dr. Kang Un-seok has developed a high-efficiency artificial photosynthetic photocatalytic source material that can convert carbon dioxide into multi-carbon aliphatic acid.

Artificial photosynthesis research that converts carbon dioxide into carbon compounds using sunlight is related to renewable energy and is a field where technological competition between countries is very fierce. Most artificial photosynthesis technologies require the use of electrical energy as an auxiliary energy, and the electrocatalyst reaction can produce only acetic acid, ethylene, and ethane composed of two carbons.

Professor Park's team succeeded in producing copper-iron oxide photocatalytic materials using electrodeposition, and the developed photocatalytic materials can produce carbon compounds consisting of six carbons with three elements: sunlight, water, and carbon dioxide without using electric energy. In most cases, natural photosynthesis and artificial photosynthesis proceed with 1% efficiency. The photocatalytic materials developed by Professor Park's team are expected to be advantageous for commercialization with high efficiency and stability as they can produce aliphatic acids (formic acids) consisting of one carbon for four months while continuously maintaining them for up to 10%.

The results of this study were published as a cover paper on September 13 of the "ACS Energy Letters," a renowned international journal in the energy field. Related photocatalytic manufacturing technologies have completed Korean patent registration and are currently undergoing a US patent registration review.

Professor Hyun Woong Park said, "Currently, research on a photocatalytic system that can synthesize expensive multi-carbon compounds in large capacity is underway, and it is expected that core material technology and mass technology strategies will be secured within the next five years. In addition, through the currently developed photocatalytic modification, we expect that polyketones and aromatic compounds necessary for the production of photosensitive solutions, which are recently regulated substances for exports to Japan, will be produced solely from carbon dioxide and water, he said.