An innovative technology has been developed to produce ammonia and glycolic acid, used as a cosmetic raw material, from waste water and waste plastic.

A research team led by Professor Seung-Ho Cho and Professor Myung-Hoon Song from the Department of Materials Science and Engineering at UNIST announced that they have developed a new photoelectrochemical system that uses solar electricity to synthesize ammonia without emitting carbon dioxide, while simultaneously producing glycolic acid, a high value-added material, from waste plastic.

Ammonia is an essential compound produced in large quantities worldwide, second only to sulfuric acid, but the existing production process, the Haber-Bosch process, produces high carbon dioxide emissions, requiring the development of sustainable alternative technologies.

The system developed by this research team converts nitrite (NO₂) in wastewater into ammonia using solar energy, while at the cathode, it performs a couple reaction to oxidize ethylene glycol obtained from waste plastic into glycolic acid.

The research team achieved world-leading levels in energy efficiency and production speed. The bipolar energy efficiency was 52.3%, breaking the highest reported record, and the ammonia production speed was 146μmol/cm2h, far exceeding the commercialization standards of the U.S. Department of Energy. This is a 46% improvement over the previous record.

Additionally, the research team developed a catalyst (RuCo-NT/CF) designed to selectively reduce nitrite, which requires less energy, among nitrate and nitrite in wastewater.

By utilizing the glycolic acid generation reaction instead of the existing energy-consuming oxygen generation reaction, we have succeeded in further reducing the required electric energy.

The system uses perovskite solar cells, which have higher efficiencies than conventional silicon solar cells, which increases the photocurrent density and thus the ammonia production rate.

The research team verified the commercialization possibility using low-level radioactive wastewater and PET bottle extracts, and confirmed high production efficiency even under the given conditions.

Professor Song Myung-hoon emphasized, “This study is an important achievement that demonstrates the possibility of a sustainable technology that can produce ammonia and glycolic acid without emitting carbon dioxide.”

Professor Cho Seung-ho said, “It is significant in that it presents a carbon-neutral energy solution using solar power and waste.”

This study was conducted with support from the Basic Research Laboratory of the Ministry of Science and ICT, and the results were published in the international academic journal Nano Letters* on February 19.