New study presents highly-active ozygenated groups in carbon materials for oxygen reduction to hydrogen peroxide

Hydrogen peroxide (H₂O₂) has found many applications in the modern industry, including acting as a green oxidant in disinfectants, bleaching agents, sanitizing agents, chemical synthesis, and even as a potential energy carrier. A new catalyst, which enables on-site generation of H₂O₂ has been developed. It has gained much attention in both academia and industry as a quick, simple and inexpensive method to produce H₂O₂, which is in constant demand.

A research team, led by Professor Jong-Beom Baek in the School of Energy and Chemical Engineering at UNIST has developed a carbon-based high-efficiency electrochemical catalyst for use to produce H₂O₂. Because it is carbon-based, it is inexpensive and requires no complicated process, and thus allows for on-site production of H₂O₂. This study is particularly meaningful as it has also identified the active sites where catalytic reactions occur.

Hydrogen peroxide (H₂O₂), commonly used as a disinfectant in pharmacies, is an eco-friendly oxidizer used as licorice in various industrial processes. In addition, hydrogen fuel cells used in electric vehicles may be used instead of hydrogen, and demand is expected to increase rapidly in the future. However, the anthraquinone process, which produces hydrogen peroxide, is complex, large, and consumes high energy. Therefore, there is a cost of transporting and storing the produced hydrogen peroxide to the site, and there is also a problem of managing highly reactive hydrogen peroxide at a high concentration.

The research team focused on the electrochemical method as a method for producing hydrogen peroxide to replace the anthraquinone process. This is to induce oxygen reduction to hydrogen peroxide by developing high-efficiency catalysts based on inexpensive carbon materials. They synthesized the catalyst by attaching functional groups such as quinone, ether, and carbonyl to thin carbon-based materials such as graphene. As a result, it succeeded in synthesizing a catalyst with a high efficiency of 97.8%.

The study also identified the exact active site where the catalytic reaction takes place. The carbon oxide-based material previously reported as a hydrogen peroxide generating catalyst contains various oxygen functional groups, so it is not known exactly which functional group is the active site of the catalyst. This time, the exact active sites were analyzed by synthesizing carbon oxide materials with separate oxygen functional groups such as quinone, ether, and carbonyl. As a result, it was confirmed that the carbon oxide material having many quinone functional groups shows the highest catalytic efficiency.

“This study is to increase understanding of the active sites important for hydrogen peroxide production,” says Gao-Feng Han, the lead author of the study. “In addition to the experiment, the density function theory calculation method was used to confirm that the quinone functional group had high catalytic activity and very small overvoltage in the hydrogen peroxide production reaction (ORHP).”

“Our findings provide guidelines for designing carbon-based catalysts, which have simultaneous high selectivity and activity for H₂O₂ synthesis,” says Professor Baek. “Through this, it is possible to reduce the cost required for transportation and storage of hydrogen peroxide and to expand the range of use of hydrogen peroxide in various industrial fields.”