A study published in ACS Applied Materials & Interfaces, the journal of the American Chemical Society, describes a new method for producing hydrogen peroxide (H.2O2) without releasing carbon dioxide (CO2), one of the world’s major greenhouse gases and one of the world’s most produced chemicals.
Hydrogen peroxide is used to bleach cloth, paper and paper, and to whiten teeth. It is also used as a fuel for satellite control, and as a disinfectant or disinfectant by hospitals. About 2 million metric tons are produced annually.
“To understand the impact of our findings, it is important first of all to remember the importance of H.2O2 in the chemical industry and the way it is now produced,” said Ivo Freitas Teixeira, professor of chemistry at the State University of São Carlos (UFSCar) in the State of São Paulo, Brazil. He has a PhD in inorganic chemistry from the University of São Paulo (USP) and was a Humboldt Fellow at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany, between 2019 and 2021.
All these peroxides are produced by a process related to anthraquinone [a compound derived from hydrolysis of anthracene, a toxic substance]. In this process, anthraquinone is reduced and oxidized to form H2O2. The drawbacks of this method are the high cost of anthraquinone and the use of precious metals such as Pd. [palladium]and H2 [hydrogen] such as reducing agents. This hydrogen is produced by steam-methane conversion, which involves high temperatures and releases CO2which contributes to global warming,” he said.
In the study, the researchers produced peroxide from oxygen (O2) using photocatalysis to guide the process. In photocatalysis, catalysts (substances that accelerate chemical reactions) are activated by visible light instead of high temperature or pressure. Another advantage of their method was the use of carbon nitride as a photocatalyst. This material consists only of carbon and nitrogen, both of which are abundant on the surface of the Earth, and can be absorbed into the visible region, which corresponds to about 45% of the solar radiation. It is therefore possible to use sunlight instead of artificial lighting, making the process more cost-effective.
After testing different reaction conditions, the researchers arrived at a system with a good rate of H2O2 production. “We have reached O2 Photocatalytic reduction in which the source of hydrogen was water in the reaction zone or a sacrificial reagent, usually glycerol, a product of biodiesel production,” Teixeira explained.
In this system, carbon nitride is used as a semiconductor to separate the charges when bathed in light, promoting reduction and changing oxidation. The O2 is reduced to H2O2 and the sacrificial reagent (glycerol) is oxidized. The H2O2 is available without the need to use H2 and therefore without CO2 production.
“The way we had to go in our research until we reached the result described in the published article was long because we discovered that at the same time as H.2O2 produced on top of the photocatalyst, it can also be destroyed,” said Teixeira. “We had to do several experiments and constantly change the photocatalyst in order to promote the formation of H.2O2 and avoid decay. To understand how H2O 2 decomposes on carbon nitride was very important to enable us to develop a suitable photocatalyst for this reaction. “
Teixeira leads a research group at UFSCar supported by FAPESP. He is the final author of the article, which is also co-signed by Andrea Rogolino (University of Padua, Italy); Ingrid Silva, Nadezda Tarakina and Markus Antonietti (Max Planck Institute of Colloids and Interfaces, Germany); and Marcos da Silva and Guilherme Rocha (UFSCar).