New Materials: Understand The Process Of Scientists Converting Carbon Dioxide Into Carbon Nanofibers

The US Department of Energy announced that researchers from Brookhaven National Laboratory and Columbia University have jointly developed a new technology coupling electrochemical and thermochemical reactions, which can convert carbon dioxide into carbon nanofibers. This material has a wide range of properties and many potential uses.

This technology can lock carbon in solid form under relatively low temperature and environmental pressure to offset carbon emissions or even achieve negative carbon emissions. This research was recently published in Nature Catalysis.

"You can put carbon nanofibers into cement," said Chen Jingguang, a professor of chemical engineering at Columbia University and one of the corresponding authors of the paper. "This will lock carbon in concrete for 50 years, or even longer."

In addition, the process can also be used to produce hydrogen, which is a promising alternative fuel and can achieve zero emissions when used.

The idea of capturing carbon dioxide or converting it into other materials to cope with climate change is not new, but simply storing carbon dioxide will lead to leakage. Many carbon based chemicals or fuels generated by the conversion of carbon dioxide will be put into use immediately, resulting in carbon dioxide being released back into the atmosphere.

Chen Jingguang said, "We are trying to convert carbon dioxide into a solid and useful substance with added value."

This solid carbon material includes carbon nanotubes and nanofibers with a size of one billionth of a meter, and has many attractive characteristics, including strength, thermal conductivity and conductivity. However, extracting carbon from carbon dioxide and transforming it into these precision materials requires a temperature of more than 1000 ℃, which is unrealistic for large-scale emission reduction.

In contrast, this process developed by researchers can be realized at about 400 ℃, and can be used in the industrial field.

Xie Zhenhua, the first author of the paper and a researcher at Brookhaven National Laboratory and Columbia University, said: "If the reaction is divided into several sub reaction steps, we can consider using different kinds of energy inputs and catalysts to make every part of the reaction work."

Researchers first realized that carbon monoxide is a better raw material than carbon dioxide in the manufacture of carbon nanofibers, so they began to find an effective way to produce carbon monoxide from carbon dioxide.

The team's early work led them to use a commercially available electric catalyst made of carbon supported palladium to decompose carbon dioxide and water into carbon monoxide and hydrogen.

In the second step, scientists turned to a thermally activated thermal catalyst made of iron cobalt alloy. The latter operates at a temperature of about 400 ℃, which is much milder than the temperature required to directly convert carbon dioxide into carbon nanofibers. They also found that adding some additional metal cobalt can promote the formation of carbon nanofibers.

Chen Jingguang said, "We are realizing the goal that can not be achieved by these two processes alone through the process of connecting electro catalysis and thermal catalysis in series."

In order to understand how these catalysts work, researchers have carried out a wide range of experiments, including computational modeling, physical and chemical characterization, and microscopic imaging using an electron microscope.

In modeling, scientists use density functional theory to analyze the atomic arrangement and other characteristics of the catalyst when it interacts with the active chemical environment, so as to accurately understand the role of the catalyst in the reaction process.

At the same time, the researchers analyzed and confirmed that with the growth of carbon nanofibers, the catalyst was pushed away from the surface, so that the catalytic metal could be recovered more easily.

"Leaching metals with acid will not damage carbon nanofibers, so we can concentrate metals and recycle them as catalysts," Chen Jingguang said.

The recyclability and commercial availability of the catalyst, as well as the relatively mild reaction conditions of the second reaction, can help to evaluate the energy and other costs associated with the process.

The research results show that this tandem strategy opens the door to decarbonizing carbon dioxide into valuable solid carbon products and producing renewable hydrogen at the same time.

The researchers said that further, if these processes are driven by renewable energy, the result will be real negative carbon emissions, opening up a new path for mitigating carbon emissions.