By Yosef Scher, Senior Science and Technology Editor
Earlier this month, scientists at Brookhaven National Laboratory made a significant breakthrough in combating our global warming crisis. Jingguang Chen, a professor of chemical engineering at Columbia University with a joint appointment at Brookhaven Lab, led a team of scientists who developed a method to convert carbon dioxide into carbon nanofibers. The idea of capturing carbon dioxide and converting it into another material is a phenomenon that has been around for a while. People have devised various ways to rid our atmosphere of carbon dioxide, such as capturing it straight from the air and storing it underground or converting it into another form of fuel. However, both of these methods tend to be ineffective because gaseous carbon dioxide usually leaks from its storage containers, and the fuels that gaseous carbon dioxide is converted into frequently release the carbon dioxide right back into the atmosphere. The novelty of Chen’s work is that he and his team have developed a way that converts carbon dioxide into solid carbon materials, like carbon nanotubes and nanofibers.
Before delving into how Chen and his team devised this new process, it is essential to understand why scientists are actively looking for ways to reduce carbon dioxide from our atmosphere. While some carbon dioxide is normal in Earth’s atmosphere, too much of it can warm the planet, causing climate change. Since the start of the Industrial Revolution in the mid-1700s, “[h]uman activities have raised the atmosphere’s carbon dioxide content by 50%” in less than a couple of centuries. Furthermore, according to the Environmental Protection Agency, carbon dioxide emissions have increased by about 90% since 1970, with emissions from fossil fuel combustion and industrial processes contributing to about 78% of the total increase in greenhouse gas emissions from 1970 to 2011. Without reversing the effects of climate change, which include more deaths and illnesses from increasingly frequent extreme weather events, such as heatwaves, storms, and floods, people will continue to suffer.
How exactly did Chen and his team find a way to convert carbon dioxide into solid carbon materials, like carbon nanotubes and nanofibers? To do this, the researchers used a two-step electrochemical and thermochemical reaction conducted at relatively low temperatures and ambient pressure. Using their knowledge of organic chemistry, the scientists realized that carbon monoxide would be a much better-starting material than carbon dioxide to make a carbon nanofiber. As such, they searched for ways to synthesize carbon monoxide from carbon dioxide, which would ultimately be used to make the carbon nanofiber. After much research and trial and error, Chen and his team found that they could use an electrocatalyst made of palladium supported on carbon to split carbon dioxide and water into carbon monoxide and dihydrogen gas, for the first step of the reaction. For the second step of the reaction process, Chen and his team discovered that they could use a heat-activated thermocatalyst made of an iron-cobalt alloy to convert carbon monoxide into a carbon nanofiber. By coupling electrocatalysis and thermocatalysis, the scientists achieved the desired outcome that none of the two processes could have done alone.
In addition to their discovery of the coupling catalysts’ two-step process reaction, Chen and his colleagues found that the coupled catalysts can be easily recycled, demonstrating that this process could occur commercially because of the catalysts’ efficiency and ease of reusability. The scientists used transmission electron microscopy to see that it is easy to recycle the catalytic metal because the catalyst gets pushed up and away from the surface as the carbon nanofiber grows. According to the researchers, “[the] ease of catalyst recycling, commercial availability of the catalysts, and relatively mild reaction conditions for the second reaction all contribute to a favorable assessment of the energy and other costs associated with the process.”
All in all, Chen and his team are optimistic that their findings will “[open] a door for decarbonizing [carbon dioxide] into valuable solid carbon products while producing renewable [dihydrogen]” renewable fuel that could potentially lead to harmful carbon emissions within the coming years.