Converting CO2 to solid carbon yields benefits for batteries and more

Developing an economy that produces net zero carbon emissions not only involves “capturing” carbon dioxide but changing it and putting it to use in new forms. 

Engineers at Washington University in St. Louis are heavily in the business of “carbon conversion” with multiple projects working on systems to pull carbon dioxide in and put it to good use.

Most recently, the Department of Energy (DOE) has awarded $29 million in grants for “carbon management” technologies, including $1.5 million of those funds going to Xinhua Liang, professor of energy, environmental & chemical engineering in WashU's McKelvey School of Engineering. 

Previously, Liang received $2 million from the DOE to convert CO₂ to concrete products, and this continues that work, with a twist. Liang and his colleagues have developed a thermocatalytic process that could yield useful parts for increasingly ubiquitous lithium-ion batteries that power electric cars and other devices. Liang will fine-tune this process with his co-principal investigator, Miao Yu, a professor in the Department of Chemical and Biological Engineering at the University at Buffalo. 

The grant will fund Liang’s development of a low-carbon process to convert CO₂ to valuable high-quality carbon nanotubes (CNTs). These nanotubes have “similar properties as commercial CNTs,” noted Liang, making them not only useful as potential anodes in batteries but doing so at a much more affordable price, a key component to scaling up these technologies. 

Lithium-ion batteries are composed of three main components: the anode (negative terminal), cathode (positive terminal) and electrolyte solution in between. The cathodes are typically made of lithium metal oxide, but the anode uses graphite, which is a form of carbon. CNTs are expected to have better performance than graphite as an anode material in lithium-ion batteries. But CNTs can be expensive to apply.

But with Liang’s thermocatalytic process, they’ve drastically reduced that expense. They are taking CO₂, converting it into an intermediate molecule and then a final conversion to a carbon nanotube with high capacity and high conductivity that makes it ideal for batteries. Carbon nanotubes can also be used in making composite metals and can be used in polymers and concrete products that Liang is also working on.

“In order to commercialize this process, there is still a long way to go,” he adds.

They will deliver a laboratory-scale prototype system capable of producing 20 grams per day of CNTs, according to the grant. Liang estimates that it could be ready for commercial use in a decade. But so far, they have found a way to lower the cost of CNT production from $100 per kilogram to less than $10.

“This is the main advantage of our technology,” Liang said.

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