Battery-like device pulls CO₂ from air using electricity and saltwater chemistry - Energy & Green Tech

U. of I. engineers Paul Rozzi, professor Kyle Smith and Jeong Le have developed a new battery-type device that captures CO₂ from the air. Credit: Michelle Hassel

Engineers have developed a new way to pull carbon dioxide directly from the atmosphere using a process similar to charging and discharging a battery—an advance that could help address the planet's excess CO₂ problem.

A new collaborative study between scientists at the University of Illinois Urbana-Champaign and Toyota focuses on direct air capture, a technology designed to reduce new emissions and remove CO₂ that has already accumulated in the atmosphere. Instead of using heat to absorb and release CO₂, as many carbon capture methods do, the new method uses electricity and water-based chemistry within an electrochemical device.

The results of the study by mechanical engineering and science professor Kyle Smith, Illinois graduate students Paul Rozzi and JeongA Lee, and Chip Roberts and Tim Arthur from the Toyota Research Institute of North America are published in the journal Environmental Science & Technology.

Targeting carbon already in the air

Most climate scientists agree that even with aggressive cuts in current emissions, the world is unlikely to meet climate targets without also removing some of the CO₂ that has already accumulated over decades. Most current carbon capture technologies work at point sources—places like power plant smokestacks where CO₂ emissions are high.

"Point source methods are important, but they don't deal with the vast amount of CO₂ already mixed into the air at much lower concentrations," Smith said. "Our work is aimed at that legacy problem."

A pH swing powered by electricity

A key advance of this work is the device's use of specialized potassium-stabilized manganese dioxide electrodes and a specific method for moving charged particles. In the lab, the team uses an electrochemical cell to change the pH of a saltwater solution. In one step, the solution is made more alkaline, allowing it to absorb CO₂ from the air effectively. In another step, the solution is made less alkaline again, which causes the CO₂ to bubble back out in a purified form, ready for storage or reuse.

"What's innovative about our work is that we use proton-intercalation electrodes in what we call a cation-compensated cell," Smith said. "That design lets us operate in an alkaline range where CO₂ is much more soluble, which is crucial for making direct air capture practical."

Designing the cycle for efficiency

To make the system as efficient as possible, the team treated the process much like a classical thermodynamic cycle, in the spirit of the cycles engineers use to design power plants. Instead of thinking in terms of pressure and volume, the team mapped out the cycle using dissolved inorganic carbon and potassium ion concentrations in the solution.

"By framing our process as a thermodynamic cycle in this particular space, we could see where energy was being wasted and how to redesign the cycle," Lee said.

Mixing losses remain a hurdle

While the early results are promising, the team said there is still work to do before this technology can be deployed on a large scale. For example, the device uses two liquid streams that ideally should remain separate. In practice, some mixing occurs when flows are switched, reducing efficiency.

"Interstream mixing is one of the biggest issues we're dealing with now," Rozzi said. "If we can limit that mixing or design around it, we can significantly improve both energy consumption and productivity."

"Our work with Professor Smith and the U. of I. team on electrochemical direct air capture provides useful insights into how materials, electrochemistry and process design can be combined to address challenging CO₂ separation problems," Roberts said. "This type of early-stage research supports Toyota's broader effort to explore innovative pathways toward long-term decarbonization." 

Provided by University of Illinois at Urbana-Champaign 

by Lois Yoksoulian, University of Illinois at Urbana-Champaign

edited by Gaby Clark, reviewed by Andrew Zinin 

Source: Battery-like device pulls CO₂ from air using electricity and saltwater chemistry