If we're going to reach the goal of keeping Earth from warming more than 1.5° C (2.7° F) this century, it's not enough to just reduce our carbon dioxide emissions – we need to actively clean it out of the atmosphere too. Inspired by the ocean's role as a natural carbon sink, researchers at Ulsan National Institute of Science and Technology (UNIST) and Georgia Tech have developed a new system that absorbs CO2 and produces electricity and useable hydrogen fuel.
The new device, which the team calls a Hybrid Na-CO2 System, is basically a big liquid battery. A sodium metal anode is placed in an organic electrolyte, while the cathode is contained in an aqueous solution. The two liquids are separated by a sodium Super Ionic Conductor (NASICON) membrane.
When CO2 is injected into the aqueous electrolyte, it reacts with the cathode, turning the solution more acidic, which in turn generates electricity and creates hydrogen. In tests, the team reported a CO2 conversion efficiency of 50 percent, and the system was stable enough to run for over 1,000 hours without causing any damage to the electrodes. Unlike other designs, it doesn't release any CO2 as a gas during normal operation – instead, the remaining half of the CO2 was recovered from the electrolyte as plain old baking soda.
"Carbon capture, utilization, and sequestration (CCUS) technologies have recently received a great deal of attention for providing a pathway in dealing with global climate change," says Professor Guntae Kim, lead researcher on the study. "The key to that technology is the easy conversion of chemically stable CO2 molecules to other materials. Our new system has solved this problem with CO2 dissolution mechanism."
This Hybrid Na-CO2 System is far from the only carbon capture system out there, but it remains to be seen whether these technologies can ever become practical enough at large scales to have much of an impact. Climeworks' direct air capture system is one of the most promising at the moment, but when it only removes 150 tons of CO2 a year (compared to the 40 billion tons released into the atmosphere annually) it feels like bailing a sinking ship with a plastic cup.
But, the team says, there's still room for improvement with every component of the new design. And the icing on the cake could be the system's ability to also produce renewable electricity and hydrogen fuel, which could be used to power hydrogen cars.
The research was published in the journal iScience.
