If we are to avoid the projected increase in world temperature of more than 1.5 degrees Celsius this century, it is not enough to simply reduce carbon dioxide emissions — we must also make every effort to reduce the amount of carbon dioxide already available in the atmosphere. Inspired by the role of the ocean as an effective natural carbon sink, scientists from the South Korean national Institute of science and technology Ulsan (UNIST) in collaboration with experts from the Georgia Institute of Technology (USA) have developed a new filtration system that absorbs CO2 and produces electricity from it and usable hydrogen fuel.
The new hybrid Na-CO2 system is essentially a large liquid battery. The system consists of an anode of metal sodium, which is placed in an organic electrolyte, and a cathode placed in a special aqueous solution. Both fluids are separated by a sodium membrane Super Ionic Conductor (NASICON).
When a stock of CO2 is fed into the aqueous solution, it reacts with the cathode, causing the solution in the tank to oxidize, which in turn leads to electricity generation and hydrogen production. Scientists note that during the tests the efficiency of conversion of CO2 into useful products was 50 percent, and the system itself was quite stable and worked more than 1000 hours in full load without any damage to the electrodes. Unlike other recycling systems, the developers say, their installation does not produce any harmful emissions. The remaining CO2 in the tank settles and is extracted from the electrolyte in the form of old baking soda.
“Carbon capture, use and storage technologies have recently received increased attention because they have the potential to help us cope with global warming. The key to these technologies is the simple conversion of chemically stable CO2 molecules into other materials. Our new system relies on the mechanism of CO2 dissolution,” comments Professor Gantt Kim, the lead author of the study, whose results were published in the journal iScience.
The Hybrid Na-CO2 system, developed by engineers and scientists, is not the only concept for the collection, storage and transfer of carbon dioxide, but it is not yet clear whether these technologies can become practical enough on a large scale to have a significant impact on the amount of CO2 in the atmosphere. For example, the technology of direct capture of carbon dioxide, developed by Climeworks, looks at the moment one of the most promising. But when you consider that for the year it is able to process only 150 tons of CO2 with annual emissions of 40 billion tons, it looks like an attempt to draw water from a sinking ship with an ordinary mug.
And yet the developers of Hybrid Na-CO2 system note that their system has room to improve any component. A “cherry on the cake” is the possibility of producing electricity and hydrogen fuel, which can be used, for example, in hydrogen transport.