If we want to avoid a global temperature rise of more than 1.5 degrees Celsius predicted already this century, it is not enough just to reduce carbon dioxide emissions - we must also make every effort to reduce the existing carbon dioxide in the atmosphere. Inspired by the ocean's role as an effective natural carbon sink, scientists at the Ulsan National Institute of Science and Technology (UNIST), in collaboration with the Georgia Institute of Technology (USA), have developed a new filtration system that captures CO2 and produces electricity from it and is usable hydrogen fuel.
The new Hybrid Na-CO2 System is essentially a large liquid battery. The system consists of a metallic sodium anode, which is placed in an organic electrolyte, and a cathode, placed in a special aqueous solution. The two fluids are separated by a Super Ionic Conductor (NASICON) sodium membrane.
Scheme for converting CO2 into electricity and hydrogen fuel.
When a supply of CO2 is added to an aqueous solution, it reacts with the cathode, causing the solution in the tank to oxidize, which in turn generates electricity and produces hydrogen. Scientists note that during the tests, the efficiency of converting CO2 into useful products was 50 percent, and the system itself was quite stable and worked for more than 1000 hours at full load without any damage to the electrodes. Unlike other recycling systems, the developers say, their installation does not produce any harmful emissions during operation. The remaining CO2 in the tank settles and is recovered from the electrolyte as old baking soda.
Developed by engineers and scientists, the Hybrid Na-CO2 System is not the only system concept for collecting, storing and transferring 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 CO2 content in atmosphere. For example, Climeworks' direct carbon dioxide capture technology looks to be one of the most promising to date. But if we consider that it is capable of processing only 150 tons of CO2 per year with annual emissions of 40 billion tons into the atmosphere, it looks like an attempt to scoop out water from a sinking ship with an ordinary mug.
Yet the developers of the Hybrid Na-CO2 System note that there is room for improvement in their system. And the "cherry on the cake" is the possibility of producing electricity and hydrogen fuel, which can be used, for example, in hydrogen transport.
Promotional video:
Nikolay Khizhnyak
