The atmosphere of Mars consists (by volume) over 95% of the elements oxygen and carbon, which are crucial for human life. However, most of it is stuck in CO2, which is a very stable molecule and difficult to break. Molten salt carbon capture and electrochemical transformation (MSCC-ET) is a technology where the CO2 molecule is broken up into solid carbon and molecular oxygen via a carbonate salt electrolyte. The electrolyte is split in an electrolysis system and regenerated from CO2 in the surrounding atmosphere.
On earth, this technology has been touted to be the solution to the rising CO2 levels in the atmosphere. On Mars, it could be a solution to two problems: energy storage and oxygen production. The carbon created on the cathode of the CO2 electrolyzer could be burnt or re-oxidized afterwards in direct carbon fuel cell.
In the literature, the charge efficiency of the deposition-oxidation of the carbon has been found to be up to 95%. On earth the deposition rate is limited by the low partial pressure of CO2, which is not a problem on Mars. On the anode side, one molecule of oxygen is created for each carbon atom added to the cathode product, which could be used to regenerate artificial air. A similar process is already in use by ESA to generate oxygen from moon regolith and in NASA's MOXIE.
We propose a study for developing a reactor technology CO2 is electrochemically split into solid carbon and gaseous oxygen, which are then separated and stored. The issues that need to be solved are:
- What is the efficiency of solid carbon storage and re-oxidation in Mars atmosphere under the minimum possible voltage (for future use with solar panels),
- What is the purity of the gaseous oxygen products in such a reactor, whether or not it can be used to regenerate artificial air and
- If the relatively high temperatures needed for melting the electrolytes are achievable in a small reactor in Mars conditions.
