Oxygen

Oxygen production on Mars

Mars tenuous atmosphere of 0.01 atm pressure which is comprised of 96% CO2, 2.1% argon, and 1.9% nitrogen

Electrolysis is very power hungry.

A good supply or water from mining frozen water transported in AI controlled dumper truck to a central refinery is in place then using Electrolysis of the water to split it into hydrogen and oxygen an important option as the Hydrogen can then be used for combining the atmospheric CO2 and also from CO2 scrubbers used within the Habitats using 'The Sabatier Reaction' with a nickel catalyst at 300–400 °C under pressure to generate oxygen and methane for fuel and a possible useful byproduct would be heat, but again requiring high energy consumption.

Using Bacteria may also be a good option.

Plants used for food production could help to generate oxygen also helping filter CO2 out of air from the habitats.

A paper has suggested that Oxygen can be generated from Zirconia electrolysis of CO2 from the atmosphere.

A zirconia electrolysis cell is an all-solid state (mainly ceramic) device consisting of two electrodes separated by a dense zirconia electrolyte. The cell electrochemically reduces carbon dioxide to oxygen and carbon monoxide at elevated temperatures (800 to 1000°C)

NASA with Mars Rover 2020 is attempting to experiment called MOXIE to collect CO2 from the Martian atmosphere, then electrochemically splits the CO2 molecules into O2 and CO using the solid oxide electrolysis process.