Pioneer Astronautics is likely doing some variant of the molten oxide electrolysis that Boston Metal is commercializing here on Earth: https://www.bostonmetal.com/moe-technology/#moe-process
This involves melting rock (potentially just random basalt) and electrolyzing it. Graphite may be used as a cathode, but the anode must be resistant to oxidation, or the anode will be consumed by reaction with the O2 and CO2 will be released instead. Earlier work used precious metals like iridium for anodes, some recent work (related to Boston Metal's process) uses chromium alloys (https://www.chemistryworld.com/news/greener-cleaner-steel-/6155.article), and I've also seen mention of ceramic electrodes that become conductive at the temperatures involved.
And of course, while oxygen is collected at the anode, the cathode collects the metallic (or semimetallic) components of the oxides...iron, silicon, copper, etc. This is the desired end product for Boston Metal, and might eventually be the primary end product on the moon as well, with the oxygen being a waste product produced in greater quantities than needed.