C 2420 (OTTO) Cobalt(II,III) oxide, ≥99.9985% Cas 1308-06-1 - used in artificial photosynthesis. C 2420 (OTTO) Cobalt(II,III) oxide, ≥99.9985% Cas 1308-06-1 - used as a magnetic semiconductor. It is also employed in supercapacitors and lithium-ion batteries.