High Quality Content by WIKIPEDIA articles! Ruthenium(IV) oxide (RuO2) is a black chemical compound containing the rare metal ruthenium and oxygen. The most often used O2 catalyst is ruthenium(IV) oxide, however care must be taken since hydrates of this oxide exist. RuO2 is generally used as a catalyst in various industrial applications or an electrode in electrochemical processes. RuO2 is highly reactive with reducing agents, due to its oxidizing properties.