The electron affinity of ozone (ca. 2.1 eV) is higher than that of oxygen (ca. 0.44 eV) [43] which can promote photocatalytic reactions in the presence of ozone (photocatalytic ozonation) more positively than in the presence of oxygen (simple photocatalysis). The hydrogen peroxide molecules that are generated can also react with photoexcited electrons on the photocatalyst surface, forming hydroxyl radicals (R7)