Review demonstrates mechanisms of reactive oxygen species generation on titanium dioxide, highlighting trapped holes as primary oxidation species.
Key Points
To synthesize and evaluate detection methods and generation mechanisms for intrinsic reactive oxygen species formed during heterogeneous photocatalysis.
Surveyed experimental detection methods and generation pathways for superoxide anion radicals, hydrogen peroxide, singlet oxygen, and hydroxyl radicals.
Analyzed photocatalytic behaviors across titanium dioxide suspensions, contrasting anatase and rutile polymorphs alongside other representative photocatalysts.
Identified adsorbed hydroxyl radicals as trapped holes participating in a rapid interfacial adsorption-desorption equilibrium strongly shifted toward adsorption on titanium dioxide.
Demonstrated that trapped surface holes function as the predominant oxidation species, whereas aqueous hydroxyl radicals primarily react with nonadsorbed substrate molecules.
Characterized formation pathways for standard reactive oxygen species as well as secondary species, including organic peroxides, ozone, and nitric oxide.