Combinatorial CVD: New Oxynitride Photocatalysts

摘要

Titanium dioxide (TiO_2) has become the leading material for semiconductor photocatalyst (SPC) applications due to its biological and chemical inertness, mechanical robustness to multiple photocatalytic cycles, durability, relatively low cost and high activity (1).rnTiO_2 has the ability to degrade a range of organic pollutants on its surface via photocatalysis in the presence of UV light and oxygen. When titania is irradiated with UV-light (typically λ < 388 nm), an electron (e~-) is promoted from the semiconductor's valence band to its conduction band, leaving a hole (h~+) in the valence band. Although this electron-hole pair is formed within the bulk, it is capable of migrating to the surface where electrons can reduce atmospheric O_2 to superoxide O_2, which can be subsequently further reduced to H_2O and holes can oxidise surface-bound hydroxyl groups to highly reactive hydroxyl radical species. The surface radicals/ reduced species formed are capable of oxidising the organic pollutant into mineral acids and CO_2. The overall process can be summarized as followsrnOrganic Pollutant + O_2 (HO_2 semiconductor) → (hν ≥ E_(bg)) CO_2 + H_2O + Minerals [1]rnwhere E_(bg) is the band-gap energy of the semiconductor.rnThe bulk of research has predominantly featured TiO_2 as a photocatalyst in the oxidation of organic pollutants (2), leading to the introduction of several commercial