oxidized products. Due to the generation of positive holes and excited electrons, oxidation-reduction reactions take place at the surface of semiconductors irradiated with light. In one mechanism of the oxidative reaction, holes react with the moisture present on the surface and produce a hydroxyl radical. The reaction starts by photo-induced exciton generation in the metal oxide (MO) surface: MO + hν → MO (h+ + e−) Oxidative reactions due to photocatalytic effect: h+ + H2O → H+ + •OH 2 h+ + 2 H2O → 2 H+ + H2O2 H2O2→ 2 •OH Reductive reactions due to photocatalytic effect: e− + O2 → •O2− •O2− + H2O + H+ → H2O2 + O2 H2O2 → 2 •OH Ultimately, hydroxyl radicals are generated in both reactions. These radicals are oxidative in nature and nonselective with a redox potential of E0 = +3.06 V. is a common choice for heterogeneous catalysis. Inertness to chemical environment and long-term photostability has made an important material in many practical applications. is a wide band-gap semiconductor. It is commonly investigated in the rutile (bandgap 3.0 eV) and anatase (bandgap 3.2 eV) phases. Photocatalytic reactions are initiated by the absorption of illumination with energy equal to or greater than the band gap of the semiconductor. This produces electron-hole (e− /h+) pairs: TiO2 ->[{hv}][{}] e-(TiO2) + h+(TiO2) where the electron is in the conduction band and the hole is in the valence band. The irradiated particle can behave as an electron donor or acceptor for molecules in contact with the semiconductor. It can participate in redox reactions with adsorbed species, as the valence band hole is strongly oxidizing while the conduction band electron is strongly reducing. Plasmonic antenna-reactor photocatalysis A plasmonic antenna-reactor photocatalyst is a photocatalyst that combines a catalyst with attached antenna that increases the catalyst's ability to absorb light, thereby increasing its efficiency. A catalyst combined with an Au light absorber accelerated hydrogen sulfide-to-hydrogen reactions. The process is an alternative to the conventional Claus process that operates at . A Fe catalyst combined with a Cu light absorber can produce hydrogen from ammonia () at ambient temperature using visible light. Conventional Cu-Ru production operates at . Applications Photoactive catalysts have been introduced over the last decade, such as and ZnO nano rodes. Most suffer from the fact that they can only perform under UV irradiation due to their band structure. Other photocatalysts, including a graphene-ZnO nanocompound counter