title: Synthesis and photocatalytic activity of perovskite niobium oxynitrides with wide visible-light absorption bands.
abstract: Photocatalytic activities of perovskite-type niobium oxynitrides (CaNbO₂N, SrNbO₂N, BaNbO₂N, and LaNbON₂) were examined for hydrogen and oxygen evolution from water under visible-light irradiation. These niobium oxynitrides were prepared by heating the corresponding oxide precursors, which were synthesized using the polymerized complex method, for 15 h under a flow of ammonia. They possess visible-light absorption bands between 600-750 nm, depending on the A-site cations in the structures. The oxynitride CaNbO₂N, was found to be active for hydrogen and oxygen evolution from methanol and aqueous AgNO₃, respectively, even under irradiation by light at long wavelengths (λ<560 nm). The nitridation temperature dependence of CaNbO₂N was investigated and 1023 K was found to be the optimal temperature. At lower temperatures, the oxynitride phase is not adequately produced, whereas higher temperatures produce more reduced niobium species (e. g., Nb³(+) and Nb⁴(+)), which can act as electron-hole recombination centers, resulting in a decrease in activity.
authors.affiliation: Department of Chemical System Engineering, The University of Tokyo, Japan.
authors.forename: Bhavin
authors.initials: B
authors.lastname: Siritanaratkul
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Maeda
authors.forename: Takashi
authors.initials: T
authors.lastname: Hisatomi
authors.forename: Kazunari
authors.initials: K
authors.lastname: Domen
mesh_terms: D000042:Absorption; D017610:Calcium Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D008027:Light; D008958:Models, Molecular; D008968:Molecular Conformation; D009556:Niobium / Q000737:chemistry*; D010087:Oxides / Q000138:chemical synthesis* / Q000737:chemistry*; D055668:Photochemical Processes; D013696:Temperature; D014025:Titanium / Q000737:chemistry*
chemical_list: D017610:Calcium Compounds; D010087:Oxides; D009556:Niobium; C059910:perovskite; D014025:Titanium