title: Synthesis of new visible light active photocatalysts of Ba(In(1/3)Pb(1/3)M'(1/3))O3 (M' = Nb, Ta): a band gap engineering strategy based on electronegativity of a metal component.
abstract: We have synthesized new, efficient, visible light active photocatalysts through the incorporation of highly electronegative non-transition metal Pb or Sn ions into the perovskite lattice of Ba(In(1/3)Pb(1/3)M'(1/3))O3 (M = Sn, Pb; M' = Nb, Ta). X-ray diffraction, X-ray absorption spectroscopic, and energy dispersive spectroscopic microprobe analyses reveal that tetravalent Pb or Sn ions exist in the B-site of the perovskite lattice, along with In and Nb/Ta ions. According to diffuse UV-vis spectroscopic analysis, the Pb-containing quaternary metal oxides Ba(In(1/3)Pb(1/3)M'(1/3))O3 possess a much narrower band gap (E(g) approximately 1.48-1.50 eV) when compared to the ternary oxides Ba(In(1/2)M'(1/2))O3 (E(g) approximately 2.97-3.30 eV) and the Sn-containing Ba(In(1/3)Sn(1/3)M'(1/3))O3 derivatives (E(g) approximately 2.85-3.00 eV). Such a variation of band gap energy upon the substitution is attributable to the broadening of the conduction band caused by the dissimilar electronegativities of the B-site cations. In contrast to the ternary or the Sn-substituted quaternary compounds showing photocatalytic activity under UV-vis irradiation, the Ba(In(1/3)Pb(1/3)M'(1/3))O3 compounds induce an efficient photodegradation of 4-chlorophenol under visible light irradiation (lambda > 420 nm). The present results highlight that the substitution of electronegative non-transition metal cations can provide a very powerful way of developing efficient visible light harvesting photocatalysts through tuning of the band structure of a semiconductive metal oxide.
authors.affiliation: Center for Intelligent Nano-Bio Materials (CINBM), Division of Nano Sciences and Department of Chemistry, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Su Gil
authors.initials: SG
authors.lastname: Hur
authors.forename: Tae Woo
authors.initials: TW
authors.lastname: Kim
authors.forename: Seong-Ju
authors.initials: SJ
authors.lastname: Hwang
authors.forename: Hyunwoong
authors.initials: H
authors.lastname: Park
authors.forename: Wonyong
authors.initials: W
authors.lastname: Choi
authors.forename: Sung Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Sun Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Jin-Ho
authors.initials: JH
authors.lastname: Choy
mesh_terms: D000327:Adsorption; D017609:Barium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D004583:Electrons; D007204:Indium / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D008027:Light; D008855:Microscopy, Electron, Scanning; D009556:Niobium / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D010777:Photochemistry; D013053:Spectrophotometry; D013635:Tantalum / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D017609:Barium Compounds; D007204:Indium; D009556:Niobium; D007854:Lead; D013635:Tantalum; D010100:Oxygen