The effects of preparation conditions for a BaNbO2 N photocatalyst on its physical properties.
BaNbO2 N is a semiconductor photocatalyst active for water oxidation under visible-light irradiation up to λ=740 nm. It is important to understand the nitridation processes of precursor materials to form BaNbO2 N to tune the physical properties and improve the photocatalytic activity. Comprehensive experiments and analyses of temperatures, durations, ammonia flow rates, and barium/niobium ratios in the precursor during the nitridation process reveals that faster ammonia flow rates and higher barium/niobium ratios in the precursors help to suppress reduction of pentavalent niobium ions in the nitridation products and that the use of a precursor prepared by a soft-chemistry route allows the production of BaNbO2 N at lower temperatures in shorter times than the use of physical mixtures of BaCO3 and Nb2 O5 because the niobium species is dispersed among the barium species. BaNbO2 N prepared by the soft-chemistry route exhibits comparatively higher activity than that prepared from physical mixtures of BaCO3 and Nb2 O5 , probably because of lower nitridation temperatures, which suppress excessive dissociation of ammonia, and thereby reduce pentavalent niobium ions, and intimate interaction of niobium and barium sources, which lowers the densities of mid-gap states associated with defects.
Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8656 Tokyo (Japan); Japan Technological Research Association of Artificial, Photosynthetic Chemical Process (ARPChem), 5-1-5 Kashiwanoha, Kashiwa-shi, 277-8589 Chiba (Japan).
Takashi
T
Hisatomi
Chisato
C
Katayama
Kentaro
K
Teramura
Tsuyoshi
T
Takata
Yosuke
Y
Moriya
Tsutomu
T
Minegishi
Masao
M
Katayama
Hiroshi
H
Nishiyama
Taro
T
Yamada
Kazunari
K
Domen
D000641:Ammonia / Q000737:chemistry; D001464:Barium / Q000737:chemistry; D017609:Barium Compounds / Q000737:chemistry*; D002254:Carbonates / Q000737:chemistry; D002384:Catalysis; D007700:Kinetics; D009556:Niobium / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D055668:Photochemical Processes; D055585:Physical Phenomena; D013696:Temperature
D017609:Barium Compounds; D002254:Carbonates; D010087:Oxides; D009556:Niobium; D001464:Barium; C006685:barium carbonate; D000641:Ammonia; C073337:niobium pentoxide; D010100:Oxygen
barium; niobium; oxygen evolution; photocatalysis; semiconductors