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(00l)-Facet-Exposed Planelike ABi2Nb2O9 (A = Ca, Sr, Ba) Powders with a Single-Crystal Grain for Enhancement of Photocatalytic Activity

Zhang, Yifeng, Yuan, Jing, Gong, Huihua, Cao, Yue, Liu, Kewei, Cao, Hongmei, Yan, Hongjian, Zhu, Jianguo
ACS sustainable chemistry & engineering 2018 v.6 no.3 pp. 3840-3852
X-ray diffraction, X-ray photoelectron spectroscopy, geometry, hydrogen production, irradiation, nanoparticles, oxidation, oxygen production, photocatalysis, photocatalysts, photoluminescence, platinum, powders, reflectance spectroscopy, scanning electron microscopy, slabs, temperature, transmission electron microscopy
(00l)-facet-exposed planelike ABi₂Nb₂O₉ (A = Ca, Sr, Ba) powders with a single-crystal grain were obtained successfully by the molten salt method. The planelike grains were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. With modification by platinum nanoparticles as a cocatalyst, these materials were tested as photocatalysts for water splitting under full arc light irradiation. The H₂ evolution activities of the planelike ABi₂Nb₂O₉ (A = Ca, Sr, Ba) prepared by the molten salt method were almost an order of magnitude higher than those of the ABi₂Nb₂O₉ (A = Ca, Sr, Ba) prepared by traditional solid-state method. The planelike ABi₂Nb₂O₉ (A = Ca, Sr, Ba) powders also have higher O₂ evolution activities than the ABi₂Nb₂O₉ (A = Ca, Sr, Ba) powders prepared by the traditional solid-state method. The oxidation and reduction catalytic sites on the planelike ABi₂Nb₂O₉ (A = Ca, Sr, Ba) are discussed in detail. With increasing temperature of the molten salt, the variation tendencies of the photocatalytic activities of CaBi₂Nb₂O₉, SrBi₂Nb₂O₉, and BaBi₂Nb₂O₉ for water splitting were different from each other due to the different growth rhythm of the planelike ABi₂Nb₂O₉ (A = Ca, Sr, Ba) grains. The CaBi₂Nb₂O₉ and SrBi₂Nb₂O₉ with an orthorhombic lattice had a higher photocatalytic activity than BaBi₂Nb₂O₉ with a tetragonal lattice because of the strong distortion of NbO₆ octahedra in the perovskite-like slabs of CaBi₂Nb₂O₉ and SrBi₂Nb₂O₉.