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The Gd₂YSbO₇/ZnBiNbO₅ heterojunction photocatalyst was synthesized for the first time by the facile in situ precipitation method. The structural properties of a Gd₂YSbO₇/ZnBiNbO₅ heterojunction photocatalyst were characterized by X-ray diffractometer, scanning electron microscope-X ray energy dispersive spectra, X-ray photoelectron spectrograph and UV-Vis diffuse reflectance spectrophotometer. The band gap energy (BGE) of Gd₂YSbO₇ or ZnBiNbO₅ was found to be 2.396 eV or 2.696 eV, respectively. The photocatalytic property of Gd₂YSbO₇ or ZnBiNbO₅ or Gd₂YSbO₇/ZnBiNbO₅ heterojunction photocatalyst (GZHP) was reported. After a visible-light irradiation of 145 minutes (VLI-145 min), the removal rate (RER) of benzotriazole reached 99.05%, 82.45%, 78.23% or 47.30% with Gd₂YSbO₇/ZnBiNbO₅ heterojunction (GZH), Gd₂YSbO₇, ZnBiNbO₅ or N-doped TiO₂ (NTO) as photocatalyst. In addition, the kinetic constant k, derived from the dynamic curve toward benzotriazole concentration and visible light irradiation time with GZH as a photocatalyst, reached 0.0213 min⁻¹. Compared with Gd₂YSbO₇ or ZnBiNbO₅ or NTO, GZHP showed maximal photocatalytic activity (PHA) for the photocatalytic degradation of benzotriazole under visible-light irradiation. The RER of total organic carbon during the photocatalytic degradation of benzotriazole reached 90.18%, 74.35%, 70.73% or 42.15% with GZH as a photocatalyst or with Gd₂YSbO₇, ZnBiNbO₅ or NTO as a photocatalyst after VLI-145 min. Moreover, the kinetic constant k, which came from the dynamic curve toward total organic carbon concentration and visible light irradiation time with GZH as a photocatalyst, reached 0.0110 min⁻¹. Based on above results, GZHP showed the maximal mineralization percentage ratio when GZHP degraded benzotriazole. The results showed that hydroxyl radicals was the main oxidation radical during the degradation of benzotriazole. The photocatalytic degradation of benzotriazole with GZH as a photocatalyst conformed to the first-order reaction kinetics. Our research aimed to improve the photocatalytic properties of the single photocatalyst. Full article

Novel photocatalysts Gd₂FeSbO₇, Gd₂InSbO₇ and Gd₂YSbO₇ were synthesized by the solid state reaction method for the first time. A comparative study about the structural and photocatalytic properties of Gd₂MSbO₇ (M = Fe, In, Y) was reported. The results showed that Gd₂FeSbO₇, Gd₂InSbO₇ and Gd₂YSbO₇ crystallized with the pyrochlore-type structure, cubic crystal system and space group Fd3m. The lattice parameter a for Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇ was 10.276026 Å, 10.449546 Å or 10.653651 Å. The band gap of Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇ was estimated to be 2.151 eV, 2.897 eV or 2.396 eV. For the photocatalytic water-splitting reaction, H₂ or O₂ evolution was observed from pure water with Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇ as catalyst under visible light irradiation (wavelength > 420 nm). Moreover, H₂ or O₂ also spilt by using Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇ as catalyst from CH₃OH/H₂O or AgNO₃/H₂O solutions under visible light irradiation (λ > 420 nm). Gd₂FeSbO₇ showed the highest activity compared with Gd₂InSbO₇ or Gd₂YSbO₇. At the same time, Gd₂InSbO₇ showed higher activity compared with Gd₂YSbO₇. The photocatalytic activities were further improved under visible light irradiation with Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇ being loaded by Pt, NiO or RuO₂. The effect of Pt was better than that of NiO or RuO₂ for improving the photocatalytic activity of Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇. Full article