Novel decahedral TiO2 photocatalysts modified with Ru or Rh NPs: Insight into the mechanism

Abstract

Novel decahedral TiO2 modified with Ru or Rh NPs were successfully synthesized by hydrothermal method. The effect of metal type as well as amount of noble metal precursor (0.05, 0.1, 0.2, 0.3 and 0.5wt.%) on the photocatalytic activity were investigated. Decahedral TiO2 decorated by Ru and Rh nanoparticles was prepared by photodeposition method, whereas Rh doped TiO2 was obtained by one-step hydrothermal method with introduction of Rh precursor to the reagents mixture. All as-prepared photocatalysts were thoroughly characterized by UV–vis diffuse-reflectance spectroscopy (DRS), scanning electron microscopy (SEM), scanning transmission microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier transforms infrared spectra (FT-IR) and photoluminescence emission spectra (PL). The photocatalytic activity under UV–vis has been estimated in phenol degradation reaction in an aqueous phase. The gas chromatography–mass spectrometry was employed to detect organic intermediates to establish degradation pathway of isotopically labeled (1-13C) phenol. Experimental results showed that the novel material exhibited enhanced optical properties and a high degradation rate for phenol under UV–vis light. In particular, the photocatalyst which contains 0.2wt.% Rh (0.2_Rh/TiO2_HT) exhibited the best photoefficiency among the prepared samples (79% of phenol was degraded after 90min of irradiation). The role of the active species in the process of the degradation was evaluated by using different types of active species scavengers as well as hydroxyl radical test with coumarin were also carried out. The active species trapping experiments indicated that under UV–vis OH radicals and generated superoxide anion O2− were actively involved as the main active species in the oxidation of phenol.