R. S. Li

Sonocatalytic degradation of RhB over LuFeO3 particles under ultrasonic irradiation.

LuFeO3 particles with an average particle size of ∼200 nm were synthesized via a polyacrylamide gel route. The sonocatalytic activity of LuFeO3 particles was evaluated by the degradation of Rhodamine B (RhB) under ultrasonic irradiation, revealing that they exhibit a good sonocatalytic activity. The effects of various experimental factors including ultrasonic frequency (f), reaction solution temperature (T), catalyst dosage (Ccatalyst), initial RhB concentration (CRhB), and pH value on the sonocatalysis efficiency were investigated. It is found that the former four factors have an important influence on the sonocatalytic degradation of RhB, where the best degradation conditions are obtained to be f=60 kHz, T=40 °C, Ccatalyst=4 g L(-1), and CRhB=5 mg L(-1). The pH value has a relatively small effect on the sonocatalytic degradation of RhB compared with other experimental factors. Hydroxyl (·OH) radicals were detected by fluorimetry using terephthalic acid as a probe molecule, revealing that they are produced over the ultrasonic-irradiated LuFeO3 particles. The addition of ethanol leads to a quenching of ·OH radicals and a simultaneous decrease in the RhB degradation. This indicates that ·OH radicals are the primary active species responsible for the dye degradation.

Enhanced photocatalytic performance of Ag–Bi4Ti3O12 nanocomposites prepared by a photocatalytic reduction method

Abstract Bi4Ti3O12 nanoparticles with size of 60–90 nm were decorated with smaller-sized Ag nanoparticles (12–25 nm) by a photocatalytic reduction method. The as-prepared Ag–Bi4Ti3O12 composites were systematically characterised by X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, photoluminescence spectroscopy and photocurrent response. It is demonstrated that the decoration of Bi4Ti3O12 with Ag nanoparticles leads to an effective separation of photogenerated electron–hole pairs. RhB was chosen as the target organic pollutant to evaluate its degradation behaviour over Ag–Bi4Ti3O12 composites under simulated sunlight irradiation. Compared to bare Bi4Ti3O12, Ag–Bi4Ti3O12 composites exhibit a significantly enhanced photocatalytic activity and the highest photocatalytic activity is observed for 5·2 wt% Ag–Bi4Ti3O12. The first-order reaction rate constant suggests that the photocatalytic activity of 5·2 wt% Ag–Bi4Ti3O12 is about 2·4 times higher than that of bare Bi4Ti3O12. AO, ethanol and BQ were, respectively, used as the scavengers of h+, •OH and • to investigate their effect on the degradation of RhB. It is found that only AO has an important suppression on the dye degradation, from which it is concluded that h+ is the dominant reactive species causing the dye degradation.

Enhanced photocatalytic performance and mechanism of Ag-decorated LaFeO3 nanoparticles

Spherical LaFeO3 nanoparticles with an average size of 35 nm were synthesized by a polyacrylamide gel route. Ag nanoparticles of 8–18 nm in size were decorated onto LaFeO3 particle surface by a chemical reduction method to yield Ag–LaFeO3 composites. The samples were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy. It is found that LaFeO3 particles have two bandgap energies of 2.59 and 2.24 eV, which undergo almost no change when decorated with Ag nanoparticles. photoluminescence spectra demonstrate that the decoration of LaFeO3 particles with Ag nanoparticles leads to a decreased recombination rate of photogenerated electrons and holes. The photocatalytic activity of the samples was evaluated by degrading Rhodamine B under simulated-sunlight irradiation. Compared to bare LaFeO3 particles, Ag–LaFeO3 composites exhibit an obviously enhanced photocatalytic activity. The formed •OH was examined by photoluminescence spectroscopy using terephthalic acid as the •OH scavenger, revealing an enhanced yield on the irradiated Ag–LaFeO3 composites. To clarify the role of active species in the photocatalysis, the effect of ammonium oxalate (h+ scavenger), ethanol (•OH scavenger), benzoquinone (•O2− scavenger), and N2 on the Rhodamine B degradation as well as the •OH yield was investigated. Based on the experimental results, •OH and •O2− are suggested to be the main active species causing the dye degradation.Graphical Abstract

Synthesis of spherical Bi 2 WO 6 nanoparticles by a hydrothermal route and their photocatalytic properties

Spherical Bi2WO6 nanoparticles were synthesized by a hydrothermal route. SEM observation shows that the size of the particles ranges from 60 to 120 nm and the average particle size is ∼85 nm. TEM investigation shows that the particles are made up of subgrains with size of 5-10 nm. The bandgap energy of the particles is measured to be 2.93 eV by ultraviolet-visible diffuse reflectance spectroscopy. RhB was chosen as the target pollutant to evaluate the photocatalytic activity of the particles under irradiation of simulated sunlight, revealing that they exhibit an obvious photocatalytic activity. The effects of ethanol, KI, and BQ on the photocatalytic efficiency of Bi2WO6 particles towards the RhB degradation were investigated. It is observed that ethanol has no effect on the photocatalytic degradation of RhB, whereas KI and BQ exhibit a substantial suppression of RhB degradation. No hydroxyl (•OH) is found, by the photoluminescence technique using terephthalic acid as a probe molecule, to be produced over the irradiated Bi2WO6 particles. Based on the experimental results, photoexcited hole (h+) and superoxide (•O2-) are suggested to be the two main active species responsible for the dye degradation, while •OH plays a negligible role in the photocatalysis.

Morphology-tailored synthesis and electrochemical performances of CuBi2O4 hierarchical architectures with the aid of KCl

Abstract The effect of the structure-directing agent KCl on the synthesis of CuBi2O4 hierarchical architectures was investigated. It is demonstrated that KCl plays an important role in tailoring the morphology of the products. By varying the KCl concentration from 0, 0.0625, 0.125, 0.25, 0.5, to 1.5 M, it brings about the synthesis of cauliflower-like agglomerate assembled by nanoparticles, cauliflower-like microsphere assembled by nanorods, dumbbell-like architecture constructed from nanorods, flower-like cluster formed from irregular nanoflakes, cuboid-like architecture made up of nanoparticles, and dumbbell-like architecture built from rectangular nanorods, respectively. Ultraviolet-visible diffuse reflectance spectroscopy reveals that the as-prepared samples have similar bandgap energy of 1.89 eV. The electrochemical performance of the samples was investigated by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy in 2 M KOH electrolyte. Among the samples, the cauliflower-like agglomerate prepared at n(KCl) = 0 M delivers a relatively higher specific capacitance, reaching 1256 F g−1 at the current density of 2 A g−1.