L. J. Di

Photocatalytic reduction synthesis of SrTiO3-graphene nanocomposites and their enhanced photocatalytic activity

SrTiO3-graphene nanocomposites were prepared via photocatalytic reduction of graphene oxide by UV light-irradiated SrTiO3 nanoparticles. Fourier transformed infrared spectroscopy analysis indicates that graphene oxide is reduced into graphene. Transmission electron microscope observation shows that SrTiO3 nanoparticles are well assembled onto graphene sheets. The photocatalytic activity of as-prepared SrTiO3-graphene composites was evaluated by the degradation of acid orange 7 (AO7) under a 254-nm UV irradiation, revealing that the composites exhibit significantly enhanced photocatalytic activity compared to the bare SrTiO3 nanoparticles. This can be explained by the fact that photogenerated electrons are captured by graphene, leading to an increased separation and availability of electrons and holes for the photocatalytic reaction. Hydroxyl (·OH) radicals were detected by the photoluminescence technique using terephthalic acid as a probe molecule and were found to be produced over the irradiated SrTiO3 nanoparticles and SrTiO3-graphene composites; especially, an enhanced yield is observed for the latter. The influence of ethanol, KI, and N2 on the photocatalytic efficiency was also investigated. Based on the experimental results, ·OH, h+, and H2O2 are suggested to be the main active species in the photocatalytic degradation of AO7 by SrTiO3-graphene composites.PACS61.46. + w; 78.67.Bf; 78.66.Sq

Enhanced Photocatalytic Activity of NaBH4 Reduced BiFeO3 Nanoparticles for Rhodamine B Decolorization

In this work, oxygen vacancies were introduced onto the surface of BiFeO3 nanoparticles by NaBH4 reduction method to yield oxygen-deficient BiFeO3−x samples. Comprehensive analysis on the basis of high-resolution transmission electron microscopy (HRTEM) observation and X-ray photoelectron spectrum (XPS) confirms the existence of surface oxygen vacancies on the BiFeO3−x nanoparticles. The photocatalytic activity of as-prepared BiFeO3−x samples was evaluated by the decolorization of rhodamine B (RhB) under simulated sunlight irradiation. The experimental results indicate that the photocatalytic activity of samples is highly related to the NaBH4 reduction time, and the BiFeO3−x sample reduced for 40 min exhibits the highest photocatalytic efficiency, which is much higher than that of pristine BiFeO3 nanoparticles. This can be explained by the fact that the surface oxygen vacancies act as photoinduced charges acceptors and adsorption sites suppress the recombination of photogenerated charges, leading to an increasing availability of photogenerated electrons and holes for photocatalytic reaction. In addition, the obtained BiFeO3−x sample exhibits good photocatalytic reusability.

Preparation of BiFeO 3 -graphene nanocomposites and their enhanced photocatalytic activities

BiFeO3 nanoparticles were prepared via a polyacrylamide gel route. BiFeO3-graphene nanocomposites were fabricated by mixing BiFeO3 nanoparticles and graphene into absolute ethanol solution followed...BiFeO3 nanoparticles were prepared via a polyacrylamide gel route. BiFeO3-graphene nanocomposites were fabricated by mixing BiFeO3 nanoparticles and graphene into absolute ethanol solution followed by thermal drying. The TEM observation demonstrates that the BiFeO3 nanoparticles are well anchored onto graphene sheets. The photocatalytic activities of the as-prepared samples were evaluated by the degradation of methyl orange (MO) under simulated sunlight irradiation. Compared to bare BiFeO3 nanoparticles, BiFeO3-graphene nanocomposites exhibit enhanced photocatalytic activity. The outstanding photocatalytic performance is mainly ascribed to the efficient transfer of photogenerated electrons from BiFeO3 to graphene, thus leading to an increased availability of h+ for the photocatalytic reaction. In addition, hydroxyl (ċOH) radicals were detected by the photoluminescence technique using terephthalic acidas a probe molecule and are found to be produced on the irradiated BiFeO3 and BiFeO3-graphene nanocomposites; in particular, an enhanced yield is observed for the latter.

Graphene-assisted enhancement of photocatalytic activity of bismuth ferrite nanoparticles

Bismuth ferrite (Bi2Fe4O9) nanoparticles were synthesized via a polyacrylamide gel route. Bi2Fe4O9–graphene nanocomposites were fabricated by mixing Bi2Fe4O9 nanoparticles and graphene into absolute ethanol solution followed by thermal drying. Transmission electron microscope observation reveals that Bi2Fe4O9 nanoparticles are well assembled onto graphene sheets. The photocatalytic activity of the prepared samples was evaluated by the degradation of methyl orange under simulated sunlight irradiation, revealing that Bi2Fe4O9–graphene nanocomposites exhibit an enhanced photocatalytic activity compared to bare Bi2Fe4O9 nanoparticles. This can be explained by the fact that the photogenerated electrons are captured by graphene, leading to an increased availability of h+ for the photocatalytic reaction. In addition, it is found that hydroxyl (·OH) radicals, detected by the photoluminescence technique using coumarin as a probe molecule, are produced on the irradiated Bi2Fe4O9 and Bi2Fe4O9–graphene nanocomposite; especially, an enhanced yield is observed for the latter.

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.

Facile Synthesis and Enhanced Visible-Light Photocatalytic Activity of Novel p-Ag 3 PO 4 /n-BiFeO 3 Heterojunction Composites for Dye Degradation

In this work, Ag3PO4 microparticles were decorated onto the surface of BiFeO3 microcuboids through a precipitation method to obtain p-Ag3PO4/n-BiFeO3 heterojunction composites. The composites were employed for the degradation of acid orange 7 (AO7) under visible-light irradiation. It is found that the composites exhibit much higher photocatalytic efficiency than bare BiFeO3. Meanwhile, the intrinsical visible-light-driven photocatalytic activity of Ag3PO4/BiFeO3 composites was further confirmed by the degradation of phenol. In addition, the photo-Fenton-like catalysis property of the composite was also evaluated. The photocurrent analysis indicates that the combination of BiFeO3 with Ag3PO4 leads to the inhibition of recombination of photoinduced electrons and holes. The obvious enhancement in the photocatalytic activity of the composite is mainly ascribed to the efficient photogenerated charge separation and interfacial charge migration caused by the formation of Ag3PO4/BiFeO3 p-n heterojunctions.

Growth of BiFeO 3 microcylinders under a hydrothermal condition

BiFeO3 microcylinders were synthesized via a hydrothermal condition. SEM observation reveals that with increasing the hydrothermal reaction time from 6 to 15 h, the microcylinders grow from ∼0.7 to ∼4.1 µm in height, whereas their diameter remains to be 3.7-3.8 µm with a minor change. The microcylinders are mainly made up of sphere-like grains of 100-150nm in size. A possible growth mechanism of the BiFeO3 microcylinders is proposed. The photocatalytic activity of the as-prepared BiFeO3 samples was evaluated by the degradation of acid orange 7 under simulated sunlight irradiation, revealing that they possess an appreciable photocatalytic activity. Magnetic hysteresis loop measurement shows that the BiFeO3 microcylinders exhibit a typical antiferromagnetic behavior at room temperature.