Changyuan Hu

TiO2–graphene composites with exposed {001} facets produced by a one-pot solvothermal approach for high performance photocatalyst

TiO2-graphene (TOG) composites with exposed TiO2 {001} facets were prepared by a solvothermal approach without any addition of surfactants or capping agents, only using titanium isopropoxide and graphene oxide ethanol suspension as the precursors. Graphene was covered uniformly and densely with anatase TiO2 nanoparticles, exposing the {001} facets. The X-ray photoelectron spectroscopy, photoluminescence spectroscopy and photocurrent measurements show the presence of electron transfer between TiO2 and graphene. The electron transfer between TiO2 and graphene will greatly retard the recombination of photoinduced charge carriers and prolong electron lifetime, which will contribute to the enhancement of photocatalytic performance. Accordingly, the TOG composites show high photocatalytic activity of methyl orange under UV light, likely due to the effective separation of photoinduced charge, exposure of highly reactive {001} facets and great adsorptivity of dyes.

A brief review of graphene–metal oxide composites synthesis and applications in photocatalysis

Graphene is a flat monolayer of carbon atoms with perfect sp2-hybridized two-dimensional carbon structure. Its fascinating high conductivity, superior electron mobility, extremely high specific surface area and easy functionalization make graphene a good substrate to produce graphene-based composites. Especially, graphene–metal oxide composites have attracted extensive attention for their potential applications in environmental and energy-related areas. In this brief review, we will summarize recent achievements of effective strategies for synthesizing high-quality graphene–metal oxide composites and their photocatalytic applications, together with a discussion on major challenges and opportunities for future research.

Au/TiO2/Graphene Composite with Enhanced Photocatalytic Activity Under Both UV and Visible Light Irradiation

Au/TiO2/graphene composite was synthesized by the combination of electrostatic attraction and photo-reduction method. In the composite, graphene sheets act as an adsorption site for dye molecules to provide a high concentration of dye near to the TiO2 and Au nanoparticles (NPs), and work as an excellent electron transporter to separate photoinduced e−/h+ pairs. Under UV irradiation, photogenerated electrons of TiO2 are transferred effectively to Au NPs and graphene sheets, respectively, retarding the recombination of electron–hole pairs. Under visible light irradiation, the Au NPs are photo-excited due to the surface plasmon resonance effect, and charge separation is accomplished by the interfacial electron injection from the Au NPs to the conduction band of TiO2 and then transfer further to graphene sheets. As a result, compared with pure TiO2, Au/TiO2/graphene composite exhibited much higher photocatalytic activity for degradation of methylene blue under both UV and visible light irradiation, based on the synergistic effect of Au, graphene in contact with TiO2, allowing response to the visible light, effective separation of photoinduced charges, and better adsorption of the dye molecules.

Synthesis of Bi 2 O 4 @TiO 2 Heterojunction with Enhanced Visible Light Photocatalytic Activity

A novel Bi2O4@TiO2 heterojunction was constructed by a simple two-step method. The charges migration between Bi2O4 and TiO2 via the heterojunction improves the electron/hole separation efficiency. Furthermore, Bi2O4@TiO2 heterostructures exhibit better adsorption capability for methyl orange molecular due to their higher specific surface area than pure Bi2O4. As a result, Bi2O4@TiO2 hybrids show an improved visible light photocatalytic activity and photostability for the degradation of methyl orange.

Zinc Oxide Thin Films Grown on Nanostructured Al Thin Layer/Glass Substrate by RF Magnetron Sputtering

ZnO films were deposited on nanostructured Al (n-Al) /glass substrate by RF magnetron sputtering. The results shows that the relation (I (002) /I (100) ≈ I annealed (002)/I annealed (100) ≈1.1) shows the rough n-Al surface is suitable for the growth of a-axis orientation. Meanwhile, the influences of substrate roughness, crystallinity and (101) plane of ZnO film deposited on n-Al layer have been discussed. XPS implies more oxygen atoms are bound to Aluminum atoms, which result in the increase of high metallic Zn in the film.