Defa Wang

Efficient photocatalytic decomposition of acetaldehyde over a solid-solution perovskite (Ag0.75Sr0.25)(Nb0.75Ti0.25)O3 under visible-light irradiation.

A green chemistry process for environmental purification is realized on a novel visible-light-active photocatalyst (Ag0.75Sr0.25)(Nb0.75Ti0.25)O3. This mixed valent solid-solution perovskite with a modulated electronic structure possesses a strong oxidative potential for efficient photocatalytic decomposition of acetaldehyde into CO2 at ambient temperature.

Nanometals for Solar-to-Chemical Energy Conversion: From Semiconductor-Based Photocatalysis to Plasmon-Mediated Photocatalysis and Photo-Thermocatalysis.

Nanometal materials play very important roles in solar-to-chemical energy conversion due to their unique catalytic and optical characteristics. They have found wide applications from semiconductor photocatalysis to rapidly growing surface plasmon-mediated heterogeneous catalysis. The recent research achievements of nanometals are reviewed here, with regard to applications in semiconductor photocatalysis, plasmonic photocatalysis, and plasmonic photo-thermocatalysis. As the first important topic discussed here, the latest progress in the design of nanometal cocatalysts and their applications in semiconductor photocatalysis are introduced. Then, plasmonic photocatalysis and plasmonic photo-thermocatalysis are discussed. A better understanding of electron-driven and temperature-driven catalytic behaviors over plasmonic nanometals is helpful to bridge the present gap between the communities of photocatalysis and conventional catalysis controlled by temperature. The objective here is to provide instructive information on how to take the advantages of the unique functions of nanometals in different types of catalytic processes to improve the efficiency of solar-energy utilization for more practical artificial photosynthesis.

Porous-structured Cu2O/TiO2 nanojunction material toward efficient CO2 photoreduction

Porous-structured Cu2O/TiO2 nanojunction material is successfully fabricated by a facile method via loading Cu2O nanoparticles on the network of a porous TiO2 substrate. The developed Cu2O/TiO2 nanojunction material has a size of several nanometers, in which the p-type Cu2O and n-type TiO2 nanoparticles are closely contacted with each other. The well designed nanojunction structure is beneficial for the charge separation in the photocatalytic reaction. Meanwhile, the porous structure of the Cu2O/TiO2 nanojunction can facilitate the CO2 adsorption and offer more reaction active sites. Most importantly, the gas-phase CO2 photoreduction tests reveal that our developed porous-structured Cu2O/TiO2 nanojunction material exhibits marked photocatalytic activity in the CH4 evolution, about 12, 9, and 7.5 times higher than the pure TiO2, Pt-TiO2, and commercial Degussa P25 TiO2 powders, respectively. The greatly enhanced activity can be attributed to the well designed nanojunction structure combined with the porous structure, which can simultaneously enhance the charge separation efficiency and facilitate the CO2 adsorption.

A new spinel-type photocatalyst BaCr2O4 for H2 evolution under UV and visible light irradiation

The photophysical and photocatalytic properties of BaCr2O4 synthesized with normal spinel-type crystal structure were studied. It was found that H2 could be photocatalytically evolved from the aqueous CH3OH solution suspended with Pt(0.2 wt%)/BaCr2O4 powder under irradiation of both ultraviolet (UV) and visible lights. The wavelength dependence of H2 evolution under visible light irradiation showed a maximum activity for k > 540 nm. A possible electronic band structure and corresponding photoexcitation modes of BaCr2O4 under irradiation of UV and visible lights were proposed in regard to the complicated photophysical and photocatalytic properties. 2003 Elsevier Science B.V. All rights reserved.

In situ surface alkalinized g-C3N4 toward enhancement of photocatalytic H2 evolution under visible-light irradiation

Surface-alkalinization over g-C3N4 was realized by an in situ synthesis approach of introducing KCl and NH4Cl during the polymerization of melamine. The characterization of the Fourier transform-infrared spectrum, X-ray photoelectron spectrum, and electron spin resonance spectrum over the sample synthesized in the presence of KCl/NH4Cl and other reference samples indicated that the K ions played an essential role in breaking the periodic chemical structure of g-C3N4 and meanwhile the trace amount of H2O in melamine could supply OH ions to graft hydroxyl groups. The NH4Cl mainly contributed to exfoliation of layered g-C3N4 particles and pushing negative shift of the conduction-band level based on the measurements of the BET surface area and valence-band X-ray photoelectron spectrum. An optimal sample, g–C3N4–KCl/0.1 g NH4Cl (CN–KCl/0.1 g NH4Cl), achieved a more than 14-fold enhancement in photocatalytic H2 evolution under visible-light irradiation compared with the pristine g-C3N4. The enhanced photocatalytic efficiency could be attributed to the fact that the surface hydroxyl groups and the more negative conduction-band level can promote the separation of photocarriers and offer a stronger potential for water reduction, respectively.

Photocatalytic reactivity of {121} and {211} facets of brookite TiO2 crystals

For the facet engineering of brookite TiO2, the surface atomic structure is known but the electronic structure has been rarely studied to date. Herein, we investigated both the surface atomic and electronic structure of brookite TiO2 with various facets exposed. Theoretical calculations reveal that the {121} surface contains more undercoordinated Ti atoms and a higher surface energy than that of the {211} surface, and the experimental results show that brookite TiO2 nanorods exposed with majority {121} facets (T121) have a lower valence band (VB) potential; those above-mentioned superior properties enable T121 to show excellent performance in RhB photodegradation. Nevertheless, the electronic structure analyzed from the Density of State (DOS) plots revealed that the electron density is dispersed in the bulk for TiO2 covered with a {121} surface, indicating that the electrons might be more reluctant to migrate from bulk to surface, which might be the reason for the poor H2 productivity of T121. In contrast, brookite TiO2 nanosheets exposed with dominant {211} facets (T211) exhibited a much higher conduction band (CB) potential resulting in a much higher H2 evolution rate (801 μmol h−1) in photocatalytic water splitting. Accordingly, combining the analyses of the surface atomic structure and electronic band structure, it is suggested that, for brookite TiO2, the {121} surface is beneficial for photocatalytic oxidation reactions while the {211} surface can facilitate the photocatalytic reduction process.

One-pot synthesis of peroxo-titania nanopowder and dual photochemical oxidation in aqueous methanol solution.

A sol-gel hydrothermal method was developed to synthesize peroxo-titania powders and their photooxidation performances were conducted in aqueous methanol solution under visible light irradiation. Three kinds of peroxo-titania were developed using TiO(2) and H(2)O(2) containing precursor sol with different dispersion mediums such as NH(3) aq NaOH aq, or pure water. Peroxo-titania powder prepared with NH(3) aq showed highest photooxidation activity. Moreover, we found unique photofunctional properties: together with formaldehyde production, the photo-excited electron also triggers oxygen evolution, although by TiO(2) (Degussa P-25) photocatalysis H(2) evolution was observed from the same solution.

Surfactant-Free Synthesis of Single Crystalline SnS2 and Effect of Surface Atomic Structure on the Photocatalytic Property

Sheetlike tin disulfide (SnS2) single crystal exposed with well-defined facets and flowerlike SnS2 mainly exposed with facets were prepared through a surfactant-free solvothermal process. Photocatalytic degradation of methyl orange (MO) under visible light irradiation indicated that the sheetlike SnS2 showed a much higher activity than flowerlike SnS2. Theoretical and experimental results revealed that the band structure derived from the surface atomic structure played a more important role than the surface energy in the photocatalytic property. The present work has provided a deep insight into the important role of the surface energy and band structure, both of which are derived from the surface atomic structure, in the photocatalytic activity.

石墨烯/电气石/二氧化钛复合材料的制备及其光催化降解异丙醇性能

Abstract We report the construction of a graphene/tourmaline/TiO 2 (G/T/TiO 2 ) composite system with enhanced charge-carrier separation, and therefore enhanced photocatalytic properties, based on tailoring the surface-charged state of graphene and/or by introducing an external electric field arising from tourmaline. A simple two-step hydrothermal method was used to synthesize G/T/TiO 2 composites and poly(diallyldimethylammonium chloride)-G/T/TiO 2 composites. In the photocatalytic degradation of 2-propanol (IPA), the catalytic activity of the composite containing negatively charged graphene was higher than of the composite containing positively charged graphene. The highest acetone evolution rate (223 μmol/h) was achieved using the ternary composite with the optimum composition, i.e., G0.5/T5/TiO 2 (0.5 wt% graphene and 5 wt% tourmaline). The involvement of tourmaline and graphene in the composite is believed to facilitate the separation and transportation of electrons and holes photogenerated in TiO 2 . This synergetic effect could account for the enhanced photocatalytic activity of the G/T/TiO 2 composite. A mechanistic study indicated that O 2 •− radicals and holes were the main reactive oxygen species in photocatalytic degradation of IPA.

Synthesis, characterization, and photocatalytic activity of g-C 3 N 4 /KTaO 3 composites under visible light irradiation

Novel graphitic carbon nitride/KTaO3 (g-C3N4/KTaO3) nanocomposite photocatalysts have been successfully synthesized via a facile and simple ultrasonic dispersion method. Compared to either g-C3N4 or KTaO3, the composite photocatalysts show significantly increased photocatalytic activity for degradation of Rhodamine B (RhB) under visible light irradiation. The increased photocatalytic performance of the composite could be attributed to the enhanced photogenerated charge carrier separation capacity. Moreover, it is observed that is the main active species in the photocatalytic degradation of RhB using the g-C3N4/KTaO3 composite photocatalysts.