Yanbiao Shi

Fabricating a g-C3N4/CuOx heterostructure with tunable valence transition for enhanced photocatalytic activity

Heterostructured g-C3N4/CuOx nanocomposites were successfully prepared with varying the content of g-C3N4 via a mixed solvent-thermal method. Organic ammonia ethanolamine was used as the reductant to adjust the valence of CuOx. Meanwhile, the bulk g-C3N4 was efficiently exfoliated into ultrathin nanoplates during the synthesis process. It is found that the different contents of g-C3N4 can effectively accelerate the valence transition of Cu in the nanocrystals. That is, the successive appearance of CuO and Cu2O with the enhancement of g-C3N4 content. These heterostructured composites were characterized for structural, morphological, elemental distribution, optical properties, specific surface area and photo-generated carrier separation efficiency by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectrum. The photocatalytic performance investigations indicate that the CN5–CuOx is stable enough and shows a remarkable photocatalytic efficiency for degrading methyl orange (MO) under simulated sunlight irradiation, compared with the pure CuOx nanocrystals. The enhanced photocatalytic performance can be attributed to the enlarged surface area, beneficial heterojunction among Cu2O@g-C3N4 and efficient carrier separation efficiency. The abundant Cu substrate in the CuOx nanocrystals functions as a rapid electron/hole pair transfer avenue and inhibits their recombination. Thus the photocatalytic efficiency is tremendously enhanced.

Designed C3N4/CdS–CdWO4 core–shell heterostructure with excellent photocatalytic activity

C3N4/CdS–CdWO4 core–shell heterostructure photocatalysts were prepared via a facile solvent volatilization method. High-resolution transmission electron microscopy (HRTEM) analysis demonstrated that an interfacial structure was present between the C3N4 shell and the CdS–CdWO4 core, and the specific function of the modification of C3N4 was investigated by room-temperature photoluminescence spectroscopy and transient photocurrent measurement. The heterostructure photocatalysts displayed enhanced photocatalytic activity in the degradation of RhB dye than that of the single components and binary composites. Among the as-prepared samples, the best photocatalytic performance was achieved by 10 wt% C3N4/CdS–CdWO4, which was about 5.7 and 14.6 times that of CdS–CdWO4 and C3N4, respectively, under UV-visible light irradiation. Owing to the formation of a C3N4/CdS–CdWO4 ternary heterostructure, its efficient pollutant-removing ability and stability can be attributed to the improved separation of photogenerated carriers and transfer efficiency for the intensive built-in electric field intensity. Radical trapping experiments proved that h+ and ˙O2− play crucial roles in the photocatalytic process.

Preparing ZnWO4–CdS composite with excellent visible light photocatalytic activity under mild conditions

AbstractZnWO4–CdS composite was designed and synthesized via a surface functionalized route under mild conditions. In this composite, CdS nanoparticle was successfully anchored on ZnWO4 nanorod with addition of citric acid. The formed composite was characterized by X-ray diffraction patterns, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller, photoluminescence and transient photocurrent response. Besides, a possible nucleation-growth mechanism was proposed. To explore the photocatalytic performance of as-prepared ZnWO4–CdS composite, methylene blue and ciprofloxacin were chosen as the representative to systematically assess the degradation ability of as-prepared composite under visible light irradiation. The obtained results indicate that the ZnWO4–CdS3 composite photocatalyst is more efficient to methylene blue and ciprofloxacin than others under same conditions. The greatly enhanced photocatalytic performance of ZnWO4–CdS composite can be attributed to larger specific surface area, wider photo adsorption range and higher photo-induced carriers separation efficiency. A reasonable mechanism of the enhanced photocatalytic activity was confirmed and demonstrated by a series of characterization methods.Graphical Abstract The formation of n-n heterojunction between ZnWO4 and CdS can effectively promote the separation and transfer efficiency of photo-generated carriers and enhance the photocatalytic performance of composite.

A flower-like TiO2 with photocatalytic hydrogen evolution activity modified by Zn(II) porphyrin photocatalysts

The Zn(II)5,10,15,20-tetrakis [m-methoxy-p-hydroxyl-phenyl] porphyrins (ZnTmMpHPP) as a photosensitizer was applied to modified TiO2 and the composite was prepared via a hydrothermal process. The as-obtained flower-like TiO2 and TiO2/ZnTmMpHPP composites were characterized by X-ray diffractometry, scanning electron microscopy, Fourier transform infared spectromotry, transient photocurrent responses and BET. Photocatalytic hydrogen production results show the TiO2/ZnTmMpHPP composite has a higher photocatalytic activity than pure TiO2 under ultraviolet light irradiation, which is due to the enhanced transfer and separation efficiency of photo-induced carriers from the ZnTmMpHPP to TiO2 with the help of conjugated π bond in ZnTmMpHPP. The recycled H2 evolution test indicates that the TiO2/ZnTmMpHPP composite is stable enough under the reaction system. In the presented paper, it is proven that the ZnTmMpHPP can greatly accelerate the separation of charges and effectively improve the photocatalytic H2 evolution activity of TiO2.