Lingling Xu

Precursor template synthesis of three-dimensional mesoporous ZnO hierarchical structures and their photocatalytic properties

In this paper, three-dimensional mesoporous Zinc oxide (ZnO) hierarchical structures were fabricated from the thermal-decomposition of layered basic zinc carbonate (LBZC) precursors, which were synthesized by an urea hydrothermal method without a surfactant. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the LBZC precursors and mesoporous ZnO hierarchical structures. The results of N2 adsorption–desorption isotherms indicated that the pore size distribution and specific surface area can be tailored by varying the urea amount and the annealing temperature. Photocatalytic activity of the mesoporous ZnO was evaluated using the degradation of methyl orange. The influence of urea content and annealing temperature on the morphology and surface specific areas and the effect of BET areas on the photocatalytic activity were discussed. Hierarchical ZnO flowers with 0.006 mol urea added annealed at 300 °C showed good photocatalytic activity.

One-step hydrothermal synthesis and optical properties of aluminium doped ZnO hexagonal nanoplates on a zinc substrate†

Controlled synthesis of Al3+ doped ZnO hexagonal nanoplates was achieved via a facile one-step hydrothermal approach. The thicknesses of nanoplates, ranging from about 60 nm to 200 nm, can be controlled by variation of Al3+ concentration. A possible mechanism was proposed for the growth of a ZnO nanoplate and Al3+ cations played a crucial role for the shape-controlled synthesis. The photoluminescence spectra clearly showed a blue shift with the increasing Al3+ content.

Ag2O–Bi2O3 composites: synthesis, characterization and high efficient photocatalytic activities

Ag2O nanoparticle modified α-Bi2O3 composite photocatalysts were synthesized and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectroscopy. XRD patterns confirmed that the composites consist of cubic phase Ag2O and monoclinic α-Bi2O3 phase. The Ag2O loading was greatly increased due to the rough surface of the acid etched Bi2O3 microrods. Photocatalytic activity of the Ag2O–Bi2O3 composites was evaluated using the degradation of methyl orange (MO). The correlation between the Ag2O content and photocatalytic activity was estimated. The composite with Ag to Bi ratio of 3 : 1 as raw material showed the highest visible light activity and the enhancement mechanism was attributed to the separation of photoinduced electron and holes by the carrier transfer.

Flower-like ZnO-Ag2O composites: precipitation synthesis and photocatalytic activity

Ag2O-decorated flower-like ZnO composites were fabricated through a chemical precipitation process. X-ray diffraction analysis confirms the co-existence of cubic Ag2O and wurtzite ZnO phases. Scanning electron microscopy images reveal Ag2O nanoparticles located on the rough surface of ZnO flowers. The photocatalytic activities of the composites with various mole ratios were evaluated by the degradation of methyl orange (MO) under ultraviolet irradiation, which confirms that the composite shows superior activity to that of pure ZnO and Ag2O. The improvement can be ascribed to the deposited Ag2O forming the p-n junction at the interface of ZnO and Ag2O, resulting in the transfer of photocarriers and suppressing the electron–hole recombination rate.

Nanosize α-Bi2O3 decorated Bi2MoO6 via an alkali etching process for enhanced photocatalytic performance

Bi2MoO6/Bi2O3 heterojunction photocatalysts were synthesized through a facile alkali etching method and their photocatalytic activity was evaluated by photodegradation of Rhodamine B (RhB) under visible-light irradiation. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM)/transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectroscopy. XRD, TEM and XPS results confirm that the Bi2MoO6/Bi2O3 heterojunctions were formed after the alkali etching process. The photocatalytic activity can be easily controlled by adjusting the etching time and the highest visible-light-responsive photocatalytic performance was observed on Bi2MoO6/Bi2O3 composite that was etched in 0.1 M NaOH for 45 min. Moreover, the mechanistic study suggested that the photoinduced holes played a major role for the RhB degradation and the photocurrent tests confirmed that the effective electron–hole separation on the interface of the p–n junction promotes the photocatalytic process.

Generation of Oxygen Vacancy and OH Radicals: A Comparative Study of Bi2WO6 and Bi2WO6−x Nanoplates

A comparative study of visible‐light‐responsive Bi2WO6 and oxygen‐deficient Bi2WO6−x nanoplates was conducted. The formation of oxygen vacancy resulted in the band gap narrowing of oxygen‐deficient Bi2WO6−x, through an elevation of both of the conduction and valence band positions. FTIR spectra revealed that much more surface hydroxyl groups have been detected after the etching process. The scavengers tests confirmed the generation of ⋅OH radicals during photochemical reaction for Bi2WO6−x, whereas no .OH radicals can be detected for pure Bi2WO6. The photocatalytic activities of optimized Bi2WO6−x on the decomposition of Rhodamine B (RhB) was three times as high as that of pure Bi2WO6. The improvement of photocatalytic activity on degradation of RhB and phenol can be ascribed to the synergistic effect of oxygen deficiency‐induced band shifts, together with the large quantities of surface hydroxyl groups providing active sites for the generation of OH radicals (.OH).

Surface plasmon enhanced ultraviolet emission and observation of random lasing from self-assembly Zn/ZnO composite nanowires

Self-assembly Zn/ZnO composite nanowires were successfully synthesized via a simple chemical vapor deposition method. The composition and crystal structure of the Zn/ZnO composite nanowires were characterized by transmission electron microscopy. The surface of the ZnO nanowires was decorated with Zn nanoparticles. Their photoluminescence properties were measured, indicating that the near-band edge emission intensity was significantly enhanced and visible emission was suppressed, which originates from the coupling between surface plasmons and the near-band edge emission of ZnO (or electromagnetic field). Random lasing from Zn/ZnO composite nanowires was observed due to the surface plasmon resonant effect. Our results show a convenient way to achieve laser action by the surface plasmon resonant effect.

Electrospun ZnO/Bi2O3 Nanofibers with Enhanced Photocatalytic Activity

ZnO/Bi2O3 nanofibers were synthesized by a simple electrospinning method and both the UV and visible light responsive photocatalytic properties were studied by the decolorization of RhB dye. Thermogravimetric analysis/differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), scanning electron microscope (SEM), and UV-vis diffuse reflectance spectra (DRS) were employed to study the structure, morphology, and optical properties of the ZnO/Bi2O3 nanofibers, respectively. The relationship between the ZnO/Bi2O3 ratio and photocatalytic activity was also studied, and the composite with a molar ratio of 23 : 1 demonstrated the best activity under both excitations. The photocatalytic mechanisms for the composite fibers can be described as the direct photocatalysis under UV excitation and photosensitation for visible light irradiation. The enhanced photocatalytic activities can be ascribed to the effective electron-hole pairs separation that leads to the promoted photocatalytic efficiency.

Colored TiO2 hollow spheres for efficient water-splitting photocatalysts

TiO2 nanomaterials have attracted tremendous interest in photocatalytic hydrogen generation. Herein we report unique colored anatase TiO2 hollow spheres consisting of crystalline-inner shell/amorphous-outer shell structured nanocrystallites, which exhibit remarkably enhanced photocatalytic performances for water splitting. The optimized TiO2 spheres delivered a H2 production rate of 0.182 mmol g−1 h−1, which was 2 times higher than that of pristine TiO2. The enhanced activity can be ascribed to the generation of oxygen vacancies and Ti3+ sites.

Ion Exchange Synthesis of Bi2MoO6/BiOI Heterojunctions for Photocatalytic Degradation and Photoelectrochemical Water Splitting

In this study, flower-like Bi2MoO6/BiOI heterostructure photocatalysts were synthesized via an anion exchange method using BiOI as precursor. The composition of Bi2MoO6/BiOI can be easily controlled by adjusting the MoO42−/I− molar ratio. Photocatalytic activity studies based on the degradation of Rhodamine B (RhB) show that Bi2MoO6/BiOI=50% photocatalyst exhibited the best performance under visible light excitation. The radical scavengers test demonstrated that holes was the main reactive species for the degradation of RhB, and⋅O2− also took part in the photodecomposition process. Photoelectrochemical measurement reveals that the Bi2MoO6/BiOI=50% exhibit enhanced carrier densities, charge separation and photocurrent compared with the original Bi2MoO6 and BiOI. Our results show that bismuth-based heterojunctions fabricated through the anion exchange method could be a cost-effective approach to improve the photocatalytic activity and photoelectrochemical performance of BiOI.