Weijia An

Novel Cu2O quantum dots coupled flower-like BiOBr for enhanced photocatalytic degradation of organic contaminant

Here we report a highly efficient novel photocatalyst consisting of Cu2O quantum dots (QDs) incorporated into three-dimensional (3D) flower-like hierarchical BiOBr (hereafter designated QDs-Cu2O/BiOBr), which were synthesized via a simple reductive solution chemistry route and applied to decontaminate the hazardous wastewater containing phenol and organic dyes. The deposition of Cu2O QDs onto the surface of the BiOBr was confirmed by structure and composition characterizations. The QDs-Cu2O/BiOBr composites exhibited superior activity for organic contaminant degradation under visible light and 3 wt% QDs-Cu2O/BiOBr composite showed the highest degrade rate for phenol and methylene blue (MB), which was 11.8 times and 1.4 times than that of pure BiOBr, indicated the QDs-Cu2O/BiOBr composite has the great potential application in purifying hazardous organic contaminant. The incorporated Cu2O QDs played an important role in improving the photocatalytic performance, due to the enhancement of visible light absorption efficiency as well as the efficient separation of the photogenerated charge carriers originating from the intimately contacted interface and the well-aligned band-structures, which was confirmed by the results of PL, photocurrent and EIS measurements. The possible photocatalytic mechanism was proposed based on the experiments and theoretical results.

Novel Cu2S quantum dots coupled flower-like BiOBr for efficient photocatalytic hydrogen production under visible light

Cu2S quantum dots (QDs) coupled three-dimensional (3D) flower-like hierarchical BiOBr (QDs-Cu2S/BiOBr) were prepared via a simple precipitation method. The Cu2S QDs, with an average diameters of 10 nm, were uniformly attached on the surface of BiOBr with an intimate contact interface as evidenced by characterization of the structure and composition of the composite. The QDs-Cu2S/BiOBr composite exhibited enhanced water splitting for hydrogen evolution, and 717 μmol g−1 of H2 was produced with 3 wt% QDs-Cu2S/BiOBr containing 1 wt% Pt, which was 3.1 times higher than that of Cu2S nanoparticles. The enhancement of hydrogen evolution was attributed to the synergic effect between BiOBr and Cu2S QDs, where the hybridization could effectively accelerate the separation of the photogenerated charge carriers.

Dramatic activity of a Bi2WO6@g-C3N4 photocatalyst with a core@shell structure

Here we report a Bi2WO6@g-C3N4 core@shell structure which was prepared by a combined ultrasonication–chemisorption method with enhanced photocatalytic degradation. The composites were extensively characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS). Compared with bare Bi2WO6 and g-C3N4, the Bi2WO6@g-C3N4 composites exhibited significantly enhanced photocatalytic activity for methylene blue (MB) degradation under visible light irradiation. The 3 wt% Bi2WO6@g-C3N4 showed the highest photocatalytic activity under visible light irradiation, which was about 1.97 times higher than Bi2WO6. In addition, the quenching effects of different scavengers displayed that the reactive h+ and ˙O2− play the major role in the MB decolorization. The core@shell hybrid photocatalyst exhibited dramatically enhanced photo-induced electron–hole separation efficiency, which was confirmed by the results of photocurrent and EIS measurements. On the basis of the experimental results and estimated energy band positions, a mechanism for the enhanced photocatalytic activity was proposed.

Synthesis of a hierarchical BiOBr nanodots/Bi2WO6 p–n heterostructure with enhanced photoinduced electric and photocatalytic degradation performance

Three-dimensional composites of flower-like Bi2WO6 decorated with BiOBr nanodots (designated BiOBr nanodots/Bi2WO6) with varying BiOBr content have been prepared by a simple method. The BiOBr nanodots, with average diameters of 50 nm, adhered tightly to the surface of Bi2WO6 and formed p–n heterojunctions between BiOBr and Bi2WO6, as evidenced by the characterization of its structure and composition. Compared to pure Bi2WO6 and BiOBr, BiOBr/Bi2WO6 showed a lower charge-transfer resistance, higher photocurrent and enhanced photoelectric properties. The photocurrent of the 15% BiOBr/Bi2WO6 composite was 17.2 and 2.39 times higher than that of pure Bi2WO6 and BiOBr, respectively. Meanwhile, this composite showed the highest degradation rate for methylene blue (MB), which was 1.7 and 2.4 times that of pure Bi2WO6 and BiOBr, respectively. The enhanced photoelectric and photocatalytic degradation performances were ascribed to the introduction of BiOBr nanodots and the formation of p–n heterojunctions, which could greatly accelerate the separation of photogenerated charge carriers. In addition, the roles of the radical species were investigated, and ·O2− and h+ are thought to dominate the photocatalytic process. Based on the experimental results, a possible photocatalytic mechanism was proposed.

Cu2O NPs decorated BiPO4 photo-catalyst for enhanced organic contaminant degradation under visible light irradiation

The surface of BiPO4 was decorated with Cu2O nanoparticles (NPs) (hereafter designed as Cu2O/BiPO4) via an interfacial self-assembly method. The physical and photophysical properties of the Cu2O/BiPO4 hybrid photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray fluorescence spectrometry (XRF), UV-vis diffuse reflectance spectroscopy (DRS) and photo-electro-chemical (PEC). Compared with bare BiPO4 and Cu2O, the Cu2O/BiPO4 composites exhibited significantly enhanced photocatalytic activity for methylene blue (MB) degradation under visible light irradiation. The 5 wt% Cu2O/BiPO4 showed the highest photocatalytic activity under visible light irradiation, which was about 12.25 times that of BiPO4. Significantly, the superior stability was also observed in the five cyclic runs. The Cu2O/BiPO4 hybrid photocatalysts exhibited dramatically enhanced photo-induced electron–hole separation efficiency, which was confirmed by the results of photocurrent measurements. On the basis of the experimental results and estimated energy band positions, the mechanism of enhanced photocatalytic activity was proposed.

Surface Decoration of ZnWO4 Nanorods with Cu2O Nanoparticles to Build Heterostructure with Enhanced Photocatalysis

The surface of ZnWO4 nanorods was decorated with Cu2O nanoparticles (Cu2O/ZnWO4) prepared through a precipitation method. The Cu2O nanoparticles were tightly deposited on the ZnWO4 surface and had average diameters of 20 nm. The nanoparticles not only promoted the absorption and utilization of visible light but also facilitated the separation of photogenerated charge carriers. This brought an improvement of the photocatalytic activity. The 5 wt % Cu2O/ZnWO4 photocatalyst displayed the highest degrade efficiency for methylene blue (MB) degradation under visible light, which was 7.8 and 2 times higher than pure ZnWO4 and Cu2O, respectively. Meanwhile, the Cu2O/ZnWO4 composite photocatalyst was able to go through phenol degradation under visible light. The results of photoluminescence (PL), photocurrent, and electrochemical impedance spectra (EIS) measurements were consistent and prove the rapid separation of charge, which originated from the match level structure and the close contact with the interface. The radical and hole trapping experiments were carried out to detect the main active substances in the photodegradation process. The holes and ·O2− radicals were predicted to dominate the photocatalytic process. Based on the characterization analysis and experiment results, a possible photocatalytic mechanism for enhancing photocatalytic activity was proposed.

Inserting AgCl@rGO into graphene hydrogel 3D structure: synergy of adsorption and photocatalysis for efficient removal of bisphenol A

An AgCl@graphene (rGO) core–shell structure was fabricated and then loaded into reduced graphene oxide hydrogel (rGH) to form AgCl@rGO-rGH by the chemical reduction method. The AgCl@rGO core–shell structure inhibited the aggregation of the AgCl particles and promoted the rapid transfer and separation of photogenerated electron–hole pairs. Moreover, the AgCl@rGO-rGH composite exhibited a high adsorption and photocatalytic degradation capacity for bisphenol A (BPA). Specifically, the degradation efficiency of BPA on AgCl@rGO-rGH-2 reached 93.7% under the synergy of adsorption and photocatalytic degradation, and the degradation efficiency of BPA reached 87.0% after five cycles of degradation, which demonstrated the great synergistic effect between graphene and AgCl. The degradation capabilities of AgCl@rGO-rGH were 6.4 and 2.8 times of pure AgCl and rGH on the synergistic degradation of BPA. In the continuous flow system, the degradation ratio of AgCl@rGO-rGH-2 remained 100% within the first 4 h under the synergy conditions. When the reaction time reached 9 h, the synergistic degradation ratio of BPA remained about 75.2%. It showed that AgCl@rGO-rGH-2 still has good degradation activity and long life in the mobile phase system.