Jinshan Hu

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.

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.

Highly ordered TiO2 nanotube arrays wrapped with g-C3N4 nanoparticles for efficient charge separation and increased photoelectrocatalytic degradation of phenol

Novel graphitic carbon nitride nanoparticles (NPs)-wrapped TiO2 nanotube arrays (NTAs) (g-C3N4/TiO2) were fabricated by a two-step method including an electrochemical anodization technique followed by impregnation under vacuum using urea as precursor. The as-prepared photoelectrode exhibited outstanding photoelectric properties and excellent photelectrocatalytic (PEC) performance for the degradation of phenol under stimulated solar light, which was due to the enhanced light absorption property and improved charge separation efficiency. The introduction of g-C3N4 NPs strongly decreased the charge transfer resistance and boosted the charge separation efficiency of TiO2. The optimum ratio of the g-C3N4/TiO2 yielded a pronounced 4.18-fold higher photocurrent density than TiO2. Besides, the combination of g-C3N4 NPs could negatively shift for the flat band potential of TiO2, resulting in an enhanced reduction property for the photoelectrocatalytic degradation of organic pollutants. The PEC process for the degradation of phenol over g-C3N4/TiO2 was much higher than the sum of photocatalytic (PC) and electrocatalytic (EC) processes indicating that a photoelectric synergy was achieved on the as-prepared photoelectrode and resulting in an improved PEC performance for the composite photoelectrode.

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.

Growth of nano Ag@AgCl on (111) facets of Cu2O microcrystals with an enhanced photocatalytic activity

Single crystalline Cu2O nanoparticles were synthesized under mild conditions. A Ag@AgCl/Cu2O photocatalyst was prepared by directly growing Ag@AgCl nanoparticles (NPs) on (111) facets of octahedral Cu2O via a facile precipitation in situ photoreduction method. The results indicate that Ag@AgCl nanoparticles have a narrow size distribution ranging from 10 to 50 nm and are uniformly distributed on the surface of Cu2O nanoparticles. The surface area of the composite reached up to 19.736 m2 g−1. The photocatalytic performance of the Ag@AgCl/Cu2O composite for the degradation of methylene blue (MB) was evaluated under visible light irradiation. The Ag@AgCl/Cu2O composite with 30 wt% Ag@AgCl showed the highest photocatalytic activity, degrading 93.61% MB after 2 h irradiation. The high photocatalytic activity of the Ag@AgCl/Cu2O composite can be attributed to its high surface area, the crystal effect of Cu2O and the surface plasmon resonance of the Ag NPs. In addition, the Ag@AgCl/Cu2O composite can be used as a photocatalyst for the degradation of phenol. Based on these experimental results, a photocatalytic mechanism for the degradation of hazardous chemical effluents over Ag@AgCl/Cu2O photocatalysts was proposed. The free radicals and holes act as the main reactive species during the degradation.

Facile hydrothermal synthesis of plasmonic photocatalyst Ag@AgCl and degradative photocatalysis under visible light irradiation

We put forward a new approach for the synthesis of Ag@AgCl plasmonic photocatalyst via a hydrothermal-deposition-photoreduction method. The cetylmethylammonium chloride (CTAC) was used alone as both a source of reactants and surfactant. The structure of the prepared photocatalyst was determined by XRD, SEM, EDX and UV-Vis spectroscoscopy. The photocatalytic properties were investigated by degradation of an organic pollutant, Rhodamine B, under visible light irradiation. The results reveal that the experimental conditions have a great effect on the morphology of Ag@AgCl crystals. Ag@AgCl crystal is cubic and the Ag@AgCl sample which is photoreduced for 40 min exhibits the highest photoactivity, and 80.6 % RhB is degraded after irradiation for 2 hours using this catalyst. The high photocatalytic activity observed is attributed to the surface plasmon resonance effect of Ag nanoparticles.

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.

Ag3PO4@UMOFNs Core–Shell Structure: Two-Dimensional MOFs Promoted Photoinduced Charge Separation and Photocatalysis

Metal-organic frameworks (MOFs) are a new type of functional material that is self-assembled by metal ions and organic ligands. In this paper, a bimetal-organic framework was synthesized and stripped into two-dimensional nanosheets structure via an ultrasonic method. We coated the UMOFNs (ultrathinning MOFs into two-dimensional nanosheets) on Ag3PO4 nanoparticles to obtain Ag3PO4@UMOFNs core-shell photocatalysts. Under visible-light irradiation, the degradation of phenol was 100% within 16 min, and the degradation of biphenyl A was 98.9% within 20 min via Ag3PO4@UMOFNs (5 wt %). These values were 1.6- and 1.8-times higher than Ag3PO4, respectively. The activity of the Ag3PO4@UMOFNs increased due to the synergistic effects. The π-π bonds of the organic ligands and weak interactions between UMOFNs and Ag3PO4 collectively promote charge transfer. In addition, matching energy-level structures and a sufficiently large contact area accelerate the separation of the photogenerated charges and improve the activity. This remarkably improves the photocatalytic activity.

Photocatalytic hydrogen evolution from the splitting of water over Cd1-xZnxS/K2La2Ti3O10 composites under visible light irradiation

A series of Cd1-xZnxS/K2La2Ti3O10 composites were synthesized via a simple co-precipitation method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDX), ultraviolet-visible diffuse reflection (UV-Vis), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) measurements. The composite structures consisted of Cd1-xZnxS nanoparticles evenly distributed on the surface of K2La2Ti3O10. The absorption edge of K2La2Ti3O10 shifted to the visible light region upon introduction of the Cd1-xZnxS nanoparticles. The photocatalytic activities of the catalysts were evaluated by hydrogen production under visible light irradiation. The prepared Cd0.8Zn0.2S(30wt%)/K2La2Ti3O10 exhibited higher photocatalytic activity, evolving 6.92 mmol/g H2 under visible light irradiation for 3 h. The promoted photocatalytic activity of the composites was attributed to the synergistic effect between Cd1-xZnxS and K2La2Ti3O10, which resulted in enhanced separation of photogenerated electrons and holes.

An oil-in-water self-assembly synthesis, characterization and photocatalytic properties of nano Ag@AgCl surface-sensitized K{sub 2}Ti{sub 4}O{sub 9}

Highlights: • The plasmatic Ag@AgCl surface-sensitized K{sub 2}Ti{sub 4}O{sub 9} composite photocatalysts. • Ag@AgCl greatly increased visible light absorption for K{sub 2}Ti{sub 4}O{sub 9}. • The photocatalysts exhibited enhanced photocatalytic dye degradation. - Abstract: Nano-sized plasmonic Ag@AgCl surface-sensitized K{sub 2}Ti{sub 4}O{sub 9} composite photocatalysts (hereafter designated as Ag@AgCl/K{sub 2}Ti{sub 4}O{sub 9}) was synthesized via a facile oil-in-water self-assembly method. The photocatalytic activity of the prepared materials for RhB (Rhodamine B) degradation was examined under visible light irradiation. The results reveal that the size of Ag@AgCl, which evenly dispersed on the surface of K{sub 2}Ti{sub 4}O{sub 9}, distributes about 20–50 nm. The UV–vis diffuse reflectance spectra indicate that Ag@AgCl/K{sub 2}Ti{sub 4}O{sub 9} samples have a significantly enhanced optical absorption in 380–700 nm. The photocatalytic activities of the Ag@AgCl/K{sub 2}Ti{sub 4}O{sub 9} samples increase first and then decrease with increasing amount of loading Ag@AgCl and the Ag@AgCl(20 wt.%)/K{sub 2}Ti{sub 4}O{sub 9} sample exhibits the best photocatalytic activity and 94.47% RhB was degraded after irradiation for 2 h. Additionally, studies performed using radical scavengers indicated that O{sub 2}·{sup −} and Cl{sup 0} acted as the main reactive species. The electronic interaction was systematically studied and confirmed by the photo-electrochemical measurements.