Shuquan Huang

High yield synthesis of nano-size g-C3N4 derivatives by a dissolve-regrowth method with enhanced photocatalytic ability

Nano-size g-C3N4 derivatives were fabricated by a simple dissolve-regrowth method in HNO3 solution followed by a calcination process. X-ray diffraction (XRD), Z-potential, elemental analysis and IR are used to investigate the structure, composition and the properties of the samples. Scanning electron microscopy (SEM) shows the average size of the nano-size g-C3N4 derivatives increases with increasing calcination temperature. Methyl orange (MO) dye was used as the target pollutant to investigate the photoactivity of the samples. The pure g-C3N4 can only degrade about 1.1% MO, while the g-C3N4 derivatives calcined at 300 °C can decompose about 31.9% of MO in 4 h. Besides, when a small amount of methylene blue (MB) solution was introduced, the g-C3N4–HNO3-300 can decompose about 75.8% in 4 h. The photoactivity of g-C3N4 was greatly enhanced after the modification process (especially with the assistance of MB). Additionally, this work supplied a simple method to modify materials with enhanced photoactivity. Finally, the possible reactive species and the possible mechanism were proposed based on Electron spin resonance (ESR) and XPS results.

A core–shell structured magnetic Ag/AgBr@Fe2O3 composite with enhanced photocatalytic activity for organic pollutant degradation and antibacterium

A core–shell structured magnetic Ag/AgBr@Fe2O3 composite was synthesized through a facile solvothermal method. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible absorption spectroscopy (UV-vis) were applied to characterize the structures and properties of the as-prepared samples. The results indicate that Fe2O3 was coated on the surface of Ag/AgBr and heterostructures were formed. Electrochemistry analysis and photoluminescence (PL) spectra analysis indicate that the introduction of Fe2O3 could improve electron and hole separation efficiency. The photocatalytic activity of the Ag/AgBr@Fe2O3 composites was evaluated by using organic dye methyl orange (MO), endocrine disrupting chemical bisphenol A (BPA) and Escherichia coli (E. coli) as the target pollutants. The as-prepared Ag/AgBr@Fe2O3 composites exhibited much higher photocatalytic activities than pure Ag/AgBr, which was attributed to the effective charge separation of the Ag/AgBr@Fe2O3 composite. In addition, the as-prepared Ag/AgBr@Fe2O3 composite has magnetic properties, therefore after the photocatalytic reaction, it can be quickly separated from solution by an extra magnetic field. Trapping experiments and ESR analysis indicate that the h+ and ˙O2− are the main active species for the photocatalytic degradation. A possible Z-scheme pathway photocatalytic mechanism was proposed.

Magnetically separable Fe2O3/g-C3N4 catalyst with enhanced photocatalytic activity

A two-step method was developed to prepare magnetic separable Fe2O3/g-C3N4 photocatalysts. The samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible absorption spectroscopy (UV-vis), photoluminescence (PL) spectroscopy and X-ray photoelectron spectroscopy (XPS). The magnetic capability of the samples was investigated by vibrating sample magnetometer (VSM) analysis. The crystal phase and the magnetic property of the Fe2O3 can be tuned by changing the calcination temperature. The Fe2O3/g-C3N4 photocatalyst showed enhanced photoactivity in degrading the rhodamine B (RhB) dye. Among the samples, the 10% Fe2O3/g-C3N4 showed the highest photocatalytic activity. It can degrade about 96.7% RhB in 4 h. The photocurrent results confirm that the combination of the two materials is beneficial for the separation of electron–hole pairs. The electron spin resonance (ESR) results indicates that ˙O2− and ˙OH are the main active species in the degradation process.

Preparation of magnetic Ag/AgCl/CoFe2O4 composites with high photocatalytic and antibacterial ability

Novel plasmonic photocatalysts, Ag/AgCl/CoFe2O4, were prepared via a two-step synthesis method. The obtained Ag/AgCl/CoFe2O4 composites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible absorption spectroscopy (UV-vis). The magnetic properties of the samples were studied by vibrating sample magnetometer (VSM) analysis. Methyl orange (MO), bisphenol A (BPA) and ciprofloxacin (CIP) were used as target pollutants to investigate the degradation capability of Ag/AgCl/CoFe2O4. Results showed that the composite can degrade both colored and colorless pollutants, while Ag/AgCl/CoFe2O4 (3 : 1) composite showed the highest photoactivity in the degradation of MO. It can degrade about 93.38% MO in 1.5 h. The reactive species scavenger results indicated that hydroxyl radicals (˙OH) were not the main photooxidant, while holes (h+) and superoxide anion radicals (˙O2−) played key roles in MO decoloration. Furthermore, the degraded solution of BPA was analyzed using high performance liquid chromatography (HPLC). The results showed that BPA was decomposed gradually. The composite was magnetically separated and investigated using three successive recycle experiments under visible light. The results exhibited that the photoactivity of Ag/AgCl/CoFe2O4 is stable. Besides, Ag/AgCl/CoFe2O4 also exhibited good antibacterial activity against Escherichia coli (E. coli). The method used to prepare the composite can be expanded and applied to synthesize other magnetically separable photocatalysts.

Core–shell magnetic Ag/AgCl@Fe2O3 photocatalysts with enhanced photoactivity for eliminating bisphenol A and microbial contamination

Core–shell magnetic Ag/AgCl@Fe2O3 photocatalysts were synthesized using a two-step method. The introduced Fe2O3 can be effectively dispersed on the surface of the Ag/AgCl. The Fe2O3 on the surface can act as a shell to prevent the inactivation of the inner Ag/AgCl by bisphenol A (BPA). The composites were investigated by XRD, SEM-EDS, XPS, UV-vis, VSM, and so on, which confirmed that the core–shell magnetic Ag/AgCl@Fe2O3 was successfully obtained. The EIS and PL results suggest that the composite has better electron–hole separation ability, which is beneficial for enhancing the photoactivity. The degradation of the BPA solution results show that the 5% Ag/AgCl@Fe2O3 has the highest photoactivity, the degradation rate of which is as high as about 13 times that of pure Ag/AgCl. Besides, the composites still have much better degradation ability than the pure Ag/AgCl in each cycle experiment. The photocatalytic antibacterial experiment showed that the composite could completely kill the pathogenic microorganism E. coli under visible light irradiation at 30 min. The results suggest that the core–shell magnetic Ag/AgCl@Fe2O3 can be used as an effective magnetic recyclable photocatalyst in eliminating the colorless pollutant bisphenol A and microbial contamination. Furthermore, a possible reaction mechanism was proposed based on the trapping experiments and the ESR results.

Facile synthesis of CNT/AgI with enhanced photocatalytic degradation and antibacterial ability

CNT/AgI composite with the diameter smaller than 1 µm was synthesized through a solvothermal method. The CNT/AgI hybrids were characterized by XRD, SEM, XPS, UV-Vis, photocurrent and so on. The results showed that the introduced CNT can greatly reduce the particle size of AgI without using surfactant. Besides, the introduced CNT transferred the electrons efficiently and enhanced the photoactivity of the CNT/AgI hybrids in degrading RhB dye. 0.3% CNT/AgI showed the highest photocatalytic activity, which was as high as about 2 times that of pure Ag/AgI. Trapping experiments and the electron spin resonance (ESR) results suggested the reactive species in the degradation process were h+, ˙OH and ˙O2−. Furthermore, the CNT/AgI still showed high photoactivity after 4 cycle experiments. Photocatalytic antibacterial experiments showed that the 0.3% CNT/AgI had better antibacterial ability than pure Ag/AgI. The results showed that the CNT/AgI can be used as a dual functional material in water treatment of removing the organic pollutant and killing the bacterium at the same time.

Synthesis and photocatalytic activity of g-C3N4/BiOI/BiOBr ternary composites

A novel ternary composite photocatalyst (g-C3N4/BiOI/BiOBr) was prepared via a facile solvothermal method. The samples were characterized by powder X-ray diffraction, transmission electron microscopy, UV-visible diffuse reflection spectrometry, X-ray photoelectron spectrometry and photoluminescence measurements. Under irradiation with visible light, the g-C3N4/BiOI/BiOBr photocatalyst showed a higher photocatalytic activity than pure g-C3N4 and BiOI/BiOBr for the degradation of methylene blue. Among the hybrid photocatalysts, 3% g-C3N4/BiOI/BiOBr showed the highest photocatalytic activity for the degradation of MB. These results suggest that the heterostructure combination of g-C3N4, BiOI and BiOBr provides a synergistic effect through an efficient charge transfer process.

A Z-scheme magnetic recyclable Ag/AgBr@CoFe2O4 photocatalyst with enhanced photocatalytic performance for pollutant and bacterial elimination

In order to construct a magnetic recyclable photocatalyst with superior photocatalytic performance and stability, Ag/AgBr photocatalysts modified by magnetic CoFe2O4 nanoparticles (NPs) were synthesized via deposition–precipitation followed by a solvothermal process. Such a synthesis strategy allows the even dispersion of CoFe2O4 NPs on the surface of Ag/AgBr. Besides, a Z-scheme photocatalyst with metallic Ag as a solid-state electron mediator was formed, which exhibits excellent photocatalytic activity and stability for photocatalytic degradation of hardly decomposed colorless phenol compounds, namely, endocrine disrupting chemical bisphenol A (BPA) and 4-chlorophenol (4-CP), in an aqueous solution. The results showed that the Ag/AgBr@CoFe2O4 composites not only exhibited enhanced photocatalytic performance but also improved stabilities. More importantly, the photocatalysts could be recycled easily by an external magnetic field. The antibacterial activity of the Ag/AgBr@CoFe2O4 composites have been investigated by eliminating Escherichia coli (E. coli) in water under visible light irradiation, and the results revealed that the Ag/AgBr@CoFe2O4 composites possessed good photocatalytic antibacterial activity. At last, the enhanced photocatalytic mechanisms were discussed by investigating the main reactive species in the photocatalytic process, which revealed that the photo-generated holes (h+) and O2˙− were the main reactive species.

Construction of solid–liquid interfacial Fenton-like reaction under visible light irradiation over etched CoxFeyO4–BiOBr photocatalysts

In this study, we constructed an in situ Fenton-like photocatalytic system driven by visible-light irradiation. First, BiOBr, a benign in situ H2O2 producer, was prepared via a simple hydrothermal method. Then, the accelerant (CoFe2O4 nanoparticles as the precursor) for H2O2 decomposition was loaded onto the surface of the BiOBr photocatalyst to build a well-contacted interface for reactive sites. CoxFeyO4 nanoparticles etched to different extents were obtained by adjusting the solution pH (pH = 1, 3 and 7) during the composite preparation process. A group of green and efficient CoxFeyO4–BiOBr photocatalysts (abbreviated as CFB) (pH = 1, 3 and 7) were successfully synthesized. The optimal CFB material used for BPA photodegradation was 0.5% CFB (pH = 3). The reaction rate constant of 0.5% CFB (pH = 3) was 3.4 times higher than BiOBr (pH = 3). H2O2 detection, ESR and radical trapping experiments demonstrated that much of the H2O2 produced by BiOBr (pH = 3) was successfully decomposed to ˙O2− and ˙OH, which played important roles with h+ in the BPA photodegradation process, thereby a possible photocatalytic mechanism was proposed. Cycling experiments indicated the good stability of 0.5% CFB (pH = 3). This work may offer a green and efficient method for in situ H2O2 generation and decomposition, thus, the secondary pollution and harsh conditions of the conventional Fenton reaction can be tactfully avoided.

Novel Ag2S quantum dot modified 3D flower-like SnS2 composites for photocatalytic and photoelectrochemical applications

Novel 3D flower-like Ag2S/SnS2 composites were fabricated by a hydrothermal and ion exchange method. Uniform Ag2S quantum dots were homogeneously interspersed on 3D flower-like SnS2. The samples were characterized through X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) analysis. As expected, the as-prepared Ag2S quantum dot modified 3D flower-like SnS2 composites exhibited enhanced photoelectrochemical (PEC) performance and photocatalytic activities. The photocurrent density of 3% 3D flower-like Ag2S/SnS2 at 2.0 V (vs. Ag/AgCl) (0.65 mA cm−2) was about 3.25 times higher than that (0.2 mA cm−2) of 3D flower-like SnS2. The photocatalytic activity of 3D flower-like Ag2S/SnS2 composites was assessed through the degradation of methyl orange and the photocatalytic H2 evolution performance under visible light irradiation. The coupling of SnS2 and Ag2S quantum dots could notably promote the photocatalytic activity. The experimental results indicated that 3% 3D flower-like Ag2S/SnS2 composites showed the best photocatalytic performance for the degradation of methyl orange. These composites also exhibited a high H2 evolution rate of 574.7 μmol h−1 g−1 under visible light irradiation, approximately 5.57 times higher than that of pure 3D flower-like SnS2. Based on the calculation, radical trapping tests and ESR, a plausible mechanism for increased photoactivity was proposed. This work provides experimental insight into the design of low-cost photocatalysts for highly efficient photodegradation and photocatalytic H2-production.