Xiao-Ju Wen

AgI nanoparticles-decorated CeO2 microsheets photocatalyst for the degradation of organic dye and tetracycline under visible-light irradiation

In this paper, CeO2 microplates were synthesized by a sol-gel auto-combustion method. AgI nanoparticles (NPs) were then deposited onto the surface of CeO2 via a facile deposition-precipitation method. The as-prepared AgI/CeO2 samples were characterized by various analytical techniques. The composites exhibited superior photocatalytic activities for the organic dyes (RhB) and the refractory pollutant (tetracycline (TC), a typical antibiotic) degradation under visible light irradiation. The CA-19.03 sample exhibited the highest photocatalytic activity. The enhanced photocatalytic performance could be ascribed to the improved separation of photogenerated charge carriers due to well-matched band structure.

Facile synthesis of a visible light α-Fe2O3/BiOBr composite with high photocatalytic performance

Novel α-Fe2O3/BiOBr composites were synthesized by a simple in hydrolysis method for the first time, and were fully characterized by X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectra (DRS). The α-Fe2O3/BiOBr composite showed much higher visible-light-driven (VLD) photocatalytic activity than pure α-Fe2O3 and BiOBr for rhodamine B (RhB) degradation. Specifically, the 10Fe/100Bi composite showed the highest photocatalytic activity for the degradation of dyes under visible light irradiation. The stability of the photocatalyst is found to be satisfying, which gives it potential in practical applications. The high photocatalytic activity could be attributed to the enhanced light absorption and the improved separation of photogenerated charge carriers, due to the formation of a p–n heterojunction between α-Fe2O3 and BiOBr.

Effective removal of colourless pollutants and organic dyes by Ag@AgCl nanoparticle-modified CaSn(OH)6 composite under visible light irradiation

A high-efficiency nanocube-like composite, Ag@AgCl/CaSn(OH)6 (Ag@AgCl/CSH), was successfully synthesized via an ultrasonic-assisted deposition-photoreduction method. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental mapping, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), BET analysis, photoluminescence emission spectroscopy (PL), and photocurrent (PC) methods. Photodegradation experiments for the decomposition of single dye, multiple dyes, and colorless organic pollutants, such as tetracycline (TC) and bisphenol A propane (BPA), were carried out under visible-light irradiation. Among the as-synthesized samples, the Ag@AgCl(20.5 wt%)/CSH composite exhibited optimal photocatalytic activities. The experimental conditions, including solar light and water source, were also considered to study their effects on photodegradation. The trapping experiment was carried out to clarify the possible mechanism of enhanced photocatalytic performance, which could be attributed to surface plasmon resonance (SPR) effects via the introduction of Ag@AgCl nanoparticles. After five recycling experiments, highly efficient photocatalytic activity was still maintained, demonstrating that the as-synthesized composite possessed excellent reusability and stability. It can be anticipated that the Ag@AgCl/CSH composite will have great potential in real applications such as in the treatment of wastewater.

Construction of highly efficient and stable ternary AgBr/Ag/PbBiO 2 Br Z-scheme photocatalyst under visible light irradiation: Performance and mechanism insight

In this work, the novel ternary AgBr/Ag/PbBiO2Br Z-scheme photocatalysts were synthesized via a CTAB-assisted calcination process. The AgBr/Ag/PbBiO2Br composites were employed for the degradation of rhodamine B (RhB) and antibiotic bisphenol A (BPA) under visible light irradiation. Results showed that the obtained AgBr/Ag-3/PbBiO2Br displayed optimal photocatalytic performance, which could remove almost all RhB within 25 min and effectively decompose 82.3% of BPA in 120 min. Three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs) were utilized for the purposes of fully grasping the behaviors of RhB molecules during the reaction process. Meanwhile, the effects of initial RhB concentration and co-existent electrolytes were investigated from the viewpoint of practical application. In addition, there was no obvious loss in degradation efficiency even after four cycles. The enhanced photocatalytic performances of AgBr/Ag/PbBiO2Br could be credited to the accelerated interfacial charge transfer process and the improved separation of the photogenerated electron-hole pairs. The existence of a small amount of metallic Ag played a significant role in preventing AgBr from being further photocorroded, resulting in the formation of a stable Z-scheme photocatalyst system. This study demonstrated that using metallic Ag as an electron mediator to construct Z-scheme photocatalytic system provided a feasible strategy in promoting the stability of Ag-based semiconductors.

Enhanced Escherichia coli inactivation and oxytetracycline hydrochloride degradation by a Z-scheme silver iodide decorated bismuth vanadate nanocomposite under visible light irradiation

Novel Z-scheme AgI/BiVO4 photocatalysts were fabricated by a chemical deposition-precipitation approach. The photocatalytic activities of the obtained catalysts were evaluated by disinfection of Escherichia coli (E. coli) and degradation of oxytetracycline hydrochloride (OTC-HCl) under visible-light irradiation. The BA3 (contained 9.09% of AgI) exhibited the highest photocatalytic activity and maintained good stability. It could completely inactivate 7.0×107 CFU/mL of E. coli in 50 min and degrade 80% of OTC-HCl in 60 min. The enhanced photocatalytic activity of AgI/BiVO4 composites could be ascribed to the lower recombination rate of electron-hole pairs. Meanwhile, radical trapping experiments revealed that the superoxide radical (O2-) and holes (h+) were the dominant reactive species in photo-disinfection process. Furthermore, the effects of bacterial initial concentration and inorganic anions were also investigated to optimize the photocatalyst for practical application. This study will give a new insight to construct the effective Z-scheme system for bacterial inactivation and organic pollutants degradation.

Co-Mn layered double hydroxide as an effective heterogeneous catalyst for degradation of organic dyes by activation of peroxymonosulfate

In this study, Co-Mn layered double hydroxide (Co-Mn LDH) was synthesized, characterized, and tested as heterogeneous catalyst to activate peroxymonosulfate (PMS) for degradation of organic dyes. The results of characterization showed that Co-Mn LDH had high purity, uniform morphology and large specific surface area (49.9379 m2/g). The degradation experiments demonstrated that five different dyes with the concentration of 50 mg/L could be decomposed completely within 240 s using only 0.025 g/L of Co-Mn LDH and 0.1 g/L of PMS. Moreover, Co-Mn LDH/PMS system presented the highest decomposition efficiency for acid orange G (AOG) compared with other related materials under the same condition. Further investigation found that Co-Mn LDH/PMS system had an excellent adaptability in a wide pH range (from 3 to 10), and the best efficiency was achieved when the solution was natural (pH = 6.87). The mineralization of AOG was assessed by Total Organic Carbon (TOC), and 52.2% of TOC was removed. Meanwhile, the good reusability and high stability of Co-Mn LDH were demonstrated by recycle tests and ion-leaching tests. The catalytic mechanism was explored through quenching tests as well as X-ray photoelectron spectroscopy (XPS) analysis. Finally, all of the results suggested that Co-Mn LDH/PMS system with high stability and decomposition efficiency was suitable for the remediation of organic dyes in wastewater.

Combination of efficient charge separation with the assistance of novel dual Z-scheme system: self-assembly photocatalyst Ag@AgI/BiOI modified oxygen-doped carbon nitride nanosheet with enhanced photocatalytic performance

Natural or artificial Z-scheme systems have been applied for tackling environment pollution and energy crisis owing to the high reduction and oxidation ability driven by the unique interface charge-pairs transfer. However, a dual Z-scheme system combining direct Z-scheme and indirect Z-scheme is seldom adopted for photocatalysis. In this study, the self-assembly photocatalyst Ag@AgI/BiOI/g-C3N4 was successfully fabricated based on the dual Z-scheme system combining direct and indirect Z-scheme systems. The synergistic effect of the dual Z-scheme system towards tetracycline (TC) degradation over the hybrid composites under visible light irradiation was investigated. Compared with single Z-scheme system composites of BiOI/g-C3N4 and AgI/BiOI, the as-synthesized composite of AgI/BiOI/g-C3N4 exhibited superior photocatalytic performance under identical conditions. The dual Z-scheme system was verified by active species generation (˙O2−, ˙OH and h+), trapping experiments and ESR analysis. Furthermore, the photostability and practical application were investigated based on a recycle experiment and controllable experiments. A possible dual Z-scheme mechanism for enhanced photocatalytic performance with ultra-fast charge-separation efficiency and high redox ability was proposed. This study will provide new insight to the design of novel heterojunction composites based on the dual Z-scheme system to deal with organic pollution and energy crisis.

A facile strategy to fabricate hollow cadmium sulfide nanospheres with nanoparticles-textured surface for hexavalent chromium reduction and bacterial inactivation

Exploring morphology and surface structure of semiconductor photocatalyst is crucial for researching their photocatalytic performance. In this paper, hollow CdS nanospheres (CdS-HSs) were successfully fabricated via simple template self-removal strategy. The prepared CdS-HSs were characterized by XRD, SEM, HR-TEM, UV-vis diffuse reflectance spectra (DRS), XPS, photocurrent response (I-T), photoluminescence (PL) and electrochemistry impedance spectroscopy (EIS). It was found that the prepared CdS-HSs have nanoparticles-textured surface composed of ultra-small CdS nanoparticles (∼20 nm) and large surface areas. DRS result demonstrated that the CdS-HSs exhibit strong visible light absorption capacity. The results of photocurrent response, photoluminescence and EIS revealed that hollow structure and nanoparticles-textured surface can effectively increase light reflection effect and decrease recombination rate of electrons and holes. Compared to the traditional CdS, the hollow CdS nanospheres exhibit higher photocatalytic activity on Cr(VI) reduction under visible light irradiation, which are primarily attributed to its rapid separation of electron-hole pairs and improved visible light absorption. Moreover, CdS-HSs was also demonstrated as an effective and potential material on photocatalytic disinfection. The result of mechanism experiments proved that h+, e- and O2- play important roles on the bacteria inactivation.

DTC-GO as Effective Adsorbent for the Removal of Cu2+ and Cd2+ from Aqueous Solution

Abstractdithiocarbamate-graphene oxide (GO) was prepared by simple method through reactions between poly3-aminopropyltriethoxysilane functionalized GO (PAS-GO) and CS2. DTC-GO can capture Cu2+ and Cd2+ effectively to generate stable structures and then remove them from aqueous solutions. The properties of the DTC-GO are characterized by Fourier transform infrared spectroscopy (FTIR). The adsorption capacity for heavy metal ions of DTC-GO was evaluated by the removal of Cu2+ and Cd2+ from aqueous solution. The effect of several factors, including the pH, contact time, and temperature, was investigated by batch experiment. The results show that the DTC-GO exhibits excellent adsorption capacity for Cu2+ and Cd2+. The adsorption kinetics study indicates that the adsorption kinetics of Cu2+and Cd2+ all could be well described by pseudo-second-order kinetic model. The adsorption isotherm was investigated by Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models, and the adsorption process was well described by the Langmuir model. The effect of temperature shows that the process of DTC-GO for Cu2+ and Cd2+ is an endothermic process. The results indicated that the DTC-GO can be used as one of the promising candidate adsorbents with enhanced removal capacity for the adsorption of Cu2+ and Cd2+.

Construction of 2D heterojunction system with enhanced photocatalytic performance: Plasmonic Bi and reduced graphene oxide co-modified Bi5O7I with high-speed charge transfer channels

The efficient electron-hole charge pair separation, ultra-fast electron migration and excellent light harvest capacity are essential for semiconductor photocatalyst with superior photocatalytic performance. In this study, we constructed layered 2D/2D heterojunction composite of Bi@Bi5O7I/rGO (BiBGOI) through a facile surface charge mediated self-assembly strategy. The unique 2D/2D heterostructure with face to face contact can increase the contact area and generate a large amount of charge transfer nanochannels in the interfacial heterojunction, resulting in the enhancement of photocatalytic activity. Addition of semimetal Bi can enhance light absorption, and the local electromagnetic field dominated by SPR effect is favorable for photoinduced charge pair separation. The novel composite showed superior photocatalytic performance for decomposing levofloxacin (LVFX), which was attributed to the unique 2D/2D structure and SPR effect. The enhanced mineralization ability of the novel composite was ascribed to the strong oxidization ability of photoinduced holes, further evaluating high charge pair separation efficiency. In addition, the strong adsorption capacity of rGO for LVFX molecules can enable active radicals transfer into the surface to decompose it. This work will shed light on constructing 2D/2D heterojunction system assisted with SPR effect for the practical application in removal of organic pollutants.