Visible light photocatalytic degradation of sulfanilamide enhanced by Mo doping of BiOBr nanoflowers

Facile synthesis of Bi3O(OH)(AsO4)2 and simultaneous photocatalytic oxidation and adsorption of Sb(III) from wastewater

Antimony (Sb) decontamination in water is necessary owing to the worsening pollution which seriously threatens human life safety. Designing bismuth-based photocatalysts with hydroxyls have attracted growing interest because of the broad bandgap and enhanced separation efficiency of photogenerated electron/hole pairs. Until now, the available photocatalysis information regarding bismuth-based photocatalysts with hydroxyls has remained scarce and the contemporary report has been largely limited to Bi3O(OH)(PO4)2 (BOHP). Herein, Bi3O(OH)(AsO4)2 (BOHAs), a novel ultraviolet photocatalyst, was fabricated via the co-precipitation method for the first time, and developed to simultaneous photocatalytic oxidation and adsorption of Sb(III). The rate constant of Sb(III) removal by the BOHAs was 32.4, 3.0, and 4.3 times higher than those of BiAsO4, BOHP, and TiO2, respectively, indicating that the introduction of hydroxyls could increase the removal of Sb(III). Additionally, the crucial operational parameters affecting the adsorption performance (catalyst dosage, concentration, pH, and common anions) were investigated. The BOHAs maintained 85% antimony decontamination of the initial yield after five successive cycles of photocatalysis. The Sb(III) removal involved photocatalytic oxidation of adsorbed Sb(III) and subsequent adsorption of the yielded Sb(V). With the acquired knowledge, we successfully applied the photocatalyst for antimony removal from industrial wastewater. In addition, BOHAs could also be powerful photocatalysts in the photodegradation of organic pollutants studies of which are ongoing. It reveals an effective strategy for synthesizing bismuth-based photocatalysts with hydroxyls and enhancing pollutants' decontamination.

Biomass-Derived Carbon Quantum Dots Chemical Bonding with Sn-Doped Bi2O2CO3 Endowed Fast Carriers' Dynamics and Stabilized Oxygen Vacancies for Efficient Decontamination of Combined Pollutants

Surface defects on photocatalysts could promote carrier separation and generate unsaturated sites for chemisorption and reactant activation. Nevertheless, the inactivation of oxygen vacancies (OVs) would deteriorate catalytic activity and limit the durability of defective materials. Herein, bagasse-derived carbon quantum dots (CQDs) are loaded on the Sn-doped Bi2O2CO3 (BOC) via hydrothermal procedure to create Bi─O─C chemical bonding at the interface, which not only provides efficient atomic-level interfacial electron channels for accelerating carriers transfer, but also enhances durability. The optimized Sn-BOC/CQDs-2 achieves the highest photocatalytic removal efficiencies for levofloxacin (LEV) (88.7%) and Cr (VI) (99.3%). The elimination efficiency for LEV and Cr (VI) from the Sn-BOC/CQDs-2 is maintained at 55.1% and 77.0% while the Sn-BOC is completely deactivated after four cycle tests. Furthermore, the key role of CQDs in stabilization of OVs is to replace OVs as the active center of H2O and O2 adsorption and activation, thereby preventing reactant molecules from occupying OVs. Based on theoretical calculations of the Fukui index and intermediates identification, three possible degradation pathways of LEV are inferred. This work provides new insight into improving the stability of defective photocatalysts.

Light-driven photocatalysis as an effective tool for degradation of antibiotics

Antibiotic contamination has become a severe issue and a dangerous concern to the environment because of large release of antibiotic effluent into terrestrial and aquatic ecosystems. To try and solve these issues, a plethora of research on antibiotic withdrawal has been carried out. Recently photocatalysis has received tremendous attention due to its ability to remove antibiotics from aqueous solutions in a cost-effective and environmentally friendly manner with few drawbacks compared to traditional photocatalysts. Considerable attention has been focused on developing advanced visible light-driven photocatalysts in order to address these problems. This review provides an overview of recent developments in the field of photocatalytic degradation of antibiotics, including the doping of metals and non-metals into ultraviolet light-driven photocatalysts, the formation of new semiconductor photocatalysts, the advancement of heterojunction photocatalysts, and the building of surface plasmon resonance-enhanced photocatalytic systems.

Zinc-Doped BiOBr Hollow Microspheres for Enhanced Visible Light Photocatalytic Degradation of Antibiotic Residues

Photocatalysis represents an effective technology for environmental remediation. Herein, a series of Zn-doped BiOBr hollow microspheres are synthesized via one-pot solvothermal treatment of bismuth nitrate and dodecyl ammonium bromide in ethylene glycol along with a calculated amount of zinc acetate. Whereas the materials morphology and crystal structure remain virtually unchanged upon Zn-doping, the photocatalytic performance toward the degradation of ciprofloxacin is significantly improved under visible light irradiation. This is due to the formation of a unique band structure that facilitates the separation of photogenerated electron-hole pairs, reduced electron-transfer resistance, and enhanced electron mobility and carrier concentration. The best sample consists of a Zn doping amount of 1%, which leads to a 99.2% degradation rate of ciprofloxacin under visible photoirradiation for 30 min. The resulting photocatalysts also exhibit good stability and reusability, and the degradation intermediates exhibit reduced cytotoxicity compared to ciprofloxacin. These results highlight the unique potential of BiOBr-based photocatalysts for environmental remediation.

Silver doped barium titanate nanoparticles for enhanced visible light photocatalytic degradation of dyes

Due to the rapid growth of global population, new, fast and reliable methods must be developed to purify contaminated water. Various photocatalysts have been developed to remove organic dyes from water. Herein, Ag doped BaTiO3 has been synthesized using a facile solvothermal method and its excellent photocatalytic activities were demonstrated in degradation of both anionic and cationic dyes under visible light illumination. Ag doped BaTiO3 nanoparticles showed greater efficacy in the degradation of methylene blue (MB) and eosin yellow (EY) than undoped BaTiO3 nanoparticles, which makes them a better candidate for photocatalysis. 1.0 AgBT sample showed the highest photocatalytic activity for MB (99.1 % in 100 min) and EY (99.3 % in 60 min) dye degradation compared with those of other samples. Further, the trapping experiments revealed that hydroxyl radicals and holes are the active species in the photocatalytic process of MB and EY dye degradation and recycle test showed excellent stability of the synthesized material.

Swallowed Embedding of Nanopetal-Rich Microflowers in Flexible Photocatalytic and Thermoresponsive Functional Composite Fibers

Developing efficient catalysts to degrade pollutants in water is a very important way to alleviate water pollution. However, it is crucial but challenging to broaden the functions of conventional photocatalysts and improve their environmental adaptability. In this paper, Bi(Er3+/Yb3+)OBr/polyacrylonitrile (BOB-EY/PAN) composite fibers with a swallowed-embedded structure assembled with nanopetal-rich microflowers were designed and fabricated, integrating photocatalytic and temperature-monitoring functions simultaneously. Their unique structure brings a large specific surface area, and the doping of rare earth ions improves the separation efficiency of electron-hole pairs, which enhances the photocatalytic efficiency and endows the fibers with a temperature-monitoring function at the same time. Under simulated sunlight irradiation, the nanofibers show a maximum degradation efficiency of 99.2% for tetracycline hydrochloride (TC) with a degradation constant of K as high as 0.078 min-1. Based on the fluorescence intensity ratio (FIR), the two thermally coupled levels of Er3+ in the nanofibers, 2H11/2 and 4S3/2, provide real-time temperature feedback, displaying a maximum relative sensitivity as high as 0.0215 K-1 at 303 K. Dual-functional BOB-EY/PAN composite nanofibers show great potential for industrial wastewater disposition, providing solutions for wastewater purification in special scenarios.

Activating two-dimensional semiconductors for photocatalysis: a cross-dimensional strategy

The emerging two-dimensional (2D) semiconductors substantially extend materials bases for versatile applications such as semiconductor photocatalysis demanding semiconductive matrices and large surface areas. The dimensionality, while endowing 2D semiconductors the unique properties to host photocatalytic functionality of pollutant removal and hydrogen evolution, hurdles the activation paths to form heterogenous photocatalysts where the photochemical processes are normally superior over these on the mono-compositional counterparts. In this perspective, we present a cross-dimensional strategy to employ thenD (n= 0-2) clusters or nanomaterials as activation partners to boost the photocatalytic activities of the 2D semiconductors. The formation principles of heterogenous photocatalysts are illustrated specifically for the 2D matrices, followed by selection criteria of them among the vast 2D database. The computer investigations are illustrated in the density functional theory route and machine learning benefitted from the vast samples in the 2D library. Synthetic realizations and characterizations of the 2D heterogenous systems are introduced with an emphasis on chemical methods and advanced techniques to understand materials and mechanistic studies. The perspective outlooks cross-dimensional activation strategies of the 2D materials for other applications such as CO2removal, and materials matrices in other dimensions which may inspire incoming research within these fields.

Fabrication of a PCN/BiOBr 2D hybrid with improved photocatalytic performance of 2,4-dichorophenol degradation

Photocatalysis has received much attention as an environmentally friendly route to manage the emerging organic pollution problems. Herein, BiOBr nanosheets have been synthesized by a hydrothermal method, and then PCN/BiOBr hybrids are designed via a facile wet chemical method. The as-prepared PCN/BiOBr hybrids are characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis DRS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The PCN/BiOBr composite exhibits remarkable improved activity in the degradation of 2,4-dichlorophenol (2,4-DCP) as compared to the pristine BiOBr. Based on the ·OH amount-related fluorescence spectra fluorescence and the photoelectrochemistry (PEC) tests, it is confirmed that the enhanced photocatalytic performance of PCN/BiOBr is attributed to the promoted charge separation. Moreover, by means of the radical-trapping experiments it is demonstrated that the formed ·O2- species, as the electron-modulated direct products, are the primary active species during the photocatalytic degradation of 2,4-DCP. This work would provide a feasible design strategy to fabricate high-activity photocatalysts for 2,4-DCP degradation.

Exposed {110} facets of BiOBr anchored to marigold-like MnCo2O4 with abundant interfacial electron transfer bridges and efficient activation of peroxymonosulfate

Precise charge transfer modification and efficient activation of peroxymonosulfate are effective methods for increasing photocatalytic efficiency. Here, BiOBr/MnCo2O4 photocatalysts with abundant Mn-Br bonds were generated by immobilizing the exposed {110} facets of BiOBr in the marigold-like MnCo2O4. The prepared BiOBr/MnCo2O4 retained the marigold-like morphology of MnCo2O4 while exhibiting good adsorption properties and interface contact effects. More importantly, the interfacial Mn-Br bond between MnCo2O4 and BiOBr functioned as charge transport bridges, allowing for a directional transfer channel and lowering the potential energy barrier for interfacial charge transfer. In addition, the exposure of the {110} facets exhibited more Mn atom-anchored sites for easy anchoring of BiOBr, significantly solving the stability problem of the bismuth material. Compared to MnCo2O4 + BiOBr, which did not form Mn-Br bonds, the MnCo2O4/BiOBr heterojunction had more efficient photocatalytic activity (1.3 times) and stability. This suggested that using electronic bridges for directional charge transfer was an efficient way to improve photocatalytic efficiency.

Degradation of sulfanilamide in aqueous solution by ionizing radiation: Performance and mechanism

Sulfonamide (SA) is an emerging contaminants and the efficient treatment of SA containing wastewater remains a challenge. Herein, SA degradation by gamma irradiation has been systematacially studied. SA (10 mg/L) could be totally removed with 1.5 kGy irradiation. Quenching experiments demonstrated that •OH and eaq- were the predominant for SA degradation. SA degradation was reduced with initial concentration increasing, and the removal was faster with pH increasing in the range of 3.1-10.8. The coexisting matters affected SA degradation through changing reactive species, and the introduction of SO42- and Cl- enhanced SA degradation, while CO32- had a negative impact on SA degradation, and the degradation was insignificantly affected when adding humic acid. Gamma irradiation could remain effective in real water matrixes. In conjunction with LC-MS analysis and DFT calculation, possible degradation pathways for SA were proposed. Gamma irradiation could reduce the toxicity of SA, while several byproducts with more toxic were also formed. Furthermore, gamma/priodate (PI) process was promising to enhance SA degradation and mineralization. k value increased by 1.85 times, and mineralization rate increased from 19.51% to 79.19% when adding PI. This study suggested that ionizing radiation was efficient to eliminate SA in wastewater.

Interfacial regulation of BiOI@Bi2S3/MXene heterostructures for enhanced photothermal and photodynamic therapy in antibacterial applications

Developing environmentally friendly, broad-spectrum, and long-lasting antibacterial materials remains challenging. Our ternary BiOI@Bi2S3/MXene composites, which exhibit both photothermal therapy (PTT) and photodynamic therapy (PDT) antibacterial properties, were synthesized through in-situ vulcanization of hollow flower-shaped BiOI on the surface of two-dimensional Ti3C2 MXene. The unique hollow flower-shaped BiOI structure with a high exposure of the (001) crystal plane amplifies light reflection and scattering, offering more active sites to improve light utilization. Under 808 nm irradiation, these composites achieved a photothermal conversion efficiency of 57.8 %, boosting the PTT antibacterial effect. The heterojunction between Bi2S3 and BiOI creates a built-in electric field at the interface, promoting hole and electron transfer. Significantly, the close-contact heterogeneous interface enhances charge transfer and suppresses electron-hole recombination, thereby boosting PDT bacteriostatic performance. EPR experiments confirmed that ∙O2- and •OH radicals play major roles in photocatalytic bacteriostatic reactions. The combined antibacterial action of PTT and PDT led to efficiencies of 99.7 % and 99.8 % against P. aeruginosa and S. aureus, respectively, under 808 nm laser irradiation. This innovative strategy and thoughtful design open new avenues for heterojunction materials in PTT and PDT sterilization. STATEMENT OF SIGNIFICANCE: Photodynamic and photothermal therapy is a promising antibacterial treatment, but its efficiency still limits its application. To overcome this limitation, we prepared three-dimensional heterogeneous BiOI@Bi2S3/MXene nanocomposites through in-situ vulcanization of hollow flower-shaped BiOI with a high exposure of the (001) crystal plane onto the surface of two-dimensional MXene material. The resulting ternary material forms a close-contact heterogeneous interface, which improves charge transfer channels, reduces electron-hole pair recombination, and amplifies photodynamic bacteriostatic performance. These nanocomposites exhibit photothermal conversion efficiency of 57.8 %, enhancing their photothermal bactericidal effects. They demonstrated antibacterial efficiencies of 99.7 % against P. aeruginosa and 99.8 % against S. aureus. Therefore, this study provides a promising method for the synthesis of environmentally friendly and efficient antibacterial materials.

Novel visible-light-active P-g-CN-based α-Bi2O3/WO3 ternary photocatalysts with a dual Z-scheme heterostructure for the efficient decomposition of refractory ultraviolet filters and environmental hormones: Benzophenones

The ubiquitous and refractory benzophenone (BP)-type ultraviolet filters, which are also endocrine disruptors, were commonly detected in the aquatic matrix and could not be efficiently removed by conventional wastewater treatment processes, thus causing extensive concern. Herein, a novel ternary nanocomposite, P-g-CN/α-Bi2O3/WO3 (P-gBW), was successfully fabricated by mixing cocalcinated components and applied to the decomposition of BP-type ultraviolet filters. The dual-Z-scheme heterostructure of P-gBW enhances visible-light absorption, efficiently facilitates separation and mobility, and prolongs the lifetime of photoinduced charge carriers via double charge transfer mechanisms. The optimum 95 wt% P-gBW exhibited excellent photocatalytic activity, degrading 96% 4-hydroxy benzophenone (4HBP) within 150 min and 93% 2,2',4,4'-tetrahydroxybenzophenone (BP-2) within 100 min under visible-light illumination, respectively. The pseudo-first-order rate constant of 4HBP (1.15 h-1) was 6.8-, 3.1-, 3.3- and 2.2-fold higher than those of WO3, P-g-CN, α-Bi2O3, and P-g-CN/α-Bi2O3, respectively, while that of BP-2 (1.71 h-1) was 5.2-, 2.2-, 3.2- and 1.5-fold higher, respectively. The improved photocatalytic degradation was attributed to efficient photoinduced charge carrier separation and migration and prevented the recombination of electron holes, as verified by photoluminescence, transient photocurrent response, and electrochemical impedance spectroscopy. Trapping experiments, electron paramagnetic resonance, and band energy position indicated an efficient dual-Z-scheme heterostructure.

Engineering of Multifunctional Nanocomposite Membranes for Wastewater Treatment: Oil/Water Separation and Dye Degradation

Multifunctional membrane technology has gained tremendous attention in wastewater treatment, including oil/water separation and photocatalytic activity. In the present study, a multifunctional composite nanofiber membrane is capable of removing dyes and separating oil from wastewater, as well as having antibacterial activity. The composite nanofiber membrane is composed of cellulose acetate (CA) filled with zinc oxide nanoparticles (ZnO NPs) in a polymer matrix and dipped into a solution of titanium dioxide nanoparticles (TiO2 NPs). Membrane characterization was performed using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR), and water contact angle (WCA) studies were utilized to evaluate the introduced membranes. Results showed that membranes have adequate wettability for the separation process and antibacterial activity, which is beneficial for water disinfection from living organisms. A remarkable result of the membranes' analysis was that methylene blue (MB) dye removal occurred through the photocatalysis process with an efficiency of ~20%. Additionally, it exhibits a high separation efficiency of 45% for removing oil from a mixture of oil-water and water flux of 20.7 L.m-2 h-1 after 1 h. The developed membranes have multifunctional properties and are expected to provide numerous merits for treating complex wastewater.

Degradation of ciprofloxacin by persulfate activated by Fe(III)-doped BiOCl composite photocatalyst

Fe-BOC-X photocatalyst was successfully prepared by solvothermal method. The photocatalytic activity of Fe-BOC-X was determined by ciprofloxacin (CIP), a typical fluoroquinolone antibiotic. Under sunlight irradiation, all Fe-BOC-X showed better CIP removal performance than original BiOCl. In comparison, the photocatalyst with iron content of 50 wt% (Fe-BOC-3) has excellent structural stability and the best adsorption photodegradation efficiency. The removal rate of CIP (10 mg/L) by Fe-BOC-3 (0.6 g/L) reached 81.4% within 90 min. At the same time, the effects of photocatalyst dosage, pH, persulfate, persulfate concentration, and combinations of different systems (PS, Fe-BOC-3, Vis/PS, Vis/Fe-BOC-3, Fe-BOC-3/PS, and Vis/Fe-BOC-3/PS) on the reaction were systematically discussed. In reactive species trapping experiments, electron spin resonance (ESR) signals revealed that the photogenerated holes (h+), hydroxyl radical (•OH), sulfate radical (•SO4-), and superoxide radical (•O2-) played an important role in CIP degradation; hydroxyl radicals (•OH) and sulfate radicals (•SO4-) play a major role. Various characterization methods have demonstrated that Fe-BOC-X has larger specific surface area and pore volume than original BiOCl. UV-vis DRS indicate that Fe-BOC-X has wider visible light absorption and faster photocarrier transfer and provides abundant surface oxygen absorption sites for effective molecular oxygen activation. Accordingly, a large number of active species were produced and participated in the photocatalytic process, thus effectively promoting the degradation of ciprofloxacin. Based on HPLC-MS analysis, two possible decomposition pathways of CIP were finally proposed. The main degradation pathways of CIP are mainly due to the high electron density of piperazine ring in CIP molecule, which is mainly attacked by various free radicals. The main reactions include piperazine ring opening, decarbonylation, decarboxylation, and fluorine substitution. This study can better open up a new way for the design of visible light driven photocatalyst and provide more ideas for the removal of CIP in water environment.

Design and assembly of Ag-decorated Bi2O3 @ 3D MXene Schottky heterojunction for the highly permeable and multiple-antifouling of fibrous membrane in the purification of complex emulsified oil pollutants

Membrane separation technology has potential for purifying emulsified oily wastewater. However, the oils, soluble organic substances, and microorganisms can cause complex membrane fouling problems, thereby reducing the separation efficiency and service life. Herein, a highly permeable and multiple-antifouling composite membrane was prepared using porous PAN fibrous mat as support backbone for the assembly of Ag-decorated Bi₂O₃ @ 3D MXene Schottky heterojunction and hydrophilic TA as the adhesive. The unique arrangement of 3D MXene heterojunction and hydrophilic functionalization effectively broke through the limitation of separation flux and synergistically enhanced the anti-fouling performance of membrane. Such fibrous composite membrane achieved an exceedingly high permeability (2717-3328 L·m^-2·h^-1) for various emulsified oils, while ensuring excellent oil/water emulsion retention rate (99.59%) and good cycle stability. Meanwhile, the composite membrane displayed favorable photocatalytic degradation performance toward degrading MeB (96.1%) and antibacterial ability. Furthermore, the MD simulation and free radical trapping experiments were carried out to unravel the molecular interactions during the separation process and the photocatalytic mechanism of composite membrane, respectively. Overall, the combination of photocatalytic self-cleaning, anti-oil adhesion, and antibacterial effect renders the membrane high permeability and multiple-antifouling performance, which provides a new strategy for dealing with complex oily wastewater in petrochemical industry.

Photocatalytic O2 activation by metal-free carbon nitride nanotube for rapid reactive species generation and organic contaminants degradation

Advanced oxidation processes (AOPs) using oxygen (O₂) as an oxidant represent a low-cost and sustainable wastewater treatment process. Herein, a metal-free nanotubular carbon nitride photocatalyst (CN NT) was prepared to activate O₂ to degrade organic contaminants. The nanotube structure allowed for sufficient O₂ adsorption, while the optical and photoelectrochemical properties enabled photogenerated charge to be efficiently transferred to the adsorbed O₂ to trigger the activation process. The developed CN NT/Vis-O₂ system based on O₂ aeration degraded various organic contaminants and mineralized 40.7% of chloroquine phosphate within 100 min. In addition, the toxicity and environmental risk of treated contaminants were reduced. Mechanistic studies suggested that the enhanced O₂ adsorption capacity and fast charge transfer behavior on CN NT surface led to reactive·O₂^-, ¹O₂ and h⁺ generation, each of which played a distinct role in contaminants degradation. Importantly, the proposed process could overcome the interference from water matrices and outdoor sunlight, and the energy and chemical reagent savings reduced the operating cost to about 1.63 US$·m^-3. Altogether, this work provides insights into the potential application of metal-free photocatalysts and green O₂ activation for wastewater treatment.

Enhanced sulfamethoxazole photodegradation by N-SrTiO3/NH4V4O10 S-scheme photocatalyst: DFT calculation and photocatalytic mechanism insight

In this study, we synthesized a N-SrTiO₃/NH₄V₄O₁₀ S-scheme photocatalyst by modifying NH₄V₄O₁₀ nanosheets with various proportions of N-doped SrTiO₃ nanoparticles using a mild hydrothermal method.Density Functional Theory(DFT) calculations were employed to elucidate thephotocatalytic mechanism, while the electron-hole transfer and separation of the S-type heterojunction were further characterized experimentally. The photocatalyst was applied to the photodegradation of sulfamethoxazole (SMX), a common water pollutant. Among all the prepared photocatalysts, 30 wt% N-SrTiO₃/NH₄V₄O₁₀ (NSN-30) displayed the highest photocatalytic performance. This was attributed to the facile electron transfer mechanism of the S-scheme heterojunction, which facilitated the effective separation of electron-holes and preserved the strong redox property of the catalyst. The possible intermediates anddegradation pathwaysin thephotocatalytic systemwere explored usingelectron paramagnetic resonance(EPR) and DFT calculations. Our findings demonstrate the potential of semiconductor catalysts to remove antibiotics from aqueous environments usinggreen energy.

Optimized fabrication of Cu-doped ZnO/calcined CoFe‒LDH composite for efficient degradation of bisphenol a through synergistic visible-light photocatalysis and persulfate activation: Performance and mechanisms

A novel magnetically separable Cu/ZnO/CoFe‒CLDH composite, whose synthesis was optimized using the Taguchi approach, was optimally synthesized by hydrothermally coupling Cu-doped ZnO and calcined CoFe-LDH. The synthesized Cu/ZnO/CoFe‒CLDH was applied to construct a synergistic process of integrating visible-light photocatalysis (VPC) with persulfate activation (PSA) and to degrade bisphenol A (BPA). Various characterizations proved that Cu/ZnO/CoFe‒CLDH possessed excellent physicochemical, optoelectronic and magnetic properties, thereby enhancing the catalytic performance. The Cu/ZnO/CoFe‒CLDH composite achieved highly efficient BPA degradation during the synergistic VPC‒PSA process, and its reaction rate constant (0.74 h^-1) was 6.17-, 4.11-, and 2.85-fold higher than that of Cu/ZnO, CoFe‒CLDH, and Cu/ZnO/CoFe‒CLDH (VPC only), respectively. Moreover, the effects of the catalyst dosage, initial pollutant concentration, solution pH, persulfate dosage and coexisting ions on BPA degradation were comprehensively investigated. Radical-trapping experiments revealed that the contributions of ·OH, SO₄·^‒, ·O₂^-, and ¹O₂ involved in BPA degradation. Based on the intermediates identified by LC/MS, the main BPA degradation pathways were determined, the overall trend of which reflects a decreasing ecotoxicity. This study verified the effectiveness of the synergistic VPC‒PSA process with Cu/ZnO/CoFe‒CLDH, which could be used as a new reference for removing organic micropollutants from water.

Accelerated redox conversion of an advanced Zn//Fe-Co3O4 battery by heteroatom doping

Herein, Fe-doped Co₃O₄ (Fe-Co₃O₄) was prepared to solve the issues of poor electrical conductivity and the lack of active sites in Co₃O₄ materials. Due to having similar radius and physical/chemical properties to Co, Fe is an ideal choice for doping Co₃O₄, as it can improve intrinsic conductivity without causing severe lattice distortion. Oxygen vacancies are gradually formed as doping reactions occur to maintain electric neutrality. Owing to the merits of oxygen vacancies in Co₃O₄, the distribution of the electrons is changed, thus optimizing the material's intrinsic charge/ion states and modifying the band gap by introducing impurity levels. Moreover, the surface area of Fe-Co₃O₄ is 1.5 times larger than that of the original material. The synergistic effect promotes the electrochemical oxidation reduction reaction and improves the capacitance and cycling stability. Finally, such an advanced Zn//Fe-Co₃O₄ battery exhibits a discharge-specific capacity of 171.97 mA h g^-1, nearly eight times higher than that of the previous Zn//Co₃O₄ battery (22.38 mA h g^-1). In addition, the attenuation of the capacity was almost negligible after 9000 cycles.

Enhanced photocatalytic reduction of CO2 on BiOBr under synergistic effect of Zn doping and induced oxygen vacancy generation

In this work, different BiOBr powders (without and with Zn doping) were prepared. Their specific properties and photocatalytic performance were studied. Zn doped BiOBr showed higher carrier transportation ability, beneficial to high performance photocatalysis. Further analysis and theoretical calculations unveiled that Zn doping resulted in more dispersive energy band structure with improved oxygen vacancy (O_V) generation due to lattice distortion. O_V acted as trap centers, playing dominant role in carrier transportation enhancement, which also synergized with more dispersive energy band due to Zn doping, improving carrier separation and transfer. Besides, Zn doping would further strengthen trapping effect under O_V existence, stimulating synergistic enhancement to spatial charge separation and transfer with O_V. With synergy of Zn doping and O_V, Zn doped samples produced 1.75 times higher CH₄ generation during gas-solid photocatalytic reduction of CO₂ under visible light, testifying successful conducting of Zn doping improved photocatalytic capacity on BiOBr.

High-Performance Photocatalytic Reduction of Nitrogen to Ammonia Driven by Oxygen Vacancy and Ferroelectric Polarization Field of SrBi4 Ti4 O15 Nanosheets

Photo-responsive semiconductors can facilitate nitrogen activation and ammonia production, but the high recombination rate of photogenerated carriers represents a significant barrier. Ferroelectric photocatalysts show great promise in overcoming this challenge. Herein, by adopting a low-temperature hydrothermal procedure with varying concentrations of glyoxal as the reducing agent, oxygen vacancies (Vo) are effectively produced on the surface of ferroelectric SrBi₄ Ti₄ O₁₅ (SBTO) nanosheets, which leads to a considerable increase in photocatalytic activity toward nitrogen fixation under simulated solar light with an ammonia production rate of 53.41 µmol g^-1 h^-1 , without the need of sacrificial agents or photosensitizers. This is ascribed to oxygen vacancies that markedly enhance the self-polarization and internal electric field of ferroelectric SBTO, and hence, facilitate the separation of photogenerated charge carriers and light trapping as well as N₂ adsorption and activation, as compared to pristine SBTO. Consistent results are obtained in theoretical studies. Results from this study highlight the significance of surface oxygen vacancies in enhancing the performance of photocatalytic nitrogen fixation by ferroelectric catalysts.

Low-cost and resource-efficient monolithic photocatalyst with enhanced solar light utilization for the photocatalytic treatment of organic wastewater

Developing low-cost, well-performing, and resource-efficient photocatalysts with enhanced solar light utilization can contribute to the practicability of photocatalytic techniques in organic wastewater treatment. This study fabricated and characterized a novel sunlight-driven BiOBr- and acetylene black (AB)-loaded monolithic photocatalyst. The fly ash-based geopolymer acts as photocatalyst support that can also provide adsorption sites and semiconductor metal oxide (Fe₂O₃). A conductive network in the geopolymer structure formed by AB can promote the separation of e^--h⁺ pairs generated by active sites (BiOBr and Fe₂O₃). Moreover, the photothermal effect induced by AB can assist the photocatalytic reaction at the microinterface of the photocatalyst. This photocatalyst was suspended on the surface of an aqueous solution for sufficient contact with oxygen from the air and is thus beneficial for producing ¹O₂ and ·OH as the main active species. Within 30 min, it exhibited higher photothermal-photocatalytic activity with 96% removal efficiency of the target pollutant methylene blue (MB), which occurred at an initial concentration of 20 mg L^-1. The demethylation and hydroxylation process induced by the active species constituted the primary degradation pathway for MB by Bi/AB/MFGP. Overall, this study provides a valuable reference for developing economical, effective, and practical photocatalysts and applying geopolymers in photocatalysis.

Enhanced Photo-Assisted Fenton Degradation of Antibiotics over Iron-Doped Bi-Rich Bismuth Oxybromide Photocatalyst

Herein, combining photocatalysis and Fenton oxidation, a photo-assisted Fenton system was conducted using Fe-doped Bi₄O₅Br₂ as a highly efficient photocatalyst to realize the complete degradation of Tetracycline antibiotics under visible light. It has been observed that the optimized photocatalyst 5%Fe-doped Bi₄O₅Br₂ exhibits a degradation efficiency of 100% for Tetracycline with H₂O₂ after 3 h visible-light irradiation, while a degradation percentage of 59.8% over the same photocatalyst and 46.6% over pure Bi₄O₅Br₂ were obtained without the addition of H₂O₂ (non-Fenton process). It is unambiguous that a boost photo-assisted Fenton system for the degradation of Tetracycline has been established. Based on structural analysis, it demonstrated that the Fe atoms in place of the Bi sites may result in the distortion of the local structure, which induced the occurrence of the spontaneous polarization and thus enhanced the built-in electric field. The charge separation efficiency is enhanced, and the recombination of electrons and holes is inhabited so that more charges are generated to reach the surface of the photocatalyst and therefore improve the photocatalytic degradation efficiency. Moreover, more Fe (II) sites formed on the 5%Fe-Bi₄O₅Br₂ photocatalyst and facilitated the activation of H₂O₂ to form oxidative species, which greatly enhanced the degradation efficiency of Tetracycline.

Thiadiazole-Based Covalent Organic Frameworks with a Donor-Acceptor Structure: Modulating Intermolecular Charge Transfer for Efficient Photocatalytic Degradation of Typical Emerging Contaminants

As novel metal-free photocatalysts, covalent organic frameworks (COFs) have great potential to decontaminate pollutants in water. Fast charge recombination in COFs yet inhibits their photocatalytic performance. We found that the intramolecular charge transfer within COFs could be modulated via constructing a donor-acceptor (D-A) structure, leading to the improved photocatalytic performance of COFs toward pollutant degradation. By integrating electron donor units (1,3,4-thiadiazole or 1,2,4-thiadiazole ring) and electron acceptor units (quinone), two COFs (COF-TD1 and COF-TD2) with robust D-A characteristics were fabricated as visible-light-driven photocatalysts to decontaminate paracetamol. With the readily excited electrons in 1,3,4-thiadiazole rings, COF-TD1 exhibited efficient electron-hole separation through a push-pull electronic effect, resulting in superior paracetamol photodegradation performance (>98% degradation in 60 min) than COF-TD2 (∼60% degradation within 120 min). COF-TD1 could efficiently photodegrade paracetamol in complicated water matrices even in river water, lake water, and sewage wastewater. Diclofenac, bisphenol A, naproxen, and tetracycline hydrochloride were also effectively degraded by COF-TD1. Efficient photodegradation of paracetamol in a scaled-up reactor could be achieved either by COF-TD1 in a powder form or that immobilized onto a glass slide (to further ease recovery and reuse) under natural sunlight irradiation. Overall, this study provided an effective strategy for designing excellent COF-based photocatalysts to degrade emerging contaminants.

A pencil graphite-based disposable device for electrochemical monitoring of sulfanilamide in honey and water samples

The present paper reports a simple, fast, and inexpensive process of manufacturing a disposable pencil graphite electrode (PGE) from widely available materials, which showed a reproducibility of at least 7.5%. The electrode was compared to the commercial glassy carbon electrode (GCE) and showed superior electroanalytical performance for sulfanilamide (SFA) with approximately 3.9-fold higher current density. Additionally, a displacement of the oxidation peak from approximately 80 mV to more cathodic regions was observed. Therefore, a method based on square wave voltammetry (SWV) was developed for the determination of the antimicrobial SFA in honey and tap water samples using the proposed sensor. The optimized method presented good detectability (LOD = 2.37 μmol L^-1), with excellent precision and accuracy (relative standard deviation < 4.2%) and percent recovery from spiked samples ranging from 92 to 97%. In addition, the sensor did not suffer significant interference from sample matrix components and other commonly evaluated antimicrobials, which demonstrates the potential of these electrodes for implementation in routine analysis and quality control.

Pore creation nanoarchitectonics from non-porous metal-organic framework to porous carbon for adsorptive elimination of sulfanilamide and chloroxylenol from aqueous solution

Three isomeric metal-organic frameworks (MOFs) such as MAF-5, - 6, and - 32 (with the same composition of [Zn(2-ethylimidazole)₂]) were carbonized and, for the first time, activated further with KOH to prepare highly porous MOF-derived carbons (MDCs). Importantly, MDC-32 derived from non-porous MAF-32 had the highest porosity among the three MDCs although it has the lowest porosity when no KOH activation was done. Adsorption of sulfanilamide and chloroxylenol from water was investigated with the MDCs. Among the MDCs, MDC-32 showed the best adsorptive performance for sulfanilamide and chloroxylenol. Moreover, MDC-32, had the highest adsorption capacity (256 mg/g) for removing sulfanilamide from water, compared with any adsorbent reported so far. Based on the observed adsorption and properties of the adsorbate and adsorbent, π-π and hydrogen bonding interactions, with a slight contribution of repulsive electrostatic interaction, could be suggested as the mechanism for the sulfanilamide adsorption over the MDC-32. Moreover, the MDC-32 could be recycled easily for up to four cycles. It could be suggested that non-porous MOFs can be a good precursor for highly porous MDCs, if activated well using KOH, for example. Finally, MAF-32-derived carbon, MDC-32, might be suggested as a plausible adsorbent to eliminate organics such as sulfanilamide from water.

Enhanced photocatalytic degradation of tetracycline hydrochloride over Au-doped BiOBr nanosheets under visible light irradiation

Bismuth(III) oxybromide (BiOBr) is a typical photocatalyst with a unique layered structure. However, the response of BiOBr to visible light is not strong enough for practical application. Moreover, the charge separation efficiency of BiOBr still needs to be improved. In this study, series of Au-doped BiOBr photocatalysts was prepared through a facile one-step hydrothermal method. The as-prepared Au_0.3-BiOBr nanosheets exhibited an excellent electrochemical performance. The charge separation efficiency of Au_0.3-BiOBr nanosheets was enhanced by 18.5 times compared with that of BiOBr. The intrinsic photocatalytic activity of Au_0.3-BiOBr nanosheets in the degradation of tetracycline hydrochloride was approximately twice higher than that of BiOBr under visible light irradiation. In addition, three pathways were identified for the photocatalytic degradation and mineralization of tetracycline hydrochloride, which involve four reactions: hydroxylation, demethylation, ring opening and mineralization. Accordingly, this study proposes a feasible and effective Au-doped BiOBr photocatalyst, and describes a promising strategy for the design and synthesis of high-performance photocatalysts.

Non-Stacked γ-Fe2O3/C@TiO2 Double-Layer Hollow Nanoparticles for Enhanced Photocatalytic Applications under Visible Light

Herein, a non-stacked γ-Fe₂O₃/C@TiO₂ double-layer hollow nano photocatalyst has been developed with ultrathin nanosheets-assembled double shells for photodegradation phenol. High catalytic performance was found that the phenol could be completely degraded in 135 min under visible light, due to the moderate band edge position (VB at 0.59 eV and CB at −0.66 eV) of the non-stacked γ-Fe₂O₃/C@TiO₂, which can expand the excitation wavelength range into the visible light region and produce a high concentration of free radicals (such as ·OH, ·O²⁻, holes). Furthermore, the interior of the hollow composite γ-Fe₂O₃ is responsible for charge generation, and the carbon matrix facilitates charge transfer to the external TiO₂ shell. This overlap improved the selection/utilization efficiency, while the unique non-stacked double-layered structure inhibited initial charge recombination over the photocatalysts. This work provides new approaches for photocatalytic applications with γ-Fe₂O₃/C-based materials.

Recent developments on bismuth oxyhalide-based functional nanomaterials for biomedical applications

Multifunctional bismuth oxyhalide (BiOX, X = F, Cl, Br, and I) nanomaterials have great potential advantages in medical diagnostic and therapeutic applications. Pure BiOX nanomaterials have some limitations such as...

Insight into the relationship between redox ability and separation efficiency via the case of α-Bi2O3/Bi5NO3O7

α-Bi2O3/Bi5NO3O7 heterojunctions are constructed, and show higher separation efficiency but lower photocatalytic activity. The reasons are related to the shift of energy band positions.