In situ fabrication of I-doped Bi2O2CO3/g-C3N4 heterojunctions for enhanced photodegradation activity under visible light

Unraveling the synergism mechanistic insight of O-vacancy and interfacial charge transfer in WO3-x decorated on Ag2CO3/BiOBr for photocatalysis of water pollutants: Based on experimental and density functional theory (DFT) studies

Photocatalysis has been widely used as one of the most promising approaches to remove various pollutants in liquid or gas phases during the last decade. The main emphasis of the study is on the synergy of vacancy engineering and heterojunction formation, two widely used modifying approaches, to significantly alter photocatalytic performance. The vacancy-induced Ag2CO3/BiOBr/WO3-x heterojunction system has been fabricated using a co-precipitation technique to efficiently abate methylene blue (MB) dye and doxycycline (DC) antibiotic. The as-fabricated Ag2CO3/BiOBr/WO3-x heterojunction system displayed improved optoelectronic characteristic features because of the rational combination of dual charge transferal route and defect modulation. The Ag2CO3/BiOBr/WO3-x system possessed 97% and 74% photodegradation efficacy for MB and DC, respectively, with better charge isolation and migration efficacy. The ternary photocatalyst possessed a multi-fold increase in the reaction rate for both MB and DC, i.e., 0.021 and 0.0078 min-1, respectively, compared to pristine counterparts. Additionally, more insightful deductions about the photodegradation routes were made possible by the structural investigations of MB and DC using density functional theory (DFT) simulations. This study advances the understanding of the mechanisms forming visible light active dual Z-scheme heterojunction for effective environmental remediation.

Constructing 3D flower-like S-scheme N-Bi2O2CO3/g-C3N4 heterojunction with enhanced photocatalytic performance

Mineral processing wastewater contains a lot of organic matter and heavy metal ions, and poor self-degradation ability makes it a key treatment object in environmental treatment. Photocatalysis is a promising technology to efficiently mineralize refractory contaminants from wastewater. In this work, 3D flower-like S-scheme N-Bi2O2CO3/g-C3N4 heterostructures were successfully constructed by hydrothermal method with the auxiliary of ionic liquids. The photocatalytic experiments show that the catalytic activity of heterojunction photocatalysts was significantly higher than that of bare g-C3N4 and N-Bi2O2CO3 for the degradation of two pollutants. NBOC/CN-2 shows the highest photocatalytic performance, and the degradation efficiency of sodium isobutyl xanthate (SIBX) on NBOC/CN-2 is 1.85 and 3 times that of bare g-C3N4 and Bi2O2CO3, respectively. The degradation efficiency of m-Cresol on NBOC/CN-2 is 8.34 and 6.93 times that of bare g-C3N4 and N-Bi2O2CO3, respectively. This significantly enhanced photocatalytic activity is attributed to the formation of flower-like heterojunctions, which can greatly increase the specific surface area and facilitate the separation and migration of photogenerated carriers. Total organic carbon (TOC) experiment proves that the two pollutants are effectively mineralized under the action of the prepared photocatalyst. The degradation path of m-Cresol degradation products was inferred based on the ion fragments. The capture experiment and Nitro-blue tetrazolium (NBT)-•O2- measurement show that superoxide radical plays a major role in photocatalytic degradation. The outstanding stability of the prepared flower-like heterojunction samples was examined by cyclic experiments. The S-scheme charge transfer mechanism has been proposed to explain the boosted activity of the flower-like heterojunction photocatalyst. This work provides a new idea for the design of efficient and stable g-C3N4-based photocatalyst for the photocatalytic degradation of refractory wastewater.

Decoding the biological toxicity of phenanthrene on intestinal cells of Eisenia fetida: Effects, toxicity pathways and corresponding mechanisms

Phenanthrene is frequently detected and exists extensively in the soil environment, and its residues inevitably impose a significant threat to soil organisms. Exposure to and toxicity of phenanthrene on earthworms has been extensively studied before, however, the possible mechanisms and related pathways associated with phenanthrene-triggered toxicity at the intestinal cell level remain unclear. Herein, primary intestinal cells isolated from Eisenia fetida (Annelida, Oligochaeta) intestine were used as targeted receptors to probe the molecular mechanisms involved in ROS-mediated damaging effects and the potential pathways of phenanthrene-induced toxicity at cellular and sub-cellular levels. Results indicated that phenanthrene exposure induced oxidative stress by activating intracellular ROS (elevated O2-, H2O2, and OH- content) bursts in E. fetida intestinal cells, causing various oxidative damage effects, including lipid peroxidation (increased MDA content), protein oxidation (enhanced PCO levels), and DNA damage (enhanced 8-OHdG levels). The enzymatic and non-enzymatic strategies in earthworm cells were activated to mitigate these detrimental effects by regulating ROS-mediated pathways involving defense regulation. Also, phenanthrene stress destroyed the cell membrane of E. fetida intestinal cells, resulting in cellular calcium homeostasis disruption and cellular energetic alteration, ultimately causing cytotoxicity and cell apoptosis/death. More importantly, the mitochondrial dysfunction in E. fetida cells was induced by phenanthrene-caused mitochondrial membrane depolarization, which in turn caused un-controlled ROS burst and induced apoptosis through mitochondria-mediated caspase-3 activation and ROS-mediated mitochondrial-dependent pathway. Furthermore, exposure to phenanthrene activated an abnormal mRNA expression profile associated with defense regulation (e.g., Hsp70, MT, CRT, SOD, CAT, and GST genes) in E. fetida intestinal cells, resulting in various cellular dysfunctions and pathological conditions, eventually, apoptotic cell death. Taken together, this study offers valuable insights for probing the toxic effects and underlying mechanisms posed by phenanthrene at the intestinal cell level, and is of great significance to estimate the detrimental side effects of phenanthrene on soil ecological health.

Insight into the improved photocatalytic removal of tetracycline hydrochloride by constructing cobalt doping in 2D/2D (BiO)2CO3/BiOCl type-II heterojunctions

Element doping coupled with heterojunction construction and morphology control is an efficient way to improve the properties of photocatalytic materials. Here, a thiourea-modified 2D/2D cobalt-doped (BiO)₂CO₃/BiOCl heterojunction photocatalyst (denoted as Co-(BC/BL)_Tu) was constructed by a simple one-pot hydrothermal method. The photocatalytic property of Co-(BC/BL)_Tu product was evaluated by the photocatalytic degradation of tetracycline hydrochloride (TC-HCl). Compared with the pure (BiO)₂CO₃ sample, the as-prepared Co-(BC/BL)_Tu product displayed outstanding visible-light-driven photodegradation property. The photodegradation rate constant k value of the Co-(BC/BL)_Tu product was 5.2 times higher than that of pure (BiO)₂CO₃, which was the result of the synergistic effect of the 2D/2D structure, cobalt doping and type-Ⅱ heterostructures. It could simultaneously boost the visible light harvesting of the photocatalytic system as well as charge separation. This study provides a facile and promising strategy for constructing a high-effective photocatalytic system by combining morphology control engineering, doping engineering, and heterostructure engineering.

A Nanocomposite of Bismuth Clusters and Bi2 O2 CO3 Sheets for Highly Efficient Electrocatalytic Reduction of CO2 to Formate

The renewable-electricity-driven CO₂ reduction to formic acid would contribute to establishing a carbon-neutral society. The current catalyst suffers from limited activity and stability under high selectivity and the ambiguous nature of active sites. Herein, we report a powerful Bi₂ S₃ -derived catalyst that demonstrates a current density of 2.0 A cm^-2 with a formate Faradaic efficiency of 93 % at -0.95 V versus the reversible hydrogen electrode. The energy conversion efficiency and single-pass yield of formate reach 80 % and 67 %, respectively, and the durability reaches 100 h at an industrial-relevant current density. Pure formic acid with a concentration of 3.5 mol L^-1 has been produced continuously. Our operando spectroscopic and theoretical studies reveal the dynamic evolution of the catalyst into a nanocomposite composed of Bi⁰ clusters and Bi₂ O₂ CO₃ nanosheets and the pivotal role of Bi⁰ -Bi₂ O₂ CO₃ interface in CO₂ activation and conversion.

Construction of 2D layered phosphorus-doped graphitic carbon nitride/BiOBr heterojunction for highly efficient photocatalytic disinfection

Infectious diseases caused by bacteria intimidate the health of human beings all over the world. Although many avenues have been tried, various operating conditions limit their actual applications. Photocatalytic nanomaterials are becoming candidates to be competent for water purification. Here, a novel and more efficient S-scheme has been engineered between two dimensional (2D) layered phosphorus-doped graphitic carbon nitride (P-g-C 3 N 4 ) and BiOBr via hydrothermal polymerization to inhibit the recombination of charge and broaden light absorption. The as-prepared P-g-C 3 N 4 /BiOBr hybrids exhibits significantly improved photocatalytic disinfection contrast to g-C 3 N 4 /BiOBr in visible wavelengths, suggesting phosphorus doping which adjusts the band structure plays a significant role in the S-scheme system. And the sterilization rate of multidrug-resistant Acinetobacter baumannii 28 ( AB 28 ) was 99.9999% within 80 min and Staphylococcus aureus ( S. aureus ) was 99.9%.

A Comprehensive Review of Graphitic Carbon Nitride (g-C3N4)-Metal Oxide-Based Nanocomposites: Potential for Photocatalysis and Sensing

g-C3N4 has drawn lots of attention due to its photocatalytic activity, low-cost and facile synthesis, and interesting layered structure. However, to improve some of the properties of g-C3N4, such as photochemical stability, electrical band structure, and to decrease charge recombination rate, and towards effective light-harvesting, g-C3N4-metal oxide-based heterojunctions have been introduced. In this review, we initially discussed the preparation, modification, and physical properties of the g-C3N4 and then, we discussed the combination of g-C3N4 with various metal oxides such as TiO2, ZnO, FeO, Fe2O3, Fe3O4, WO3, SnO, SnO2, etc. We summarized some of their characteristic properties of these heterojunctions, their optical features, photocatalytic performance, and electrical band edge positions. This review covers recent advances, including applications in water splitting, CO2 reduction, and photodegradation of organic pollutants, sensors, bacterial disinfection, and supercapacitors. We show that metal oxides can improve the efficiency of the bare g-C3N4 to make the composites suitable for a wide range of applications. Finally, this review provides some perspectives, limitations, and challenges in investigation of g-C3N4-metal-oxide-based heterojunctions.

Harmonious K-I-O Co-modification of g-C3N4 for Improved Charge Separation and Photocatalysis

Co-modification of graphitic carbon nitride (g-C3N4) photocatalysts can maximally optimize its intrinsic photoelectric structures, but usually involve complex multistep reactions, thus is challenging because the structural collapse and active sites...

Optimized strategies for (BiO)2CO3 and its application in the environment

Photocatalysis is a new type of technology, which has been developed rapidly for solving environmental problems such as wastewater or air pollutants in recent years. Also, the effective performance and non-secondary pollution of photocatalytic technology attract much attention from researchers. As a "sillén" phase oxide, the (BiO)₂CO₃ (BOC) is a great potential photocatalyst attributing to composed of alternate Bi₂O₂²⁺ and CO₃^2- layers, which is a benefit for transportation of electrons. Besides, BOC has attracted much attention from researchers because of its excellent characters of non-toxic, environmentally friendly, and low-cost. However, BOC has a defect on wide band gap, which is limited for the usage of visible light, so a great number of published papers focus on the modifications of BOC to improve its photocatalytic efficiency. This article mainly summarizes the modifications of BOC and its application in the environment, guiding for designing BOC-based materials with high photocatalytic activity driven by light. Moreover, the research trend and prospect of BOC photocatalyst were briefly summarized, which could lay the foundation for forming a green and efficient BOC-based photocatalytic reaction system. Importantly, this review might provide a theoretical basis and guidance for further research in this field.

1D/2D constructed Bi2S3/Bi2O2CO3 direct Z-Scheme heterojunction: A versatile photocatalytic material for boosted photodegradation, photoreduction and photoelectrochemical detection of water-based contaminants

In this work, two-dimensional Bi₂O₂CO₃ disk is synthesized, followed by the growth of Bi₂S₃ over Bi₂O₂CO₃ via topotactic transformation by controlling the amount of thiourea under hydrothermal conditions. The synthesized composite catalyst is investigated for photocatalytic oxidation and reduction of tetracycline hydrochloride and hexavalent chromium under visible light irradiation. High interfacial contact between the Bi₂O₂CO₃ disk0 and Bi₂S₃ fiber is confirmed via high-resolution microscopic imaging. Enhanced light absorption and increased charge carrier separation is observed after the formation of the Bi₂S₃/Bi₂O₂CO₃ composite. The Bi₂S₃/Bi₂O₂CO₃ composite grown using 1 mmol of thiourea shows approximately 98% degradation of tetracycline hydrochloride after 120 min and 99% Cr(VI) reduction after 90 min of photochemical reaction under visible light irradiation. The charge separation is due to the formed internal electric field at the interface, which upon light irradiation follows a z-scheme charge transfer hindering the recombination at the Bi₂S₃ and Bi₂O₂CO₃ interface, thereby contributing efficiently to the photochemical process. In addition, the mechanism of the photochemical reaction for the degradation of pollutants is supported using quencher and probe experiments. Furthermore, photoelectrochemical detection of antibiotic in aqueous solution is conducted to understand the sensing feasibility of the synthesized system.

Photo-electro-Fenton-like process for rapid ciprofloxacin removal: The indispensable role of polyvalent manganese in Fe-free system

The residual ciprofloxacin (CIP) in water seriously menaces the ecological safety and public health. Here, a Fe-free photo-electro-Fenton-like (PEF) system was designed for efficient degradation of CIP in water. A Z-scheme MnO_x/g-C₃N₄ (MCN) nanocomposite with low-cost, large specific surface area and abundant active sites was successfully synthesized as a photoelectric catalyst. The XPS analysis indicated the presence of Mn²⁺, Mn³⁺ and Mn⁴⁺ in the MCN (1:6) composite, and the conversion among polyvalent manganese made the decomposition of H₂O₂ more efficient. Therefore, the manganese ions replaced the Fe element in traditional Fenton system. With the MCN (1:6), the PEF system could also produce O₂^-, OH and h⁺ under the visible light irradiation. The synergetic excitation of multiple active species promoted the rapid decomposition of CIP. Besides, the polyvalent property of manganese oxide resulted in the presence of oxygen vacancies which could improve the electrocatalytic reactivity of the catalyst. Finally, the degradation efficiency of CIP was 96.23% in 120 min and the mineralization efficiency was 80.02% in 240 min.

Interlocked 3D active carbon fibers and monolithic I-doped Bi2O2CO3 structure built by 2D face-to-face interaction: endowed with cycling stability and photocatalytic activity

Photocatalysis is considered a remarkable green method in the catalytic degradation of wastewater; however, the collection and loading of the powdered catalyst is still a problem.

A Novel CdS Quantum Dots Decorated 3D Bi2O2CO3 Hierarchical Nanoflower with Enhanced Photocatalytic Performance

Heterojunction engineering has shown great potential in the field of photocatalysis to deal with environmental pollutants. The design and synthesis of heterojunction photocatalysts with high efficiency and stability still face great challenges. In this work, a novel CdS quantum dots (QDs) decorated 3D Bi2O2CO3 hierarchical nanoflower heterojunction photocatalyst (Bi2O2CO3/CdS QDs) was synthesized to investigate the photocatalytic Rhodamine B (RhB) degradation performance. CdS QDs were evenly distributed on the surface of the Bi2O2CO3 nanoflower. Bi2O2CO3/CdS QDs showed significantly enhanced photocatalytic RhB degradation performance compared with pristine Bi2O2CO3 and CdS QDs. The enhanced photocatalytic performance was attributed to the synergistic effect of hierarchical structure and heterojunction, which greatly increased the active sites of the reaction and the photogenerated carriers transfer.

The Preparation of Amorphous Aluminum Oxide Modified g-C3N4 to Improve Photocatalytic Performance in Contaminant Degradation Applications

For the first time, aluminum alloy was used as the main source to prepare aluminum oxide-modified carbon nitride with a melamine–cyanuric acid supramolecular complex. The introduction of amorphous aluminum oxide confers macroporosity to the skeletons of g-C3N4-AlOx. Its surface area increased to 75.5 m2g−1, about 1.5 times that of single g-C3N4. After modification, the visible light response range was expanded, especially at 450~500 nm, while the band structure could be adjusted. Compared with g-C3N4, g-C3N4-AlOx has better photocatalytic performance, the adsorption rate for the dye rhodamine B (RhB) is about 2.1 times that of g-C3N4, and the RhB removal rate is 1.2 times that of g-C3N4.

Carbon Quantum Dots Modified (002) Oriented Bi2O2CO3 Composites with Enhanced Photocatalytic Removal of Toluene in Air

In work, (002) oriented flower-like Bi2O2CO3(BOC) composites are synthesized by a facile chemical route and carbon quantum dots (CQDs) are modified on their surfaces through a hydrothermal method. The synthesized samples (CQD/BOC) are characterized by X-ray diffraction (XRD), SEM, X-ray photoelectron spectroscopy (XPS), UV-Vis diffuser reflectances (DRS), BET and TEM/HRTEM. The morphologies of CQD/BOC composites are the flower-like shapes, the irregular flaky structures and the fine spherical particles of CQDs attached. Photocatalytic performances were investigated in terms of removing gaseous toluene at a concentration of 94.3ppm in air, with the assistance of CQD/BOC under artificial irradiation. Our results show that CQDs modified (002) oriented Bi2O2CO3 exhibits good photocatalytic activity for toluene decomposition, which can be attributed to the enhanced efficient charge separation. A certain ratio composite photocatalyst (BOC-CQD-15) shows a toluene removal rate of 96.62% in three hours, as well as great stability. CO2 was verified to be the primary product. The oriented flower-like Bi2O2CO3 with carbon quantum dots on the surface shows great potential in the field of solar driven air purification.

An innovative magnetic Ni0.1Co0.9Fe2O4/g-C3N4 nano-micro-spherical heterojunction composite photocatalyst with an extraordinarily prominent visible-light-irradiation degradation performance toward organic pollutants

Environmental pollution removal is attracting more attention these days because of increasing environmental problems. The use of photodegradation catalysts is a promising avenue in resolving environmental issues and therefore high-performance photocatalysts are urgently needed. Herein, we solvothermally synthesized a micro-spherical g-C3N4 photocatalyst and a nanospherical Ni0.1Co0.9Fe2O4 photocatalyst, and then innovatively employed small amounts of Ni0.1Co0.9Fe2O4 nanospheres coupled with g-C3N4 microspheres to fabricate a novel magnetic Ni0.1Co0.9Fe2O4/g-C3N4 nano-micro-spherical heterojunction photocatalyst through post co-calcination. Various techniques, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy and UV-vis diffuse reflectance spectroscopy, were employed to analyze the as-synthesized hybrid photocatalyst. The resultant photocatalyst exhibits a record high photocatalytic degradation activity against methylene blue under visible-light irradiation with a 100% degradation rate within only 10 min, corresponding to an extraordinarily prominent degradation reaction rate constant k value of up to 0.586 min-1. Our strategy opens a new effective way for fabricating high-performance photocatalysts and our novel Ni0.1Co0.9Fe2O4/g-C3N4 heterojunction photocatalyst is of great potential for application in environmental treatments.

In-situ construction of Bi/defective Bi4NbO8Cl for non-noble metal based Mott-Schottky photocatalysts towards organic pollutants removal

The strategy to improve the photocatalytic performance is still a challenge for the novel Sillen-Aurivillius perovskite type Bi₄NbO₈Cl. Herein, heterostructured Bi/Bi₄NbO₈Cl was fabricated via in-situ solvothermal method, without the additional introduction of Bi-sources. Simultaneously, the amount of oxygen vacancies (OVs) were increased, as the [Bi₂O₂] blocks released in the solvothermal process to serve as precursors for Bi particles. Due to the large work function of Bi, a Schottky barrier formed at the Bi/Bi₄NbO₈Cl interface, promoting photo-induced charge separation generated in the Bi₄NbO₈Cl semiconductor, supplying more holes for the organic compounds decomposition, which could be widely applied in water decontamination. Furthermore, the OVs facilitate the consumption of photo-induced electrons by assisting oxygen activation to produce superoxide radicals (·O₂^-), leaving more holes in the valence band of Bi₄NbO₈Cl, and thus result in the enhancement of Rhodamine B (RhB) degradation by 1.82 times over Bi/Bi₄NbO₈Cl photocatalysts. Through the synergistic effect of Bi and OVs, the Bi/Bi₄NbO₈Cl also exhibits enhanced photocatalytic performance towards various organic water-contaminants, such as methyl orange, acid orange 7, p-nitrophenol and tetracycline hydrochloride.

In situ synthesis of Cl-doped Bi2O2CO3 and its enhancement of photocatalytic activity by inducing generation of oxygen vacancies

Cl-Doped Bi₂O₂CO₃ is prepared using ionic liquids as dopants and the oxygen-vacancy-induced photocatalytic mechanism is revealed.