Recent developments on bismuth oxyhalides (BiOX; X = Cl, Br, I) based ternary nanocomposite photocatalysts for environmental applications

Synthesis of a 3D Flower-Like BiOCl/Bi-MOF Heterostructure for High-Performance Removal of Rhodamine B and Tetracycline Hydrochloride

Semiconductor materials based on bismuth metal have been extensively explored for their potential in photocatalytic applications owing to their distinctive crystal structure. Herein, we present the development of a hybrid photocatalyst, CAU-17/BiOCl, featuring a flower-like nanosheet morphology tailored for the photocatalytic degradation of organic contaminants such as rhodamine B (RhB) and tetracycline hydrochloride (TCH). The composite material is obtained by growing thin CAU-17 layers directly onto the host flower-like BiOCl nanosheets under solvothermal conditions. The optimized CAU-17/BiOCl composite possesses excellent photocatalytic performance, achieving a notable 96.0% removal rate for RhB and 78.4% for TCH after 60 and 90 min of LED light irradiation, respectively. This boosted activity is attributed to the heightened absorption of visible light caused by BiOCl and the provision of additional reaction sites due to the thin CAU-17 layers. Furthermore, the establishment of an S-scheme heterojunction mechanism enables efficient charge separation between CAU-17 and BiOCl, facilitating the separation of photoinduced electrons (e-) and holes (h+). Analysis of the degradation mechanism of RhB and TCH reveals the predominant role of superoxide radicals (•O2-), e-, and h+ in the photocatalytic degradation process. Moreover, the removal efficiency of TCH can reach approximately 64.5% after four cycles of recycling of CAU-17/BiOCl. Our work provides a facile, effective solution and a theoretically explained approach for the effective degradation of pollutants using heterojunction photocatalysts.

Recent advances on bismuth oxyhalides for photocatalytic CO2 reduction

Photocatalytic conversion of CO2 into fuels such as CO, CH4, and CH3OH, is a promising approach for achieving carbon neutrality. Bismuth oxyhalides (BiOX, where X = Cl, Br, and I) are appropriate photocatalysts for this purpose due to the merits of visible-light-active, efficient charge separation, and easy-to-modify crystal structure and surface properties. For practical applications, multiple strategies have been proposed to develop high-efficiency BiOX-based photocatalysts. This review summarizes the development of different approaches to prepare BiOX-based photocatalysts for efficient CO2 reduction. In the review, the fundamentals of photocatalytic CO2 reduction are introduced. Then, several widely used modification methods for BiOX photocatalysts are systematacially discussed, including heterojunction construction, introducing oxygen vacancies (OVs), Bi-enrichment, heteroatom-doping, and morphology design. Finally, the challenges and prospects in the design of future BiOX-based photocatalysis for efficient CO2 reduction are examined.

A comprehensive review of oxygen vacancy modified photocatalysts: synthesis, characterization, and applications

Photocatalytic technology is a novel approach that harnesses solar energy for efficient energy conversion and effective pollution abatement, representing a rapidly advancing field in recent years. The development and synthesis of high-performance semiconductor photocatalysts constitute the pivotal focal point. Oxygen vacancies, being intrinsic defects commonly found in metal oxides, are extensively present within the lattice of semiconductor photocatalytic materials exhibiting non-stoichiometric ratios. Consequently, they have garnered significant attention in the field of photocatalysis as an exceptionally effective means for modulating the performance of photocatalysts. This paper provides a comprehensive review on the concept, preparation, and characterization methods of oxygen vacancies, along with their diverse applications in nitrogen fixation, solar water splitting, CO2 photoreduction, pollutant degradation, and biomedicine. Currently, remarkable progress has been made in the synthesis of high-performance oxygen vacancy photocatalysts and the regulation of their catalytic performance. In the future, it will be imperative to develop more advanced in situ characterization techniques, conduct further investigations into the regulation and stabilization of oxygen vacancies in photocatalysts, and comprehensively comprehend the mechanism underlying the influence of oxygen vacancies on photocatalysis. The engineering of oxygen vacancies will assume a pivotal role in the realm of semiconductor photocatalysis.

Fabrication of CuFe2O4/Bi12O17Cl2 photocatalyst with intrinsic p-n junction for highly efficient bisphenol A degradation

The construction and application of novel highly efficient photocatalysts have been the focus in the field of environmental pollutant removal. In this work, a novel CuFe2O4/Bi12O17Cl2 photocatalysts were synthesized by simple hydrothermal and chemical precipitation method. The fabricated CuFe2O4/Bi12O17Cl2 composite exhibited much higher photocatalytic activity than pristine CuFe2O4 and Bi12O17Cl2 in the removal of bisphenol A (BPA) under visible-light illumination, which ascribed to the intrinsic p-n junction of CuFe2O4 and Bi12O17Cl2. The photocatalytic degradation rate of BPA on CuFe2O4/Bi12O17Cl2 with an optimized CuFe2O4 content (1.0 wt.%) reached 93.0% within 30 min. The capture experiments of active species confirmed that the hydroxyl radicals (•OH) and superoxide radicals (•O2-) played crucial roles in photocatalytic BPA degradation process. Furthermore, the possible degradation mechanism and pathways of BPA was proposed according to the detected intermediates in photocatalytic reaction process.

Boosting the performance of LaCoO3/MoS2 perovskite interface for sustainable decontaminants under visible light-driven photocatalysis

The novel composite LaCoO3/MoS2 hybrid nanostructure was synthesized via a combination of sol-gel, hydrothermal, and ultrasonication methods. Alizarin Red S (ARS) and Rhodamine B (RhB) were employed as a model pollutant, to assess the photodegradation efficiency of synthesized catalysts. The effect of MoS2 (2.5%, 5%, 7.5%, and 10%) on LaCoO3 (LCO) and its photocatalytic performance was studied. The properties of synthesized catalysts were assessed using various material characterization techniques. The photocatalytic dye degradation of ARS and RhB was investigated under visible light. Among the synthesized catalyst LM-5% composite (LaCoO3 with 5% MoS2) is determined to be the best photocatalyst as it degrades 96 % (ARS) and 90 % (RhB) in 40 min and 80 min, respectively. The photocatalyst is stable even after multiple runs and exhibits negligible loss in degradation efficiency during the cyclic test. Trapping experiments reveal the significance of superoxide anion and hydroxyl radicals against the photodegradation of ARS and RhB. The kinetics of photodegradation of ARS and RhB by LM-5% is found to be 5.70 × 10-2 and 2.25 × 10-2 min-1, respectively. Herein, we demonstrated a catalyst possessing excellent photodegradation activity which may ignite the possibilities of using efficient photocatalysts for environmental remediation.

Efficient Hg0 catalytic removal by direct S-scheme heterostructure of two-dimensional Bi2MoO6 (2 0 0)/g-C3N4 nanosheets under visible light

The gaseous elemental mercury (Hg0) emitted from coal-fired flue gas is extremely harmful to the atmospheric environment and human health. In this study, a 2D/2D Bi2MoO6(2 0 0)/g-C3N4 heterojunction photocatalyst was synthesized and exhibited a high visible-light driven Hg0 removal efficiency up to 99.5% in an atmosphere consisting of N2, O2 (6%), CO2 (12%), NO (100 ppm), SO2 (800 ppm), and H2O (5%). The introduction of surfactant CTAB led to further exposure of the highly active (2 0 0) crystal facet of Bi2MoO6, with a higher reactive oxygen species ratio than the original mainly exposed (1 3 1) crystal facet, and inhibited the agglomeration of Bi2MoO6, thereby greatly reducing the micro-thickness and improving the specific surface area. The smaller thickness effectively promoted the separation of photoinduced carriers and the speed of transfer to the interface. Additionally, through EPR characterization and work function calculation, we observed that the change in the exposed crystal facet regulated the Fermi level of Bi2MoO6 nanosheets, altering the direction of the built-in electric field at the interface with g-C3N4. This formation of an S-scheme 2D/2D Bi2MoO6(2 0 0)/g-C3N4 heterostructure further facilitated the recombination of unintentional carriers and strengthened the separation and catalysis of effective photogenerated carriers. To a certain extent, this work provides a guidance for the research of photocatalysis to achieve efficient and sustainable mercury removal from coal-fired flue gas.

Boosting the adsorptive and photocatalytic performance of MIL-101(Fe) against methylene blue dye through a thermal post-synthesis modification

Photocatalytic degradation under ultra-low powered light is a viable advanced oxidation process technique against extensive emerging contaminants. As a new and remarkable class of nanoporous materials, metal-organic frameworks (MOFs), attract interest for the supreme adsorptive and photocatalytic functionalities. An outstanding MOF, MIL-101(Fe) chosen as a photocatalyst template for the synthesis of α-Fe2O3 by a simple thermal modification to improve the structural properties toward methylene blue (MB) eradication. Octahedron-like α-Fe2O3 photocatalyst (Modified MIL-101(Fe), M-MIL-101(Fe)) was superior in dispersion and separation properties in aqueous medium. Moreover, the adsorptive and catalytic performance was increased for modified form by ~ 7.3% and ~ 17.1% compared to pristine MIL-101(Fe), respectively. Synergistic improvement of MB removal achieved by simultaneous adsorption/degradation under 5-W LED irradiation. Parametric study indicated an 18.1% and 44.5% improvement in MB removal was observed by increasing pH from 4 to 10, and M-MIL-101(Fe) dose from 0.2 to 1 g L-1, respectively. MB removal followed the pseudo-second-order kinetics model and the process efficiency dropped by 38% as MB concentration increased from 5 to 20 mg L-1. Radical trapping tests revealed the significant role of [Formula: see text] and electron radicals as the major participants in dye degradation. A significant loss in the efficiency of M-MIL-101(Fe) was observed in the reusability tests that is good to study further. In conclusion, a simple thermal post-synthesis modification on MIL-101(Fe) improved its structural, catalytic, and adsorptive properties against MB.

Constructing BiOBr1-xIx-y with Abundant Surface Br Vacancies for Excellent Visible-Light Photodegradation Capability of High-Concentration Refractory Contaminants

Bismuth oxybromide (BiOBr) is a promising photocatalytic semiconductor material due to its unique hierarchical structure and band structure. However, its photocatalytic applications are restricted due to its narrow visible-light absorption range and poor photooxidation capability. In this study, BiOBr1-xIx-y with rich surface Br vacancies (BrVs-rich BiOBr1-xIx-y) was created via a facile indirect substitution strategy. Benefiting from the broadened visible-light response range and reduced recombination rate of photogenerated carriers, BiOBr1-xIx-y shows excellent visible-light photodegradation ability for high-concentration refractory contaminants, such as phenol, tetracycline, bisphenol A, rhodamine B, methyl orange, and even real wastewater. At the same time, the Br vacancies can regulate the band structure of BiOBr1-xIx-y and serve as trap states to promote charge separation, thus facilitating surface photoredox reactions. An in-depth investigation of the Br vacancy effect and photodegradation mechanism was conducted. This novel study revealed the significance of Br vacancies in enhancing the photocatalytic performance of BiOBr under visible light, providing a promising strategy for improving the utilization efficiency of sunlight in wastewater treatment.

Noble metals (Pd, Ag, Pt, and Au) doped bismuth oxybromide photocatalysts for improved visible light-driven catalytic activity for the degradation of phenol

The doping of noble metals onto the semiconductor metal oxides has a great impact on the intrinsic properties of the materials. This present work reports the synthesis of noble metals doped BiOBr microsphere by a solvothermal method. The various characteristic findings reveal the effective incorporation of Pd, Ag, Pt, and Au onto the BiOBr and the performance of synthesized samples was test for the degradation of phenol over visible light. The Pd-doped BiOBr material showed enhanced phenol degradation efficacy, which is ∼4-fold greater than pure BiOBr. This improved activity was on reason of good photon absorption, lower recombination rate, and higher surface area facilitated by surface plasmon resonance. Moreover, Pd-doped BiOBr sample displayed good reusability and stability after 3 cycles of run. A plausible charge transfer mechanism for phenol degradation is disclosed in detail over Pd-doped BiOBr sample. Our findings disclose that the incorporation of noble metal as the electron trap is a feasible approach to enhance visible light activity of BiOBr photocatalyst used in phenol degradation. This work represents new vision interested in the outline and development of noble metal doped semiconductor metal oxides as a visible light material for the elimination of colorless toxins from untreated wastewater.

Bi3.64Mo0.36O6.55 nanoparticles anchored in BiOI: A p-n heterojunction photocatalyst to enhance water purification

Selective constructing of heterojunctions enables directional electron-hole migration and favorable charge separation. In this study, a novel p-n junction Bi_3.64Mo_0.36O_6.55 (BMO) nanoparticles anchored in BiOI construct by hydrothermal and subsequent in-situ synthesis. The construction of tight heterojunctions that enhance the characteristic absorption of visible light by Bi_3.64Mo_0.36O_6.55/BiOI (BIMO) and expose more reactive sites can be used to facilitate the rapid degradation of antibiotics (Tetracycline, TC), endocrine disruptors (Bisphenol A, BPA) and dyes in water. In addition, the BIMO catalyst maintained the rapid degradation rate of TC despite the interference of inorganic anions and aqueous substrates. The charge transfer pathways and radical species between the heterojunction components were investigated. In addition, the intermediates and toxicological analysis showed that TC was further mineralized and the small molecule products were generated significantly less toxic and less contaminated. In conclusion, this study synthesized photocatalysts based on p-n heterojunctions, which have potential applications for the degradation of TC.

Self-Assembly of Bi2Sn2O7/β-Bi2O3 S-Scheme Heterostructures for Efficient Visible-Light-Driven Photocatalytic Degradation of Tetracycline

Fabrication of S-scheme heterojunctions with enhanced redox capability offers an effective approach to address environmental remediation. In this study, high-performance Bi₂Sn₂O₇/β-Bi₂O₃ S-scheme heterojunction photocatalysts were fabricated via the in situ growth of Bi₂Sn₂O₇ on β-Bi₂O₃ microspheres. The optimized Bi₂Sn₂O₇/β-Bi₂O₃ (BSO/BO-0.4) degradation efficiency for tetracycline hydrochloride was 95.5%, which was 2.68-fold higher than that of β-Bi₂O₃. This improvement originated from higher photoelectron-hole pair separation efficiency, more exposed active sites, excellent redox capacity, and efficient generation of ^·O₂ ^- and ^·OH. Additionally, Bi₂Sn₂O₇/β-Bi₂O₃ exhibited good stability against photocatalytic degradation, and the degradation efficiency remained >89.7% after five cycles. The photocatalytic mechanism of Bi₂Sn₂O₇/β-Bi₂O₃ S-scheme heterojunctions was elucidated. In this study, we design and fabricate high-performance heterojunction photocatalysts for environmental remediation using S-scheme photocatalysts.

Bismuth-based semiconductors applied in photocatalytic reduction processes: fundamentals, advances and future perspectives

Bismuth-based semiconductors (BBSs) with their typical layered structures and unique electronic properties are considered an attractive visible light-responsive photocatalysts. Recently, BBS exhibited promising properties and was rapidly developed in photoreduction reactions. In this review, we firstly focus on the photoreduction reactions of BBS with a description of the basic principles. Specifically, the restrictive factors of the photoreduction reactions and the design directions of the catalysts are addressed. BBS photocatalysts, such as bismuth oxide, bismuth halide oxide and bismuth-based oxygenates, are presented in terms of the catalyst material design, crystal structure and other features. Furthermore, the primary applications of BBS in photoreduction reactions are described, including CO₂ reduction, N₂ reduction, H₂ evolution, and nitrate reduction. Additionally, the advances and shortages of BBS applied in these processes are summarized and comprehensively discussed. Future works for BBS applied in photoreduction processes are also proposed.

BiOI@CeO2@Ti3C2 MXene composite S-scheme photocatalyst with excellent bacteriostatic properties

As an influential antifouling material, photocatalytic materials have drawn attention increasingly over recent years owing to their potential bacteriostatic property in the domain of marine antifouling. Herein, a flower-like BiOI@CeO2@Ti3C2 S-scheme photocatalyst was contrived and prepared by hydrothermal method. The innovative combination of Ti3C2 and narrow band gap semiconductor BiOI was implemented to modify CeO2 and the photocatalytic bacteriostatic mechanism of BiOI@CeO2@Ti3C2 was elucidated. Schottky junction was formed between CeO2 and Ti3C2, and a p-n junction was formed between CeO2 and BiOI. By photoelectrochemical characterization, BCT-10 exhibits the best photoelectrochemical performance of which photogenerated carrier transport can be performed more readily at 10 % CeO2@Ti3C2 addition. 99.76 % and 99.89 % of photocatalytic bacteriostatic efficiency of BCT-10 against Escherichia coli and Staphylococcus aureus were implemented respectively, which were 2.98 and 3.07 times higher than that of pure CeO2. The ternary heterojunction can suppress photogenerated electron-hole complexes more effectively and enhance the photocatalytic bacteriostatic effect of CeO2, which also provided a new concept to the further broadened application of CeO2 in the marine bacteriostatic and antifouling field.

Effects of high pressure on the lattice structure and electrical transport properties of BiOI

To reveal the pressure effects on BiOX semiconductors, we performed in-situ Raman spectroscopy and electrical transport measurements on BiOI up to 26.1 GPa and 19.2 GPa. BiOI showed good structural stability, while the electron conduction characteristics maintained dominance throughout the pressure range. The influence of grain boundary conduction disappeared at pressures above 9.2 GPa. With pressure elevation, the pressure-induced lattice fragmentation and grain refinement introduced a large number of relevant levels in the energy gap and resulted in a significant increase in the conductivity of BiOI under compression. The conductivity increased by 10⁶ at 19.2 GPa from the initial value and maintained an increase of 10² after depressurization until ambient conditions were attained. At the same time, the space charge polarization of the crystal interface layer became weaker with pressure elevation resulting in a decrease in the relative permittivity of BiOI. The calculation results of the complex permittivity showed that the frequency of orientation polarization response decreases with pressure elevation, and the complex permittivity becomes constant in the high-frequency region. Our work proves that pressure could significantly increase the carrier concentration and mobility, thus effectively improving the conductivity of BiOX semiconductors.

Interface Engineering in 2D/2D Heterogeneous Photocatalysts

Assembling different 2D nanomaterials into heterostructures with strong interfacial interactions presents a promising approach for novel artificial photocatalytic materials. Chemically implementing the 2D nanomaterials' construction/stacking modes to regulate different interfaces can extend their functionalities and achieve good performance. Herein, based on different fundamental principles and photochemical processes, multiple construction modes (e.g., face-to-face, edge-to-face, interface-to-face, edge-to-edge) are overviewed systematically with emphasis on the relationships between their interfacial characteristics (e.g., point, linear, planar), synthetic strategies (e.g., in situ growth, ex situ assembly), and enhanced applications to achieve precise regulation. Meanwhile, recent efforts for enhancing photocatalytic performances of 2D/2D heterostructures are summarized from the critical factors of enhancing visible light absorption, accelerating charge transfer/separation, and introducing novel active sites. Notably, the crucial roles of surface defects, cocatalysts, and surface modification for photocatalytic performance optimization of 2D/2D heterostructures are also discussed based on the synergistic effect of optimization engineering and heterogeneous interfaces. Finally, perspectives and challenges are proposed to emphasize future opportunities for expanding 2D/2D heterostructures for photocatalysis.

Advanced oxidation processes for the removal of mono and polycyclic aromatic hydrocarbons - A review

Aromatic hydrocarbons (AHs) are toxic environmental contaminants presented in most of the environmental matrices. Advanced oxidation processes (AOPs) for the removal of AHs in the account of complete mineralization from various environmental matrices have been reviewed in this paper. An in-depth discussion on various AOPs for mono (BTEX) and polyaromatic hydrocarbons (PAHs) and their derivatives is presented. Most of the AOPs were effective in the removal of AHs from the aquatic environment. A comparative study on the degradation of various AHs revealed that the oxidation of the AHs is strongly dependent on the number of aromatic rings and the functional groups attached to the ring. The formation of halogenated and nitrated derivatives of AHs in the real contaminated water containing chloride, nitrite, and nitrate ions seems to be a challenge in using the AOPs in real systems. The phenolic compounds, quinone, alcohols, and aliphatic acids are the important byproducts formed during the oxidation of AHs, initiated by the attack of reactive oxygen species (ROS) on their electron-rich center. In conclusion, AOPs are the adaptable method for the removal of AHs from different environmental matrices. The persulfate-based AOPs were applied in the soil phase removal as an in situ chemical oxidation of AHs. Moreover, the combination of AOPs will be a conclusive solution to avoid or minimize unexpected or other toxic intermediate products and to obtain rapid oxidation of AHs.

Construction of a Z-scheme Ag2MoO4/BiOBr heterojunction for photocatalytically removing organic pollutants

How to facilitate photogenerated-carrier separation is an important step in developing excellent semiconductor photocatalysts for environmental pollutant removal. Herein, Ag₂MoO₄ (AMO) nanoparticles were assembled onto the surface of BiOBr (BOB) nanosheets to construct a highly efficient Z-scheme AMO/BOB heterojunction photocatalyst. Several analytical techniques were used to elucidate the characteristics and photocatalytic mechanism of the AMO/BOB heterojunction. Photodegradation experiments for removing methylene blue under simulated-sunlight irradiation reveal that a 20%AMO/BOB heterojunction exhibits excellent photodegradation activity with η(30 min) = 93.8% and k_app = 0.08638 min^-1, which were greater by 4.5 and 5.6 times in comparison with that of pure BOB and AMO, respectively. Based on the experimental and density functional theory (DFT) calculation results, it is proposed that the Z-scheme carrier transfer/separation mechanism dominates the enhanced photodegradation performance of the composite photocatalysts. Additionally, the potential application of AMO/BOB photocatalysts in degrading various organic pollutants (including organic dyes, antibiotics and other serious organic pollutants) was also investigated.

A facile synthesis of visible light driven Ni3V2O8 nano-cube/BiVO4 nanorod composite photocatalyst with enhanced photocatalytic activity towards degradation of acid orange 7

Photocatalysis is one of the promising method to degrade harmful organic pollutants under visible light exposure. In this work, a novel Ni₃V₂O₈/BiVO₄ nanocomposite has been prepared by one-pot hydrothermal method, and investigated through X-ray diffraction, FT-IR, UV-visible diffuse reflectance spectroscopy, scanning and transmission electron microscopy and photoluminescence techniques. Subsequently, the photocatalytic performance of Ni₃V₂O₈/BiVO₄ nanocomposite has been examined by degrading AO7 under visible light illumination. The photocatalytic efficiency of the optimized 1:2 ratio of Ni₃V₂O₈/BiVO₄ nanocomposite photocatalyst is found to be 87% with a rate constant value of 0.03387 min^-1 which are higher than those of other prepared photocatalysts. This nanocomposite exhibits excellent stability even after 3 three cycles, and shows 1.135- and 1.17-times higher photocurrent intensity than pure BiVO₄ and Ni₃V₂O₈ respectively. The mechanism for the degradation of AO7 over Ni₃V₂O₈/BiVO₄ nanocomposite photocatalyst has been proposed.

A review on bismuth-based nanocomposites for energy and environmental applications

Bismuth, a heavy metal which is found to be inexpensive and at a reduced cost, is utilized in the synthesis of different nanomaterials with novel structure, remarkable physical and chemical properties, adjustable bandgap, notable efficiency for photothermal conversion. These characteristics have made this element desirable for various applications such as storage and conversion of energy, electronics, sensors, photocatalysis, and other biomedical applications. These review papers are the vital points for the students, this report guides them to the research papers which focus on the impressive development in the area of bismuth and similar nanostructures. The purpose of the present review is to discuss the various synthesis routes of bismuth-based nanomaterials along with green synthesis, different nanostructures of bismuth, their significant properties, diverse applications and directions for the upcoming research. Therefore, with these different tuneable synthesis methods of bismuth-based nanomaterials combined with their novel properties, would elucidate on the future devices based on various nanostructures of bismuth.

Zinc iron selenide nanoflowers anchored g-C3N4 as advanced catalyst for photocatalytic water splitting and dye degradation

Hydrogen has been considered as a promising clean energy source owing to its renewability and zero carbon emission. Accordingly, photocatalytic water splitting has drawn much attention as a key green technology of producing hydrogen. However, it has remained as a great challenge due to the low production rate and expensive constituents of photocatalytic systems. Herein, we synthesised nanostructures consisting of transition metal selenide and g-C₃N₄ for photocatalytic water splitting reaction. They include ZnSe, FeSe₂, Zn/FeSe₂ and ZnFeSe₂ nanoflowers and a nanocomposite made of Zn/FeSe₂ and g-C₃N₄. Hydrogen evolution rates in the presence of ZnSe, FeSe₂, Zn/FeSe₂ and ZnFeSe₂ photocatalysts were measured as 60.03, 128.02, 155.11 and 83.59 μmolg^-1 min^-1, respectively. On the other hand, with the nanocomposite consisting of Zn/FeSe₂ and g-C₃N₄, the hydrogen and oxygen evolution rates were significantly enhanced up to 202.94 μmol g^-1min^-1 and 90.92 μmol g^-1min^-1, respectively. The nanocomposite was also examined as a photocatalyst for degradation of rhodamine B showing that it photodegrades the compound two times faster compared to pristine Zn/FeSe₂ nanoflowers without g-C₃N_4. Our study suggests the nanocomposite of Zn/FeSe₂ and g-C₃N₄ as a promising photocatalyst for energy and environmental applications.

Dynamic control of pentachlorophenol photodegradation process using P25/PDA/BiOBr through regulation of photo-induced active substances and chemiluminescence

Photodegradation is a new approach for the removal of pentachlorophenol (PCP). Photooxidation degradation (using hydroxyl radicals) exhibits better performance to remove PCP than photoreduction degradation, but the former will lead to an increase in the production of toxic by-products such as tetrachloro-1,4-benzoquinone (TCBQ). Thus, a new strategy is required to enhance PCP photodegradation and simultaneously inhibit toxic intermediates production. Herein, TiO₂ (P25)/polydopamine (PDA)/BiOBr was synthesized and used to photodegrade PCP. Based on the relative position of the CB and VB of P25 and BiOBr, and PDA as an electron transfer mediator, a high number of holes, electrons, and superoxide anions were produced instead of hydroxyl radicals. The photocatalytic activity of P25/PDA/BiOBr exhibited the best performance among as-prepared samples, reaching a k_(pcp) value of 0.4 min^-1 (20 μM PCP) under UV light irradiation within 10 min. According to chemiluminescence and acute toxicity assays, relative to P25, the toxic intermediates of TCBQ and trichlorohydroxy-1,4-benzoquinone (OH-TrCBQ) generation was greatly reduced over P25/PDA/BiOBr, with a lack of toxic product generation during PCP photodegradation process. These findings provide an alternative strategy to achieve greener and more efficient organic pollutant photodegradation.

Abdelhamid A, Alzamly A. Visible-Light-Driven Photocatalytic Coupling of Neat Benzylamine over a Bi-Ellagate Metal-Organic Framework

Selective aerobic oxidation of benzylamine to N,N-benzylidenebenzylamine was achieved using a bismuth ellagate (Bi-ellagate) metal-organic framework (MOF) under simulated visible light irradiation. The bismuth ellagate photocatalyst was characterized using several spectroscopic techniques: powder X-ray diffraction (PXRD), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and nitrogen sorption measurements. Product formation was confirmed using ¹H-NMR, ¹³C-NMR, and FTIR. The photocatalytic performance of Bi-ellagate was studied for the first time, which exhibits a band gap value of 2.62 eV, endowing it with a high photocatalytic activity under visible light irradiation. The reaction product, N,N-benzylidenebenzylamine, was selectively obtained with a high conversion yield of ∼96% under solvent-free conditions compared to other control experiments. The Bi-ellagate photocatalyst was recovered and reused four times without any significant loss in its activity, which provides an eco-friendly, low-cost, recyclable, and efficient photocatalyst for potential photocatalytic applications.

Low temperature energy- efficient synthesis methods for bismuth-based nanostructured photocatalysts for environmental remediation application: A review

Bismuth-based composite materials have unique structural, chemical, optical, and electrical properties that are highly beneficial in Photocatalysis. The layered structure and tunable bandgap properties of the Bismuth-based composites are advantageous for the absorption of solar light efficiently. Also, these properties help the separation and recombination of photogenerated charge carriers, leading to enhancement in the photocatalytic activity. Synthesis of the catalyst at a lower temperature to produce catalyst reduces the production cost and electrical energy consumption. This review provides an overview of the recent development in Bismuth-based composite nanostructured photocatalytic materials, mainly using low-temperature driven synthesis methods. Herein, we have mainly summarized the primarily used low temperature-based synthetic routes, particularly in the temperature range of 50-300 °C for synthesizing Bismuth-based composite materials. In addition to this, the photocatalytic mechanism, the textural, structural, electronic, and photocatalytic properties of the synthesized photocatalysts are discussed. The literature shows that the surface area of the composite Bismuth-based photocatalytic materials synthesized using the low-temperature synthetic route is in the range of 1.5-81 m²/g and can be activated by solar, ultraviolet, and Light Emitting Diode (LEDs) light irradiation based on the synthetic route. Their photocatalytic performance and structural stability are excellent and utilized for several runs. The comprehensive understanding of the low-temperature synthesis of Bismuth-based composite materials for visible light-activated photocatalytic applications provided will be useful for developing photocatalytic materials on an industrial scale due to energy-efficient synthetic routes. Furthermore, the prospects of low temperature-driven Bismuth-based composite synthesis routes are discussed.

Role of p-n junction initiated mixed-dimensional 0D/2D, 1D/2D, and 2D/2D BiOX (X = Cl, Br, and I)/TiO2 nanocomposite interfaces for environmental remediation applications: A review

Nowadays, we are critically facing various environmental issues. Among these, water contamination is the foremost issue, which worsens our health and living organisms in the water. Thus, it is necessary to provide an avenue to minimize the toxic matter through the development of facile technique and harmless photocatalyst. In this review, we intended to uncover the findings associated with various 0D, 1D, and 2D nanostructures featured photocatalysts for advancements in interfacial characteristics and toxic matter degradation. In this context, we evaluated the promising mixed-dimensional 0D/2D, 1D/2D, and 2D/2D bismuth oxyhalides BiOX (X = Cl, Br, and I) integrated TiO₂ nanostructure interfaces. Tunable mixed-dimensional interfaces highlighted with higher surface area, more heterojunctions, variation in the conduction and valence band potential, narrowed band gap, and built-in electric field formation between BiOX and TiO₂, which exhibits remarkable toxic dye, heavy metals, and antibiotics degradation. Further, this review further examines insights into the charge carrier generation, separation, and shortened charge transfer path at reduced recombination. Considering the advantages of type-II, S-scheme, and Z-scheme charge transfer mechanisms in the BiOX/TiO₂, we heightened the combination of various reactive species generation. In a word, the concept of mixed-dimensional BiOX/TiO₂ heterojunction interface endows toxic matter adsorption and decomposition into useful products. Challenges and future perspectives are also provided.

Morphological guided sphere to dendrite BiVO4 for highly efficient organic pollutant removal and photoelectrochemical performance under solar light

Monoclinic BiVO₄ (m-BiVO₄) has been reported as promising phase for solar light driven photocatalysis. However, in the case of morphology guided BiVO₄ with different synthetic conditions maintaining the m-BiVO₄ phase remains a substantial challenge for achieving an efficient photocatalyst driven by solar light. Herein, a simple hydrothermal approach was used to produce well-defined template free m-BiVO₄ dendrites with distinct branches for photo catalytically removal of organic pollutant and photocurrent generation. The development of monoclinic dendrite BiVO₄ was confirmed after comprehensive structural, morphological, and optical examinations. FE-SEM images of m-BiVO₄ revealed transformation of spherical to dendritic morphology with distinct branches by simply changing the HNO₃ to NaOH ratios from 2:1 to 2:2, which are named as BVO 2-1 and BVO 2-2, respectively. The BVO 2-2 dendrites exhibited improved activity of 98% towards methylene blue (MB) photodegradation upon simulated solar light irradiation. The BVO 2-2 dendrites photoelectrode showed an outstanding photocurrent density of 1.4245 mAcm^-2 than that of the BVO 2-1 spherical photoelectrode (0.7367 mAcm^-2). Enhanced photocatalytic and photoelectrochemical action, could be ascribed to the unique morphological changes provides photoactive sites, harvest more light utilization together with higher separation of e^-/h⁺ pairs. Furthermore, photocatalytic mechanism is investigated based on scavenger trapping agent, valence band XPS, UV Visible DRS and PL study. Our findings could pave the way for the development of dendritic nanostructure photocatalysts with improved photocatalytic activity.

Photocatalytic degradation of tetracycline using hybrid Ag/Ag2S@BiOI nanowires: Degradation mechanism and toxicity evaluation

The wide use of antibiotics has caused their continual release and persistence in the eco-system, subsequently giving birth to antibiotic resistant bacterial species in the aquatic environment, thereby necessitating immediate and efficient remediation of the contaminated environment. In the present study, we synthesized Ag/Ag₂S@BiOI nanowires with an average diameter of ∼150 nm and length of 3-5 μm using a hydrothermal method and employed them as photocatalysts for photocatalytic degradation of tetracycline as a model antibiotic. The nanowire achieved nearly complete degradation of tetracycline (∼99%) within 60 min at the optimal condition of 100 mg/L TC concentration and pH 2. The degradation followed pseudo-first order kinetics, with a rate constant of 0.06228 min^{- 1}. Our toxicity tests showed that the nanowire has negligible toxicity towards PBMC cells, suggesting it as a promising photocatalyst.

Synthesis of novel graphene aerogel encapsulated bismuth oxyiodide composite towards effective removal of methyl orange azo-dye under visible light

Development of novel and eco-friendly composite photocatalysts for the efficient removal of contaminants from wastewater is the need of the hour. In this study, visible light responsive novel graphene aerogel/bismuth oxyiodide (GA/BiOI) composite was synthesized via low-temperature solvothermal method. The synthesized GA/BiOI composite was tested for methyl orange (MO) azo-dye degradation under visible light. The graphene aerogel nanosheets were wrapped onto the surface of the each individual BiOI microsphere, which encourages the interconnection charge transfer process. The light absorption properties of GA/BiOI composite were increased with the addition of graphene aerogel. The optimal 5%-GA/BiOI composite displayed higher MO removal efficiency, which is ∼2 fold more than the bare BiOI photocatalyst. This enhanced photocatalytic activity was on account of lower recombination rate of charge carriers, improved light absorption, and the high surface area. In addition, the 5%-GA/BiOI composite showed good stability until 3 cycles without deactivation. The plausible MO degradation mechanism was also proposed over GA/BiOI under visible light. This work provides a new perspective on the design and synthesis of graphene aerogel-based composite for environmental applications.

Improved visible-light-driven photocatalytic removal of Bisphenol A using V2O5/WO3 decorated over Zeolite: Degradation mechanism and toxicity

WO₃/Zeolite/V₂O₅ (TZV) composite synthesized through co-precipitation was used for the degradation of Bisphenol-A (BpA). XRD and Raman spectra were employed to ascertain the crystallinity of the composite. The pristine nature of the compound without any free particles over the zeolite surface was established through FESEM, thus, substantiating the composite character of the material. The enhancement in activity after doping with WO₃ was ascertained by DRS-UV. Photocatalytic degradation studies clearly established the superiority of TZV 10 over bare V₂O₅. Complete BpA degradation (100%) was attained at 50 min of incubation with 0.75 g/L TZV-10 in acidic medium (pH 3) for an initial BpA concentration of 100 mg/L. HPLC-MS/MS analysis was used to decipher the degradation pathway. The catalyst was stable even after 9 cycles. Phytotoxicity studies and lake water treatment results proved the environmental efficiency of the synthesized material.

Novel fabrication of the recyclable MoS2/Bi2WO6 heterostructure and its effective photocatalytic degradation of tetracycline under visible light irradiation

Developing cost-effective and highly effective visible-light-driven photocatalysts for decomposition of organic contaminants has been deliberated as an important and viable strategy for environmental remediation. Herein, MoS₂/Bi₂WO₆ heterostructure photocatalysts were fabricated with excellent visible light absorption performance and efficient electron/hole (e^-/h⁺) separation efficacy. As-prepared all photocatalysts were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution TEM, X-ray photoelectron spectroscopy (XPS). Although photocatalytic experiments were examined by UV-vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence spectroscopy (PL), and transient photocurrent (I-t). Among all the photocatalysts, that synthesized by using the components 10 mg of Bi₂WO₆ with 100 mg of MoS₂ (denoted as MSBW-10), displayed high photocatalytic performance (96.31%) for tetracycline (TC) under visible light irradiation within 90 min. The kinetic rate constant of the MSBW-10 heterostructure was 5.51 and 6.71 times higher than those of MoS₂ and Bi₂WO₆, respectively. Further, radical trapping experiments revealed that ˙OH radicals and holes were the predominant reactive species involved in the photocatalytic course. The recycle tests revealed the stability of the photocatalyst, which exhibited 91.85% TC removal efficacy without obvious decay even after the fourth cycle. Furthermore, the type-II MoS₂/Bi₂WO₆ heterostructure photocatalyst exhibited a slighter band gap with energy band alignments and enhanced visible-light absorption, separation of charge carriers, and good oxidation/reduction capacities. These deeper insights and synergetic effects can afford a new approach for flourishing novel heterostructure photocatalysts.

Outlook on bismuth-based photocatalysts for environmental applications: A specific emphasis on Z-scheme mechanisms

Semiconductor photocatalysis is thought to be a viable solution for addressing the growing problem of environmental pollution. Bismuth (Bi) metal oxides can function as a direct plasmonic photocatalyst or cocatalyst to accelerate the photogenerated charge separation and thus improve their photocatalytic activity. Hence, Bi-based photocatalysts have received a lot of attention due to their extensive environmental applications, including pollutant remediation and energy concepts. Massive efforts have been undertaken in the recent decade to find superior Bi-metal oxides (Bi₂XO_6, X = MO, W, or Cr) and to uncover the corresponding photocatalytic reaction mechanism for the degradation of organic contaminants in water. Herein, the unique crystalline and electronic properties and main synthesis methods, as well as the major Bi-Based direct Z-scheme photocatalysts, are timely discussed and summarized in their usage in water treatment. Besides, the impact of Bi₂XO₆ in energy storage devices and solar energy conversion is reviewed as an energy application. Finally, the future development and challenges of Z-scheme-based Bi₂XO₆ photocatalysts are briefly explored, summarized, and forecasted.

BiFeO3/Fe2O3 electrode for photoelectrochemical water oxidation and photocatalytic dye degradation: A single step synthetic approach

Herein, mixed-phase BiFeO₃/Fe₂O₃ (BF-M) nanocomposite has been successfully prepared in a simple single-step synthetic strategy and its structural, physicochemical and magnetic properties have been characterized. The performance of as-synthesized mixed-phase BF-M catalyst has been investigated in photoelectrochemical (PEC) water oxidation and photocatalytic dye degradation analysis by comparing with the partials Fe₂O₃ with BiFeO₃ (BF-P). The BF-M photocatalyst has degraded 95.7% of the rhodamine B (RhB) dye while BF-P has degraded 82.1% in 80 min. In addition, the BF-M electrode exhibited 0.57 mA cm^-2 photocurrent density which was 1.83 times higher than the BF-P electrode (0.31 mA cm^-2), signifying that the formation of a mixed-phase nanostructure interface is advantageous in enhancing light absorption capacity and reducing the rate of electron-hole recombination.

Bismuth quantum dots anchored one-dimensional CdS as plasmonic photocatalyst for pharmaceutical tetracycline hydrochloride pollutant degradation

Earth abundant metal based plasmonic photocatalysis is one of the most proficient approaches to degrade the emergent organic pollutants in contaminated water. Here, we report that using one-dimensional CdS/zero-dimensional Bi quantum dot (QD) heterostructures (1D/0D CdS/Bi HSs) were obtained via a simple solvothermal reaction. The results specified that the Bi QDs were grown onto CdS NRs through the reduction of Bi³⁺ ions. The Bi modified CdS HSs were employed as a photocatalyst for pharmaceutical pollutant tetracycline degradation and the optimized sample showed the maximum photocatalytic degradation activity of 90% under visible light radiation within 60 min, which is greater than the pure CdS (52%) under identical conditions. Based on the structural characterizations and degradation efficiency, the obtained CdS/Bi is a promising photocatalyst for the treatment of wastewater which contains emerging pollutants such as organic dyes and pharmaceutical antibiotics during the industrial processes. The boosted photocatalytic degradation efficiency is credited to the doped Bi³⁺ species; surface plasmon resonance effect that raised from metallic Bi QDs and proficient photoinduced charge carriers separation.

Advances in preparation, mechanism and applications of various carbon materials in environmental applications: A review

Carbon-related materials are now widely investigated in a various industrial field due to their excellent and unique qualities. It must be tailored to the application in such a way that it fits the application. At the same time, it needs to be generated in sufficient quantities for commercial use, and the synthesis method is the major sticking point here. Because most new materials are discovered by chance, the synthesis process described here may not be the most effective way to create them. The research is merely a steppingstone to discovering a different approach, and it will continue until the substance is no longer being used. If you're developing materials for any purpose, synthesis processes are essential. Fullerene, carbon nanotubes (CNT), graphene, and MXene are only a few of the carbon-based compounds discussed in this overview study, which also gives a brief prognosis on the materials future. Furthermore, the environmental application of these carbon materials was discussed and commented.

In-situ Pt nanoparticles decorated BiOBr heterostructure for enhanced visible light-based photocatalytic activity: Synergistic effect

Advanced functional materials for photocatalytic hydrogen (H₂) generation using abundant solar energy are the core of new and renewable energy research. In this paper, we report the in-situ deposition of platinum quantum-sized particles (Pt QDs) on bismuth oxybromide (BBr) 3D marigold flowers with exposed (101)/(110) facets (i.e. BBr-Pt) hierarchies prepared by a simple solvo-thermal method acting as a surfactant/structure stabilizer in the presence of CTAB. Synthesized samples were characterized by a series of analytical techniques. Intimate contact as demonstrated by HRTEM, effect of Pt loading in 3D-BiOBr nanostructure on photocatalytic H₂ production and crystal violet (CV) dye degradation rate under white LED light irradiation was studied. This was greatly improved by loading Pt QDs on BBr, the latter showing the highest photocatalytic activity for BBr-2Pt nanostructure, due to the synergistic effect of quantum-sized Pt nanoparticles and exposed ((101) and (110) planes). The BBr-2Pt nanostructure photocatalysts showed highest H₂ generation of 320.69 μmol g^-1, which is 142 folds larger than bare BBr (2.26 μmol g^-1).

Visible-light-driven indium vanadium oxide nanosheets supported bismuth tungsten oxide nanoflakes heterostructure as an efficient photocatalyst for the tetracycline degradation

The development of excellent photocatalysts is of great significance for the efficient photocatalytic degradation process, however, the low carrier separation efficiency and poor light absorption ability typically limit the performance of photocatalysts. Herein, a visible light responsive heterostructure composed with indium vanadium oxide nanosheets supported bismuth tungsten oxide nanoflakes (InVO₄/Bi₂WO₆) was synthetized through in-situ hydrothermal method. Further, the photocatalytic activity was performed for tetracycline (TC) under visible light illumination. The InVO₄/Bi₂WO₆ heterostructure builds a strong interface between InVO₄ and Bi₂WO₆ to hinder reunion of photoinduced charge carriers, and provides the sensitive agents for the removal of TC. In particular, the InVO₄/Bi₂WO₆ photocatalyst prepared by taking 5.0 mg of Bi₂WO₆ shows the highest degradation of TC about 97.42% in 72 min. The quenching experiments identified that hydroxyl radicals, and holes dominated in the photocatalytic process. Furthermore, the optimized nanocomposite is stable even after four cycles, which exposes the excellent photostability and reusability of the photocatalyst. In addition, a plausible degradation pathway and mechanism of TC over InVO₄/Bi₂WO₆ nanocomposite is also projected.

Emerging bismuth-based direct Z-scheme photocatalyst for the degradation of organic dye and antibiotic residues

Organic dye and antibiotic residues are some of the key substances that can contaminate the environment due to their wide usage in various industries and modern medicine. The degradation of these substances present in waterbodies is essential while contemplating human health. Photocatalysts (PSs) are promising materials that develop highly reactive species instantly by simple solar energy conversion for degrading the organic dye and antibiotic residues and converting them into nontoxic products. Among numerous semiconductors, the bismuth (Bi)-containing PS has received great attention due to its strong sunlight absorption, facile preparation, and high photostability. Owing to the technology advancement and demerits of the traditional methods, a Bi-containing direct Z-scheme PS has been developed for efficient photogenerated charge carrier separation and strong redox proficiency. In this review, a synthetic Bi-based Z-scheme heterojunction that mimics natural photosynthesis is described, and its design, fabrication methods, and applications are comprehensively reviewed. Specifically, the first section briefly explains the role of various semiconductors in the environmental applications and the importance of the Bi-based materials for constructing the Z-scheme photocatalytic systems. In the successive section, overview of Z-scheme PS are concisely discussed. The fourth and fifth sections extensively explain the degradation of the organic dyes and antibiotics utilizing the Bi-based direct Z-scheme heterojunction. Eventually, the conclusions and future perspectives of this emerging research field are addressed. Overall, this review is potentially useful for the researchers involved in the environmental remediation field as a collection of up-to-date research articles for the fabrication of the Bi-containing direct Z-scheme PS.

Aurivillius Oxides Nanosheets-Based Photocatalysts for Efficient Oxidation of Malachite Green Dye

Aurivillius oxides ferroelectric layered materials are formed by bismuth oxide and pseu-do-perovskite layers. They have a good ionic conductivity, which is beneficial for various photo-catalyzed reactions. Here, we synthesized ultra-thin nanosheets of two different Aurivillius oxides, Bi₂WO₆ (BWO) and Bi₂MoO₆ (BMO), by using a hard-template process. All materials were characterized through XRD, TEM, FTIR, TGA/DSC, DLS/ELS, DRS, UV-Vis. Band gap material (E_g) and potential of the valence band (E_VB) were calculated for BWO and BMO. In contrast to previous reports on the use of multi composite materials, a new procedure for photocatalytic efficient BMO nanosheets was developed. The procedure, with an additional step only, avoids the use of composite materials, improves crystal structure, and strongly reduces impurities. BWO and BMO were used as photocatalysts for the degradation of the water pollutant dye malachite green (MG). MG removal kinetics was fitted with Langmuir—Hinshelwood model obtaining a kinetic constant k = 7.81 × 10⁻² min⁻¹ for BWO and k = 9.27 × 10⁻² min⁻¹ for BMO. Photocatalytic dye degradation was highly effective, reaching 89% and 91% MG removal for BWO and BMO, respectively. A control experiment, carried out in the absence of light, allowed to quantify the contribution of adsorption to MG removal process. Adsorption contributed to MG removal by a 51% for BWO and only by a 19% for BMO, suggesting a different degradation mechanism for the two photocatalysts. The advanced MG degradation process due to BMO is likely caused by the high crystallinity of the material synthetized with the new procedure. Reuse tests demonstrated that both photocatalysts are highly active and stable reaching a MG removal up to 95% at the 10th reaction cycle. These results demonstrate that BMO nanosheets, synthesized with an easy additional step, achieved the best degradation performance, and can be successfully used for environmental remediation applications.

Graphitic carbon-encapsulated V2O5 nanocomposites as a superb photocatalyst for crystal violet degradation

To materialize the excellent photocatalyst for crystal violet dye-degradation, the graphitic carbon-encapsulated vanadium pentoxide (GC-V₂O₅) nanocomposites were synthesized through the simple sonication method by using the green tea waste-derived GC nanoflakes and the sonochemically synthesized V₂O₅ nanorods. The nanocomposites were confirmed to comprise an aggregated morphology, in which the orthorhombic V₂O₅ nanorods were well anchored with the intertwingled GC nanoflakes. Owing to the encapsulation of defective V₂O₅ by conductive GC, the GC-V₂O₅ nanocomposites exhibited the enhanced photocatalytic dye-degradation efficiency up to 98.4% within 105 min. Namely, the encapsulated GC nanosheets might compensate the native defects (i.e., charge traps) on the V₂O₅ surface; hence, the charge transport could be enhanced during the dye-degradation process while the photocarrier recombination could be suppressed. The results suggest the conducting layer-encapsulated semiconducting oxide nanocomposites (e.g., GC-V₂O₅) to be of good use for future green environmental technology, particularly, as a superb photocatalyst for dye degradation.

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...