Constructing a plasmonic p-n heterojunction photocatalyst of 3D Ag/Ag6Si2O7/Bi2MoO6 for efficiently removing broad-spectrum antibiotics

Advanced photocatalytic materials based degradation of micropollutants and their use in hydrogen production - a review

The use of pharmaceuticals, dyes, and pesticides in modern healthcare and agriculture, along with expanding industrialization, heavily contaminates aquatic environments. This leads to severe carcinogenic implications and critical health issues in living organisms. The photocatalytic methods provide an eco-friendly solution to mitigate the energy crisis and environmental pollution. Sunlight-driven photocatalytic wastewater treatment contributes to hydrogen production and valuable product generation. The removal of contaminants from wastewater through photocatalysis is a highly efficient method for enhancing the ecosystem and plays a crucial role in the dual-functional photocatalysis process. In this review, a wide range of catalysts are discussed, including heterojunction photocatalysts and various hybrid semiconductor photocatalysts like metal oxides, semiconductor adsorbents, and dual semiconductor photocatalysts, which are crucial in this dual function of degradation and green fuel production. The effects of micropollutants in the ecosystem, degradation efficacy of multi-component photocatalysts such as single-component, two-component, three-component, and four-component photocatalysts were discussed. Dual-functional photocatalysis stands out as an energy-efficient and cost-effective method. We have explored the challenges and difficulties associated with dual-functional photocatalysts. Multicomponent photocatalysts demonstrate superior efficiency in degrading pollutants and producing hydrogen compared to their single-component counterparts. Dual-functional photocatalysts, incorporating TiO2, g-C3N4, CeO2, metal organic frameworks (MOFs), layered double hydroxides (LDHs), and carbon quantum dots (CQDs)-based composites, exhibit remarkable performance. The future of synergistic photocatalysis envisions large-scale production facilitate integrating advanced 2D and 3D semiconductor photocatalysts, presenting a promising avenue for sustainable and efficient pollutant degradation and hydrogen production from environmental remediation technologies.

Synergistic effects of rare earth doping and carbon quantum dots on BiOF/Bi2MoO6 heterojunctions for enhanced visible-near-infrared photocatalysis

Herein, we designed and synthesized a series of rare earth doped BiOF/Bi₂MoO₆ heterojunctions. The doping locations of rare earth ions were altered to determine the influence on the visible and near-infrared photocatalytic activity of heterojunctions. It is experimentally and theoretically confirmed that doping with Tm³⁺/Yb³⁺ in one semiconductor of the heterojunction produces superior photocatalytic efficiency than doping in both semiconductors. In addition, the near infrared photocatalytic efficiency strongly relied on upconversion luminescence from the Re³⁺ doped semiconductor in the heterojunction. By further modifying with CQDs, the CQDs/BiOF:Tm³⁺,Yb³⁺/Bi₂MoO₆ sample shows excellent visible and near-infrared photocatalytic performance, with 90% degradation of RhB occurring in the first 20 min under visible irradiation. This can be attributed to the large BET area, efficient photoinduced carrier separation and the upconversion process of the composite. This research will provide a systematic solution for realizing full-spectrum responsive and highly efficient photocatalysis by combination of rare earth ion doping, quantum dot modification and Z-scheme heterojunctions.

Highly photoactive novel NiS/BiOI nanocomposite photocatalyst towards efficient visible light organic pollutant degradation and carcinogenetic Cr (VI) reduction for environmental remediation

Heterojunction engineering in catalyst structures is a promising approach for solving the main restriction of the narrow photoabsorption range and quick recombination of photogenerated charge carriers in the photocatalysts. Herein, a simple, eco-friendly, non-toxic, and novel Z-scheme heterojunction of nanoflower-like NiS/BiOI was systematically designed using the low-temperature solvothermal and precipitation methods. The physicochemical and photo-electrochemical properties of the as-synthesized nanomaterials were characterized using XRD, FESEM, FT-IR, XPS, BET, UV-vis, PL, and EIS. NiS/BiOI nanomaterials exhibited a wide photoabsorption range (200-1000 nm), a narrow bandgap energy (1.76 eV), a large surface area (35.82 m² g^-1), and a low charge carrier recombination rate because of the synergistic effects of the NiS and BiOI photocatalysts, which could be the basis for superior photocatalytic efficiency. Particularly, the optimal 40% NiS/BiOI nanocomposite exhibited better stability and efficiency than the pure NiS and BiOI. The maximum degradation efficiency of rhodamine B (RhB) was 99.8% after 200 min, tetracycline (TC) was 96.3% after 140 min, and the photoreduction of Cr(VI) was 92.8% after 180 min rather than the pure NiS and BiOI under visible light irradiation. The constant rate (k) of RhB was approximately 10 and 4, TC was 12 and 4, and Cr(VI) was 10 and 8 times that of pristine NiS and BiOI, respectively. Radical trapping experiments and Tauc plot analysis proposed the design of the plausible Z-scheme reaction mechanism between NiS and BiOI, which has a crucial role in the rate of transportation and separation of electron/hole pairs. This investigation provides a venue for the design of a photoactive NiS-based nanocomposite for environmental remediation.

A review on plasmonic-based heterojunction photocatalysts for degradation of organic pollutants in wastewater

Organic pollutants in wastewater are the biggest problem facing the world today due to population growth, rapid increase in industrialization, urbanization, and technological advancement. There have been numerous attempts to use conventional wastewater treatment techniques to address the issue of worldwide water contamination. However, conventional wastewater treatment has a number of shortcomings, including high operating costs, low efficiency, difficult preparation, fast recombination of charge carriers, generation of secondary waste, and limited light absorption. Therefore, plasmonic-based heterojunction photocatalysts have attracted much attention as a promising method to reduce organic pollutant problems in water due to their excellent efficiency, low operating cost, ease of fabrication, and environmental friendliness. In addition, plasmonic-based heterojunction photocatalysts contain a local surface plasmon resonance that enhances the performance of photocatalysts by improving light absorption and separation of photoexcited charge carriers. This review summarizes the major plasmonic effects in photocatalysts, including hot electron, local field effect, and photothermal effect, and explains the plasmonic-based heterojunction photocatalysts with five junction systems for the degradation of pollutants. Recent work on the development of plasmonic-based heterojunction photocatalysts for the degradation of various organic pollutants in wastewater is also discussed. Lastly, the conclusions and challenges are briefly described and the direction of future development of heterojunction photocatalysts with plasmonic materials is explored. This review could serve as a guide for the understanding, investigation, and construction of plasmonic-based heterojunction photocatalysts for various organic pollutants degradation.

GRAPHICAL ABSTRACT

Herein, the plasmonic effects in photocatalysts, such as hot electrons, local field effect, and photothermal effect, as well as the plasmonic-based heterojunction photocatalysts with five junction systems for the degradation of pollutants are explained. Recent work on plasmonic-based heterojunction photocatalysts for the degradation of various organic pollutants in wastewater such as dyes, pesticides, phenols, and antibiotics is discussed. Challenges and future developments are also described.

Highly efficient flower-like ZnIn2S4/CoFe2O4 photocatalyst with p-n type heterojunction for enhanced hydrogen evolution under visible light irradiation

The construction of a p-n heterojunction structure is considered to be an effective method to improve the separation of electron-hole pairs in photocatalysts. A series of ZnIn₂S₄/CoFe₂O₄ (ZIS/CFO) photocatalysts with p-n heterojunctions were prepared via a method involving ultrasonication and calcination. The synthesized photocatalysts were tested and analyzed via various testing techniques, and their hydrogen evolution rates were evaluated. Compared with pure ZIS, ZIS/CFO with different mass ratios of CFO to ZIS showed improved photocatalytic hydrogen production performance, and the optimal photoactivity showed a nearly 12-fold increase, which can be attributed to the formation of p-n junctions and the formed internal electric field, accelerating the separation of electron-hole pairs and effectively improving the photocatalytic hydrogen evolution rate. The excellent stability of the ZIS/CFO composite was proven by three cycle experiments. In addition, the ZIS/CFO composite also possessed excellent magnetic properties to realize facial magnetic recoverability. This work paves the way for the design and preparation of magnetically recoverable p-n heterojunction photocatalysts.

Construction of activated biochar/Bi2WO6 and /Bi2MoO6 composites to enhance adsorption and photocatalysis performance for efficient application in the removal of pollutants and disinfection

To synergistically enhance the adsorption and photocatalytic performance of Bi2WO6 and Bi2MoO6, using activated biochar (ACB) as substrate, ACB-Bi2WO6 and ACB-Bi2MoO6 composites were facilely prepared by hydrothermal synthesis. Their adsorption-photocatalytic degradation effects on rhodamine B (RhB), tetracycline (TC), and norfloxacin (NOR) were comparatively investigated. Additionally, the effects of environmental factors, wastewater treatment tests, and disinfection were systematically studied, and the enhancement mechanisms and reasons for the degradation differences were highlighted. The results showed that ACB-Bi2WO6 and ACB-Bi2MoO6 were confirmed to form intimately contacted heterojunctions by various advanced characterization techniques. The introduction of ACB narrowed the band-gap energy of Bi2WO6 and Bi2MoO6, and improved the visible light absorption range and specific surface area. The optimal loading ratios of ACB-Bi2WO6 and ACB-Bi2MoO6 were 1:1.06 and 1:0.58, respectively. The removal rate of ACB-Bi2WO6 for high concentrations of RhB (200 mg·L-1), TC and NOR (50 mg·L-1) were 89.15%, 87.27%, and 72.17%, respectively, which were higher than those of ACB-Bi2MoO6 and significantly stronger than those of Bi2WO6 and Bi2MoO6. This was attributed to the more effective inhibition of photogenerated carrier recombination, higher absorbance, and uniform morphology via ACB-Bi2WO6. ·OH and holes were dominant active species in photocatalysis, and the possible photogenerated carrier transfer path is type II heterojunction. Furthermore, ACB-Bi2WO6 possessed good reusability, and the removal of RhB and TC from the actual wastewater exceeded 80.63% and 58.54%, respectively. The sterilization rates of ACB-Bi2WO6 reached 99% and 95% for E. coli and S. aureus within 24 h, respectively. Therefore, ACB-Bi2WO6 was more recommended for environmental applications.

Photocatalytic Degradation of Tetracycline under Visible Light Irradiation on BiVO4 Microballs Modified with Noble Metals

Monoclinic scheelite bismuth vanadate (BVO) microballs were prepared by a facile hydrothermal method and subsequently modified with 2 wt% of noble metals (NM = Au, Ag, Cu, Pt and Pd) by a photodeposition route. All materials were characterized by diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). The photocatalytic performance was investigated by degradation of tetracycline antibiotic under visible light irradiation. Moreover, photocurrent generation under UV/vis was also examined. It was found that BVO modification with all tested NMs resulted in a significant improvement in photocatalytic performance. The highest activity was obtained for Cu/BVO with mainly oxidized forms of copper. Based on scavenger tests (∙O2− and ∙OH as the main responsible species for TC degradation) and redox properties, it was proposed that the Z-scheme mechanism between copper oxides and BVO was responsible for enhanced photocatalytic activity. However, the co-participation of zero-valent forms of NMs should also be considered, either as electron scavengers, plasmonic sensitizers or conductors. Presented data reveal that porous microballs, highly attractive for practical applications due to micro-sized diameter and efficient light harvesting inside the structure, could be efficiently used for environmental and energy purposes under solar radiation.

Light-driven Au-ZnO nanorod motors for enhanced photocatalytic degradation of tetracycline

The abuse of antibiotics in human medicine and animal husbandry leads to the enrichment of antibiotic residues in aquatic environments, which has been a major problem of environmental pollution over the past decades. Therefore, it is urgent to develop a highly efficient approach to remove antibiotics from aquatic environments. Inspired by the motion characteristics of semiconductor-based micro-/nanomotors, a light-driven Au-ZnO nanomotor system based on vertically aligned ZnO arrays is successfully developed for the enhanced photocatalytic degradation of tetracycline (TC). Under UV light (λ = 365 nm) illumination, these Au-ZnO nanomotors exhibit a high speed in deionized water and TC solution. Due to their efficient motion capability and Au-enhanced charge separation, these light-driven Au-ZnO nanomotors removed almost all TC (40 mg L^-1) within 30 min and displayed stable photocatalytic activity for four cycles without any apparent deactivation. The as-developed motor-based strategy for enhanced antibiotic degradation has excellent potential in environmental governance.

In suit constructing S-scheme FeOOH/MgIn2S4 heterojunction with boosted interfacial charge separation and redox activity for efficiently eliminating antibiotic pollutant

Photocatalytic elimination of antibiotic pollutant is an appealing avenue in response to the water contamination, but it still suffers from sluggish charge detachment, limited redox capacity as well as poor visible light utilization. Herein, a particular S-scheme FeOOH/MgIn₂S₄ heterojunction with wide visible light absorption was triumphantly constructed by in-situ growth of MgIn₂S₄ nanoparticles onto the surface of FeOOH nanorods, and employed as a high-efficiency visible light driven photocatalyst for removing tetracycline (TC). Conspicuously, the as-obtained FeOOH(15 wt%)/MgIn₂S₄ elucidated the optimal TC removal rate of 0.01258 min^-1 after 100 min of visible light illumination, which was almost 33.1 and 6.6 times larger than those of neat FeOOH and MgIn₂S₄, separately. The exceptional degradation performance was principally put down to the establishment of S-scheme heterojunction between FeOOH and MgIn₂S₄, which could not merely accelerate the detachment of photogenerated carriers, but also retain the powerful reducing ability of photoinduced electrons for MgIn₂S₄ and high oxidizing capacity of photoexcited holes for FeOOH, strongly driving the generation of plentiful active species including holes, superoxide and hydroxyl radicals. Additionally, the possible degradation mechanism and pathways of TC were also speculated. This work offers a valuable perspective for constructing high-efficiency S-scheme heterojunction photocatalysts for eradicating antibiotics.

Magnetic Metal Oxide-Based Photocatalysts with Integrated Silver for Water Treatment

In this review, the most recent advances in the field of magnetic composite photocatalysts with integrated plasmonic silver (Ag) is presented, with an overview of their synthesis techniques, properties and photocatalytic pollutant removal applications. Magnetic attributes combined with plasmonic properties in these composites result in enhancements for light absorption, charge-pair generation-separation-transfer and photocatalytic efficiency with the additional advantage of their facile magnetic separation from water solutions after treatment, neutralizing the issue of silver’s inherent toxicity. A detailed overview of the currently utilized synthesis methods and techniques for the preparation of magnetic silver-integrated composites is presented. Furthermore, an extended critical review of the most recent pollutant removal applications of these composites via green photocatalysis technology is presented. From this survey, the potential of magnetic composites integrated with plasmonic metals is highlighted for light-induced water treatment and purification. Highlights: (1) Perspective of magnetic properties combined with plasmon metal attributes; (2) Overview of recent methods for magnetic silver-integrated composite synthesis; (3) Critical view of recent applications for photocatalytic pollutant removal.

Active site regulated Z-scheme MIL-101(Fe)/Bi2WO6/Fe(III) with the synergy of hydrogen peroxide and visible-light-driven photo-Fenton degradation of organic contaminants

Water pollution control is one of the major challenges currently faced. With the development of photocatalytic technology, an increasing number of new and efficient catalysts have been developed, but most of the catalysts have limited light capture ability and catalytic degradation efficiency. Therefore, in this work, hydrogen peroxide was further introduced to establish a photo-Fenton system to improve the photocatalytic effect by constructing a Z-scheme, and the degradation ability of the catalyst was maximized. Moreover, we successfully adhered bismuth tungstate nanosheets onto the surface of a MIL-101(Fe) framework and changed the number of active sites with iron ions of different doping amounts. We found that the number of active sites in the photo-Fenton system does not increase linearly, but increases and decreases regularly, which is similar to the change in band structure after doping. In addition, the results of the radical scavenger experiment and electron paramagnetic resonance (EPR) revealed that both hydroxide radical (˙OH) and superoxide radical (˙O₂^-) participated in methylene blue (MB) degradation, of which ˙OH was the main active species for pollutant degradation. Based on high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, the possible degradation pathways were proposed. We believed that this work will provide insights into the heterojunction photo-Fenton system.

Organic-Inorganic Hybrid Flower-Shaped Microspheres Applied in Photoelectrochemical Sensing

Organic-inorganic hybrid materials are rarely applied in photoelectrochemical (PEC) sensing because of the serious charge-carrier recombination in organic conjugated polymers. In this work, a series of poly(3,4-ethylenedioxythiophene) (PEDOT)/ZnIn2S4 hybrid flower-shaped microspheres were synthesized using ionic liquids (ILs) as the supporting electrolyte for EDOT electropolymerization and as the regulating reagent for controlling ZnIn2S4 growth, respectively. It was found that the hybrid material [HOEMIM]NTf2-PEDOT/[HOEMIM]BF4-ZnIn2S4 ([HOEMIM]+: 1-hydroxyethyl-3-methylimidazolium cation; NTf2-: bis(trifluoromethanesulfonyl)amide) was the optimal one, with a smooth, transparent, and continuous polymer film covering the uniform and ordered cross-linked nanosheet arrays. The hybrid material could produce a high anodic photocurrent, which was about 78 times as high as that produced by the [HOEMIM]BF4-ZnIn2S4. The enhancement effect should be the highest among all the organic-inorganic hybrid materials reported so far. This was related to its unique micromorphology structure, p-n heterojunction, and the coexisting ILs, which restrained the charge-carrier recombination in PEDOT and enhanced PEDOT sensitization to ZnIn2S4. Then, a carcinoembryonic antigen PEC immunosensor was constructed based on the photoanodic sensing platform, and it exhibited good performance. Furthermore, the [HOEMIM]BF4-ZnIn2S4 was treated with NaClO solution to create the [HOEMIM]NTf2-PEDOT/[HOEMIM]BF4-S-ZnwInxSyOz general platform for both photoanodic and photocathodic sensing. As a proof of concept, L-cysteine and dissolved oxygen were used as models for photoanodic and photocathodic sensing, respectively. The results demonstrated that the general PEC platform was quite competent. This work opens up a window for the design of organic-inorganic hybrid PEC materials and will promote the application of such hybrid materials in PEC biosensing.

Zn-doped Bi2MoO6 supported on reduced graphene oxide with increased surface active sites for degradation of ciprofloxacin

The reduced graphene oxide supported Zn-doped Bi₂MoO₆ nanocomposites (Zn_xBi_2-xMoO₆/RGO) are synthesized by an easy one-step solvothermal method for the rapid degradation of ciprofloxacin (CIP). Characterization analyses show that Bi₂MoO₆ nanosheets are uniformly supported on RGO, for which the agglomeration of Bi₂MoO₆ is effectively inhibited, leading to more exposure of surface active sites. The degradation rate of Zn_0.1Bi_1.9MoO₆/RGO₅ on CIP reached 90% after 120 min of visible light irradiation, which was 10.4 times the rate of unsupported Bi₂MoO₆. Zn doping and RGO loading synergistically reduce the recombination rate of photogenerated electron-hole pairs and result in the enhanced photocatalytic performance. Compared with previously reported catalysts, Zn_0.1Bi_1.9MoO₆/RGO₅ can get higher degradation efficiency with shorter time and less dosage. In addition, after five cycles, the degradation efficiency is maintained at about 85%, showing perfect cycling stability of Zn_0.1Bi_1.9MoO₆/RGO₅. Photocatalytic mechanism suggests that the photogenerated •O₂^- and h⁺ are main species for degrading CIP based on Zn_xBi_2-xMoO₆/RGO complex.

Nanohybrids-assisted photocatalytic removal of pharmaceutical pollutants to abate their toxicological effects - A review

Advancement in medication by health care sector has undoubtedly improved our life but at the same time increased the chemical burden on our natural ecosystem. The residuals of pharmaceutical products become part of wastewater streams by different sources such as excretion after their usage, inappropriate way of their disposal during production etc. Hence, they are serious health hazards for human, animal, and aquatic lives. Due to rapid urbanization, the increased demand for clean drinking water is a burning global issue. In this regard it is need of the present era to explore efficient materials which could act as photocatalyst for mitigation of pharmaceuticals in wastewater. Nanohybrid as photocatalyst is one of the widely explored class of materials in photocatalytic degradation of such harmful pollutants. Among these nanohybrids; metal based nanohybrids (metals/metal oxides) and carbon based nanohybrids (carbon nanotubes, graphene, fullerenes etc.) have been explored to remove pharmaceutical drugs. Keeping in view the increasing harmful impacts of pharmaceuticals; the sources of pharmaceuticals in wastewater, their health risk factors and their mitigation using efficient nanohybrids as photocatalysts have been discussed in this review.

Enhanced photocatalytic activity of TiO2/UiO-67 under visible-light for aflatoxin B1 degradation

TiO2 has great potential in photocatalytic degradation of organic pollutants, but poor visible light response and low separation efficiency of photogenerated electron-hole pairs limit its wide applications. In this study, we have successfully prepared TiO2/UiO-67 photocatalyst through an in situ solvothermal method. The degradation rate of aflatoxin B1 (AFB1) is 98.9% in only 80 min, which is superior to the commercial P25, commercial TiO2 and most of reported photocatalysts under visible light irradiation. In addition, the TiO2/UiO-67 photocatalyst showed excellent recyclability. We demonstrated that the enhanced photocatalytic mechanism was owing to the heterojunction between TiO2 and UiO-67, which enhanced effectively the separation photogenerated charge carriers and visible light response. The free radical trapping tests demonstrated that superoxide radicals (˙O2 -), holes (h+) and hydroxyl radicals (˙OH) were the main active species and then oxidized AFB1 to some small molecules.

Spinning disc photoreactor based visible-light-driven Ag/Ag2O/TiO2 heterojunction photocatalyst film toward the degradation of amoxicillin

The presence of antibiotics in waste and drinking water is causing increasing concern around the world, thereby an advanced sustainable technology needs to be developed to eliminate the antibiotics from water resources. Hence, an efficient spinning disc photoreactor (SDPR) equipped with visible light-activated Ag/Ag₂O/TiO₂ heterostructure thin film photocatalyst was assessed for the degradation of amoxicillin (AMX) as a typical antibiotic. The surface morphology, optoelectronic and structural features of Ag/Ag₂O/TiO₂ heterojunction were characterized by TEM, BET, mott Schottky, FESEM, EDS, AFM, XRD, UV-Vis-DRS, and contact angle measurements. Results confirm that Ag and Ag₂O have a significant effect on the photocharge carrier separation and transfer of the as-developed photocatalyst system. The operative variables including illumination time, rotational speed, solution flow rate, aeration rate, pH, and initial AMX concentration were optimized by CCD. The results displayed the maximum AMX photodegradation (97.91%) could be achieved at optimal conditions involving illumination time of 80 min, a rotational speed of 225 rpm, the solution flow rate of 0.6 L/min, aeration rate of 20 L/min, pH = 6, and initial AMX concentration of 20 mg/L. Interestingly, more than 79% COD and 64% TOC were removed under optimum conditions during 80 min illumination time, respectively. Active species tests confirmed the dominant role of ·OH and ·O₂^- in AMX degradation. finally, the XRD pattern confirmed that the reusability assessments of the heterojunction film could successfully retain its stability for six consecutive photocatalytic degradation runs. This work demonstrates the feasibility of utilizing visible-light-driven thin-film photocatalysts in spinning disc photoreactors in treating the tenacious antibiotic pollutants.

Facile interface engineering of hierarchical flower spherical-like Bi-metal-organic framework microsphere/Bi2MoO6 heterostructure for high-performance visible-light photocatalytic tetracycline hydrochloride degradation

The self-assembled Bi-based metal-organic framework microspheres (Bi-MOF-M) by nanorods were successfully constructed by the glycol-assisted solvothermal method. Using Bi-MOF-M as a homologous template, a petal-like Bi₂MoO₆ (BMO) layer was grown in situ on its surface to facilely construct a chemically bonded heterojunction interface, realizing a micro/nano hierarchical flower spherical-like Bi-MOF-M/BMO heterojunction composite photocatalyst. The as-prepared series of Bi-MOF-M/BMO-x catalysts show higher visible light catalytic performance for tetracycline hydrochloride (TC) degradation. Among them, Bi-MOF-M/BMO-0.3 has the optimal catalytic activity, and the degradation efficiency can reach 93.6% within 60 min of light irradiation with superior mineralization ability and structural stability, and the degradation kinetic constant is 6.12 times that of Bi-MOF-M and 5.69 times that of BMO, respectively. The homologously grown Bi-MOF-M/BMO chemically bonded heterojunction not only effectively broadens the spectral absorption range and enhances the absorption intensity but also promotes the efficient separation of photogenerated carriers through forming a favorable interfacial electric field and well-matched energy band alignment. A reasonable mechanism for the visible light degradation of TC by the Bi-MOF-M/BMO composite catalyst with h⁺ and ¹O₂ as the main reactive species is proposed. The micro/nano hierarchical structure of the Bi-MOF/BMO catalyst allows it to exhibit the easy recovery advantage of micron-scale materials while maintaining the high catalytic activity of the primary nano-components.

Incorporation of a Z-scheme AgI/Ag6Si2O7 heterojunction to PET fabric for efficient and repeatable photocatalytic dye degradation

Anchoring the Z-scheme AgI/Ag6Si2O7 photocatalyst on PET fabric facilitates reuse. AgI enhances the separation effect of photogenerated carriers. The photocatalytic activity and stability of AgI/Ag6Si2O7/PET composites are greatly improved.

In situ construction of a C3N5 nanosheet/Bi2WO6 nanodot S-scheme heterojunction with enhanced structural defects for the efficient photocatalytic removal of tetracycline and Cr(vi)

A novel 2D/0D C3N5/Bi2WO6 S-scheme heterojunction with enhanced structural defects has been designed for the efficient elimination of pharmaceutical antibiotics and Cr(vi).

Construction of visible light driven silver sulfide/graphitic carbon nitride p-n heterojunction for improving photocatalytic disinfection

Compared with the Z-scheme and type-II heterojunctions, p-n type heterojunctions are more favorable for the migration of photo-induced carriers owing to the advantage of built-in electric fields. In addition, it is still of great significance to understand the carrier migration properties of the p-n heterojunction. Therefore, the development of new p-n heterojunctions and the development of high-efficiency catalysts with effective modulation of light responsiveness and rapid transfer of charge to achieve photocatalytic inactivation have attracted much attention. In this study, we synthesized a Ag₂S/g-C₃N₄ heterojunction via the in situ deposition of Ag₂S onto the g-C₃N₄ substrate. The prepared Ag₂S/g-C₃N₄ composite facilitated photo-generated charge carrier transfer and exhibited outstanding photocatalytic inactivation of bacteria compared to that of a single catalyst under visible light irradiation. In addition, the ACN-2 composites fully deactivated 7 log10 CFU/mL E. coli and 7 log10 CFU/mL S. aureus cells in 90 min under visible light. The quenching experiments confirmed that photo-generated active species (O₂^-, OH, and h⁺) were the major reactive oxygen species that contributed to the inactivation of bacteria. Energy band alignment analysis indicated that a type-II band alignment was formed in the p-n heterostructure, thereby providing strong support for the photocatalytic mechanism. This study not only provides insights into the design of p-n heterostructures, but also presents a promising strategy to enhance the photocatalytic capacities of g-C₃N₄ based materials for pathogen inactivation.

Preparation of F-doped H2Ti3O7-{104} nanorods with oxygen vacancies using TiOF2 as precursor and its photocatalytic degradation activity

Photocatalytic degradation is an eco-friendly and sustainable method for the treatment of water pollutants especially tetracycline hydrochloride (TCH). Herein, we developed F-doped H2Ti3O7-{104} nanorods with oxygen vacancies using TiOF2 as a precursor by simple alkali hydrothermal and ion-exchange methods. The phase structure, surface composition, optical properties, specific surface areas and charge separation were analysed by a series of measurements. The effects of KOH concentration on the structure and properties of H2Ti3O7 were investigated. It is confirmed that the TiOF2/H2Ti3O7 composite can be formed in low concentration KOH solution (1 mol L-1), while the H2Ti3O7 single phase can be formed in high concentration KOH solution (>3 mol L-1). The prepared F-doped H2Ti3O7-{104} nanorods provide a high specific surface area of 457 m2 g-1 and a macroporous volume of 0.69 cm3 g-1. The appropriate mesoporous structure of the photocatalyst makes TCH have a stronger affinity on its surface, which is more conducive to the subsequent photodegradation. Moreover, a synergistic mechanism of photosensitization and ligand-metal charge transfer (LMCT) in the photocatalytic degradation of TCH was proposed. In addition, the prepared F-doped H2Ti3O7-{104} nanorods showed excellent cycle stability and resistance to light corrosion. After five cycles of photodegradation, the degradation rate of TCH was only reduced from 92% to 83%. This low-cost strategy could be used for the mass production of efficient photocatalysts, which can be used for TCH clean-up in wastewater treatment.

Heterojunction photocatalysts for degradation of the tetracycline antibiotic: a review

Antibiotic pollution is a major health issue inducing antibiotic resistance and the inefficiency of actual drugs, thus calling for improved methods to clean water and wastewater. Here we review the recent development of heterojunction photocatalysis and application in degrading tetracycline. We discuss mechanisms for separating photogenerated electron-hole pairs in different heterojunction systems such as traditional, p-n, direct Z-scheme, step-scheme, Schottky, and surface heterojunction. Degradation pathways of tetracycline during photocatalysis are presented. We compare the efficiency of tetracycline removal by various heterojunctions using quantum efficiency, space time yield, and figures of merit. Implications for the treatment of antibiotic-contaminated wastewater are discussed.

Facile construction of novel organic-inorganic tetra (4-carboxyphenyl) porphyrin/Bi2MoO6 heterojunction for tetracycline degradation: Performance, degradation pathways, intermediate toxicity analysis and mechanism insight

Developing durable photocatalysts with highly efficient antibiotics degradation is crucial for environment purification. Herein, tetra (4-carboxyphenyl) porphyrin (TCPP) was loaded onto the surface of Bi₂MoO₆ microspheres to gain hierarchical organic-inorganic TCPP/Bi₂MoO₆ (TCPP/BMO) heterojunctions via a facile impregnation strategy. The catalytic properties of these catalysts were comprehensively investigated through the photodegradation of tetracycline hydrochloride (TC) under visible light. Among all the TCPP/BMO heterojunctions, the highest photodegradation rate constant (0.0278 min^-1) was achieved with 0.25 wt% TCPP (TCPP/BMO-2), which was approximately 1.15 folds greater than that of pristine Bi₂MoO₆ and far superior to pure TCPP. The extremely high photocatalytic performance is attributed to the interfacial interaction between TCPP and Bi₂MoO₆, which favors the efficient separation of charge carriers and the enhancement of visible-light absorbance. TCPP/BMO-2 possesses high mineralization capability and good recycling performance. Photo-induced O₂^-, h⁺, and OH were mainly responsible for the degradation of TC. The degradation pathways of TC and toxicity of degradation intermediates were analyzed based on the intermediates detected by the high performance liquid chromatography-mass spectrometer (HPLC-MS) and the toxicity assessment by the quantitative structure-activity relationship (QSAR) prediction. A possible photocatalytic mechanism over TCPP/BMO is proposed. This work offers an insight in developing the porphyrin-based organic-inorganic heterojunctions for effectively remedying pharmaceutical wastewater.