Photocatalytic degradation of RhB by fluorinated Bi2WO6 and distributions of the intermediate products

Synthesis of Silver(I) Complexes through In Situ Reactions of dppeda with dmp in the Presence of Silver Halides for Photocatalysis

Due to the unique photosensitivity of silver compounds, they exhibit good photocatalytic activity as photocatalysts in the degradation of water pollutants. However, silver compounds have poor cycling stability and are prone to decomposition and reaction under light to form metallic silver, which greatly limits their practical application. Herein, a (2-(2-(diphenylphosphaneyl)ethyl)-9-methyl-1.10-phenanthroline (PSNNP)) pincer ligand was designed for stabilizing the central metal. The in situ-formed PSNNP ligand could be readily generated in one pot with the participation of silver halides. The reaction of silver halides with dppeda (N,N,N',N'-tetra(diphenylphosphanylmethyl)ethylene diamine) in the presence of dmp (2,9-dimethyl-1,10-phenanthroline) in acetonitrile afforded complexes Ag2X2 (PSNNP)2 (complexes 1, 2) (X = Cl, Br). Single-crystal X-ray diffraction shows that the tridentate coordination of the pincer ligand provides strong binding with metal centers and leads to high stability of the pincer metal unit. The removal rate of rhodamine B (RhB) by complexes 1 and 2 can reach up to 100%, demonstrating an excellent photocatalytic degradation performance for organic dyes. The important effect of PSNNP ligands on photocatalytic properties after coordination with central metals was studied through experiments and discrete Fourier transform (DFT) calculations. The photocatalytic reaction mechanism of complexes 1 and 2 was also studied. This result provides an effective pathway for the first synthesis of PSNNP and interesting insights into photocatalytic degradation chemistry.

Morphology-Dependent Photocatalytic Activity of Nanostructured Titanium Dioxide Coatings with Silver Nanoparticles

This study aims to improve the photocatalytic properties of titanium dioxide nanorods (TNRs) and other related nanostructures (dense nanorods, needle-like nanorods, nanoballs, and nanoflowers) by modifying them with silver nanoparticles (AgNPs). This preparation is carried out using a two-step method: sol-gel dip-coating deposition combined with hydrothermal crystal growth. Further modification with AgNPs was achieved through the photoreduction of Ag+ ions under UV illumination. The investigation explores the impact of different growth factors on the morphological development of TiO2 nanostructures by modulating (i) the chemical composition, the water:acid ratio, (ii) the precursor concentration involved in the hydrothermal process, and (iii) the duration of the hydrothermal reaction. Morphological characteristics, including the length, diameter, and nanorod density of the nanostructures, were analyzed using scanning electron microscope (SEM). The chemical states were determined through use of the X-ray photoelectron spectroscopy (XPS) technique, while phase composition and crystalline structure analysis was performed using the Grazing Incidence X-ray Diffraction (GIXRD) method. The results indicate that various nanostructures (dense nanorods, needle-like nanorods, nanoballs, and nanoflowers) can be obtained by modifying these parameters. The photocatalytic efficiency of these nanostructures and Ag-coated nanostructures was assessed by measuring the degradation of the organic dye rhodamine B (RhB) under both ultraviolet (UV) irradiation and visible light. The results clearly show that UV light causes the RhB solution to lose its color, whereas under visible light RhB changes into rhodamine 110, indicating a successful photocatalytic transformation. The nanoball-like structures' modification with the active metal silver (TNRs 4 Ag) exhibited high photocatalytic efficiency under both ultraviolet (UV) and visible light for different chemical composition parameters. The nanorod structure (TNRs 2 Ag) is more efficient under UV, but under visible-light photocatalyst, the TNRs 6 Ag (dense nanorods) sample is more effective.

Construction of BiOCl/bismuth-based halide perovskite heterojunctions derived from the metal-organic framework CAU-17 for effective photocatalytic degradation

The designed synthesis of an S-scheme heterojunction has possessed a great potential for improving photocatalytic wastewater treatment by demonstrating increased the photoredox capacity and improved the charge separation efficiency. Here, we introduce the fabrication of a heterojunction-based photocatalyst comprising bismuth oxychloride (BiOCl) and bismuth-based halide perovskite (BHP) nanosheets, derived from metal-organic frameworks (MOFs). Our composite photocatalyst is synthesized through a one-pot solvothermal strategy, where a halogenation process is applied to a bismuth-based metal-organic framework (CAU-17) as the precursor for bismuth sourcing. As a result, the rod-like structure of CAU-17 transforms into well-defined plate and nanosheet architectures after 4 and 8 h of solvothermal treatment, respectively. The modulation of the solvothermal reaction time facilitates the establishment of an S-scheme heterojunction, resulting in an increase in the photocatalytic degradation efficiency of rhodamine B (RhB) and sulfamethoxazole (SMX). The optimized BiOCl/BHP composite exhibits superior RhB and SMX degradation rates, achieving 99.8% degradation of RhB in 60 min and 75.1% degradation of SMX in 300 min. Also, the optimized BiOCl/BHP composite (CAU-17-st-8h sample) exhibited the highest rate constant (k = 3.48 × 10-3 min-1), nearly 6 times higher than that of the bare BHP in the photocatalytic degradation process of SMX. The enhanced photocatalytic efficiency can be endorsed to various factors: (i) the in-situ formation of two-components BiOCl/BHP photocatalyst, derived from CAU-17, effectively suppresses the aggregation of pristine BHP and BiOCl particles; (ii) the S-scheme heterostructure establishes a closely-knit interfacial connection, thereby facilitating efficient pathways for charge separation/transfer; and (iii) the BiOCl/BHP heterostructure enhances its capacity to absorb visible light. Our investigation establishes an effective strategy for constructing heterostructured photocatalysts, offering significant potential for application in photocatalytic wastewater treatment.

Can Microplastics Accumulate Toxic dye in Water? An adsorption-desorption Study under Different Experimental Conditions

The adsorption/desorption of Rhodamine B (RhB) on Polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC) microplastics (MPs) was investigated in this study. The results showed that RhB adsorption on the selected MPs was fast. The adsorption coefficients (Kd) of RhB were 2036 ± 129, 1557 ± 91, and 63 ± 8.5 L kg- 1 for PS, PP, and PVC, respectively. RhB adsorption on PS and PP increased with increasing temperature and decreasing ionic strength, whereas RhB adsorption on PVC showed a completely opposite trend. The binding strength of RhB on the three types of MPs was weak as demonstrated by the high total desorption percentage, which ranged from 79.59 ~ 89.39%. This study shows that PP and PS MPs can accumulate RhB in the aquatic environment and their potential combined toxic risks should be taken seriously.

A Comparative Study in the Design of TiO2 Assisted Photocatalytic Coatings Monitored by Controlling Hydrophilic Behavior and Rhodamine B Degradation

This work presents a comparative study related to the photocatalytic efficiency associated with wettability measurements and organic dye degradation, as well as other relevant properties (i.e., corrosion resistance, roughness, wettability, and adhesion to a substrate). The photocatalytic precursors are titanium dioxide nanoparticles (TiO₂ NPs) which are dispersed onto a polymeric electrospun fiber matrix by using three different deposition techniques such as electrospraying, spraying, and dip-coating, respectively. In this work, the host electrospun matrix is composed of poly(acrylic acid) fibers crosslinked with cyclodextrin (β-CD), which shows a good chemical affinity and stability with the other deposition techniques which are responsible for incorporating the TiO₂ NPs. In order to evaluate the efficacy of each coating, the resultant photocatalytic activity has been monitored by two different tests. Firstly, the reduction in the water contact angle is appreciated, and secondly, the degradation of an organic dye (Rhodamine B) is observed under UV irradiation. In addition, the final roughness, adherence, and pitting corrosion potential have also been controlled in order to determine which solution provides the best combination of properties. Finally, the experimental results clearly indicate that the presence of TiO₂ NPs deposited by the three techniques is enough to induce a super hydrophilic behavior after UV irradiation. However, there are notable differences in photocatalytic efficiency on the Rhodamine B as a function of the selected deposition technique.

Catalytic Wet Peroxide Oxidation of Anionic Pollutants over Fluorinated Fe3O4 Microspheres at Circumneutral pH Values

Fluorinated Fe3O4 microspheres with 7.1 ± 1.4 wt% of fluoride (F-Fe3O4-1) were prepared via glycothermal synthesis. Fluorination significantly enhanced the activity of F-Fe3O4-1 in catalytic wet peroxide oxidation of anionic dyes (including orange G (OG) and congo red) at pH ~7. However, the promotional effect of fluorination became less obvious for amphoteric rhodamine B and was not observed for cationic methylene blue. After reacting with H2O2 (40 mM) for 2 h at pH 6.5 and 40 °C, the decolorization rates of OG (0.1 mM) and the pseudo-first-order rate constant were 96.8% and 0.0284 min−1 over F-Fe3O4-1 versus 17.6% and 0.0011 min−1 over unmodified Fe3O4. The effects of reaction parameters (initial H2O2 concentration and pH value and reaction temperature) on OG decolorization with H2O2 over F-Fe3O4-1 were investigated. The reusability of F-Fe3O4-1 was demonstrated by OG decolorization in eight consecutive runs. Fluorination increased the isoelectric point of F-Fe3O4-1 to 8.7 and facilitated the adsorption and degradation of anionic dyes on the surface of F-Fe3O4-1 at pH ~7. Scavenging tests and EPR spectra supported that hydroxyl radicals were the main reactive species for the OG decolorization over F-Fe3O4-1.

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.

Synthesis of Tin-Doped Three-Dimensional Flower-like Bismuth Tungstate with Enhanced Photocatalytic Activity

Photocatalytic degradation of harmful organic matter is a feasible and environmentally friendly method. Bi2WO6 has become a hotspot of photocatalysts because of its unique layered structure and visible light response. In the present study, Sn doping was adopted to modified Bi2WO6 by hydrothermal method. The Sn-doped Bi2WO6 photocatalysts were characterized by XRD, SEM, TEM, BET, XPS, PL, and DRS, respectively. The results show that Sn-doped Bi2WO6 shows three-dimensional (3D) flower-like morphology, which is composed of two-dimensional (2D) nanosheets. Sn4+ ions enter into the Bi2WO6 lattice, producing a degree of Bi2WO6 lattice distortion, which is in favor of reducing the recombination of photogenerated electrons and holes. Moreover, the specific surface area of Bi2WO6 is significantly increased after doping, which is beneficial to providing more active sites. The photocatalytic results show that 2%Sn-Bi2WO6 exhibits the highest photocatalytic activity. After 60 min of irradiation, the photocatalytic degradation degree of methylene blue (MB) increases from 80.6% for pure Bi2WO6 to 92.0% for 2%Sn-Bi2WO6. The first-order reaction rate constant of 2%Sn-Bi2WO6 is 0.030 min−1, which is 1.7 times than that of pure Bi2WO6.

Bismuth-based complex oxides for photocatalytic applications in environmental remediation and water splitting: A review

As an emerging group of visible-light-driven photocatalysts, bismuth-based complex oxides have attracted considerable attention owing to their outstanding photo-oxidation ability and high performance in decomposition of organic contaminants and water oxidation via photocatalytic processes. However, the relatively low level of the conduction band limits their further application in photocatalytic hydrogen evolution and overall water splitting processes. In this paper, three representative and most-studied Bi-based complex oxides of BiOX (X = Cl, Br, I)/BiFeO₃/Bi₂WO₆ are discussed mainly for environmental pollutants degradation and oxygen generation from water splitting. We present a comprehensive overview of their fundamental compositions, electronic structures and synthesis strategies. On the basis of analyzing the structural-property-activity relationships, detailed approaches for enhancement of their photocatalytic performance have been addressed and compared including morphology/facets control, heterostructures construction and introduction of oxygen vacancies. In addition, several techniques such as engineering energy band and building a Z-scheme system have been proposed to modulate the energy band positions of the photocatalysts and overcome the bottleneck to realize overall water splitting into H₂ and O₂ simultaneously. Finally, remarks on the current challenges, research directions and future perspectives are presented to provide guidance for designing and configuring highly efficient solar-light-driven photocatalysts in the field of environmental purification and energy conversion.

Urchin-like hollow SiO2@γ-MnO2 microparticles for the rapid degradation of organic dyes

In this paper, using hollow silica microspheres as carriers, we developed a facile one-pot method for the preparation of hollow SiO2@MnO2 composite microparticles. Under a certain proportion of hollow silica microspheres and manganese salt, a novel kind of hollow urchin-like SiO2@γ-MnO2 microparticles was obtained. The structure and morphology of the composite microparticles were characterized by XRD, SEM and TEM. On this basis, using rhodamine B and methyl orange as model molecules, the oxidative degradation ability of the hollow SiO2@γ-MnO2 microparticles for organic dyes in water was investigated through UV-vis analysis technology. The urchin-like SiO2@γ-MnO2 microparticles showed excellent performance for the rapid oxidative degradation of organic dyes under acidic conditions. This study indicated that γ-MnO2 loaded on hollow materials can be used as an efficient tool for treating organic dye wastewater, and shows broad application prospects for solving environmental problems in the related industry.

Preparation of spherical filler-like ZnFe2O4/Bi2MoO6 surrounded by nanosheets and its photocatalytic applications

In this article, the spherical filler-like ZnFe₂O₄/Bi₂MoO₆ (ZFO/BMO) surrounded by nanosheets were synthesized by a solvothermal method using spherical ZnFe₂O₄ as a matrix. Scanning electron microscope (SEM), X-ray diffraction (XRD), Photoluminescence (PL), Fourier transform infrared spectroscopy (FT-IR) and Diffuse reflectance spectra (DRS) were used to characterize the prepared samples. The photocatalytic performance of the material was detected under 420 nm visible light by Rhodamine B (RhB). The degradation results indicated that the ZFO/BMO photocatalyst with 20% ZnFe₂O₄ content (ZFO/BMO-2) demonstrated highly efficient performance. The constructed Z-type ZFO/BMO heterojunction lengthens the visible light absorption threshold and improves the photocatalytic activity. Furthermore, ZFO/BMO heterojunction composite photocatalyst can be recycled effectively by applying an appropriate external magnetic field. It has important research value in photocatalysis and recycling.

Bismuth-Graphene Nanohybrids: Synthesis, Reaction Mechanisms, and Photocatalytic Applications—A Review

Photocatalysis is a classical solution to energy conversion and environmental pollution control problems. In photocatalysis, the development and exploration of new visible light catalysts and their synthesis and modification strategies are crucial. It is also essential to understand the mechanism of these reactions in the various reaction media. Recently, bismuth and graphene’s unique geometrical and electronic properties have attracted considerable attention in photocatalysis. This review summarizes bismuth-graphene nanohybrids’ synthetic processes with various design considerations, fundamental mechanisms of action, heterogeneous photocatalysis, benefits, and challenges. Some key applications in energy conversion and environmental pollution control are discussed, such as CO2 reduction, water splitting, pollutant degradation, disinfection, and organic transformations. The detailed perspective of bismuth-graphene nanohybrids’ applications in various research fields presented herein should be of equal interest to academic and industrial scientists.

Atomic-Level Charge Separation Strategies in Semiconductor-Based Photocatalysts

Semiconductor-based photocatalysis as a productive technology furnishes a prospective solution to environmental and renewable energy issues, but its efficiency greatly relies on the effective bulk and surface separation of photoexcited charge carriers. Exploitation of atomic-level strategies allows in-depth understanding on the related mechanisms and enables bottom-up precise design of photocatalysts, significantly enhancing photocatalytic activity. Herein, the advances on atomic-level charge separation strategies toward developing robust photocatalysts are highlighted, elucidating the fundamentals of charge separation and transfer processes and advanced probing techniques. The atomic-level bulk charge separation strategies, embodied by regulation of charge movement pathway and migration dynamic, boil down to shortening the charge diffusion distance to the atomic-scale, establishing atomic-level charge transfer channels, and enhancing the charge separation driving force. Meanwhile, regulating the in-plane surface structure and spatial surface structure are summarized as atomic-level surface charge separation strategies. Moreover, collaborative strategies for simultaneous manipulation of bulk and surface photocharges are also introduced. Finally, the existing challenges and future prospects for fabrication of state-of-the-art photocatalysts are discussed on the basis of a thorough comprehension of atomic-level charge separation strategies.

In situ construction of a direct Z-scheme AgBr/α-Ag2WO4 heterojunction with promoted spatial charge migration and photocatalytic performance

A hierarchical AgBr/α-Ag₂WO₄ Z-scheme heterojunction was facially constructed for greatly improved photocatalytic activity towards pollutant elimination due to promoted spatial separation of carriers with high redox capacity.

Construction of S-doped MgO coupled with g-C3N4 nanocomposites with enhanced photocatalytic activity under visible light irradiation

In the present work, a series of photocatalysts in which S-MgO (SM) was coupled with g-C3N4 (CN) were synthesized and characterized in detail using various characterization techniques.

Promoting superoxide generation in Bi2WO6 by less electronegative substitution for enhanced photocatalytic performance: an example of Te doping

Doping with elements with lower electronegativity, like Te, shifts the band potentials of Bi2WO6 to the point that superoxide radical generation is feasible. As a result, an optimum of 2.5 at% Te doping improves the activity of Bi2WO6 by 48 times.

γ-ray induced formation of oxygen vacancies and Ti3+ defects in anatase TiO2 for efficient photocatalytic organic pollutant degradation

Oxygen vacancies and Ti³⁺ defects in anatase TiO₂ have attracted great attention to address the insufficient optical absorption and photoinduced charge-carrier separation in photocatalysis. In this study, we demonstrate a superficial and innovative approach for synthesizing anatase TiO₂ nanoparticles with abundant oxygen vacancies via γ-ray irradiation reduction at room temperature. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) confirm that oxygen vacancies and Ti³⁺ defects can be quantitatively and extensively obtained by merely regulating the irradiation dosage. Photoelectrochemical measurements suggest that oxygen vacancies and Ti³⁺ defects promoted the separation of electron-hole pairs and then enhanced the photocatalytic degradation performance for organic pollutant. In comparison with TiO₂ (no irradiation), the sample (49.5 kGy irradiation) exhibited a 20.0-fold enhancement in visible-light decomposition of phenol. In addition, the results of scavenge experiments and mechanism analysis revealed that O₂^- are the dominant active species. The excited electrons generated at the conduction band and oxygen vacancy level of TiO_2-x-49.5 conspicuously contributes to generate much more ·O₂^- species. This novel study shows at room temperature, the γ-ray approach of irradiation leads to faster formation and quantification of oxygen vacancies in the semiconductor materials.

Enhanced photocatalytic destruction of pollutants by surface W vacancies in VW-Bi2WO6 under visible light

W vacancies containing Bi₂WO₆ (V_W-Bi₂WO₆) was synthesized by a reductant-involved hydrothermal process. The photoactivity of Bi₂WO₆ was enhanced by 3.3 times and the TOC removal rate increased from 38.3% to 64.7% after the introduction of surface W vacancies. Positron annihilation spectrometry (PAS), XPS, Raman spectra and other characterization results indicated that W vacancies existed on the catalyst surface. The surface W vacancies were proved to widen the band gap and negatively shift CB edge to produce more O₂^•- and photoexcited holes at catalyst surface, as confirmed by ESR and radicals trapping experiments. Further, according to the results of pyridine adsorbed FTIR and Zeta potentials, the enhanced interaction between pollutants and V_W-Bi₂WO₆ was confirmed. As a result, the active species produced at surface were able to be accelerated to directly react with organic pollutants, leading to the highly efficient degradation and mineralization of pollutants in water.

Insights into Interface Charge Extraction in a Noble-Metal-Free Doped Z-Scheme NiO@BiOCl Heterojunction

It is of great significance to thoroughly explore the interface charge extraction and migration in heterojunction systems, which could guide us to synthesize higher-efficiency photocatalytic materials. A novel noble-metal-free doped Z-scheme NiO@BiOCl heterojunction was found in this work. The corresponding heterostructure, interface electron extraction, and electron migration were investigated via first-principles calculation. 5,5′-dimethyl-1-pyrroline-N-oxide (DMPO) spin-trapping electron spin resonance (ESR) and time-resolved photoluminescence (TRPL) tests were implemented to confirm the calculation results, which showed that electrons and holes stayed in the NiO (100) facet and BiOCl (110) facet, respectively. Owing to the large chemical potential of 2.40 V (vs ENHE) for the BiOCl valence-band hole, it possessed super activity to oxidize water into hydroxyl radicals or molecular oxygen. We hope this promising multifunctional photocatalytic material, therefore, NiO@BiOCl can be applied in advanced treatment of organic wastewater and oxygen production from photolysis water.

Agro-waste extracted cellulose supported silver phosphate nanostructures as a green photocatalyst for improved photodegradation of RhB dye and industrial fertilizer effluents

The efficiency and reusability of photocatalysts are the dominant factors for their pragmatic use. The visible light induced semiconductor silver phosphate is a superior photocatalyst effective under visible light but its stability is still an undiscussed issue. To overcome this stability issue in this present manuscript, eco-friendly agro-waste extracted cellulose supported silver phosphate nanostructures have been designed for the first time through a simple chemical process. At first, silver phosphate nanostructures were synthesized by the co-precipitation method. Then, different weights of cellulose were added to the silver nitrate solution to form cellulose supported silver phosphate nanostructures. The photodegradation efficiency for each weight ratio was examined in which the photocatalyst Ag-8 nanostructures showed a high rate (0.024 min^-1) for degradation of Rhodamine B (RhB) using a low intensity tungsten bulb. Real sample analysis has also been carried out using this photocatalyst for the degradation of industrial fertilizer effluents. The degradation rate of all the nanostructures was found to be high in comparison to pristine silver phosphate as well as the extracted bare cellulose. The photocatalytic activity is enhanced because of the participation of cellulose as a support which makes an interface for silver phosphate and assists it in delaying the charge recombination period under visible light. To understand the photochemical reaction of electrons and holes, scavenger studies were also performed.

Enhanced Photocatalytic Degradation of the Imidazolinone Herbicide Imazapyr upon UV/Vis Irradiation in the Presence of CaxMnOy-TiO2 Hetero-Nanostructures: Degradation Pathways and Reaction Intermediates

The determination of reaction pathways and identification of products of pollutants degradation is central to photocatalytic environmental remediation. This work focuses on the photocatalytic degradation of the herbicide Imazapyr (2-(4-methyl-5-oxo-4-propan-2-yl-1H-imidazol-2-yl) pyridine-3-carboxylic acid) under UV-Vis and visible-only irradiation of aqueous suspensions of Ca_xMnO_y-TiO₂, and on the identification of the corresponding degradation pathways and reaction intermediates. Ca_xMnO_y-TiO₂ was formed by mixing Ca_xMnO_y and TiO₂ by mechanical grinding followed by annealing at 500 °C. A complete structural characterization of Ca_xMnO_y-TiO₂ was carried out. The photocatalytic activity of the hetero-nanostructures was determined using phenol and Imazapyr herbicide as model pollutants in a stirred tank reactor under UV-Vis and visible-only irradiation. Using equivalent loadings, Ca_xMnO_y-TiO₂ showed a higher rate (10.6 μM·h⁻¹) as compared to unmodified TiO₂ (7.4 μM·h⁻¹) for Imazapyr degradation under UV-Vis irradiation. The mineralization rate was 4.07 µM·h⁻¹ for Ca_xMnO_y-TiO₂ and 1.21 μM·h⁻¹ for TiO₂. In the Ca_xMnO_y-TiO₂ system, the concentration of intermediate products reached a maximum at 180 min of irradiation that then decreased to a half in 120 min. For unmodified TiO₂, the intermediates continuously increased with irradiation time with no decrease observed in their concentration. The enhanced efficiency of the Ca_xMnO_y-TiO₂ for the complete degradation of the Imazapyr and intermediates is attributed to an increased adsorption of polar species on the surface of Ca_xMnO_y. Based on LC-MS, photocatalytic degradation pathways for Imazapyr under UV-Vis irradiation have been proposed. Some photocatalytic degradation was obtained under visible-only irradiation for Ca_xMnO_y-TiO₂. Hydroxyl radicals were found to be main reactive oxygen species responsible for the photocatalytic degradation through radical scavenger investigations.

Effect of Dual-Cocatalyst Surface Modification on Photodegradation Activity, Pathway, and Mechanisms with Highly Efficient Ag/BaTiO3/MnOx

Cocatalyst surface-loading has been regarded as an effective strategy to promote solar-energy-conversion efficiency. However, the potential influence of surface modification with cocatalysts on the photodegradation pathway and the underlying mechanisms is still unclear. Herein, we have used ferroelectric BaTiO₃ as the substrate, and both the reduction cocatalyst Ag and the oxidation cocatalyst MnO_x have been successfully loaded onto BaTiO₃ simultaneously by a one-step photodeposition method as evidenced by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The influence of dual-cocatalyst surface-loading on photodegradation of rhodamine B has been systematically investigated for the first time. First, the dual-cocatalyst-modified BaTiO₃ outperformed over the single-cocatalyst-loaded BaTiO₃, and the photodegradation rate of Ag/BaTiO₃/MnO_x is about 3 times and 12 times as high as that of Ag/BaTiO₃ and BaTiO₃/MnO_x, respectively. The credit is given to the synergistic effect between the reduction and oxidation cocatalysts, prompting charge carrier separation and migration as verified by the transient photocurrent, electrochemical impedance, and photoluminescence (PL) spectrum investigation. Second, in addition to the boosted photodegradation activity, the photodegradation pathway is found to be altered as well when using Ag/BaTiO₃/MnO_x. High-performance liquid chromatography (HPLC) analysis indicated that a highly selective stepwise deethylation process predominates over chromophore cleavage in the Ag/BaTiO₃/MnO_x system, while it is reverse for the Ag/BaTiO₃ system. This phenomenon is attributed to the different dye molecule adsorption modes. Furthermore, the radical trapping experiment shows that holes play a major role in the degradation process, and the recycle test proves the excellent stability of Ag/BaTiO₃/MnO_x. Our findings may add another layer of understanding depth to cocatalyst surface modification in photodegradation applications.

Performance promotion of Ag2O photocatalyst by particle size and crystal surface regulation

Photocatalytic performance of Ag₂O was greatly improved by adjusting the crystal plane structure and size with pyridine, which promoted the application of Ag₂O to actual industrial printing and dyeing wastewater treatment systems.

Enhanced Photoluminescence and Photocatalytic Efficiency of La-Doped Bismuth Molybdate: Its Preparation and Characterization

Herein, a systematic study of the enhanced physicochemical properties of lanthanide doped (La-doped) bismuth molybdate (Bi₂MoO₆) is performed. For this purpose, Bi₂MoO₆ and La-doped Bi₂MoO₆ were prepared by the sol-gel method. BiCl₃, Na₂MoO₄^·2H₂O, and LaCl₃·7H₂O were taken as the main precursors while sodium dodecyl sulfate was used as a surfactant. Both Bi₂MoO₆ and La-doped Bi₂MoO₆ were calcined at 650 °C for 2 h. These prepared materials were characterized by spectroscopic techniques such as UV–VIS, FT-IR, XRD, photoluminescence, XPS, along with other techniques such as SEM, TEM, TGA, etc. The investigation of luminescence behavior revealed that the La-doped Bi₂MoO₆ nanocomposite exhibited much greater luminescence compared to the undoped Bi₂MoO₆. The photocatalytic behavior of the prepared materials was explored by studying the degradation of methylene blue (MB) at room temperature. The degradation of MB with Bi₂MoO₆ and La-doped bismuth molybdate were observed to be 68% and 75% @ 45 s, respectively, indicating an enhancement of catalytic performance due to the La doping.

Metal-Free Enhanced Photocatalytic Activation of Dioxygen by g-C3N4 Doped with Abundant Oxygen-Containing Functional Groups for Selective N-Deethylation of Rhodamine B

To develop highly efficient heterogeneous photocatalysts for the activation of dissolved oxygen is very interesting in the field of green degradation of organic pollutants. In the paper, oxygen atom doped g-C3N4 (O-g-C3N4) was prepared via a facile chemical oxidation of g-C3N4 by peroxymonosulfate. X-ray photoelectron spectroscopy analysis suggests the oxidative treatment of g-C3N4 by peroxymonosulfate evidently increased atomic percentage of oxygen on O-g-C3N4 surface to 6.9% as compared with 1.8% for g-C3N4. Meanwhile, the doped oxygen atom mainly existed as carbonyl and carboxyl groups. Optical characterization indicates the introduction of oxygen improved the response of O-g-C3N4 to visible light, and more obviously, separation of photo-generated h+-e−. 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) probe measurement indicates the formation of O2•− was dramatically enhanced through activation of dioxygen by photo-generated electrons in the O-g-C3N4 photocatalytic system. Through high performance liquid chromatography (HPLC) and Liquid chromatography–mass spectrometry (LC-MS) analysis, it was found rhodamine B (RhB) photocatalytic degradation by O-g-C3N4 followed step by step N-deethylation reaction pathways induced by the formed O2•−, rather than the non-selective decomposition of the chromophore in RhB by other radicals, such as hydroxyl radicals. This study provides a facile method to develop oxygen atom doped g-C3N4 photocatalyst, and also clarifies its photocatalytic activation mechanism of molecular oxygen for N-deethylation reaction of RhB.

Construction of ZnFe2O4/rGO composites as selective magnetically recyclable photocatalysts under visible light irradiation

This paper reports on highly active ZnFe₂O₄/reduced graphene oxide (ZnFe₂O₄/rGO) nanocomposites synthesized by a modified sol-gel method. The as-prepared samples have been characterized by XRD, TEM, XPS and other detection methods, which demonstrate that ZnFe₂O₄ nanoparticles (NPs) with a diameter of 15 ∼ 50 nm were densely grown on the rGO substrates. The photocatalytic activities of ZnFe₂O₄/rGO catalysts were evaluated by the degradation of Methylene blue (MB) under visible light. The results showed that the ZnFe₂O₄/rGO catalysts had high photocatalytic activity, and the degradation efficiency of MB was almost 100% within 180 min. Moreover, the ZnFe₂O₄/rGO catalysts also had a great removal effect on Rhodamine B (RhB) and Methyl orange (MO). Mechanistic studies revealed that the rGO acted as a stabilizer to prevent ZnFe₂O₄ from aggregation and improved the separation of photo-generated electrons. The high efficiency for dye degradation was attributed to the generation of hydroxyl radicals (·OH) via the photochemical decomposition of H₂O₂ on ZnFe₂O₄/rGO catalysts, which was responsible for the oxidation of the dyes. Of note, the ZnFe₂O₄/rGO catalyst maintained an efficiency of over 90% after five cycles. The XRD, XPS and VSM characterization revealed that the ZnFe₂O₄/rGO catalysts had a stable crystal structure and can be easily separated.

Highly Active Agro-Waste-Extracted Cellulose-Supported CuInS2 Nanocomposite for Visible-Light-Induced Photocatalysis

Agro-waste-extracted cellulose-supported CuInS₂ nanocomposites were hydrothermally synthesized with significant photocatalytic activity under the influence of cellulose as a polymeric natural support that offers delay in electron-hole life. Delayed recombination process of electrons and holes was perceived by parting of cellulose as a barrier or edge during photochemical reaction, which overall enhances the lifetime of photocatalyst. The photodegradation efficiency over five consecutive cycles along with scavenging studies have been examined for RhB dye under visible light. The boosted photodegradation rate was observed at an optimum amount of cellulose (200 mg), which is ∼10 times higher than pristine CuInS₂.