Boosting the photocatalytic performance of Bi2Fe4O9 through formation of Z-scheme heterostructure with In2S3: Applications towards water decontamination

Design of biocompatible nano-heterostructure photocatalyst with broad UV-visible spectrum response and strong redox ability is a promising approach with potential application in micropollutant degradation and pathogen deactivation from aqueous sources. Herein, we have reported the facile fabrication of In₂S₃/Bi₂Fe₄O₉ (ISxBFO) binary heterostructure by hydrothermally depositing In₂S₃ nanoparticles (20-40 nm) over Bi₂Fe₄O₉ nanocuboids/nanoplates prepared by combustion synthesis route. In depth characterization study revealed broad spectrum UV-Vis absorption, large interfacial contact, improved charge carrier separation and mobility and a longer excited state life time (4.7 ns) for the ISxBFO heterostructure materials. The integration of In₂S₃ with Bi₂Fe₄O₉ strongly boosts the optoelectrical and photocatalytic property of pristine Bi₂Fe₄O₉. The ISxBFO heterostructure material exhibited enhanced photocatalytic efficiency for aqueous phase degradation of sulfamethoxazole antibiotics (k_app = 0.06 min^-1) and phenyl urea herbicides (k_app = 0.028 min^-1) with reaction rates 3-8 times higher than the pure BFO component. The MTT assay experiments confirmed non-cytotoxic nature of treated sulfamethoxazole and diuron solutions. The composite materials also displayed convincing antibacterial behavior towards toxigenic Vibrio cholerae pathogen. Haemagglutination assay study revealed excellent biocompatibility of the binary composite up to 200 mg L^-1. Radical trapping study suggested expeditious generation of ^•OH and ^•O₂^- radicals over the ISxBFO surface which is nearly 3.8 and 2.3 times higher than pure BFO and In₂S₃ respectively. The occurrence of a direct Z-scheme mechanism is inferred from radical trapping and XPS study which accounted for the improved photocatalytic activity and strong radical generation property of the ISxBFO heterostructure material.

Performance comparison of distinct bismuth molybdate single phases for asymmetric supercapacitor applications

The enticing features of metal molybdates make them an attractive candidate for energy storage systems. This report describes the synthesis of three distinct single-phase bismuth molybdates (Bi₂Mo_xO_y; α-Bi₂Mo₃O₁₂, β-Bi₂Mo₂O₉, and γ-Bi₂MoO₆) using the gel matrix particle growth method and their application in high-performance asymmetric supercapacitors. The single phase and purity of the synthesized Bi₂Mo_xO_y particles were confirmed by X-ray diffraction (XRD) and further verified by Raman analysis. The UV-visible spectra show the electronic and optical behaviours of the as-synthesized α, β, and γ Bi₂Mo_xO_y. The morphologies of the as-synthesized three different Bi₂Mo_xO_y phases were analysed using scanning electron microscopy (SEM). The particle formation was further investigated by transmission electron microscopy (TEM), and the interplanar spacings of the Bi₂Mo_xO_y phases were in accordance with the planes. The surface area and pore volume of the prepared samples were analysed using Brunauer-Emmett-Teller (BET) analysis. The electrochemical properties of the products were confirmed by various tests, including cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 3 M KOH. Among the three phases, α-Bi₂Mo₃O₁₂ exhibits a huge specific capacitance (Cs) of 714 F g^-1 at a current density of 1 A g^-1. Furthermore, it displays an admirable cycling stability of 86.55% after 5000 cycles. The chosen α-Bi₂Mo₃O₁₂ electrode possesses an increased energy density of 47.5 W h kg^-1 at 1 A g^-1 with a capacitive retention rate of 71.90% at 5 A g^-1 after 10 000 cycles. A remarkable electrochemical performance of Bi₂Mo₃O₁₂ with an exceptional power density of 750 W kg^-1 was observed for the prepared asymmetric device. Bismuth molybdate's notable performance indicates that it can be an active material for energy storage applications.

Developing sustainable, high-performance perovskites in photocatalysis: design strategies and applications

Solar energy is attractive because it is free, renewable, abundant and sustainable. Photocatalysis is one of the feasible routes to utilize solar energy for the degradation of pollutants and the production of fuel. Perovskites and their derivatives have received substantial attention in both photocatalytic wastewater treatment and energy production because of their highly tailorable structural and physicochemical properties. This review illustrates the basic principles of photocatalytic reactions and the application of these principles to the design of robust and sustainable perovskite photocatalysts. It details the structures of the perovskites and the physics and chemistry behind photocatalytic reactions and describes the advantages and limitations of popular strategies for the design of photoactive perovskites. This is followed by examples of how these strategies are applied to enhance the photocatalytic efficiency of oxide, halide and oxyhalide perovskites, with a focus on materials with potential for practical application, that is, not containing scarce or toxic elements. It is expected that this overview of the development of photocatalysts and deeper understanding of photocatalytic principles will accelerate the exploitation of efficient perovskite photocatalysts and bring about effective solutions to the energy and environmental crisis.

Effect of HCl treatment on physico-chemical properties and photocatalytic performance of Fe-TiO2 nanotubes for hexavalent chromium reduction and dye degradation under visible light

In this study, we prepared Fe₂O₃/TNT composite (Fe-TNT) foil by combining anodization with the hydrothermal method. Photocatalytic reaction was restricted by a cluster of iron particles accumulated on the foil surface and the photocatalytic reaction sites reduces. Herein, using XPS determined that these iron particles are composed of iron oxide. An acid treatment, hydrochloric acid (HCl) was used to successfully remove the surface accumulation of iron oxide particles on the photocatalyst. Using cleaned Fe-TNT foil, the photocatalytic activity of 5 mg/L Congo red (CR) and hexavalent chromium reduction was significantly increased under visible irradiation. In addition, the influence of different aspects such as pH, the concentration of Fe, and the effect of different acid treatment time was evaluated. Removing the surface accumulated iron oxide and adjusting the pH in acidic medium, 73% hexavalent chromium reduction achieved within 180 min. The reusability was also explored by monotonous CR degradation. The CR degradation using Fe_0.25-TNT was lessened from 78% in the first cycle to 71% in the 3rd cycle. It was also confirmed experimentally that photocatalytic activity improvement of HCl treated Fe-TNT was not due to alternation in nanotube structure.

Experimental studies on water matrix and influence of textile effluents on photocatalytic degradation of organic wastewater using Fe-TiO2 nanotubes: Towards commercial application

The application of photocatalysis for the effective removal of textile dyes is dependent on various parameters related with both water quality and different chemicals discharge during the dying process. Because the oxidation rates of the particular mixtures mainly influenced by the elements of the water matrix. These elements comprised of organic, inorganic salts, heavy metals, and ions. The impact of water matrices (Tap water, DI water, seawater, surface water, and ultra-pure water) on the Congo red decolorization, total organic carbon, and chemical oxygen demand removal efficacy has been assessed using Fe-TiO₂ nanotubes as a photocatalyst. The photocatalytic degradation rate decreased in unclean water due to the interferences of dissolved organics and minerals. However, all the environmental water matrices depict the significant decrease in turbidity and conductivity after treating with photocatalytic process. The photoactivity and capacity for decantation are the two crucial elements that have an impact on the "practical efficiency" of photocatalysts. Moreover, the textile wastewater contains a large quantity of dyes mixed with number of detrimental chemicals and other effluents discharged into the water which consequently pollute ecosystem and cause serious risks to human health. For environmental applications, we investigated individually the impact of various harmful chemicals commonly discharged from each step of textile wet processing which can have inhibiting or promoting effect on the azo dye photocatalytic degradation.

Insights into the impurities of Bi2WO6 synthesized using the hydrothermal method

Bismuth tungstate (Bi2WO6) nanomaterials are widely used as visible-light driven photocatalysts. However, limited attention has been paid to the purity of prepared Bi2WO6 nanoparticles, which may affect the photocatalytic performance and hinder in-depth study of Bi2WO6. In this work, the impurities of Bi2WO6 formed during the hydrothermal process under a wide range of acid-base conditions (from 1.5 M HNO3 to 0.5 M NaOH) were qualitatively analyzed and accurately quantified for the first time. After confirmation of Bi2WO6 stability, the impurities were dissolved using acid or base treatment, followed by measurements of the ion concentrations using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Furthermore, various characterization techniques including XRD, FE-SEM, TEM, UV-Vis DRS, XPS and FTIR were implemented to explore the change in morphology and optical properties of Bi2WO6 prepared in different acid-base environments, and to facilitate qualitative analysis of impurities. The hydrolytic properties of raw materials used for the synthesis of Bi2WO6 were also analyzed with UV-Vis transmittance observation. Following these analyses, the types and contents of impurities in Bi2WO6 prepared by the hydrothermal method under different acid-base conditions were determined. Results show that the primary impurity is WO3·0.33H2O (41.09%) for the precursor prepared in 1.5 M nitric acid solution. When the pH of the precursor was in the range of 0.97-7.01, the synthesized Bi2WO6 has relatively high purity, and the impure products were identified as BiONO3. Bi2O3 began to appear when pH reached 9.01 and it reached 18.88% when pH was 12.98. The final product was Bi2O3 exclusively for the precursor conditioned in 0.5 M NaOH solution. In addition, the accuracy of the proposed quantitative method using ICP-MS was validated for several scenarios by weight difference experiments.

Optimization of hydrothermal synthesis of Fe-TiO2 nanotube arrays for enhancement in visible light using an experimental design methodology

We designed an experiment to optimize the hydrothermal modification of iron on anodized TiO₂ nanotubes. A central composite design that included five design points was used to determine the condition parameters for hydrothermal reaction time (1-5 h) and hydrothermal temperature (120-180 °C). A statistical method was used to observe the effects of hydrothermal conditions on the material properties and photocatalytic activity of a Fe-TiO₂ nanotube catalyst. Scanning electron microscopic (SEM) analysis shows the iron is doped on the TNTs, which is further confirmed by energy-dispersive X-ray spectroscopy. X-ray diffraction indicate the existing states of iron in the form of iron oxide on the TNT. The maximum degradation efficiency (92.3%) was achieved at a hydrothermal temperature of 150 °C and time of 3 h. It is found that the optimal medication of the Fe-TNT catalyst occurred at a particular combination of temperature (150 °C) and reaction time (3 h), that provide the more active sites for iron to enter the crystal lattice of TNT, and that the maximum CR degradation could be achieved.

Preparation of Pt/γ-Bi2MoO6 Photocatalysts and Their Performance in α-Alkylation Reaction under Visible Light Irradiation

Bi(NO3)3·5H2O and (NH4)6Mo7O24·4H2O were used as precursors to synthesize flaky γ-Bi2MoO6 samples by a hydrothermal method, and Pt/γ-Bi2MoO6 samples with different mass fractions were prepared by an NaBH4 reduction method. Alpha alkylation of benzyl alcohol and acetophenone with photocatalysts under visible light irradiation was performed, and the activity of 4 wt % Pt/γ-Bi2MoO6 (γ-Bi2MoO6 was prepared by a nitric acid method, pH = 9, and reaction temperature 180 °C) was the best. The photocatalytic reaction conditions were optimized by changing various kinds of variables, such as the type of catalyst, solvent, and base, and the amount of base, catalyst, and reactant. The optimal conditions for the organic reaction were 75 mg 4 wt % Pt/γ-Bi2MoO6, 6 mL n-heptane, 1.2 mmol NaOH, 1 mmol acetophenone, and 3 mmol benzyl alcohol. Under the optimal reaction conditions, the effects of different light wavelengths and light intensities on the reaction were measured, and the cycling ability of the photocatalyst was tested. After five cycles, the photochemical properties of the catalyst were relatively stable. Finally, the active substances were identified (such as electrons (e-), holes (h+), hydroxyl radicals (•OH), and superoxide radicals (•O2-).

Effects of Particle Size on the Structure and Photocatalytic Performance by Alkali-Treated TiO2

Particle size of nanomaterials has significant impact on their photocatalyst properties. In this paper, TiO₂ nanoparticles with different crystalline sizes were prepared by adjusting the alkali-hydrothermal time (0–48 h). An annealing in N₂ atmosphere after hydrothermal treatment caused TiO₂ reduction and created defects, resulting in the visible light photocatalytic activity. The evolution of physicochemical properties along with the increase of hydrothermal time at a low alkali concentration has been revealed. Compared with other TiO₂ samples, TiO₂-24 showed higher photocatalytic activity toward degrading Rhodamine B and Sulfadiazine under visible light. The radical trapping and ESR experiments revealed that O₂^•- is the main reactive specie in TiO₂-24. Large specific surface areas and rapid transfer of photogenerated electrons are responsible for enhancing photocatalytic activity. The above findings clearly demonstrate that particle size and surface oxygen defects can be regulated by alkali-hydrothermal method. This research will deepen the understanding of particle size on the nanomaterials performance and provide new ideas for designing efficient photocatalysts.

Surface oxygen vacancies enriched FeOOH/Bi2MoO6 photocatalysis- fenton synergy degradation of organic pollutants

To achieve rapid separation of photogenerated charges, increase photocatalytic degradation activity, a visible light-driven FeOOH/Bi₂MoO₆-OVs photocatalyst was designed and successfully fabricated via solvothermal synthesis and calcination. H₂O₂ was added under visible light irradiation to form a heterogeneous photocatalysis-Fenton synergy system. Using visible light irradiation, 10% FeOOH/Bi₂MoO₆-OVs had the best degradation activity. The removal efficiency of phenol was 100% within 3 h, which was 1.54 times and 1.33 times of the degradation efficiency of photocatalysis and Fenton alone, respectively. The catalyst has high removal activity for various pollutants and good cycle stability. Hydroxyl radicals and superoxide radicals have proven to be the main active substances and a reasonable catalytic mechanism was proposed. Surface oxygen vacancy can not only reduce the width of band gap, promote the separation and migration of photogenerated electron-hole pairs, but also make the OO bond of H₂O₂ elongate and weaken, making it easier to react with FeOOH and realize the synergistic effect of photocatalysis-Fenton. Simultaneously, the oxygen vacancies located near the valence band can capture holes, and the holes are rapidly transferred to the surface of the catalyst and participated in the degradation of pollutants.

Effective charge kinetics steering in surface plasmons coupled two-dimensional chemical Au/Bi2WO6-MoS2 heterojunction for superior photocatalytic detoxification performance

Developing and designing a rational heterojunction with efficient charge kinetics properties have been a research hotspot for improving photocatalytic performance. Herein, a surface plasmons coupled two-dimensional chemical Au/Bi₂WO₆-MoS₂ heterojunction was synthesized. In thus a system, Au nanoparticles are tightly attached to the sides of Bi₂WO₆ nanosheets, conducting a HEI effect with additional visible light response to inject "hot electrons" into Bi₂WO₆, resulting in additional charge generation. Meanwhile, few-layer MoS₂ nanosheets were chemically assembled onto ultrathin Bi₂WO₆ nanosheets via interfacial SO bonds to form a intimate 2D-2D nanojunction, the separated and injected electrons on the surface of Bi₂WO₆ were further directional transfer to MoS₂ nanosheets through SO bonds for detoxification of heavy metal ions Cr(VI), and the corresponding holes left on Bi₂WO₆ nanosheets were applied for simultaneous degradation of tetracycline antibiotic. The photocatalytic detoxification activity of Au/Bi₂WO₆-MoS₂ was nearly 4.84, 3.47 and 1.90 times higher than that of pristine Bi₂WO₆, Au/Bi₂WO₆ and Bi₂WO₆-MoS₂ composites, which could be ascribed to the effective charge kinetics steering and well manipulation of charge flow by virtue of the rational structural and compositional features. This work provides a new perspective for the construction of high-activity detoxification photocatalysts through steering charge kinetics.

A less harmful system of preparing robust fabrics for integrated self-cleaning, oil-water separation and water purification

Although the development of constructing oil-water separation materials is quick, the defects of using harmful regents, weak stability and single function still exist. Here, we report an effective and less-harmful system with poly-dimethylsiloxane (PDMS)/ZnO composite solution to fabricate robust superhydrophobic surfaces for oil-water separation and removal of organic pollutant. The obtained samples were characterized by a range of instruments. The water contact angle (WCA) of coated cotton was 155.6°, which attributed to the synergetic effect of low surface energy of PDMS and roughness of ZnO nanoparticles. The coated cotton was tolerant to mechanical damage, various corrosive solvents and temperature conditions. The emphasis of this study is the combination of superhydrophobicity and photocatalysis, resulting in multifunctional cotton with dual self-cleaning properties, outstanding oil-water separation ability and efficient water purification property. When utilized a simple laboratory facility, the cotton could separate water from oil-water mixture with a high efficiency (99.3%). Furthermore, the dyed water could be purified with coated cotton through photocatalysis under UV light and became colorless. Meanwhile, this mild and facile method could also be utilized to modify other porous substrates, such as PET, silk, non-woven and sponge. Therefore, the characteristics of environmental protection and easy operation make this cotton a desirable candidate for extensive applications in self-cleaning, oil-water separation and water purification.

Modulation of Bi2 MoO6 -Based Materials for Photocatalytic Water Splitting and Environmental Application: a Critical Review

Highly active photocatalysts driving chemical reactions are of paramount importance toward renewable energy substitutes and environmental protection. As a fascinating Aurivillius phase material, Bi₂ MoO₆ has been the hotspot in photocatalytic applications due to its visible light absorption, nontoxicity, low cost, and high chemical durability. However, pure Bi₂ MoO₆ suffers from low efficiency in separating photogenerated carriers, small surface area, and poor quantum yield, resulting in low photocatalytic activity. Various strategies, such as morphology control, doping/defect-introduction, metal deposition, semiconductor combination, and surface modification with conjugative π structures, have been systematically explored to improve the photocatalytic activity of Bi₂ MoO₆ . To accelerate further developments of Bi₂ MoO₆ in the field of photocatalysis, this comprehensive Review endeavors to summarize recent research progress for the construction of highly efficient Bi₂ MoO₆ -based photocatalysts. Furthermore, benefiting from the enhanced photocatalytic activity of Bi₂ MoO₆ -based materials, various photocatalytic applications including water splitting, pollutant removal, and disinfection of bacteria, were introduced and critically reviewed. Finally, the current challenges and prospects of Bi₂ MoO₆ are pointed out. This comprehensive Review is expected to consolidate the existing fundamental theories of photocatalysis and pave a novel avenue to rationally design highly efficient Bi₂ MoO₆ -based photocatalysts for environmental pollution control and green energy development.

Influence of cobalt substitution on the crystal structure, band edges and photocatalytic properties of hierarchical Bi2WO6 microspheres

An efficient Bi₂WO₆ catalyst with Co²⁺ substitution was synthesized via a facile hydrothermal route.

Fabrication and Photocatalytic Property of Novel SrTiO3/Bi5O7I Nanocomposites

The novel SrTiO3/Bi5O7I nanocomposites were successfully fabricated by a thermal decomposition approach. The as-prepared samples were characterized by XRD, XPS, SEM, EDS, FTIR, DRS and PL spectra. The results show that the SrTiO3/Bi5O7I nanocomposites are composed of perovskite SrTiO3 nanoparticles and tetragonal Bi5O7I nanorods. The SrTiO3/Bi5O7I nanocomposites exhibit an excellent photocatalytic performance for the degradation of RhB solution under simulated solar light irradiation, which is superior to that of pristine Bi5O7I and SrTiO3. In particular, the 30 wt% SrTiO3/Bi5O7I nanocomposite is found as the optimal composites, over which the dye degradation reaches 89.6% for 150 min of photocatalysis. The photocatalytic degradation rate of the 30 wt% SrTiO3/Bi5O7I nanocomposite is found to be 3.97 times and 12.5 times higher than that of bare Bi5O7I and SrTiO3, respectively. The reactive species trapping experiments suggest that [Formula: see text] and holes are the main active species responsible for the RhB degradation. In addition, the PL spectra elucidate the effective separation of photoinduced electron-hole pairs. Further, the possible photocatalytic mechanism of the SrTiO3/Bi5O7I nanocomposites is also elucidated based on the experimental evidences.

Novel two-dimensional Bi4V2O11 nanosheets: controllable synthesis, characterization and insight into the band structure

Novel two-dimensional Bi₄V₂O₁₁ nanosheets were controllably prepared using a stable [Bi(EDTA)]⁻ complex, and their band structures were investigated as well.

Synthesis of NiTiO3–Bi2MoO6 core–shell fiber-shaped heterojunctions as efficient and easily recyclable photocatalysts

NiTiO₃–Bi₂MoO₆ core–shell fiber-shaped heterojunctions have been prepared, and they can be used as efficient and easily recyclable photocatalysts for environmental remediation.

Facile preparation of 2D Bi2MoO6 nanosheets–RGO composites with enhanced photocatalytic activity

To the best of our knowledge, few studies had reported Bi₂MoO₆–RGO as a catalyst for photodegradation of ciprofloxacin.