Preparation of nanosized Bi3NbO7 and its visible-light photocatalytic property

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

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

Effective Disposal of Methylene Blue and Bactericidal Benefits of Using GO-Doped MnO2 Nanorods Synthesized through One-Pot Synthesis

Graphene oxide (GO)-doped MnO2 nanorods loaded with 2, 4, and 6% GO were synthesized via the chemical precipitation route at room temperature. The aim of this work was to determine the catalytic and bactericidal activities of prepared nanocomposites. Structural, optical, and morphological properties as well as elemental composition of samples were investigated with advanced techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible (vis) spectroscopy, photoluminescence (PL), energy-dispersive spectrometry (EDS), and high-resolution transmission electron microscopy (HR-TEM). XRD measurements confirmed the monoclinic structure of MnO2. Vibrational mode and rotational mode of functional groups (O-H, C=C, C-O, and Mn-O) were evaluated using FTIR results. Band gap energy and blueshift in the absorption spectra of MnO2 and GO-doped MnO2 were identified with UV-vis spectroscopy. Emission spectra were attained using PL spectroscopy, whereas elemental composition of prepared materials was recorded with scanning electron microscopy (SEM)-EDS. Moreover, HR-TEM micrographs of doped and undoped MnO2 revealed elongated nanorod-like structure. Efficient degradation of methylene blue enhanced the catalytic activity in the presence of a reducing agent (NaBH4); this was attributed to the implantation of GO on MnO2 nanorods. Furthermore, substantial inhibition areas were measured for Escherichia coli (EC) ranging 2.10-2.85 mm and 2.50-3.15 mm at decreased and increased levels for doped MnO2 nanorods and 3.05-4.25 mm and 4.20-5.15 mm for both attentions against SA, respectively. In silico molecular docking studies suggested the inhibition of FabH and DNA gyrase of E. coli and Staphylococcus aureus as a possible mechanism behind the bactericidal activity of MnO2 and MnO2-doped GO nanoparticles (NPs).

Fabrication of MOF-derived tubular In2O3@SnIn4S8 hybrid: Heterojunction formation and promoted photocatalytic reduction of Cr(VI) under visible light

Tubular In₂O₃@SnIn₄S₈ hierarchical hybrid photocatalyst was firstly fabricated by a two-step method. The morphology and composition were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The XRD results show that the obtained In₂O₃ microtubes were highly crystallized, while the SnIn₄S₈ flakes prepared at low temperature were poorly crystallized. The SEM image of the hybrid shows that numerous SnIn₄S₈ nanoflakes were assembled over the surface of In₂O₃ microtubes. In₂O₃ served as dispersing-templates have reduced the agglomeration of SnIn₄S₈ flakes. Meanwhile, the heterojunctions formed at the interfaces between In₂O₃ and SnIn₄S₈ could facilitate the interfacial charge transfer, as well as promote the photocatalytic activity of the hybrid. In the treatment of Cr(VI)-containing wastewater, the In₂O₃@SnIn₄S₈ hybrid not only exhibited strong adsorption ability, but also showed remarkably enhanced photocatalytic activity compared with pure SnIn₄S₈. The photocatalytic reaction constant k for In₂O₃@SnIn₄S₈ was approximately 2.54 times higher than that of SnIn₄S₈. The efficient activity of this hybrid photocatalyst should be ascribed to the promoted separation efficiency of electron/hole pairs, which was proved by the following three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs), photocurrent responds, and EIS characterizations.

Phase control synthesis of α, β and α/β Bi2O3 hetero-junction with enhanced and synergistic photocatalytic activity on degradation of toxic dye, Rhodamine-B under natural sunlight

Nano particles of a few α/β Bi₂O₃ hetero-junctions of various compositions synthesized by one- pot hydrothermal method, exhibit exceptional and synergistic photo-catalytic activity for the degradation of Rhodamine-B in aqueous solution under natural sunlight. Pure α and pure β Bi₂O₃ are also synthesized by control post heating of synthesized hetero-junction. The nano-materials were characterized by diffraction (XRD), microscopic and spectroscopic techniques. The XRD reveals α-β phase hetero-junctions of Bi₂O₃ are made of α-Bi₂O₃ and β-Bi₂O₃ with average dimensions within 13-113 and 5-71 nm respectively and having band gap range of 2.4- 2.9 eV. The spectrophotometrically determined % degradation of the dye and associated rate constant on the best hetero-junction are increased by 4.5(/2.1) and 3.3(/1.2) times than these on pure α (/β). The effects of operational parameters and trapping agents have been analyzed. The maximum removal of the dye was achieved up to 99.6% in 3 h using 0.5 g/L photo-catalyst at pH 3. The reusability test shows that the photo-catalytic activity is retained excellently due to change in chemical nature of the catalyst from α -Bi₂O₃ to β-Bi₂O_3, Bi₂O₂CO₃ and BiOCl. A suitable mechanism is proposed.

Fe(Ⅲ) ions enhanced catalytic properties of (BiO)2CO3 nanowires and mechanism study for complete degradation of xanthate

The wire-like Fe³⁺-doped (BiO)₂CO₃ photocatalyst was synthesized by a hydrothermal method. The photocatalytic property of Fe³⁺-doped (BiO)₂CO₃ nanowires was evaluated through degradation of sodium isopropyl xanthate under UV-visible light irradiation. The as-prepared Fe³⁺-doped (BiO)₂CO₃ nanowires were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) in detail. The results of XRD showed that the crystallinity of (BiO)₂CO₃ nanowires decreased when Fe³⁺ ions were introduced into the solution system. XPS results illustrated that xanthate could be absorbed on the surface of Fe³⁺-doped (BiO)₂CO₃ nanowires to produce BiS bond at the beginning of the reaction, which could broaden the visible light absorption. FTIR spectra confirmed the formation of SO₄^2- after photocatalytic decomposition of xanthate solution. The Fe³⁺-doped (BiO)₂CO₃ nanowires showed an enhanced photocatalytic activity for decomposition of xanthate due to the narrower band gap and larger BET surface area, comparing with pure (BiO)₂CO₃ nanowires. By the results of UV-vis spectra of the solution and FTIR spectra of recycled Fe³⁺-doped (BiO)₂CO₃, the xanthate was oxidized completely into CO₂ and SO₄^2-. The photocatalytic degradation process of xanthate followed a pseudo-second-order kinetics model. The mechanism of enhanced photocatalytic activity was proposed as well.

Synergetic effects of Sr-doped CuBi2O4 catalyst with enhanced photoactivity under UVA- light irradiation

Sr-doped CuBi2O4 micro-particles were successively synthesized via a solid-state technique and were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and UV-vis diffuse reflectance spectroscopy (UV-vis-DRS) techniques. Results show that Sr-doped CuBi2O4 was crystallized with a spinel-type structure and tetragonal crystal system, and the band gap energy was about 1.35 eV. The as-prepared Sr-doped CuBi2O4 treated at 573 °C for 12 h exhibited the highest efficiency, as a result of 97.22 % of CR degradation within 220 min, which is approximately 31 times greater than CR photodegradation when catalyzed by CuBi2O4 (3.13 %) and about 2.3 times superior than that catalyzed by the untreated Sr-doped CuBi2O4 sample (42.08 %). Pseudo-first-order kinetic model gave the best fit, with highest correlation coefficients (R (2) = 0.94-0.97). The Sr-doping and extending reaction time up to 12 h could be effective in producing Sr-doped CuBi2O4 materials that delay electron-hole recombination, thereby increasing the lifetime of the electron electron-hole separation and support the charge carrier transfer to the catalyst surface. On the basis of the calculated energy band positions, superoxide radical anions (O2 (•-)) were the main oxidative species responsible for the photocatalytic degradation of CR dye solution.

Thickness-tunable solvothermal synthesis of BiOCl nanosheets and their photosensitization catalytic performance

BiOCl nanosheets with different thickness have been successfully synthesized via a solvothermal process with the mediation of metal ions (Fe³⁺, Co²⁺ and Na⁺) and exhibited thickness-dependent photosensitization activity for RhB degradation.

Plasmonic Z-scheme α/β-Bi2O3–Ag–AgCl photocatalyst with enhanced visible-light photocatalytic performance

The plasmonic Z-scheme α/β-Bi₂O₃–Ag–AgCl photocatalysts were successfully synthesized and their photocatalytic performance for the degradation of Rhodamine B and acid orange 7 dyes were systematically investigated.

Recent advances in synthesis and applications of clay-based photocatalysts: a review

Clay-based photocatalysts with high adsorbability and special structures have attracted extensive attention because of their applications in environment and energy fields.

Enhanced visible-light-driven photocatalytic inactivation of Escherichia coli by Bi2O2CO3/Bi3NbO7 composites

The Bi2O2CO3/Bi3NbO7 (BiCO/BiNbO) composite was successfully fabricated by a simple hydrothermal method and found to be an effective visible-light-driven photocatalyst for inactivation of Escherichia coli (E. coli). The BiCO/BiNbO composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectrum (UV-vis DRS), and Fourier transform infrared (FT-IR) spectroscopy. The BiCO/BiNbO composite exhibited largely enhanced photocatalytic inactivation of E. coli as compared to the pure Bi3NbO7 under visible light irradiation. The enhanced photocatalytic performance can be attributed to the improved separation efficiency of the photogenerated holes and electrons. In addition, the possible bactericidal mechanism of the BiCO/BiNbO composite under visible light irradiation was discussed.

Preparation and properties of visible light responsive Y3+ doped Bi5Nb3O15 photocatalysts for Ornidazole decomposition

Nanoparticle of Bi(5)Nb(3)O(15) doped with Y(3+) was prepared for the first time by the sol-gel method combined with impregnation. The degradation of Ornidazole reacting with Y(3+)-Bi(5)Nb(3)O(15) was investigated to explore the feasibility of using Y(3+)-Bi(5)Nb(3)O(15) to treat antibiotics in wastewater. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, UV-vis diffuse reflectance spectrum and X-ray photoelectron spectroscopy. The results showed that the Y(3+)-Bi(5)Nb(3)O(15) exhibited single-crystalline orthorhombic structure with small particle size (20-100 nm); additionally, its UV-vis absorbance edges significantly shift to the visible-light region. The as-prepared nanoparticles exhibited a high photocatalytic activity in the decomposition of Ornidazole and several possible pathways of degradation of Ornidazole were proposed according to the results of ultra-performance liquid chromatography tandem mass spectrometry.

Photocatalytic removal of organic pollutants in aqueous solution by Bi(4)Nb(x)Ta((1-x))O(8)I

In this work, Bi(4)Nb(x)Ta((1-x))O(8)I photocatalysts have been synthesized by solid state reaction method and characterized by powder X-ray diffraction, scanning electron microscope and UV-Vis near infrared diffuse reflectance spectroscopy. The photocatalytic activity of these photocatalysts was evaluated by the degradation of methyl orange (MO) in aqueous solutions under visible light, UV light and solar irradiation. The effects of catalyst dosage, initial pH and MO concentration on the removal efficiency were studied, and the photocatalytic reaction kinetics of MO degradation as well. The results indicated that Bi(4)Nb(x)Ta((1-x))O(8)I exhibited high photocatalytic activity for the removal of MO in aqueous solutions. For example, the removal efficiency of MO by Bi(4)Nb(0.1)Ta(0.9)O(8)I was as high as 92% within 12 h visible light irradiation under the optimal conditions: initial MO concentration of 5-10 mg L(-1), catalyst dosage of 6 g L(-1) and natural pH (6-8), the MO molecules could be completely degradated by Bi(4)Nb(0.1)Ta(0.9)O(8)I within 40 min under UV light irradiation, and the photodegradation efficiency reaches to 60% after 7 h solar irradiation. Furthermore, the photocatalytic degradation of Bisphenol A (BPA) was also investigated under visible light irradiation. It is found that 99% BPA could be mineralized by Bi(4)Nb(0.1)Ta(0.9)O(8)I after 16 h visible light irradiation. Through HPLC/MS, BOD, TOC, UV-Vis measurements, we determined possible degradation products of MO and BPA. The results indicated that MO was degradated into products which are easier to be biodegradable and innocuous treated, and BPA could be mineralized completely. Furthermore, the possibility for the photosensitization effect in the degradation process of MO under visible light irradiation has been excluded.

Hierarchical nitrogen doped bismuth niobate architectures: controllable synthesis and excellent photocatalytic activity

Nitrogen doped bismuth niobate (N-Bi(3)NbO(7)) hierarchical architectures were synthesized via a facile two-step hydrothermal process. XRD patterns revealed that the defect fluorite-type crystal structure of Bi(3)NbO(7) remained intact upon nitrogen doping. Electron microscopy showed the N-Bi(3)NbO(7) architecture has a unique peony-like spherical superstructure composed of numerous nanosheets. UV-vis spectra indicated that nitrogen doping in the compound results in a red-shift of the absorption edge from 450nm to 470nm. XPS indicated that [Bi/Nb]N bonds were formed by inducing nitrogen to replace a small amount of oxygen in Bi(3)NbO(7-x)N(x), which is explained by electronic structure calculations including energy band and density of states. Based on observations of architectures formation, a possible growth mechanism was proposed to explain the transformation of polyhedral-like nanoparticles to peony-like microflowers via an Ostwald riping mechanism followed by self-assembly. The N-Bi(3)NbO(7) architectures due to the large specific surface area and nitrogen doping exhibited higher photocatalytic activities in the decomposition of organic pollutant under visible-light irradiation than Bi(3)NbO(7) nanoparticles. Furthermore, an enhanced photocatalytic performance was also observed for Ag/N-Bi(3)NbO(7) architectures, which can be attributed to the synergetic effects between noble metal and semiconductor component.

A survey of photocatalytic materials for environmental remediation

Heterogeneous photocatalysis is an advanced oxidation process which has been the subject of a huge amount of studies related to air cleaning and water purification. All these processes have been carried out mainly by using TiO(2)-based materials as the photocatalysts and ca. 75% of the articles published in the last 3 years is related to them. This review illustrates the efforts in the search of alternative photocatalysts that are not based on TiO(2), with some exceptions concerning particularly innovative modifications as nanoassembled TiO(2) or TiO(2) composites with active carbon, graphite and fullerene. Papers reporting preparation, characterization and testing of binary, ternary and quaternary compounds, have been reviewed. Despite many of these photocatalysts being effective for the photodecomposition of many pollutants, most of them do not allow a complete mineralization of the starting compounds, differently from TiO(2).