Synthesis of nanometer-size Bi3TaO7 and its visible-light photocatalytic activity for the degradation of a 4BS dye

Insight into the mechanism of deep NO photo-oxidation by bismuth tantalate with oxygen vacancies

Deeply photocatalytic oxidation of nitrogen oxides is still difficult to achieve, mainly limited by few intrinsic active sites and inefficient carrier separation of photocatalysts. Accordingly, we develop a simple room temperature tactic to introduce oxygen vacancies (OVs) into Bi₃TaO₇ (BTO). Based on solid experimental and DFT theoretical supports, we explore the mechanism of NO removal over OVs decorated BTO (OVs-BTO). OVs can not only alter the distribution of local electrons to result in the formation of a fast charge transfer channel between OVs and the adjacent Ta atoms, which improves the transport rate of photogenerated carriers; but also function as active sites to adsorb small molecules (NO, O₂ and H₂O), which being activated and positively drive the NO oxidation reaction. In order to investigate a possible reaction path, a combination of in-situ DRIFTS and simulated Gibbs free energy reveals that the intermediate products of OVs-BTO are helpful to promote the deep oxidation of NO to NO₃^-, while pristine BTO is more likely to produce NO₂ intermediate toxic by-products, which greatly hinders the deep photocatalytic oxidation of NO. This work provides insights into the role of OVs in photocatalysts, and also points out a guideline for the mechanism of semiconductor photocatalysts in eliminating gaseous pollutants.

Construction of Z-scheme Bi3TaO7/Zn0.5Cd0.5S composites with high efficiency for levofloxacin degradation under visible light irradiation

Direct Z-scheme Bi₃TaO₇/Zn_0.5Cd_0.5S composite photocatalysts were successfully prepared via an in situ growth hydrothermal method. The photocatalytic activities of composites were investigated by the degradation of levofloxacin under visible light. All composites exhibited enhanced photocatalytic activities compared with Bi₃TaO₇ and Zn_0.5Cd_0.5S. The structure composition and photoelectric performance of the photocatalysts were investigated by related experiments. The dominant active species (h⁺ and ˙O₂^-) during levofloxacin degradation were identified through capture experiments. Meanwhile, the stability and cyclicity of the optimal photocatalyst (BZCS-2) were studied by cycling experiments. Finally, we proposed a possible direct Z-scheme charge-migration mechanism for levofloxacin degradation. This work would provide a feasible idea and theoretical support for the in-depth research of direct Z-scheme photocatalysts and Zn_xCd_1-xS-based semiconductor materials in the future.

Bi3TaO7/Ti3C2 heterojunctions for enhanced photocatalytic removal of water-borne contaminants

Novel catalysts are of great interest for improved photocatalytic environmental remediation. Using a hydrothermal method, 0D/2D Bi₃TaO₇/Ti₃C₂ heterojunctions were designed rationally and characterized systematically as excellent photocatalysts for photocatalytic degradation. The hybrid catalyst exhibits superior performance in visible-light-driven photocatalytic degradation of methylene blue (about 99% degradation efficiency after 2 h) and excellent stability (up to 10 cycles) under visible light irradiation (300 W Xe lamp; λ > 420 nm; light intensity 150 mW cm^-2). In addition, Bi₃TaO₇/Ti₃C₂ has a larger rate constant (0.032 min^-1) than pristine Bi₃TaO₇ (0.006 min^-1). Quantum yield (2.27 × 10^-5 molecules/photon) and figure of merit (23.3) of the system were obtained, suggesting that our catalyst has potential for application. Both experimental and computational results indicate that synergistic effects between Bi₃TaO₇ and Ti₃C₂ improve photocatalytic performance by enhancing electron-hole pair separation, electronic transmission efficiency, and interfacial charge transfer. These findings contribute to the synthesis of efficient visible-light-driven Bi-based photocatalysts and to the understanding of photocatalytic degradation reactions.

Bi3TaO7 film: a promising photoelectrode for photoelectrochemical water splitting

Most of the transition metal bismuth salts have excellent visible absorption range and carrier transport properties due to their unique structure capable of orbits and s-p bonds. As one of the transition metal bismuth salts, Bi₃TaO₇ is firstly directly prepared on fluorine-doped SnO₂ transparent conductive glass (FTO) as a photoanode for photoelectrochemical (PEC) water oxidation via a simple hydrothermal method using a special precursor solution. The growth mechanism of the Bi₃TaO₇ film is investigated in detail. Besides, the Bi₃TaO₇ photoanode exhibits a wide visible light response range with an optical band gap of 2.88 eV, which is useful for its PEC properties. Bi₃TaO₇ achieves an excellent PEC performance by tuning the calcination temperature, producing a photocurrent density of 23.0 μA cm^-2 at 1.23 V vs. RHE and showing excellent stability that decays by only 2% after illumination for 6000 s. The above results indicate that Bi₃TaO₇ has broad application prospects in the field of PEC water oxidation.

Carbon dots sensitized 2D-2D heterojunction of BiVO4/Bi3TaO7 for visible light photocatalytic removal towards the broad-spectrum antibiotics

Focused on the removal of the complicated residual antibiotic in aqueous environment, in this work, a novel carbon dots (C-dots) sensitized 2D-2D heterojunction of BiVO₄/Bi₃TaO₇ were assembled through a simple hydrothermal process. The characteristic by TEM, SEM, and XPS confirmed C-dots evenly anchored on the surface of BiVO₄/Bi₃TaO₇ heterojunction. The as-prepared C-dots/BiVO₄/Bi₃TaO₇ showed superior performance for the degradation of the various antibiotics under visible light illumination. When the concentration of C-dots in the composite is 3 wt.%, the photodegraded rates are obtained to be 91.7%, 89.3%, 87.1%, for tetracycline (TC), amoxicillin (AMX) and ciprofloxacin (CIP), respectively, without significant deactivation during consecutive ten recycle experiments. Furthermore, by assessing the antibiotics mixture solution of TC, AMX and CIP, it is proposed that the prepared samples are potentially effective for the wastewater effluents. A probable mechanism was reasonably proposed. The improved photocatalytic activities could be attributed to the unique construction of the C-dots mediated heterojunction, which could expedite electron migration, improve light harvesting capacity and enhance charge separation efficiency. The present investigation may provide a new perspective to design C-dots mediated heterojunction which could be a potential visible-light-driven photocatalysts for the better practical applications in remediation of broad-spectrum antibiotic residues.

Visible light active Bi3TaO7 nanosheets for water splitting

Tantalate semiconductors are potential photocatalysts for hydrogen generation via photocatalytic water splitting reaction because the conduction band of tantalates is composed of the tantalum 5d orbital, which is located at a more negative potential than that of the H+/H2 half reaction, i.e., 0.0 V vs. NHE. Bi3TaO7 is a stable tantalate under acidic or alkaline conditions, with a band gap suitable for visible light absorption. However, the photocatalytic properties of Bi3TaO7 are only reported based on the dye degradation reactions, probably due to the fast electron/hole recombination losses. 2D crystal-like nanosheets with a thickness of a few nanometers show unique features such as high carrier mobility, the quantum Hall effect, high specific surface area, and excellent electrical/thermal conductivity. 2D structures can also enhance the photocatalytic properties because photo-generated charge carriers in nanosheets are less prone to fast recombinations as compared to their bulk counterparts. In this study, nanosheets of Bi3TaO7 are produced by a liquid exfoliation method and the photocatalytic hydrogen generation reaction is investigated for both the as-synthesized Bi3TaO7 nanoparticles and Bi3TaO7 nanosheets.

Ultrafine Bi3TaO7 Nanodot-Decorated V, N Codoped TiO2 Nanoblocks for Visible-Light Photocatalytic Activity: Interfacial Effect and Mechanism Insight

Bi₃TaO₇ is a potential photocatalyst because of its high chemical stability, defective fluorite-type structure, and superior mobility of photoinduced holes. However, few studies have focused on the interfacial effects of Bi₃TaO₇-based photocatalysts. In this work, 0D Bi₃TaO₇ nanodot-hybridized 3D V and N codoped TiO₂ nanoblock (B/VNT) composites were first synthesized for the photocatalytic removal of oxytetracycline hydrochloride, 2,4,6-trichlorophenol, and tetrabromobisphenol A. The fabricated B/VNT had a photocatalytic performance superior to that of pristine components, and probable degradation pathways were proposed according to the primary intermediates identified by a gas chromatography-mass spectrometer. Interestingly, on B/VNT, the transfer of interfacial electrons was observed from V/N-TiO₂ to Bi₃TaO₇, and the formed built-in electronic field led to a direct Z-scheme structure, rather than type II, as confirmed by the generated ^•OH and ^•O₂^- radicals and band structures from the density functional theory calculation. Therefore, the strong interfacial electronic interaction on the B/VNT was significant, which drove faster photogenerated charge transfer, more visible-light adsorption, and active ^•OH and ^•O₂^- generation, thus improving the photocatalytic activity.

Ultrasound assisted synthesis of Bi2NbO5F/rectorite composite and its photocatalytic mechanism insights

Enhancing the adsorbability of the photocatalysts is an effective way to improve the photocatalytic performance. Herein, we firstly synthesized a novel Bi₂NbO₅F/rectorite (BF/R) composite photocatalyst with high adsorption capacity via the ultrasound assisted route. The X-ray photoelectron spectrometer (XPS) analysis has demonstrated that the Bi₂NbO₅F and rectorite were connected with each other by weak chemical bonds. The introduced rectorite in the composite provided rich adsorption active sites for the adsorption of rhodamine B (RhB). The catalytic activity of the BF/R catalyst was evaluated by degrading RhB (5 mg/L) under UV-light irradiation. The BF/R composite with 32% rectorite exhibited the best photocatalytic degradation efficiency for degrading RhB in aqueous solution, which was 6.6 times higher than that of the bare BF sample. The improved activity of the BF/R composite can be ascribed to its strong adsorbability and enhanced light absorption. More importantly, the BF/R catalyst still showed good stability and high activity for degrading RhB after four recycles. Lastly, a possible photocatalytic mechanism on the BF/R composite was proposed. This work would provide helpful insights into the synthesis of the clay combined with Bi-based adjustable structure materials via ultrasound method.

0D/2D Z-Scheme Heterojunctions of Bismuth Tantalate Quantum Dots/Ultrathin g-C3N4 Nanosheets for Highly Efficient Visible Light Photocatalytic Degradation of Antibiotics

Constructing 0D/2D Z-scheme photocatalysts is a great promising path to improve photocatalytic activity by  efficiently enhancing charge separation. Herein, we fabricated a visible-light-responsive Bi₃TaO₇ quantum dots (QDs)/g-C₃N₄ nanosheets (NSs) 0D/2D Z-scheme composite via a facile ultrasound method, and Bi₃TaO₇ QDs could be interspersed on the surface of g-C₃N₄ NSs uniformly. Furthermore, the strong interaction between Bi₃TaO₇ QDs and g-C₃N₄ NSs disturbed the CN heterocycles by forming C═O bonds between C atoms of the N-(C)₃ group and O atoms of the Ta-O bond. The optimum composite with 20 wt % g-C₃N₄ NSs showed the superior photocatalytic activity for degradation of ciprofloxacin (CIP) over the composites prepared by mechanical mixing and solid-state methods, the photocatalytic efficiency of which were 4 and 12.2 times higher than those of bare Bi₃TaO₇ and g-C₃N₄. Photoluminescence (PL), time-resolved transient PL decay spectra, and photocurrent together verify that the photogenerated hole-electron pairs in this 0D/2D Z-scheme composite have been effectively separated. The enhanced photocatalytic activity of as-synthesized photocatalysts could be attributed to the synergistic effect of efficient Z-scheme charge separation, highly dispersed 0D Bi₃TaO₇ nanocrystals, coordinating sites of 2D g-C₃N₄ NSs and the strong coupling between them. This study might pave the way toward designing novel visible-light-induced 0D/2D photocatalyst systems for highly efficient degradation of antibiotics.

Highly efficient visible-light-driven photocatalytic degradation of tetracycline by a Z-scheme g-C3N4/Bi3TaO7 nanocomposite photocatalyst

Highly efficient visible-light-driven photocatalytic degradation of tetracycline by a fabricated Z-scheme g-C₃N₄/Bi₃TaO₇ nanocomposite photocatalyst.

The fabrication of CdS/CoFe2O4/rGO photocatalysts to improve the photocatalytic degradation performance under visible light

A magnetic photocatalyst, CdS/CoFe₂O₄/rGO, has been successfully prepared via a simple hydrothermal method. The photocatalytic activity of the as-obtained composite photocatalyst was evaluated using the degradation of tetracycline.

Fabrication of a Ag/Bi3TaO7 Plasmonic Photocatalyst with Enhanced Photocatalytic Activity for Degradation of Tetracycline

A novel Ag/Bi3TaO7 plasmonic photocatalyst has been prepared by a simple photoreduction process. The as-prepared Ag/Bi3TaO7 photocatalyst exhibited an enhanced photocatalytic activity for the degradation of tetracycline (TC) compared to that of a bare Bi3TaO7 catalyst. The 1 wt % Ag-loaded Bi3TaO7 sample showed the highest photocatalytic efficiency for TC degradation (85.42%) compared with those of the other samples. The enhanced photocatalytic activity could be ascribed to the synergistic effect of the surface plasmon resonance caused by Ag nanoparticles. Electrochemical impedance spectroscopy demonstrated that the incorporation of silver nanoparticles onto the Bi3TaO7 surface promoted the separation of photogenerated carriers. In addition, an electron spin resonance (ESR) and trapping experiment revealed that the photoinduced active species hydroxyl radical and superoxide radical were the main active species in the photocatalytic process of TC degradation. The photocatalytic reaction mechanism was discussed by active species trapping and ESR analysis.

Controllable synthesis of InTaO4 catalysts of different morphologies using a versatile sol precursor for photocatalytic evolution of H2

For the first time, InTaO₄ photocatalysts with different morphologies and structures were facilely prepared using a versatile sol precursor.

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.

Preparation of BiXY(2-X)O3 and its Photocatalytic Degradation of Molasses Fermentation Wastewater under Visible-Light Irradiation

A series of BixY(2-x)O3photocatalysts were successfully prepared by a solid-state reaction and were subsequently characterized by powder X-ray diffraction, UV-vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy (XPS). The UV-vis diffuse reflectance spectra revealed that the BixY(2-x)O3samples absorbed light in the visible-light range (400-800 nm). The XPS results indicated that active oxygen species were generated on the Bi1.8Y0.2O3surface, which displayed a higher photocatalytic activity. When using photocatalytic degradation molasses fermentation wastewater as a model reaction, the Bi1.8Y0.2O3showed higher photocatalytic activity in comparison to Bi0.2Y1.8O3under visible-light irradiation.

Efficient degradation of tetrabromobisphenol A by heterostructured Ag/Bi5Nb3O15 material under the simulated sunlight irradiation

Heterostructured metallic silver-layered bismuth niobate two-component system (Ag/Bi(5)Nb(3)O(15)) was developed for the first time by a mild hydrothermal method combined with photodeposition. The Ag/Bi(5)Nb(3)O(15) exhibited single-crystalline orthorhombic structure with small particle size (50-200 nm) and octahedral as well as sheet-like shape; additionally, it possessed photoresponse in both UV and visible region. As a novel alternative photocatalysts to TiO(2), the photocatalytic activity of the Ag/Bi(5)Nb(3)O(15) was evaluated by the degradation of tetrabromobisphenol A, a member from the family of the brominated flame retardant, under solar simulating Xe lamp irradiation, and enhanced photocatalytic activity in compared to Bi(5)Nb(3)O(15) itself and Degussa P25 was obtained.

Single-crystalline Bi(5)O(7)NO(3) nanofibers: Hydrothermal synthesis, characterization, growth mechanism, and photocatalytic properties

A new photocatalyst, namely single-crystalline Bi(5)O(7)NO(3) nanofibers, was prepared by a facile hydrothermal method in the presence of Triton X-100 and ammonia. Bi(5)O(7)NO(3) possessing a crystalline sheet morphology could be dissolved and transformed into nanofibers by controlling the reaction time. Samples were characterized by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy. The Bi(5)O(7)NO(3) nanofiber growth mechanism is discussed in detail. The band gap energy of the as-prepared Bi(5)O(7)NO(3) photocatalyst was about 2.70-2.90eV. Results of first-principle density functional theory calculations confirmed that Bi(5)O(7)NO(3) had a narrow band gap. They revealed that the conduction band bottom was predominantly composed of Bi 6s, Bi 6p, N 2p and O 2p orbitals, while the valence band (VB) top primarily consisted of Bi 6p, Bi 6s and O 2p orbitals. The as-obtained Bi(5)O(7)NO(3) nanofibers showed good photocatalytic activity and stability for the degradation of Rhodamine B (RhB) under visible light irradiation, which may be ascribed to the highly mobile conduction band (CB) and VB charge carriers.