Characterization and photocatalytic activity of Bi 3 TaO 7 prepared by hydrothermal method

Fe3O4 quantum dots mediated P-g-C3N4/BiOI as an efficient and recyclable Z-scheme photo-Fenton catalyst for tetracycline degradation and bacterial inactivation

Photo-Fenton technology integrated by photocatalysis and Fenton reaction is a favorable strategy for water remediation. Nevertheless, the development of visible-light-assisted efficient and recyclable photo-Fenton catalysts still faces challenges. This study successfully constructed a novel separable Z-scheme P-g-C₃N₄/Fe₃O₄QDs/BiOI (PCN/FOQDs/BOI) heterojunction via in-situ deposition method. The results showed that the photo-Fenton degradation efficiency for tetracycline over optimal ternary catalyst reached 96.5% within 40 min at visible illumination, which was 7.1 and 9.6 times higher than its single photocatalysis and Fenton system, respectively. Moreover, PCN/FOQDs/BOI possessed excellent photo-Fenton antibacterial activity, which could completely inactivate 10⁸ CFU·mL^-1 of E. coli and S. aureus within 20 and 40 min, respectively. Theoretical calculation and in-situ characterization revealed that the enhanced catalysis behavior resulted from the FOQDs mediated Z-scheme electronic system, which not only facilitated photocreated carrier separation of PCN and BOI while maintaining maximum redox capacity, but also accelerated H₂O₂ activation and Fe³⁺/Fe²⁺ cycle, thus synergistically forming more active species in system. Additionally, PCN/FOQDs/BOI/Vis/H₂O₂ system displayed extensive adaptability at pH range of 3-11, removal universality for various organic pollutants and attractive magnetic separation property. This work would provide an inspiration for design of efficient and multifunctional Z-scheme photo-Fenton catalyst in water purification.

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.

Addition of MnO2 in synthesis of nano-rod erdite promoted tetracycline adsorption

Erdite is a rare sulphide mineral found in mafic and alkaline rocks. Only weakly crystallised fibrous erdite has been artificially synthesised via evaporation or the hydrothermal method, and the process generally requires 1–3 days and large amounts of energy to complete. In this study, well-crystallised erdite nanorods were produced within 3 h by using MnO₂ as an auxiliary reagent in a one-step hydrothermal method. Results showed that erdite could synthesised in nanorod form with a diameter of approximately 200 nm and lengths of 0.5–3 μm by adding MnO₂; moreover, the crystals grew with increasing MnO₂ addition. Without MnO₂, erdite particles were generated in irregular form. The capacity of the erdite nanorods for tetracycline (TC) adsorption was 2613.3 mg/g, which is higher than those of irregular erdite and other reported adsorbents. The major adsorption mechanism of the crystals involves a coordinating reaction between the −NH₂ group of TC and the hydroxyl group of Fe oxyhydroxide produced from erdite hydrolysis. To the best of our knowledge, this study is the first to synthesise erdite nanorods and use them in TC adsorption. Erdite nanorods may be developed as a new material in the treatment of TC-containing wastewater.

Synthesis of Bi3TaO7–Bi4TaO8Br composites in ambient air and their high photocatalytic activity upon metal loading

Cocatalyst loading on ambient-air synthesized Bi₃TaO₇–Bi₄TaO₈X (X = Cl, Br) composites for highly suppressed exciton recombination and efficient solar light harvesting.

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.