Visible light β-Bi2O3/BiOCl heterojunction photocatalyst with highly enhanced photocatalytic activity

Structure-phase transformation of bismuth oxide to BiOCl/Bi24O31Cl10 shoulder-by-shoulder heterojunctions for efficient photocatalytic removal of antibiotic

Developing heterojunction photocatalyst with well-matched interfaces and multiple charge transfer paths is vital to boost carrier separation efficiency for photocatalytic antibiotics removal, but still remains a great challenge. In present work, a new strategy of chloride anion intercalation in Bi2O3 via one-pot hydrothermal process is proposed. The as-prepared Ta-BiOCl/Bi24O31Cl10 (TBB) heterojunctions are featured with Ta-Bi24O31Cl10 and Ta-BiOCl lined shoulder-by-shouleder via semi-coherent interfaces. In this TBB heterojunctions, the well-matched semi-coherent interfaces and shoulder-by-shoulder structures provide fast electron transfer and multiple transfer paths, respectively, leading to enhanced visible light response and improved photogenerated charge separation. Meanwhile, a type-II heterojunction for photocharge separation has been obtained, in which photogenerated electrons are drove from the CB (conduction band) of Ta-Bi24O31Cl10 to the both of bilateral empty CB of Ta-BiOCl and gathered on the CB of Ta-BiOCl, while the photogenerated holes are left on the VB (valence band) of Ta-Bi24O31Cl10, effectively hindering the recombination of photogenerated electron-hole pairs. Furthermore, the separated electrons can effectively activate dissolved oxygen for the generation of reactive oxygen species (·O2-). Such TBB heterojunctions exhibit remarkably superior photocatalytic degradation activity for tetracycline hydrochloride (TCH) solution to Bi2O3, Ta-BiOCl and Ta-Bi24O31Cl10. This work not only proposes a Ta-BiOCl/Bi24O31Cl10 shoulder-by-shoulder micro-ribbon architectures with semi-coherent interfaces and successive type-II heterojunction for highly efficient photocatalytic activity, but offers a new insight into the design of highly efficient heterojunction through phase-structure synergistic transformation strategy.

Non-radical activation of persulfate with Bi2O3/BiO1.3I0.4 for efficient degradation of propranolol under visible light

Non-radical activation of persulfate (PS) by photocatalysts is an effective approach for removing organic pollutants from aqueous environments. In this study, a novel Bi2O3/BiO1.3I0.4 heterojunction was synthesized using a facile solvothermal approach and used for the first time for non-radical activation of PS to degrade propranolol (PRO) in the presence of visible light. The findings found that the degradation rate of PRO in the Bi2O3/BiO1.3I0.4/PS system was significantly increased from 19% to more than 90% within 90 min compared to the Bi2O3/BiO1.3I0.4 system. This indicated that the composite system exerted an excellent synergistic effect between the photocatalyst and the persulfate-based oxygenation. Quenching tests and electron paramagnetic resonance demonstrated that the non-radical pathway with singlet oxygen as the active species played a major role in the photocatalytic process. The existence of photo-generated holes during the reaction could also be directly involved in the oxidation of pollutants. Meanwhile, a possible PRO degradation pathway was also proposed. Furthermore, the impacts of pH, humic acid and common anions on the PRO degradation by the Bi2O3/BiO1.3I0.4/PS were explored, and the system's stability and reusability were also studied. This study exhibits a highly productive catalyst for PS activation via a non-radical pathway and provides a new idea for the degradation of PRO.

Study on the Preparation and PEC-Type Photodetection Performance of β-Bi2O3 Thin Films

Bismuth-based compounds have been regarded as a kind of promising material due to their narrow bandgap, high carrier mobility, low toxicity, and strong oxidation ability, showing potential applications in the field of photoelectrochemical (PEC) activities. They can be applied in sustainable energy production, seawater desalination and treatment, optical detection and communication, and other fields. As a member of the broader family of bismuth-based materials, β-Bi2O3 exhibits significant advantages for applications in engineering, including high photoelectric response, stability in harsh environments, and excellent corrosion resistance. This paper presents the synthesis of β-Bi2O3 thin films utilizing the mist chemical vapor deposition (CVD) method at the optimal temperature of 400 °C. Based on the β-Bi2O3 thin film synthesized at optimal temperature, a PEC-type photodetector was constructed with the highest responsivity R of 2.84 mA/W and detectivity D of 6.01 × 1010 Jones, respectively. The photodetection performance was investigated from various points like illumination light wavelength, power density, and long-term stability. This study would broaden the horizontal and practical applications of β-Bi2O3.

In situ synthesis of a Bi2O3 quantum dot decorated BiOCl heterojunction with superior photocatalytic capability for organic dye and antibiotic removal

As a decoration method, coupling a photocatalyst with semiconductor quantum dots has been proven to be an efficient strategy for enhanced photocatalytic performance. Herein, a novel BiOCl nanosheet decorated with Bi₂O₃ quantum dots (QDs) was first synthesized by a facile one-step in situ chemical deposition method at room temperature. The as-prepared materials were characterized by multiple means of analysis. The Bi₂O₃QDs with an average diameter of about 8.0 nm were uniformly embedded on the surface of BiOCl nanosheets. The obtained Bi₂O₃QDs/BiOCl exhibited significantly enhanced photocatalytic performance on the degradation of the rhodamine B and ciprofloxacin, which could be attributed to the band alignment, the photosensitization effect and the strong coupling between Bi₂O₃ and BiOCl. In addition, the dye photosensitization effect was demonstrated by the monochromatic photodegradation experiments. The radical trapping experiments and the ESR testing demonstrated the type II charge transfer route of the heterojunction. Finally, a reasonable photocatalytic mechanism based on the relative band positions was discussed to illustrate the photoreaction process. These findings provide a good choice for the design and potential application of BiOCl-based photocatalysts in water remediation.

Ternary Polyaniline@Bi2O3-BiOCl Nanocomposites as Innovative Highly Active Photocatalysts for the Removal of the Dye under Solar Light Irradiation

Ternary PANI@Bi₂O₃-BiOCl nanocomposites were successfully synthesized during the oxidative polymerization of aniline monomer in the presence of Bi₂O₃. PANI@Bi₂O₃-BiOCl nanocomposites were characterized by several analytical techniques, including X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), N₂ physisorption, UV-Vis Diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The effective PANI-semiconductor interaction promotes the fast separation and transfer of photogenerated electrons and holes, enhancing the photocatalytic efficiency of the materials towards methylene blue (MB) degradation under solar light irradiation. The best results were obtained by 0.5%PANI@Bi₂O₃-BiOCl, leading to 80% MB degradation in 2 h, four times higher than pristine Bi₂O₃-BiOCl. Moreover, 0.5%PANI@Bi₂O₃-BiOCl maintained stable photocatalytic performances for four cycles without significant activity loss. Various scavengers (isopropyl alcohol, formic acid, and benzoquinone) were used to identify the active species by trapping holes and radicals generated during the photocatalytic degradation process. Finally, a probable photocatalytic mechanism of PANI@Bi₂O₃-BiOCl photocatalyst was suggested.

Facile Synthesis of Nano-Flower β-Bi2O3/TiO2 Heterojunction as Photocatalyst for Degradation RhB

Photocatalysis is a hopeful technology to solve various environmental problems, but it is still a technical task to produce large-scale photocatalysts in a simple and sustainable way. Here, nano-flower β-Bi₂O₃/TiO₂ composites were prepared via a facile solvothermal method, and the photocatalytic performances of β-Bi₂O₃/TiO₂ composites with different Bi/Ti molar ratios were studied. The nano-flower Bi₂O₃/TiO₂ composites were studied by SEM, XRD, XPS, BET, and PL. The PL result proved that the construction of staggered heterojunction enhanced the separation efficiency of carriers. The degradation RhB was applied to study the photocatalytic performances of prepared materials. The results showed that the degradation efficiency of RhB increased from 61.2% to 99.6% when the molar ratio of Bi/Ti was 2.1%. It is a mesoporous approach to enhance photocatalytic properties by forming heterojunction in Bi₂O₃/TiO₂ composites, which increases the separation efficiency of the generated carriers and improves photocatalytic properties. The photoactivity of the Bi₂O₃/TiO₂ has no evident changes after the fifth recovery, indicating that the Bi₂O₃/TiO₂ composite has distinguished stability.

Calcination-Induced Oxygen Vacancies Enhancing the Photocatalytic Performance of a Recycled Bi2O3/BiOCl Heterojunction Nanosheet

With the rapid development of industry, bismuth-based semiconductors have been widely used for the photocatalytic degradation of organic contaminants discharged into wastewater. Herein, a Bi₂O₃/BiOCl (BBOC) heterojunction was constructed with high photocatalytic activity toward Rhodamine B (RhB) in the first cycle of the photocatalysis test, while the photocatalytic performance was drastically reduced after repeated testing. The adsorbed RhB molecules occupying the facial active sites of BBOC contributed to the decline of photocatalytic activity. The spent BBOC can be reactivated by the decomposition of the adsorbed RhB and the introduction of oxygen vacancies during calcination under an air atmosphere. The BBOC thus recovered exhibited a superior apparent rate constant of 0.08087 min^-1 compared with 0.05228 min^-1 of pristine BBOC. This study provided an effective strategy to investigate the deactivation/activation mechanism of bismuth-based heterojunction photocatalysts.

In-situ fabrication of 3D hierarchical flower-like β-Bi2O3@CoO Z-scheme heterojunction for visible-driven simultaneous degradation of multi-pollutants

Development of an efficient heterojunction catalyst with a superior visible-light driven activity is regarded as a promising strategy to decontaminate organic wastewater. Herein, a novel direct Z-scheme β-Bi₂O₃@CoO heterojunction was well designed and successfully fabricated by in situ incorporating the two energy band-matched semiconductors. The obtained β-Bi₂O₃@CoO hybrid presented a unique 3D hierarchical structure with a mass of open channels and mesoporous, which afforded not only rapid mass transfer of targets but also good light-harvesting in view of the multiple reflections. Compared to the pristine β-Bi₂O₃ and CoO, the β-Bi₂O₃@CoO hybrid exhibited remarkably improved photocatalytic activity towards the simultaneous degradation of chlorotetracycline (CTC), tetracycline hydrochloride (TCH), oxytetracycline (OTC) and nitrobenzene (NB) under visible-light irradiation. The possible intermediates and degradation pathways were also tracked by mass spectra (MS) analysis. Moreover, a direct Z-scheme charge transfer mechanism in the intimate contact interface between β-Bi₂O₃ and CoO was verified for the improved catalytic activity, endowing the effective separation/transportation of the photo-excited charge carriers and maintenance of the strong redox ability in β-Bi₂O₃@CoO heterojunction. The present work affords a simple approach to design and construct 3D hierarchical direct Z-scheme photocatalysts with promising applications in water environment remediation.

Promoted Photocharge Separation in 2D Lateral Epitaxial Heterostructure for Visible-Light-Driven CO2 Photoreduction

Photocarrier recombination remains a big barrier for the improvement of solar energy conversion efficiency. For 2D materials, construction of heterostructures represents an efficient strategy to promote photoexcited carrier separation via an internal electric field at the heterointerface. However, due to the difficulty in seeking two components with suitable crystal lattice mismatch, most of the current 2D heterostructures are vertical heterostructures and the exploration of 2D lateral heterostructures is scarce and limited. Here, lateral epitaxial heterostructures of BiOCl @ Bi₂ O₃ at the atomic level are fabricated via sonicating-assisted etching of Cl in BiOCl. This unique lateral heterostructure expedites photoexcited charge separation and transportation through the internal electric field induced by chemical bonding at the lateral interface. As a result, the lateral BiOCl @ Bi₂ O₃ heterostructure demonstrates superior CO₂ photoreduction properties with a CO yield rate of about 30 µmol g^-1 h^-1 under visible light illumination. The strategy to fabricate lateral epitaxial heterostructures in this work is expected to provide inspiration for preparing other 2D lateral heterostructures used in optoelectronic devices, energy conversion, and storage fields.

Coverage Layer Phase Composition-Dependent Photoactivity of One-Dimensional TiO2-Bi2O3 Composites

TiO₂–Bi₂O₃ composite rods were synthesized by combining hydrothermal growth of rutile TiO₂ rod templates and sputtering deposition of Bi₂O₃ thin films. The TiO₂–Bi₂O₃ composite rods with β-Bi₂O₃ phase and α/β-Bi₂O₃ dual-phase decoration layers were designed, respectively, via in situ radio-frequency magnetron sputtering growth and post-annealing procedures in ambient air. The crystal structure, surface morphology, and photo-absorption performances of the pristine TiO₂ rods decorated with various Bi₂O₃ phases were investigated. The crystal structure analysis reveals that the crystalline TiO₂–Bi₂O₃ rods contained β-Bi₂O₃ and α/β-Bi₂O₃ crystallites were separately formed on the TiO₂ rod templates with different synthesis approaches. The morphology analysis demonstrates that the β-Bi₂O₃ coverage layer on the crystalline rutile TiO₂ rods showed flat layer morphology; however, the surface morphology of the α/β-Bi₂O₃ dual-phase coverage layer on the TiO₂ rods exhibited a sheet-like feature. The results of photocatalytic decomposition towards methyl orange dyes show that the substantially improved photoactivity of the rutile TiO₂ rods was achieved by decorating a thin sheet-like α/β-Bi₂O₃ coverage layer. The effectively photoinduced charge separation efficiency in the stepped energy band configuration in the composite rods made from the TiO₂ and α/β-Bi₂O₃ explained their markedly improved photoactivity. The TiO₂-α/β-Bi₂O₃ composite rods are promising for use as photocatalysts and photoelectrodes.

Preparation of Hollow Flower-Like Microspherical β-Bi2O3/BiOCl Heterojunction and High Photocatalytic Property for Tetracycline Hydrochloride Degradation

Tetracycline cannot be effectively degraded in wastewater treatment. Therefore, the development of excellent photocatalysts is of significant importance for environmental protection. In this study, a β-Bi₂O₃/BiOCl heterojunction photocatalyst with hollow flower-like microspheres was successfully synthesized by the in-situ reaction of HCl and β-Bi₂O₃ hollow spheres. The prepared samples are characterized by Scanning electron microscopy, Transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N₂ physical adsorption, UV-vis diffuse reflectance spectroscopy, and Photoluminescence. Then, research on the photocatalytic performance for the degradation of tetracycline hydrochloride was conducted. The results show that the photocatalytic performance of the β-Bi₂O₃/BiOCl composite is significantly better than the β-Bi₂O₃ and BiOCl. The increase in photocatalytic activity is due to the formation of a heterojunction between β-Bi₂O₃ and BiOCl, which effectively promotes the separation of photogenerated electron-hole pairs. Additionally, the heterojunction nanocomposite demonstrated the outstanding photocatalytic stability after five cycles, which indicates that the material can be used for water environment purification. This paper provides assistance for studying the photocatalytic mechanism of heterojunction photocatalytic materials.