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.

g-C3N4/ZnCdS heterojunction for efficient visible light-driven photocatalytic hydrogen production

To suppress the aggregation behavior caused by the high surface energy of quantum dots (QDs), ZnCdS QDs were grown in situ on a g-C₃N₄ support. During the growth process, the QDs tightly adhered to the support surface. The ZnCdS QDs were prepared by low-temperature sulfurization and cation exchange with a zeolitic imidazolate framework precursor under mild conditions. The heterojunction of g-C₃N₄/ZnCdS-2 (CN/ZCS-2, with a g-C₃N₄ to ZIF-8 ratio of 2.0) not only showed excellent optical absorption performance, abundant reactive sites, and a close contact interface but also effectively separated the photogenerated electrons and holes, which greatly improved its photocatalytic hydrogen production performance. Under visible light irradiation (wavelength > 420 nm) without a noble metal cocatalyst, the hydrogen evolution rate of the CN/ZCS-2 heterojunction reached 1467.23 μmol g⁻¹ h⁻¹, and the durability and chemical stability were extraordinarily high.

The zeolitic imidazolate framework-8 (ZIF-8) is used as a precursor to prepare ZnCdS/C₃N₄ heterojunctions to achieve visible light-driven water splitting hydrogen production effectively.

An Fe-doped ZnO/BiVO4 heterostructure-based large area, flexible, high-performance broadband photodetector with an ultrahigh quantum yield

Pristine ZnO has been widely explored for its use in UV photodetectors; however, the utility of ZnO in broadband photodetectors is still a challenge as it absorbs in the UV region only with low quantum efficiency and responsivity that can be accredited to the high recombination rate of photo-generated charge carriers. To address this issue, we report an Fe-doped 2D ZnO thin film, obtained through band gap engineering, and a 1D electrospun mixed-inorganic monoclinic BiVO₄ nanofiber heterostructure on an ITO-coated PET substrate-based broadband photodetector (PD) with ultra-high responsivity and EQE values in comparison to PDs fabricated using expensive cleanroom techniques. BiVO₄ plays the dual role of absorbing photons in the visible and NIR regions and creating local electric fields at the interface of the Fe-doped ZnO (FZO)-BiVO₄ heterostructure, which helps in the separation of electron-hole pairs. The robustness of the flexible PD was further examined under the conditions of repeated bending cycles (up to 500), yielding a stable response. The responsivity values obtained for UV, visible and NIR irradiation are 7.35 A W^-1, 3.8 A W^-1 and 0.18 A W^-1 with very high EQE values of 2501.7%, 851.2% and 28.3%, respectively. The facile and cost-effective fabrication of the device with high performance provides a new approach for developing flexible electronics and high-performance optoelectronic devices.

In situ synthesis of C-doped BiVO4 with natural leaf as a template under different calcination temperatures

In this work, a series of C-doped BiVO₄ (BiVO₄-T) with natural leaf structures were synthesized by a dipping-calcination method with the leaf of Chongyang wood seedling as a template under different calcination temperatures. The structures and morphologies of BiVO₄-T were observed by FE-SEM observations. The doped carbon in BiVO₄-T was formed in situ from the natural leaf during the calcination process and the amount of doping could be regulated from 0.51–1.16 wt% by controlling the calcination temperature. It was found that the sample calcined at 600 °C (BiVO₄-600) with a C-doping content of 1.16 wt% showed the best photocatalytic degradation activity. After 120 min visible light irradiation, the photocatalytic decomposition efficiency of RhB for BiVO₄-600 is 2.2 times higher than that of no template BiVO₄. The enhanced photocatalytic performance is ascribed to the combined action of the unique morphology and doped-carbon. It is considered that the unique structures and carbon doping of BiVO₄-600 are in favor of the enhancement of visible light absorption, which was supported by UV-vis DRS. Furthermore, the C-doping can enhance the efficient separation and transfer of the photo-generated electron–hole pairs, as proved by PL measurements. This study provides a simple dipping-calcination method and found the best calcination temperature to fabricate a high-performance BiVO₄, which simultaneously achieves morphology and C-doping control in one step.

A series of C-doped BiVO₄ with natural leaf as a template were synthesized under different calcination temperatures by the dipping-calcination method, which simultaneously achieves morphology and C-doping control in one step.

Construction of an artificial inorganic leaf CdS–BiVO4 Z-scheme and its enhancement activities for pollutant degradation and hydrogen evolution

An artificial inorganic leaf CdS–BiVO₄ micro-nano Z-scheme photocatalytic system was synthesized by the BT–DC–SILAR method taking a leaf as a template.

Review on nanoscale Bi-based photocatalysts

Nanoscale Bi-based photocatalysts are promising candidates for visible-light-driven photocatalytic environmental remediation and energy conversion. However, the performance of bulk bismuthal semiconductors is unsatisfactory. Increasing efforts have been focused on enhancing the performance of this photocatalyst family. Many studies have reported on component adjustment, morphology control, heterojunction construction, and surface modification. Herein, recent topics in these fields, including doping, changing stoichiometry, solid solutions, ultrathin nanosheets, hierarchical and hollow architectures, conventional heterojunctions, direct Z-scheme junctions, and surface modification of conductive materials and semiconductors, are reviewed. The progress in the enhancement mechanism involving light absorption, band structure tailoring, and separation and utilization of excited carriers, is also introduced. The challenges and tendencies in the studies of nanoscale Bi-based photocatalysts are discussed and summarized.

Quantum dot-decorated semiconductor micro- and nanoparticles: A review of their synthesis, characterization and application in photocatalysis

Quantum dot (QD)-decorated semiconductor micro- and nanoparticles are a new class of functional nanomaterials that have attracted considerable interest for their unique structural, optical and electronic properties that result from the large surface-to-volume ratio and the quantum confinement effect. In addition, because of QDs' excellent light-harvesting capacity, unique photoinduced electron transfer, and up-conversion behaviour, semiconductor nanoparticles decorated with quantum dots have been used widely in photocatalytic applications for the degradation of organic pollutants in both the gas and aqueous phases. This review is a comprehensive overview of the recent progress in synthesis methods for quantum dots and quantum dot-decorated semiconductor composites with an emphasis on their composition, morphology and optical behaviour. Furthermore, various approaches used for the preparation of QD-based composites are discussed in detail with respect to visible and UV light-induced photoactivity. Finally, an outlook on future development is proposed with the goal of overcoming challenges and stimulating further research into this promising field.

Construction of the Bi2WO6/Bi4V2O11 heterojunction for highly efficient visible-light-driven photocatalytic reduction of Cr(vi)

Bi₂WO₆/Bi₄V₂O₁₁ heterojunctions constructed by anchoring Bi₄V₂O₁₁ nanocrystals onto Bi₂WO₆ nanoflakes exhibit excellent photocatalytic Cr(vi) reduction activity and cycling stability under visible light irradiation.

Oxygen-Induced Bi5+-Self-Doped Bi4V2O11 with a p-n Homojunction Toward Promoting the Photocatalytic Performance

Bi⁵⁺-self-doped Bi₄V₂O₁₁ (Bi⁵⁺-BVO) nanotubes with p-n homojunctions are fabricated via an oxygen-induced strategy. Calcinating the as-spun fibers with abundant oxygen plays a pivotal role in achieving Bi⁵⁺ self-doping. Density functional theory calculations and experimental results indicate that Bi⁵⁺ self-doping can narrow the band gap of Bi₄V₂O₁₁, which contributes to enhancing light harvesting. Moreover, Bi⁵⁺ self-doping endows Bi₄V₂O₁₁ with n- and p-type semiconductor characteristics simultaneously, resulting in the construction of p-n homojunctions for retarding rapid electron-hole recombination. Benefiting from these favorable properties, Bi⁵⁺-BVO exhibits a superior photocatalytic performance in contrast to that of pristine Bi₄V₂O₁₁. Furthermore, this is the first report describing the achievement of p-n homojunctions through self-doping, which gives full play to the advantages of self-doping.