Fabrication of Graphene Quantum Dots Modified BiOI/PAN Flexible Fiber with Enhanced Photocatalytic Activity

Abstract

In environment remediation, photocatalytic oxidation is a promising technique for removing organic pollutants. Compared to adsorption, biodegradation, and chemical oxidation, photocatalytic oxidation can eliminate organic pollutants completely, conveniently, and cheaply in an environmentally friendly manner. Visible-light-driven photocatalytic oxidation is particularly advisable because of the high proportion of visible light energy in solar energy. Bismuth oxyiodide (BiOI) is a promising visible-light-driven photocatalyst for the oxidization of pollutants, not only because of its narrow band gap, but also for its relatively low valence band (VB), which is adequate for photogenerated holes to oxidize a variety of organic compounds. However, the shortcomings of BiOI powder, such the difficulty of recycling it, its low surface area, and fast carrier recombination, limit its practical applications. Meanwhile, the flexibility and hierarchical structure of photocatalysts are particularly advisable because these properties are beneficial for the convenient operation, recycling, and performance improvement of these materials. Herein, based on an electro-spun polyacrylonitrile (PAN) nanofiber substrate, a hierarchical BiOI/PAN fiber was prepared through an in situ reaction. In the as-prepared BiOI/PAN fibers, BiOI flakes were aligned vertically and uniformly around the PAN fibers. BiOI nuclei generated from preintroduced Bi(III) in the PAN fiber act as seeds for the growth of BiOI nanoplates, which is crucial for the formation of a hierarchical structure. Such a hierarchical structure can improve both the light absorption and carrier generation of the BiOI/PAN fibers, as demonstrated by UV-Vis diffuse reflectance spectra and photoluminescence emission. Therefore, the BiOI/PAN fibers exhibited higher photocatalytic activity than BiOI powder. When the BiOI/PAN fibers were decorated with pre-prepared graphene quantum dots (GQDs), a GQD-modified BiOI/PAN fibrous composite (GQD-BiOI/PAN) was fabricated. The morphology of the obtained GQD-BiOI/PAN fibers was nearly the same as that of the BiOI/PAN fibers. A step-scheme (S-scheme) heterojunction was formed between the GQDs and BiOI, which was confirmed by the fabrication method, photoluminescence emission, reactive radical tests, and XPS analysis. This kind of S-scheme heterojunction can not only effectively suppress the recombination of photogenerated holes, but can also reserve the more reductive electrons on the lowest unoccupied molecular orbital of GQDs and the more oxidative holes on the VB of BiOI, for the photocatalytic degradation of phenol. Because of the fibrous hierarchical structure and S-scheme heterojunction, GQD-BiOI/PAN outperformed BiOI nanoparticles and BiOI/PAN nanofibers in the photocatalytic oxidation of phenol under visible light. In addition, because of tight bonding, GQD-BiOI/PAN can be tailored and operated by hand, which is convenient for recycling. During recycling, no obvious loss of sample or decrease in photocatalytic activity was observed. This w...

Emerging S‐Scheme Photocatalyst

“…[52] And natural self-degradation of these massive pollutants is slow and time-consuming. [53] Thus, it is urgent to find a convenient and efficient method to remove these toxic pollutants. Traditional treatment processes may not be suitable for some common pollutants.…”

Novel Z‐scheme 2D/2D Bi4O5Br2/BiOCl heterojunction with enhanced photocatalytic activity for RhB degradation

“…Correspondingly, it suggested that the BiOCl in BC2 possessed denser electron cloud. Obviously, partial electrons of Bi 4 O 5 Br 2 transferred to BiOCl after contact, implying formation of internal electric field between their surfaces 41,42,46,47 . In view of the large contact area, this internal electric field may be well dispersed in the large interface and play a significant role in further improvement of photoinduced carrier transfer.…”

Visible-Light-Driven Zr-MOF/BiOBr Heterojunction for the Efficient Synchronous Removal of Hexavalent Chromium and Rhodamine B from Wastewater

“… 40 − 42 As a kind of semiconductor, bismuth oxyhalides (BiOX, X = halogens) belong to the tetragonal crystal system with layered structures composed of X – and [Bi 2 O 2 ] 2+ layers. 43 , 44 Different electric densities between layers lead to orbital polarization, which in turn produces a self-built electric field and further promotes the separation of photoinduced carriers. 45 Among these compounds, BiOBr has attracted extensive interest for its visible-light catalytic activity.…”