Shijie Li

Facile synthesis of flower-like Ag3VO4/Bi2WO6 heterojunction with enhanced visible-light photocatalytic activity

Constructing novel semiconductor heterojunctions is one of the most significant approaches to improving the photocatalytic performance of a photocatalyst. Herein, the Ag3VO4/Bi2WO6 heterojunction was prepared through in-situ anchoring Ag3VO4 nanoparticles (size: ∼21nm) on the surface of Bi2WO6 microflowers (diameter: 2.5-4.5μm) by a facile deposition route. The photocatalytic activity of these heterojunctions were studied by decomposing cationic dye rhodamine B (RhB), anionic dye methyl orange (MO) and neutral para-chlorophenol (4-CP) under visible light irradiation (λ>400nm). Among all the tested catalysts, the heterojunction with a Ag3VO4/Bi2WO6 molar ratio of 0.15/1 displays the maximum activity with the RhB degradation rate constant of up to 0.0392min-1, a 6.7 or 1.7 times more enhancement compared with the pure Bi2WO6 or Ag3VO4. It is found that the introduction of Ag3VO4 is in favor of suppressing the electron-hole pair recombination of Bi2WO6, leading to an enhanced photocatalytic activity with good stability. The photogenerated holes (h+) and superoxide radicals (O2-) play critical roles during the photocatalytic process. Ag3VO4/Bi2WO6 will have great potential in applications for environmental remediation due to the facile preparation method and superior photocatalytic activity.

Facile synthesis of Fe2O3 nanoparticles anchored on Bi2MoO6 microflowers with improved visible light photocatalytic activity

Constructing novel semiconductor heterojunctions is emerging as one of the efficient methods to develop excellent photocatalysts. Herein, we report the design and synthesis of Bi2MoO6 microflowers decorated by Fe2O3 nanoparticles as an efficient visible-light-driven photocatalyst via a simple solvothermal precipitation-calcination method. The as-prepared Fe2O3/Bi2MoO6 heterojunctions were systematically characterized by using several techniques. The photocatalytic properties of these heterojunctions were estimated by degrading rhodamine B (RhB) and para-chlorophenol (4-CP) under visible light (λ>400nm). They showed much higher photocatalytic activity than pure Fe2O3 or Bi2MoO6. The heterojunction with Fe/Bi molar ratio of 0.2 presented the highest activity. The RhB degradation rate constant was about 4.8 times or 3.8 times higher than that of Bi2MoO6 or a mechanical mixture of Fe2O3 and Bi2MoO6. The remarkable enhanced photocatalytic activity is attributed to the effective suppression of electron-hole recombination. The photogenerated holes (h+) and superoxide radical anions (O2-) were found to be the major active species. Fe2O3/Bi2MoO6 has great potential as an effective and stable visible-light-driven photocatalysts for wastewater treatment.

Understanding the effect of polypyrrole and poly(3,4-ethylenedioxythiophene) on enhancing the supercapacitor performance of NiCo2O4 electrodes

Herein, two of the most well-known conducting polymers (CP), polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), were coated onto mesoporous NiCo2O4 nanosheet arrays through an efficient and controllable electrodeposition process. We considered such a unique nanostructure to be an ideal model to accurately compare and understand the effects of PPy and PEDOT on electrochemical performances. Comparing the electrochemical performances of NiCo2O4@CP and pure NiCo2O4 electrodes, we found that the NiCo2O4@PPy electrode possesses the highest areal capacitance of 4.1 F cm−2 at 2 mA cm−2, which is significantly higher than the values obtained for the NiCo2O4@PEDOT (0.86 F cm−2) and NiCo2O4 electrodes (0.65 F cm−2). For rate capability, even at a high current density of 30 mA cm−2, an areal capacitance of 2.7 F cm−2 can be achieved for the NiCo2O4@PPy electrode. Moreover, the NiCo2O4@PPy electrode shows considerably smaller equivalent series resistance (ESR) than that of the NiCo2O4@PEDOT and NiCo2O4 electrodes. Therefore, the NiCo2O4@PPy hybrid composites are considered to be ideal supercapacitor electrode materials with enhanced electrochemical performances, which makes them suitable for many practical applications.

Ta3N5-Pt nonwoven cloth with hierarchical nanopores as efficient and easily recyclable macroscale photocatalysts.

Traditional nanosized photocatalysts usually have high photocatalytic activity but can not be efficiently recycled. Film-shaped photocatalysts on the substrates can be easily recycled, but they have low surface area and/or high production cost. To solve these problems, we report on the design and preparation of efficient and easily recyclable macroscale photocatalysts with nanostructure by using Ta3N5 as a model semiconductor. Ta3N5-Pt nonwoven cloth has been prepared by an electrospinning-calcination-nitridation-wet impregnation method, and it is composed of Ta3N5 fibers with diameter of 150–200u2005nm and hierarchical pores. Furthermore, these fibers are constructed from Ta3N5 nanoparticles with diameter of ~25u2005nm which are decorated with Pt nanoparticles with diameter of ~2.5u2005nm. Importantly, Ta3N5-Pt cloth can be used as an efficient and easily recyclable macroscale photocatalyst with wide visible-light response, for the degradation of methylene blue and parachlorophenol, probably resulting in a very promising application as “photocatalyst dam” for the polluted river.

Flower-like Bi2S3/Bi2MoO6 heterojunction superstructures with enhanced visible-light-driven photocatalytic activity

A prerequisite for the development of photocatalytic technology is to obtain efficient visible-light-driven photocatalysts. Herein, we have reported a flower-like Bi2S3/Bi2MoO6 heterojunction as a novel and efficient visible-light-driven photocatalyst. The Bi2S3/Bi2MoO6 heterojunction has been prepared by a solvothermal method. It consists of flower-like superstructures with diameters ranging from 1 to 3 μm, which are built from Bi2MoO6 nanosheets with a thickness of about 15 nm decorated with Bi2S3 nanoparticles with diameters of ∼3.5 nm. Furthermore, the photocatalytic activity of the Bi2S3/Bi2MoO6 heterojunction has been evaluated through the degradation of rhodamine B (RhB) dye and colorless parachlorophenol (4-CP) under visible-light irradiation (λ > 400 nm). The results demonstrate that the Bi2S3/Bi2MoO6 heterojunction exhibits higher photocatalytic activity in degrading RhB and 4-CP than single Bi2S3 or Bi2MoO6. More importantly, the photocatalytic activity of the Bi2S3/Bi2MoO6 heterojunction is superior to the sum of the activities of two individual photocatalysts (Bi2MoO6 and Bi2S3). The recycling experiment confirms that the Bi2S3/Bi2MoO6 heterojunction is essentially stable during the photocatalytic process. Therefore, the Bi2S3/Bi2MoO6 heterojunction can be used as an efficient and stable visible-light-driven photocatalyst for the purification of the environment.

Fe2O3–AgBr nonwoven cloth with hierarchical nanostructures as efficient and easily recyclable macroscale photocatalysts

A prerequisite for the development of photocatalytic application is to obtain efficient and easily recycled visible-light-driven (VLD) photocatalysts. Usually, nanosized photocatalysts exhibit excellent photocatalytic performances but cannot be easily recycled, and film-shaped nanostructured photocatalysts on substrates (or magnetic photocatalysts) can be easily recycled but have low surface area and/or high production cost. To solve this problem, herein we report on the design and preparation of nonwoven cloth based on semiconductor–semiconductor (Fe2O3–AgBr as the model) nanojunctions as efficient and easily recyclable macroscale photocatalysts with nanostructure. Fe2O3–AgBr nonwoven cloth has been prepared by a simple electrospinning–calcination method. Such macroscale cloth is free-standing and it consists of hierarchical pores with diameters of 600–750 nm and nanofibers with diameters of 150–350 nm. Furthermore, these nanofibers are constructed from Fe2O3 and AgBr nanoparticles with diameters of ∼60 nm. In addition, Fe2O3–AgBr nonwoven cloth has magnetic properties and a broadened visible-light photo-response range (400–750 nm). Under the irradiation of visible light, Fe2O3–AgBr nonwoven cloth exhibits higher photocatalytic activity than Fe2O3 nonwoven cloth and AgBr nonwoven cloth containing the same weight of visible-light-active component, for the degradation of rhodamine B (RhB) and parachlorophenol (4-CP). Higher photocatalytic activity of Fe2O3–AgBr nonwoven cloth should result from the synergic effects between Fe2O3 and AgBr due to the broadening photoabsorption and the energy level matching. Importantly, Fe2O3–AgBr nonwoven cloth can be easily transferred and/or recycled by the dipping/pulling method and/or external magnetic field, and it has excellent photocatalytic stability during recycling tests. Therefore, this work provides some insight into the design and development of novel, efficient and easily recyclable macroscale nonwoven cloths, for future practical photocatalytic application, for example, degrading organic pollutants in polluted rivers.

Hierarchical architectures of bismuth molybdate nanosheets onto nickel titanate nanofibers: Facile synthesis and efficient photocatalytic removal of tetracycline hydrochloride

A huge challenge in the field of pollutant removal is the scarcity of visible-light-driven (VLD) photocatalysts that are efficient, stable, easily recyclable and capable of mineralizing organic pollutants. In this regard, a novel hierarchical architecture of Bi2MoO6 nanosheets onto NiTiO3 nanofibers for tetracycline hydrochloride (TC) removal was rationally designed and fabricated via a facile approach. In this heterojunction system, highly homogeneous-distributed Bi2MoO6 nanosheets were anchored on electrospun NiTiO3 nanofibers, endowing the heterojunction with compact interfacial contact. By virtue of the favorable interfacial contact and matched band alignment, promoted suppression of photo-generated electron-hole recombination is achieved in Bi2MoO6/NiTiO3 system, as confirmed by photoluminescence measurement. As a result, the heterojunction with Bi2MoO6/NiTiO3 molar ratio of 1:1 exhibits an outstanding VLD photocatalytic activity and good stability for tetracycline hydrochloride (TC) degradation. The photodegradation rate constant (k) is 26.0, 5.4 or 3.7 folds higher than that of pristine NiTiO3, Bi2MoO6, or the mechanical mixture (20.2u202fwt% NiTiO3u202f+u202f79.8u202fwt% Bi2MoO6). The holes and superoxide radicals are detected as the dominant active species responsible for TC removal. Moreover, this work reports an efficient VLD photocatalyst for TC removal and will open up new insights into the design of novel fiber-shaped VLD heterojunction photocatalyts for environment remediation.

Construction of fiber-shaped silver oxide/tantalum nitride p-n heterojunctions as highly efficient visible-light-driven photocatalysts

Constructing novel and efficient p-n heterojunction photocatalysts has stimulated great interest. Herein, we report the design and synthesis of fiber-shaped Ag2O/Ta3N5p-n heterojunctions as a kind of efficient photocatalysts. Ta3N5 nanofibers were prepared by an electrospinning-calcination-nitridation method, and then the in-situ anchoring of Ag2O on their surfaces was realized by a facile deposition method. The resulting Ag2O/Ta3N5 heterojunctions were comprised of porous Ta3N5 nanofibers (diameter: ∼150nm) and Ag2O nanoparticles (size: ∼12nm). The photocatalytic activity of these heterojunctions were studied by decomposing rhodamine B (RhB) dye and tetracycline (TC) antibiotic under visible light (λ>400nm). In all the samples, the heterojunction with Ag2O/Ta3N5 molar ratio of 0.2/1 displays the best activity. It is found that a synergistic effect contributes to the effective suppression of charges recombination between Ta3N5 and Ag2O, leading to an enhanced photocatalytic activity with good stability. The photogenerated holes (h+) and superoxide radicals (O2-) play dominant roles in the photocatalytic process. These p-n heterojunctions will have great potential for environmental remediation because of the facile preparation process and exceptional photocatalytic activity.

Synthesis of Ta3N5/Bi2MoO6 core–shell fiber-shaped heterojunctions as efficient and easily recyclable photocatalysts

Developing efficient and easily recyclable photocatalysts has drawn much attention. Herein, we report the design and synthesis of Ta3N5/Bi2MoO6 core–shell fiber-shaped heterojunctions as a kind of efficient and easily recyclable photocatalyst. Ta3N5 nanofibers have been prepared by an electrospinning–calcination–nitridation method, and then in situ growth of Bi2MoO6 on their surfaces is realized by a solvothermal method. The resulting Ta3N5/Bi2MoO6 heterojunctions are composed of porous Ta3N5 nanofibers (diameter: ∼200 nm) whose surfaces are decorated with Bi2MoO6 nanosheets (length: 100–200 nm; thickness: ∼15 nm). They exhibit remarkably enhanced photocatalytic activities for the degradation of rhodamine B (RhB) and para-chlorophenol (4-CP) under visible light, compared with pure Bi2MoO6 or Ta3N5. In particular, the heterojunction with a Ta3N5/Bi2MoO6 molar ratio of 1/1 achieves the highest photodegradation efficiency of RhB (99.5%), which is about 1.85 times that (53.7%) of Bi2MoO6 and 1.66 times that (60.1%) of the mechanical mixture (49.8 wt% Bi2MoO6 + 50.2 wt% Ta3N5). The superior photocatalytic properties can be attributed to the efficient separation of photo-induced electron–hole pairs and the high BET surface area. The dominant active species are determined to be superoxide and the photogenerated holes. More importantly, the Ta3N5/Bi2MoO6 heterojunction can be easily recycled by simple sedimentation while maintaining good stability. This work offers more valuable insights into the design of efficient and easily recyclable photocatalysts for environmental remediation.

A novel heterostructure of BiOI nanosheets anchored onto MWCNTs with excellent visible-light photocatalytic activity

Developing efficient visible-light-driven (VLD) photocatalysts for environmental decontamination has drawn significant attention in recent years. Herein, we have reported a novel heterostructure of multiwalled carbon nanotubes (MWCNTs) coated with BiOI nanosheets as an efficient VLD photocatalyst, which was prepared via a simple solvothermal method. The morphology and structure were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and specific surface area measurements. The results showed that BiOI nanosheets were well deposited on MWCNTs. The MWCNTs/BiOI composites exhibited remarkably enhanced photocatalytic activity for the degradation of rhodamine B (RhB), methyl orange (MO), and para-chlorophenol (4-CP) under visible-light, compared with pure BiOI. When the MWCNTs content is 3 wt %, the MWCNTs/BiOI composite (3%M-Bi) achieves the highest activity, which is even higher than that of a mechanical mixture (3 wt % MWCNTs + 97 wt % BiOI). The superior photocatalytic activity is predominantly due to the strong coupling interface between MWCNTs and BiOI, which significantly promotes the efficient electron-hole separation. The photo-induced holes (h+) and superoxide radicals (O2−) mainly contribute to the photocatalytic degradation of RhB over 3%M-Bi. Therefore, the MWCNTs/BiOI composite is expected to be an efficient VLD photocatalyst for environmental purification.