Zhijie Zhang

Enhancement of visible-light photocatalysis by coupling with narrow-band-gap semiconductor: a case study on Bi2S3/Bi2WO6.

To overcome the drawback of low photocatalytic efficiency brought by electron-hole recombination and narrow photoresponse range, we designed a novel Bi(2)S(3)/Bi(2)WO(6) composite photocatalyst. The composite possesses a wide photoabsorption until 800 nm, which occupies nearly the whole range of the visible light. Compared with bare Bi(2)WO(6), the Bi(2)S(3)/Bi(2)WO(6) composite exhibits significantly enhanced photocatalytic activity for phenol degradation under visible light irradiation. On the basis of the calculated energy band positions, the mechanism of enhanced photocatalytic activity was proposed. The present study provides a new strategy to design composite materials with enhanced photocatalytic performance.

Low-temperature combustion synthesis of Bi2WO6 nanoparticles as a visible-light-driven photocatalyst.

Visible-light-induced Bi(2)WO(6) photocatalyst has been successfully synthesized via a facile low-temperature combustion synthesis method, using glycine as the fuel. The photocatalytic activities of the as-synthesized samples were evaluated by the photodegradation of rhodamine B (RhB) and phenol under visible-light irradiation (lambda>420 nm). The results showed that the molar ratio of fuel to oxidizer had an important influence on the photocatalytic activities of the products. When the molar ratio of fuel to oxidizer was 1, the photocatalyst exhibited the highest degradation efficiency, which can completely degrade RhB with a concentration up to 10(-4)M within 75 min. Besides decoloring, the markable reduction of chemical oxygen demand (COD) was also observed in the degradation of RhB, further demonstrating the photocatalytic performance of Bi(2)WO(6). Additionally, the photocatalyst showed much enhanced visible photocatalytic efficiency, up to 94.2% in 4h, than the bulk Bi(2)WO(6) powder (SSR) in the degradation of phenol.

Enhanced photocatalytic activity of Bi2WO6 with oxygen vacancies by zirconium doping

To overcome the drawback of low photocatalytic efficiency brought by electron-hole recombination, Bi(2)WO(6) photocatalysts with oxygen vacancies were synthesized by zirconium doping. The oxygen vacancies as the positive charge centers can trap the electron easily, thus inhibiting the recombination of charge carriers and prolonging the lifetime of electron. Moreover, the formation of oxygen vacancies favors the adsorption of O(2) on the semiconductor surface, thus facilitating the reduction of O(2) by the trapped electrons to generate superoxide radicals, which play a key role in the oxidation of organics. Visible-light-induced photodegradation of rhodamine B (RhB) and phenol were carried out to evaluate the photoactivity of the products. The results showed that oxygen-deficient Bi(2)WO(6) exhibited much enhanced photoactivity than the Bi(2)WO(6) photocatalyst free of oxygen deficiency. This work provided a new concept for rational design and development of high-performance photocatalysts.

Electrospun nanofibers of Bi-doped TiO2 with high photocatalytic activity under visible light irradiation.

Bi-doped TiO(2) nanofibers with different Bi content were firstly prepared by an electrospinning method. The as-prepared nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence spectra (PL), and UV-vis diffuse reflectance spectroscopy (DRS). The results indicated that Bi(3+) ions were successfully incorporated into TiO(2) and extended the absorption of TiO(2) into visible light region. The photocatalytic experiments showed that Bi-doped TiO(2) nanofibers exhibited higher activities than sole TiO(2) in the degradation of rhodamine B (RhB) and phenol under visible light irradiation (λ>420 nm), and 3% Bi:TiO(2) samples showed the highest photocatalytic activities.

Polypyrrole/Bi2WO6 composite with high charge separation efficiency and enhanced photocatalytic activity

The recombination of photogenerated electrons and holes is a crucial factor that limits the efficiency of photocatalysis and dye-sensitized solar cells. Conducting polymers are known to have high charge carrier mobility. Herein, a polypyrrole (PPy)/Bi2WO6 composite with promoted charge separation efficiency was designed by a “photocatalytic oxidative polymerization” method. The photo-degradation of a typical model pollutant, phenol, demonstrated that the PPy/Bi2WO6 composite possessed significantly enhanced photo-activity than pure Bi2WO6 under simulated sunlight irradiation. The higher photo-activity was attributed to the synergetic effect between PPy and Bi2WO6. The photogenerated holes on the valence band of Bi2WO6 could transfer to the highest occupied molecular orbital of PPy, leading to rapid photoinduced charge separation and enhancing the photocatalytic activity. This work provided a new concept for rational design and development of highly efficient polymer-semiconductor photocatalysts for environmental purification under simulated sunlight.

Polythiophene/Bi2MoO6: A novel conjugated polymer/nanocrystal hybrid composite for photocatalysis

Polythiophene (PT)/Bi2MoO6 nanocomposites were synthesized by an in situ chemical oxidative polymerization method. The photo-degradation of a typical model pollutant, rhodamine B (RhB) under visible-light irradiation (λxa0>xa0420xa0nm), demonstrated that the PT/Bi2MoO6 composite showed higher photocatalytic activity than bare Bi2MoO6. The good performance of the PT/Bi2MoO6 composite could be attributed to the high separation efficiency of the photo-generated charge carriers contributed by the synergic effect between PT and Bi2MoO6, as well as the high charge transfer rate due to the hole transporting ability of PT. The results may provide some insights into the design and development of other effective polymer-semiconductor photocatalysts for pollutant degradation under sunlight irradiation.

Enhancing the charge separation and migration efficiency of Bi2WO6 by hybridizing the P3HT conducting polymer

In order to improve the charge separation and migration efficiency, a conducting polymer, poly(3-hexylthiophene) (P3HT), was introduced into a Bi2WO6 photocatalyst. The hall mobility of the P3HT/Bi2WO6 composite and bare Bi2WO6 were 4.7197 × 102 cm2 V−1 s−1 and 3.0159 × 102 cm2 V−1 s−1, respectively, indicating the high charge transfer ability of the P3HT/Bi2WO6 composite. The photo-degradation of a model pollutant, rhodamine B (RhB) under simulated solar light irradiation, demonstrated that the P3HT/Bi2WO6 composite showed more enhanced photocatalytic activity than bare Bi2WO6. The excellent photocatalytic performance of the P3HT/Bi2WO6 composite could be ascribed to the internal electric field formed between n-type Bi2WO6 and p-type P3HT, which facilitates the separation of photo-generated electron–hole pairs, as well as the high charge carrier mobility of P3HT, which can transport the photo-generated holes to the surface of the semiconductor quickly to participate in the oxidation of pollutants.

Carbon Quantum Dots/Bi2WO6 Composites for Efficient Photocatalytic Pollutant Degradation and Hydrogen Evolution

In this study, we report the facile fabrication of carbon quantum dots (CQDs)/Bi2WO6 nanocomposites, as well as their effective photocatalytic activity for the photodegradation of organic pollutants and hydrogen production. The observed results here revealed that CQDs/Bi2WO6 composites possessed much higher photocatalytic activity in the degradation of both rhodamine B and phenol under simulated solar light after optimizing the hybridization with CQDs, which was attributed to the excellent up-converted photoluminescence, photo-induced electron transfer and electron reservoir properties of CQDs. Significantly different from pure Bi2WO6, the CQDs/Bi2WO6 composites also displayed excellent photocatalytic H2 production activity, which can be ascribed to the suitable conduction band edge and sufficient reduction ability of CQDs.