Photocatalytic Activity Of Bi2O3 Research Articles

Crystal phase transition of β-Bi2O3 and its enhanced photocatalytic activities for tetracycline hydrochloride

The crystal phase has an important effect on the photocatalytic activity of Bi2O3. However, due to the high recombination of photo-induced charge carriers in single crystal phase Bi2O3, the photocatalytic activity was still unsatisfied. Herein, we prepared a novel α/β-Bi2O3 hetero-phase junction (xB) by a simple solvothermal-calcination method, the photocatalyst was well characterized by XRD, SEM, TEM, UV–vis DRS, XPS, photoelectrochemical technology, etc. The characterizations indicated that the crystal phase of Bi2O3 gradually transformed from β phase to α phase as the calcination temperature increased, and the Bi2O3 of different crystal phases were in close contact with a clear interface. With the optimum calcination temperature at 400 ℃, 400B sample showed the highest photocatalytic activity for tetracycline hydrochloride (TC-HCl) degradation, 91.4% removal within 120 min, the kinetic rate (0.0188 min−1) was 3.2 and 3.1 times higher than that of β-Bi2O3 (0.0058 min−1) and α-Bi2O3 (0.0061 min−1), respectively. This work provides an ideal strategy to synthesize hetero-phase junction photocatalysts with the crystal phase transition of semiconductors.

Enhanced luminescence and photocatalytic activity of Bi2O3:Ho3+ needles

Abstract A series of Bi2O3:Ho3+ (0.2–5 mol% Ho) phosphors with a crystalline monoclinic phase was synthesized using a co-precipitation route. The particle morphology and size were determined using a field emission scanning electron microscope (FESEM). The FESEM showed that the synthesized material consisted of needle-like particles. The oxidation state of the Bi as well as oxygen vacancies were investigated using X-ray photoelectron spectroscopy. It was found that Bi3+ was the dominant oxidation state in the samples, although Bi2+ was also detected. The doped Bi2O3 revealed a decrease in bandgap with an increase in Ho3+ concentration. The photoluminescence (PL) revealed that Ho3+ was the emitting centre in the samples. The 5F4/5S2→5I8 transition was responsible for the most intense emission in the visible region, whereas the near infrared emissions resulted from the 5S2→5I6, 5I6→5I8 and 5S2→5I5 transitions. A superior catalytic activity and a high PL intensity were observed due to the presence of a higher number of oxygen vacancies and defects. The 4 mol% Ho3+ doped sample was found to have the optimum doping concentration for both the PL intensity and photocatalysis activity. The results revealed that Bi2O3:Ho3+ can be potentially used for solid state displays as well as a photocatalyst under UV–visible light exposure.

Synthesis, characterization, and visible-light-induced photocatalytic activity of powdered semiconductor oxides of bismuth and zinc toward degradation of Alizarin Red S.

Semiconductor oxides of bismuth and zinc have been synthesized using modified sol-gel method and sol-combustion method, respectively. The synthesized catalysts were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy. The photocatalytic activity of Bi2 O3 and ZnO was evaluated for the degradation of Alizarin Red S (ARS), as a model pollutant, at 20mg/L level in water under visible light irradiation. The percentage of photocatalytic degradation was determined using UV-vis spectrophotometer. The photocatalytic results revealed that Bi2 O3 and ZnO could effectively degrade 73% and 53% of ARS, respectively, within 13hr under visible light illumination, indicating that synthesized Bi2 O3 is a better photocatalyst than ZnO. Photodegradation of ARS with Bi2 O3 and ZnO is remarkably influenced by change in pH of the dye solution, and pH 8 was found to be the most favorable for maximum removal of ARS in case of both Bi2 O3 (75%) and ZnO (58%) photocatalyst. PRACTITIONER POINTS: Photocatalytic degradation of ARS dye depends on pH of the solution. Calcination temperature influences the crystallite size of prepared semiconductor oxides of bismuth and zinc. Bi2 O3 shows better photocatalytic degradation efficiency than ZnO under visible light illumination.

GQD/Bi2O3 Composite for high-efficient photocatalysts

Bismuth oxide (Bi2O3) is one of the potential visible-light photocatalytic materials, however, due to low electron mobility and short minority carrier diffusion length, the photocatalytic activity of Bi2O3 is restricted. The GQD/Bi2O3 composites were synthesized stably depositing single-crystalline graphene quantum dots (GQDs) with absorption edge at ~10nm, prepared by using a top-down method. The GQDBi2O3 heterojunctions were successfully established, the photo-generated electrons transfer from the Bi2O3 to the GQDs at the interface of the GQD-Bi2O3 heterojunctions, result in efficient electron-hole pairs separation and higher photocatalytic efficiency. The optimum visible performance is achieved at GQD content of 1.0 wt %, the RhB dye was nearly completely decoloured after 90 min of visible-light irradiation, and then decrease at higher doping levels due to the thicker GQD layer will cover the active sites of Bi2O3, thus leading to the greatly reduced catalytic activity.

Enhancement of Photocatalytic Activity of Bi2 O3 -BiOI Composite Nanosheets through Vacancy Engineering.

Vacancy engineering is an effective strategy to enhance solar-driven photocatalytic performance of semiconductors. It is highly desirable to improve the photocatalytic performance of composite nanomaterials by the introduction of vacancies, but the role of vacancies and the heterostructure in the photocatalytic process is elusive to the composite nanomaterials. Herein, the introduction of I vacancies can significantly enhance the photocatalytic activity of Bi2 O3 -BiOI composite nanosheets in a synergistic manner. The excellent photocatalytic performance of the Bi2 O3 -BiOI composites is attributed to the combination of Bi2 O3 and BiOI and the existence of I vacancies in Bi2 O3 -BiOI composites. Specifically, density functional theory calculation shows that the existence of I vacancies would create a new electric states vacancy band below the conduction band of BiOI and thus can reduce the bandgap of BiOI nanosheets. This greatly facilitates the scavenging of the photogenerated electron on the surface of BiOI by Bi2 O3 , therefore, enhancing the overall photocatalytic activity of the composites. The enhanced photocatalytic efficiency is demonstrated by the degradation of tetracycline (TC), which reaches 96% after 180 min and by the high total organic carbon (TOC) removal (89% after 10 h visible light irradiation). This study provides a novel approach for the design of high-performance composite catalysts.

Nd-doped Bi2O3 nanocomposites: simple synthesis and improved photocatalytic activity for hydrogen production under visible light

Bi2O3 has 2.4 eV band gap energy, which means it absorb in visible region. Though the photocatalytic activity of Bi2O3 is extremely little due to rapid rate of photogenerated electron–hole recombination. To face the economical and practical needs, the photocatalytic efficiency of Bi2O3 should be upgraded. In this paper, this was achieved by addition of neodymium to Bi2O3 nanosheets and Nd/Bi2O3 nanocomposites were prepared by a easy process at room temperature using a surfactant of Pluronic F127. The Bi2O3 nanosheets and Nd/Bi2O3 nanocomposites were investigated by many tools. The photocatalytic activity of Nd/Bi2O3 samples is better than Bi2O3 due to reduced band gap and reduced electron–hole recombination of Bi2O3 with addition of neodymium. In addition, Nd/Bi2O3 nanocomposites exhibit photocatalytic stability for hydrogen production which enables it to be reused on other occasions also.

Fine cutting edge shaped Bi2O3rods/reduced graphene oxide (RGO) composite for supercapacitor and visible-light photocatalytic applications

Bi2O3 rods/RGO composite has been synthesized by a simple precipitation and calcination method. The crystallnity, structural, and morphological features were studied by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and high resolution transmission electron microscopy (HR-TEM) techniques. The supercapacitor behavior was studied using cyclic voltammetry, galvanostatic charge discharge and impedance analysis, respectively. The Bi2O3 rods/RGO nanocomposite exhibits a maximum specific capacitance of 1041Fg−1 at a current density of 2Ag−1. The photocatalytic activity of Bi2O3 rods/RGO composite was evaluated by photocatalytic degradation of methylene blue (MB) dye under visible-light irradiation. The enhancement of photocatalytic properties of Bi2O3 rods/RGO composite attributed to the synergistic effect between Bi2O3 rods and graphene sheets which effectively prevents recombination of the photogenerated electron-hole pairs in Bi2O3 rods. The present study provides a new approach in improving the performance of Bi2O3 rods/RGO composite in energy and environmental applications.

Improved photocatalytic activity of Bi2O3 composites derived from a layered precursor

ZnO/Al2O3/Bi2O3 mixed-metal oxide (ZnAlBi-MMO) has been successfully prepared by the coprecipitation method and controllable calcination. Powder X-ray diffraction, high-resolution transmission electron microscopy and UV–Vis diffuse reflectance spectra confirmed the structure of as-synthesized solids. The results reveal that the synthetic methods can provide the heterostructure of MMO. The photocatalytic activity of ZnAlBi-MMO was evaluated by the photodegradation of methylene blue (MB) under visible light irradiation. Factors that may affect the photodegradation behavior were studied such as calcination temperature, catalyst dose and pH. Furthermore, the stability of synthesized photocatalysts was investigated by studying the photocatalytic ability of reclaimed ZnAlBi-MMO. The results showed the removal efficiency of MB was higher than 83 % even after four successive photoreactions, demonstrating the great potential of layered double hydroxides as catalyst supports. The possible mechanism underlying the enhanced photocatalytic activity of Bi2O3 was also discussed.

Synthesis of room temperature bismuth oxide and its photocatalytic activity

A simple room temperature chemical route is selected for the preparation of phase pure bismuth oxide (Bi2O3) without applying any post heat treatment. The phase pure form of Bi2O3 is confirmed from X-ray diffraction. The surface morphology of the powder is observed by a scanning electron microscope and it reveals that the powder consists of agglomerates. The photocatalytic activity of Bi2O3 is evaluated by photocatalytic decolorization of methyl orange aqueous solution for 2h. The crystallite size dependence of degradation is confirmed by annealing the sample at two different temperatures (200 and 600°C) for 2h. The photocatalytic degradation property of Bi2O3 varies with the crystallite size. The degradation percentage of MeO using Bi2O3 as catalyst are 76%, 52% and 24% for the as-prepared and the annealed sample at 200 and 600°C respectively.

Fabrication of Pr-Doped Bi<sub>2</sub>O<sub>3</sub> with Enhanced Photocatalytic Performance under Visible Light

This paper reveals that photocatalytic activity of Bi2O3 under visible light towards the decolorization of Methyl Orange solution can be greatly enhanced by doping Pr into the lattice of Bi2O3 using a sol-gel method. The photocatalysts were characterized by BET, UV-Vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy (SPS), respectively. The result shows that 4%Pr doped Bi2O3 possesses the best photocatalytic activity under visible light.

Photocatalytic Performance of Bi<sub>2</sub>O<sub>3</sub> Prepared with NH<sub>3</sub>•H<sub>2</sub>O under Different pH Value

In this paper, parallel flaw precipitation method has been employed to fabricate nanostructured Bi2O3. It is found that the surface parameters, bandgap, the photoinduced charge separation rate and photocatalytic performance of Bi2O3 have a strong dependence on the pH value of precipitation reaction.The prepared photocatalysts were characterized by BET, XRD, UV-Vis diffuse reflectance and surface photovoltage spectroscopy (SPS). The results show that Bi2O3 prepared under pH value10.0 exhibits the best photocatalytic activity among the experimented compositions. The results of further experiments show that surface parameters, bandgap, the photoinduced charge separation rate all play an important role in promotion of photocatalytic activity of Bi2O3 prepared under pH value 10.0.

Photocatalytic Activity of Bi<sub>2</sub>O<sub>3</sub> Prepared by Different pH Value

Abstract. Bismuth oxide is an important metal-oxide semicondutor, the interest in developing methods which can prepare Bi2O3 with unique properties has been a hot issue recently. In this paper, paralled flaw precipitation method has been employed to synthesize nanostructured Bi2O3. It is found that the bandgap and photocatalytic performance of Bi2O3 has a strong dependence on the pH value of precipitation reaction.The prepared photocatalysts were characterized by BET, XRD and UV-Vis diffuse reflectance. The results show that Bi2O3 prepared under pH value 8.5 has the highest BET surface area, pore volume, the smallest pore size and the average crystal size. Bi2O3 prepared under pH value 8.5 exhibits the best photocatalytic activity. The results of further experiments show that bandgap and the specific surface area all play an important role in promotion of photocatalytic activity of Bi2O3 prepared under pH 8.5.

Photocatalytic Activity of Bi<sub>2</sub>O<sub>3</sub> Prepared by Different Precipitants

Paralled flaw precipitation method has been employed to synthesize nanostructured Bi2O3. It is found that the bandgap and photocatalytic performance of Bi2O3 has a strong dependence on the kind of precipitants. The prepared photocatalysts were characterized by BET, XRD, UV-Vis diffuse reflectance and SEM. The results show that Bi2O3 prepared by NH3·H2O has the highest BET surface area, pore volume, the smallest pore size and the particle average size. Bi2O3 prepared by NH3·H2O exhibits the best photocatalytic activity. The results of further experiments show that bandgap and the specific surface area all play an important role in promotion of photocatalytic activity of Bi2O3 prepared by NH3·H2O.