Danjun Wang

Monodispersed Ag nanoparticles loaded on the surface of spherical Bi2WO6 nanoarchitectures with enhanced photocatalytic activities

Spherical Bi2WO6 nanoarchitectures with scale of 2–4 μm were prepared by a hydrothermal reaction using bismuth nitrate and ammonium tungstate as raw materials. Ag was deposited on the surface of Bi2WO6via a following facile photoreduction process. The as-prepared samples were characterized by UV-Vis-DRS, BET, XRD, XPS, FE-SEM, and HR-TEM. The results revealed that the monodispersed metallic Ag nanoparticles with average size of 10–15 nm were deposited on the surface of the spherical Bi2WO6 nanoarchitectures. The photocatalytic activities of the samples were evaluated by the photodegradation of RhB and thiophene under visible light irradiation. The results showed that Ag loading greatly improved the photocatalytic activity of Bi2WO6, and the content of loading silver has an impact on the catalytic activity of Bi2WO6. The 0.5at%Ag-loaded Bi2WO6 sample exhibited the best photocatalytic activity in both the decolorization of RhB and desulfurization of thiophene. In addition, the mechanism for the enhancement of the photocatalytic activity of Ag-loaded Bi2WO6 was also investigated by comparison of their PL spectra.

AgBr quantum dots decorated mesoporous Bi2WO6 architectures with enhanced photocatalytic activities for methylene blue

Spherical mesoporous nest-like Bi2WO6 nanoarchitectures with scales of 2–4 μm were prepared via a hydrothermal process, and AgBr quantum dots (QDs) were decorated on the surface of Bi2WO6 to form a novel p–n AgBr/Bi2WO6 heterojunction via a followed facile precipitation–deposition process. Evidence of AgBr QDs decorating mesoporous nest-like Bi2WO6 nanoarchitectures was obtained from XRD, XPS, FE-SEM and HR-TEM, which revealed that monodispersed AgBr QDs with an average size of about 10 nm were deposited on the surface of the three-dimensional Bi2WO6 nanoarchitectures. The photocatalytic activities of the samples were evaluated by the photodegradation of methylene blue dye (MB) and phenol under visible light irradiation. The results showed that the decoration of AgBr QDs significantly improved the photocatalytic activity of Bi2WO6, and the content of deposited AgBr nanodots impacted the catalytic activity of Bi2WO6. The 2.0at%AgBr-loaded Bi2WO6 sample exhibited the best photocatalytic activity for the decolorization of MB. It is elucidated that AgBr/Bi2WO6 generates superoxide radical anions in aqueous aerated solution but no hydroxyl radicals are formed. In addition, the mechanism for the enhancement of photocatalytic activity of AgBr/Bi2WO6 was also investigated by a comparison of their PL spectra. The catalytic efficiency enhancement of the p–n AgBr/Bi2WO6 heterojunctions relative to pure Bi2WO6 can be attributed to the formation of heterojunctions between AgBr QDs and Bi2WO6, which suppresses the recombination of photogenerated electron–hole pairs. The test of radical scavengers confirmed that O2˙− was the main reactive species during the photocatalytic process.

Synthesis of mesoporous Bi2WO6 architectures and their gas sensitivity to ethanol

Uniform hierarchical multilayered Bi2WO6 architectures were synthesized by a facile template-free hydrothermal process, and their synthesis conditions and formation mechanism were carefully investigated. XRD, XPS, FE-SEM, and HR-TEM techniques were employed to determine their phase composition, morphology and microstructure. Nitrogen adsorption and desorption isotherms were conducted to examine the specific surface area and the pore nature of the as-prepared sample. The results show that the as-prepared Bi2WO6 architectures consist of secondary nanoplates and have a mesoporous nest-like morphology with a diameter of 3–4 μm, and have very large specific surface areas. The largest surface area of 47.72 m2 g−1 is achieved when synthesized at 190 °C for 2.0 h. Furthermore, the Bi2WO6 samples were fabricated into a gas sensor, and the experimental results showed that the samples exhibited high sensitivity and a fast response–recovery to ethanol gas at lower temperatures (300 °C). For 100 ppm ethanol, the sensitivity of the best sensor (GS2) was 34.6, which is about 3-fold higher than the reported mesoporous ZnO based gas sensor because its mesoporous structure provided a high surface-to-volume ratio and surface accessibility for the ethanol. A plausible enhancement gas responding mechanism of the nest-like Bi2WO6 sensors was also proposed based on the structure and response–recovery properties.

Design and construction of the sandwich-like Z-scheme multicomponent CdS/Ag/Bi2MoO6 heterostructure with enhanced photocatalytic performance in RhB photodegradation

A sandwich-like Z-scheme tricomponent CdS/Ag/Bi2MoO6 photocatalytic system was rationally designed and successfully fabricated, in which Ag was loaded onto Bi2MoO6 microspheres by a facile photoreduction method and CdS was subsequently deposited onto the surface of Bi2MoO6 and Ag/Bi2MoO6 through a deposition–precipitation method. During this process, a series of Ag/Bi2MoO6 and CdS/Bi2MoO6 were also prepared. All the composites were characterized by XRD, TEM, SEM, EDX, XPS, UV-vis DRS, and IR spectra to confirm the successful integration of Ag or (and) CdS with Bi2MoO6, the alteration of morphology and the formation of a new phase before and after Ag or (and) CdS loading. The degradation of rhodamine B (RhB) dye under visible light irradiation (>420 nm) revealed that the CdS/Ag/Bi2MoO6 composite exhibited a highly visible-light-responsive photocatalytic performance compared to single Bi2MoO6 or CdS and dual Ag/Bi2MoO6 or CdS/Bi2MoO6. The enhanced photocatalytic performance of CdS/Ag/Bi2MoO6 was ascribed to its special structure – a typical Z-scheme photocatalytic system, in which Ag nanoparticles directly connected to the surface of CdS and Bi2MoO6 to form a solid–solid interface (ohmic contact), acting as a conductor that greatly shortened the distance for photogenerated electron transfer and combined photogenerated electrons from the CB of Bi2MoO6 with the photogenerated holes from the VB of CdS through ohmic contact, and thereby led to the efficient separation of photogenerated electrons and holes and showed stable and strong reducibility and oxidizability. Moreover, the surface plasmon resonance effect of metallic Ag nanoparticles also played an important role in the enhanced photocatalytic performance of RhB degradation under visible light irradiation. Furthermore, investigations on photoluminescence and photoelectrochemical properties also demonstrated indirectly the highly efficient separation of photogenerated electrons and holes in the Z-scheme CdS/Ag/Bi2MoO6 photocatalytic system. This new Z-scheme photocatalytic system will be applied to more photoreactions in further exploration.

La and F co-doped Bi2MoO6 architectures with enhanced photocatalytic performance via synergistic effect

Novel La and F co-doped Bi2MoO6 architectures were first successfully synthesized via a facile solvothermal process, and characterized using XRD, SEM, TEM/HR-TEM, XPS, EDS, UV-Vis DRS and PL spectra. The enhanced photocatalytic activities of La and F co-doped Bi2MoO6 architectures were evaluated by the photodegradation of rhodamine B (RhB) under visible-light irradiation. The results demonstrated that the F-1.0 at% La–Bi2MoO6 photocatalyst exhibits significantly enhanced photocatalytic activity, which is 6.54 times higher than that of pure Bi2MoO6. The cause can be attributed to the co-incorporation of La and F into Bi2MoO6 broadening the absorption in the visible-light region and thereby leading to the formation of new energy levels on top of the valence band of F–La–Bi2MoO6, and on the other hand, the synergistic effect of F and La, in which F doping led to the increase of absorptivity of F–Bi2MoO6 and acted as an n-type impurity to supply a hole carrier. The doped La3+ ions act in a key role to capture and transfer/release the photogenerated electrons for conversion from O2 to ·O2− to delay the recombination of the photogenerated electrons and holes, greatly suppressing the recombination of photogenerated electron–hole pairs and thus significantly improving photocatalytic activity in RhB photodegradation. The radical capture experiment confirmed that h+ and ·O2− were the main active species and were responsible for RhB photodegradation. Moreover, on the basis of the PL spectra, active species trapping detection and photocurrent response experiments, the mechanism of the enhanced photocatalytic activity for F–La–Bi2MoO6 was proposed.

AgBr nanoparticles decorated BiPO4 microrod: a novel p–n heterojunction with enhanced photocatalytic activities

AgBr nanoparticles loaded BiPO4 microrods have been successfully synthesized via a facile deposition–precipitation method. XRD, FE-SEM, TEM, EIS, UV-Vis-DRS techniques were employed to characterize the phase composition, morphology and light absorption properties of the as-synthesized samples. Methylene blue (MB) and phenol (Ph) were selected as model pollutant to investigate the photocatalytic activity of the as-synthesized samples under visible-light irradiation. The experimental results show that different amount of AgBr on BiPO4 exhibit an obvious effect on the degradation of MB and the optimum molar ratio of AgBr and BiPO4 is 1 : 10. In particular, the photocatalytic activity of AgBr/BiPO4 is superior to the activities of two individual photocatalyst, indicating the presence of a synergic effect between two component in AgBr/BiPO4. On the basis of photocatalytic results and energy band diagram, the activity enhancement mechanism of AgBr/BiPO4 composite has also been investigated. The p-type semiconductor AgBr and n-type semiconductor BiPO4 can match each other and form a novel p–n heterojunction, thus increasing the photogenerated electron–hole pair separation efficiency. Therefore, this work provides some help for the design of novel and efficient BiPO4-based photocatalyst with multi-components for enhancing visible-light-driven photocatalytic activity.

Synthesis of Porous-Bi2WO6 and Its Photocatalytic Oxidative Desulfurization (Photo-ODS) Activity of Simulation Fuel: Synthesis of Porous-Bi2WO6 and Its Photocatalytic Oxidative Desulfurization (Photo-ODS) Activity of Simulation Fuel

采用水热法合成了多孔结构Bi 2 WO 6 光催化剂, 借助X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、X射线能量色散谱(EDS)、紫外-可见漫反射(UV-Vis-DRS)、N2吸附/脱附等测试手段对样品的物相组成、形貌、比表面-孔径分布和光吸收特性等进行了表征。考察了水热温度、水热反应时间对Bi 2 WO 6 的形貌、比表面-孔径分布和光吸收特性影响, 并探讨了Bi 2 WO 6 光催化剂对模拟燃油的脱硫活性。结果表明, 在强酸性条件下水热温度和水热时间对Bi 2 WO 6 的形貌、比表面积和催化活性影响显著, 190℃水热反应2 h所得Bi 2 WO 6 为新颖的鸟巢状微晶, 且鸟巢状Bi 2 WO 6 由片层状二级结构组装而成。XRD和EDS表明, 鸟巢状结构的Bi 2 WO 6 为正交晶系, 纯度较高。N 2 吸附-脱附测试结果表明, 鸟巢状Bi 2 WO 6 具有多孔结构, 孔主要分布在10 nm, 比表面积大约为17.49 m 2 /g。催化活性测试结果表明, 三维介孔结构Bi 2 WO 6 具有较好的模拟燃油脱硫效果, 在空气流量为100 mL/min, 催化剂加入量为1.2 g/L, 可见光照射180 min, 模拟汽油脱硫率高达91.2%, 且催化剂的稳定性能较好。采用水热法合成了多孔结构Bi 2 WO 6 光催化剂, 借助X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、X射线能量色散谱(EDS)、紫外-可见漫反射(UV-Vis-DRS)、N2吸附/脱附等测试手段对样品的物相组成、形貌、比表面-孔径分布和光吸收特性等进行了表征。考察了水热温度、水热反应时间对Bi 2 WO 6 的形貌、比表面-孔径分布和光吸收特性影响, 并探讨了Bi 2 WO 6 光催化剂对模拟燃油的脱硫活性。结果表明, 在强酸性条件下水热温度和水热时间对Bi 2 WO 6 的形貌、比表面积和催化活性影响显著, 190℃水热反应2 h所得Bi 2 WO 6 为新颖的鸟巢状微晶, 且鸟巢状Bi 2 WO 6 由片层状二级结构组装而成。XRD和EDS表明, 鸟巢状结构的Bi 2 WO 6 为正交晶系, 纯度较高。N 2 吸附-脱附测试结果表明, 鸟巢状Bi 2 WO 6 具有多孔结构, 孔主要分布在10 nm, 比表面积大约为17.49 m 2 /g。催化活性测试结果表明, 三维介孔结构Bi 2 WO 6 具有较好的模拟燃油脱硫效果, 在空气流量为100 mL/min, 催化剂加入量为1.2 g/L, 可见光照射180 min, 模拟汽油脱硫率高达91.2%, 且催化剂的稳定性能较好。

Efficient degradation of phenol and 4-nitrophenol by surface oxygen vacancies and plasmonic silver co-modified Bi2MoO6 photocatalysts

In this work, the surface plasmon resonance effect of metallic Ag, surface oxygen vacancies (SOVs), and Bi2 MoO6 (BMO) material were rationally combined to construct new oxygen-vacancy-rich Ag/Bi2 MoO6 (A/BMO-SOVs) photocatalysts. Their synergistic effect on the photocatalytic degradation of phenol and 4-nitrophenol under visible-light irradiation (λ≥420 nm) was also investigated. TEM, EPR, and Raman spectra demonstrate the co-existence of metallic Ag nanoparticles, surface oxygen vacancies, and Bi2 MoO6 due to a controlled calcination process. The experimental results disclose that the 2 %A/BMO-SOVs-375 sample exhibited the highest photocatalytic activity for the degradation of both phenol and 4-nitrophenol under visible-light irradiation, achieving nearly 100 and 80 % removal efficiency, respectively, and demonstrated the apparent reaction rate constants (kapp ) 183 and 26.5 times, respectively, higher than that of pure Bi2 MoO6 . The remarkable photodegradation performance of A/BMO-SOVs for organic substances is attributed to the synergistic effect between the surface oxygen vacancies, metallic Ag nanoparticles, and Bi2 MoO6 , which not only improves the visible-light response ability, but also facilitates charge separation. Thus, this work provides an effective strategy for the design and fabrication of highly efficient photocatalysts through integrating surface oxygen vacancies and the surface plasmon resonance effect of nanoparticles, which has the potential for both water treatment and air purification.

Bis(di-2-pyridylmethane­diol-κ3N,O,N′)copper(II) dl-tartrate

The reaction of di-2-pyridyl ketone with copper dichloride dihydrate and tartaric acid in water afforded the title compound, [Cu(C11H10N2O2)2]C4H4O6. The CuII atom lies on an inversion center N,O,N′-chelated by two di-2-pyridylmethanediol ligands in a tetragonally distorted octahedral geometry. The tartrate anion is also located on an inversion center and has disordered hydroxyl groups, each with an occupancy factor of 0.5. The hydroxyl groups of the complex cation are hydrogen bonded to the carboxylate groups of the anion, thus connecting the two building units.

Crystal structure of 1,2-bis(4-pyridyl)-glycol,C24H24N4O4

c24h24n4o4, orthorhombic, pbca (no. 61), a = 8.060(2) angstrom, b = 11.318(2) angstrom, c = 11.547(2) angstrom, v = 1053.4 angstrom(3), z = 2, r-gt(f) = 0.046, wr(ref)(f-2) = 0.135, t = 298 k.