Excellent Visible Photocatalytic Activity Research Articles

Visible-Light Photocatalytic Degradation Efficiency of Tetracycline and Rhodamine B Using a Double Z-Scheme Heterojunction Catalyst of UiO-66-NH2/BiOCl/Bi2S3.

BiOCl is a promising photocatalyst, but due to its weak visible light absorption capacity and low photogenerated electron-hole pair separation rate, its practical application is limited to a certain extent. In this study, a novel double Z-scheme heterojunction UiO-66-NH2/BiOCl/Bi2S3 catalyst was constructed to broaden the visible light response range and promote high photogenerated hole-electron separation of BiOCl. Its photocatalytic performance is evaluated by dissociating tetracycline (TC) and rhodamine B (RhB) in visible light. The optimal proportion of UiO-66-NH2/BiOCl/Bi2S3 hybrids exhibits the best degradation efficiency of visible light illumination (∼93% in 120 min for TC and ∼98% in 60 min for RhB). The synergistic effect of a large visible light response range and the Z-scheme charge transfer mechanism ensure the excellent visible photocatalytic activity of UiO-66-NH2/BiOCl/Bi2S3. It is proven that h+ and •O2- are the main active substances in the photocatalysis process by active substance capture experiments and electron spin resonance tests. The intermediates and degradation processes are analyzed by high-performance liquid chromatography-mass spectrometry. This study proves that the new UiO-66-NH2/BiOCl/Bi2S3 photocatalyst has great application potential in the field of water pollution degradation and will provide a new idea for the optimization of BiOCl.

Preparation of Bi2O2CO3/BiOBr0.9I0.1 photocatalyst and its degradation performance for 2,4-dichlorophenoxyacetic acid

Pesticide pollution has caused serious harm to the ecological environment and presents a major risk to human health due to drinking water resource contamination. 2,4-dichlorophenoxyacetic acid (2,4-D), as a class II toxic compound, can cause human health hazards, including neurotoxicity, hepatotoxicity, nephrotoxicity, reproductive defects and abortion. In this study, pure Bi2O2CO3/BiOBr0.9I0.1 photocatalyst material was prepared for the degradation of pesticides using a solvothermal method. The structure, morphology, and optical properties of the photocatalyst were characterized through X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), Steady-state photoluminescence (PL), and Electrochemical Impedance Spectroscopy (EIS). The Bi2O2CO3/BiOBr0.9I0.1 catalyst could degrade 89.1% of 2,4-D within 120 min under visible light. After four cycles of reuse, Bi2O2CO3/BiOBr0.9I0.1 retained a high degradation performance for 2,4-D. The results of active substance capture experiments and ESR, showed that ·O2- and h+ were the main active substances. Under the synergistic effects of heterojunction and the solid solution, 10 wt%Bi2O2CO3/BiOBr0.9I0.1 was able to efficiently photocatalyze 2,4-D degradation. The use of the double modification method of solid solution and heterojunction construction regulates the band structure of BiOBr, resulting in a high photogenerated carrier separation efficiency and good light response capability. The Z-type heterojunction provides the photogenerated carriers with a high redox capacity. The synergistic effect of the two modification strategies results in the BiOBr based composite photocatalyst exhibiting excellent visible photocatalytic activity.

Stearic acid modified Co2+-doped ZnO: The construction of micro-nano structure for its superhydrophobic performance and visible-light photocatalytic degradation of methylene blue

Herein, the Co2+-doped ZnO nanoarrays with high photocatalytic activity were grown on the stainless steel wire mesh (Co2+-ZnO@SSM) by the hydrothermal method, and the special micro-nano structure with high surface roughness was obtained through stearic acid (STA) surface modification for the superhydrophobicity. By changing the concentrations of STA, the hydrophilic and hydrophobic structure of Co2+-ZnO/STA@SSM could be controlled, and the water contact angle in air reached 154.9° when the STA concentration was 0.04 mol/L. In different oil/water mixtures, the Co2+-ZnO/STA@SSM showed excellent oil/water separation efficiency and separation flux, and after 16 separation cycles and bending tests, the separation efficiency remained above 89%. In addition, the Co2+-ZnO/STA@SSM still maintained excellent visible photocatalytic activity, and the photocatalytic efficiency for methylene blue degradation could reach 93% in water. This dual-functional Co2+-ZnO/STA@SSM membrane with visible-light photocatalysis and oil/water separation provides a potential purification strategy for the complex industrial wastewater.

Effective shell wall thickness of vertically aligned ZnO-ZnS core-shell nanorod arrays on visible photocatalytic and photo sensing properties

Development of hierarchical core-shell semiconductor heterostructures ensue significant advancement in catalytic functional structures with improvised optical functionalities. Shell wall controlled vertically aligned ZnO-ZnS core-shell nanorod (NR) heterostructures were grown on transparent conductive substrates along the c-axis by sulfidation of aligned ZnO nanorod arrays for visible photocatalytic properties. The effects of the sulfidation time on the morphology, crystalline properties, optical property, photocurrent response, and photocatalytic activity of the catalyst arrays were studied under UV and visible light irradiation. The shell wall thickness of these heterostructures influenced in great extent the effective photo responsive charge separation and improved carrier mobility. ZnO-ZnS core-shell heterostructure having the shell wall thickness of 20 nm has exhibited more efficient visible photocatalytic behavior due to effective separation of carriers and improved visible absorption. On further increasing the wall thickness the catalytic efficiency was reduced due to the poor carrier (hole) mobility in the polycrystalline shell grains which induced the higher recombination rate. Stability and reusability of ZnO-ZnS core-shell nanostructures reveals that the ZnS acted as a protective layer over the ZnO NR arrays. In appraisal with ZnO NR arrays, the control over the shell wall thickness of ZnO-ZnS core-shell NR array attributed to the excellent visible photocatalytic activity and improvised absorption of light in visible region at ZnO-ZnS interface and effective separation of photogenerated electron-hole pairs at ZnO-ZnS heterojunctions.

Template-free synthesis of three-dimensional porous CdS/TiO2 with high stability and excellent visible photocatalytic activity

A novel stereo porous and highly stable photocatalyst CdS/TiO2-400 (composite CdS/TiO2 calcined at 400 °C) was synthesized by hydrolysis-hydrothermal-calcined method without the assistance of template. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet–visible diffuse reflectance spectra (UV–vis DRS), transient photocurrents, photoluminescence emission spectra (PL) and Brunauer-Emmett-Teller (BET) to study their crystallinity, morphologies, structure, optical properties and specific surface area. The experimental results validated that as-prepared CdS/TiO2-400 could effectively improve the separation efficiency of photogenerated electron-hole pairs and displayed superior photocatalytic activity in the degradation process of methyl orange (MO), oxytetracycline (OTC) and tetracycline (TC). The promoted photocatalytic activity was attributed to the calcination procedure and high specific surface area. A possible photocatalytic mechanism of CdS/TiO2-400 was proposed on the basis of trapping experiments.

One-pot electrochemical synthesis of carbon dots/TiO2 nanocomposites with excellent visible light photocatalytic activity

We propose a novel electrochemical method to one-pot synthesize carbon dots/titanium dioxide (CDs/TiO2) nanocomposites for the first time. The as-prepared CDs/TiO2 nanocomposites exhibit excellent visible photocatalytic activity for degradation of methylene blue (MB) under a 50W halogen tungsten lamp irradiation.

Au–Pt alloy nanoparticles site-selectively deposited on CaIn2S4nanosteps as efficient photocatalysts for hydrogen production

Au–Pt/CaIn2S4composites were site-selectively synthesized for the first time and demonstrated to show excellent visible photocatalytic activity for hydrogen production compared to that of CaIn2S4, Au/CaIn2S4and Pt/CaIn2S4.

Facile synthesis of Ag/AgCl/BiPO4 plasmonic photocatalyst with significantly enhanced visible photocatalytic activity and high stability

Highly efficient Ag/AgCl/BiPO4 plasmonic photocatalyst was synthesized for the first time. The catalyst showed excellent visible photocatalytic activity and high stability. A surface plasmon resonance mechanism was investigated.

Comparative study on the visible light driven photocatalytic activity between substitutional nitrogen doped and interstitial nitrogen doped TiO2

Nitrogen-doped TiO2 nanomaterial attracts enormous attention due to its excellent visible photocatalytic activity. A simple annealing method assisted by adjusting gas composition to control the positions of nitrogen dopants in TiO2 lattice is presented. The nitrogen doping sites are confirmed by XPS. The photo-degradation results of gaseous benzene under visible light illumination reveal that photocatalytic activity in as-prepared samples containing the substitutional nitrogen species is higher than that in samples containing interstitial nitrogen species. The improvement of photocatalytic performance is ascribed to the increased amounts of surface hydroxyl group in N-TiO2 samples. The efficient separation of electron-hole pairs was also responsible for the enhanced photocatalytic activity. In addition, an important conclusion is pointed out: the presence of oxygen during annealing process has an important effect on the formation of interstitial nitrogen dopants. The present work is believed to have guiding significance for preparing nitrogen-doped TiO2 with high photocatalytic activity.

Highly Visible Photocatalytic Activity of Fluorine and Nitrogen Co-doped Nanocrystalline Anatase Phase Titanium Oxide Converted From Ammonium Oxotrifluorotitanate

The formation of high-quality fluorine and nitrogen co-doped nanocrystalline anatase phase titanium oxide converted from ammonium oxotrifluorotitanate discoid crystal by means of thermal treatment is reported in this study. The decomposition rate of methylene blue under 450 nm light-emitting diode illumination demonstrates an excellent visible photocatalytic activity. The highest visible photocatalytic activity is obtained at the thermal treatment temperature of 600 degC. We confirm the positive roles of fluorine and nitrogen in titanium oxide in the area of visible photocatalytic activity. There is one-to-one correspondence between the life of an electron and hole pair and photocatalytic activity