Solar Light Photocatalytic Performance Research Articles

Microwave synthesized g-C3N4 nanofibers with modified properties for enhanced solar light photocatalytic performance

Graphitic carbon nitride (g-C3N4) nanomaterials have been eco-friendly synthesized using microwave and compared to the materials prepared by conventional thermal and solvothermal methods. The properties of as-synthesized g-C3N4 nanomaterials were investigated by various techniques. The results demonstrated the successful synthesis of g-C3N4 either by conventional or microwave methods. However, morphology and surface area have been changed by changing the method used. While small sheets were obtained using thermal decomposition of melamine for 4 hrs. at 500 °C, and irregular particles were obtained from the solvothermal synthesis by heating melamine and cyanuric chloride for 16 hrs. at 180 °C, nanofibers structure with the largest surface area was obtained by microwave irradiation of melamine and cyanuric chloride for 1hr. The photocatalytic performance of the synthesized materials has been assessed for the decomposition of phenol and methyl orange (MO) dye. All prepared g-C3N4 materials have shown better solar light photocatalytic performance compared to TiO2 nanoparticles. This has been directly correlated to the narrower band gab energies of g-C3N4 materials (Eg(TGCN) = 2.8 eV, Eg(SGCN) = 2.4 eV, Eg(MGCN) = 2.45 eV) compared to TiO2 (3.1 eV). Moreover, the photocatalytic activity of microwave prepared g-C3N4 (MGCN) is about 2 times higher than those prepared by the other methods (TGCN & SGCN) and ∼ 7 times higher than that of TiO2. This can be readily related to the modified fibrous structure and the highest surface area of MGCN (31.84 m2/g) compared to other materials.

Sodium Ligninsulfonate-assisted Synthesis of Lithium Bismuthate/bismuth Oxide Microspheres and Solar Light Photocatalytic Performance

Background: Great attention has been paid to the environmental pollution by organic dyes, which are difficult to be degraded in the natural environment and have been an unavoidable and urgent global problem. It is essential to develop green wastewater treatment technology with high removal efficiency and low-cost for protecting the surrounding and human health. Objective: The aim of the research is to synthesize lithium bismuthate/bismuth oxide microspheres with good photocatalytic performance for the removal of gentian violet (GV). Methods: Lithium bismuthate/bismuth oxide microspheres were successfully prepared by a sodium ligninsulfonate-assisted hydrothermal synthesis route. The lithium bismuthate/bismuth oxide microspheres were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform infrared spectroscopy (FTIR), and solid UV-vis diffuse reflectance spectrum. Results: XRD pattern and SEM observation show that the lithium bismuthate/bismuth oxide microspheres are composed of cubic LiBi12O18.50 and monoclinic Bi2O3 with a diameter of 250 nm-1 μm. Irregular microscale and nanoscale particles are formed under low hydrothermal temperature, low sodium ligninsulfonate concentration, and short duration time. By increasing the sodium ligninsulfonate concentration, hydrothermal temperature, and duration time, irregular particles are transferred into microspheres. Lithium bismuthate/bismuth oxide microspheres possess a band gap energy of 1.85 eV, suggesting good visible light absorption ability. The photocatalytic removal ability for GV is enhanced by prolonging light irradiation time and microspheres dosage. GV solution with the concentration of 10 mg•L-1 is able to be totally degraded by 10 mg lithium bismuthate/bismuth oxide microspheres in 10 mL GV solution under solar light irradiation for 6 h. Conclusion: The lithium bismuthate/bismuth oxide microspheres show good photocatalytic removal ability toward GV in wastewater under solar light irradiation.

Enhanced solar light photocatalytic performance of Fe-ZnO in the presence of H2O2, S2O82−, and HSO5− for degradation of chlorpyrifos from agricultural wastes: Toxicities investigation

This study reported Fe doped zinc oxide (Fe-ZnO) synthesis to degrade chlorpyrifos (CPY), a highly toxic organophosphate pesticide and important sources of agricultural wastes. Fourier transform infrared, X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectroscopic analyses showed successful formation of the Fe-ZnO with highly crystalline and amorphous nature. Water collected from agricultural wastes were treated with Fe-ZnO and the results showed 67% degradation of CPY by Fe-ZnO versus 39% by ZnO at 140 min treatment time. Detail mechanism involving reactive oxygen species production from solar light activated Fe-ZnO and their role in degradation of CPY was assessed. Use of H2O2, peroxydisulfate (S2O82−) and peroxymonosulfate (HSO5−) with Fe-ZnO under solar irradiation promoted removal of CPY. The peroxides yielded hydroxyl (OH) and sulfate radical (▪) under solar irradiation mediated by Fe-ZnO. Effects of several parameters including concentration of pollutant and oxidants, pH, co-existing ions, and presence of natural organic matter on CPY degradation were studied. Among peroxides, HSO5− revealed to provide better performance. The prepared Fe-ZnO showed high reusability and greater mineralization of CPY. The GC-MS analysis showed degradation of CPY resulted into several transformation products (TPs). Toxicity analysis of CPY as well as its TPs was performed and the formation of non-toxic acetate imply greater capability of the treatment technology.

Novel 3D hierarchical nanostructure of Fe3O4/ZnO hybrid composites for enhanced solar light photocatalytic performance

Novel 3D hierarchical nanostructure of Fe3O4/ZnO hybrid composites for enhanced solar light photocatalytic performance

A novel dual-ligand Fe-based MOFs synthesized with dielectric barrier discharge (DBD) plasma as efficient photocatalysts

A novel dual-ligand Fe-based MOFs (D-Fe-MOFs) was synthesized with dielectric barrier discharge (DBD) plasma for the first time, which exhibited efficient simulated solar light photocatalytic performance. 1,3,5-Benzenetricarboxylicacid (H3BTC) and 2-methylimidazole (2MI) were used as organic ligands for D-Fe-MOFs synthesis. Compared with S-Fe-MOFs, which used H3BTC as organic ligand, D-Fe-MOFs showed larger specific surface area and larger pore volume. The molar ratio of different organic ligands had a great influence on the photocatalytic performance of the catalyst, and H3BTC:2MI = 1:1 was the most beneficial to the photocatalytic performance. D-Fe-MOFs synthesized under the conditions of discharge voltage 15.6 kV, discharge current 1.5A and discharge time 1.5 h had higher thermal stability and showed high photocatalytic performance with degradation rate of 97% in 48 min for MO (20 mg/L) under simulated solar light. D-Fe-MOFs synthesized with DBD plasma exhibited sufficient conduction and valence band positions, which was beneficial for photocatalysis, where ·O2–, ·OH and h+played important roles.

Facile Cetyltrimethylammonium Bromide (CTAB)-assisted Synthesis of Calcium Bismuthate Nanoflakes with Solar Light Photocatalytic Performance

Background: Wastewater with dyes pollutes the environment and causes serious risk to human health and aquatic biota. Gentian violet (GV) belongs to typical triphenylmethane dyes and is difficult to be degraded. Calcium bismuthate nanoflakes possess good photocatalytic activity toward GV under solar light irradiation. Objective: The aim of the study was to prepare calcium bismuthate nanoflakes by the hydrothermal method and research on the solar light photocatalytic performance of the calcium bismuthate nanoflakes for GV degradation. Methods: The calcium bismuthate nanoflakes possess single crystalline monoclinic CaBi2O4 phase. The size of the whole nanoflakes is about 10 μm and the thickness of the nanoflakes is about 40 nm. The morphology, size and phase of the products are closely relative to CTAB concentration, reaction temperature and reaction time. The bandgap of the calcium bismuthate nanoflakes is 2.21 eV. The photocatalytic activity of the calcium bismuthate nanoflakes is high enough to completely degrade GV under solar light irradiation for 6 h. Results: The calcium bismuthate nanoflakes possess single crystalline mono clinic CaBi2O4 phase. The size of the whole nanoflakes is about 10 μm and thickness of the nanoflakes is about 40 nm. The morphology, size and phase of the products are closely relative to CTAB concentration, reaction temperature and reaction time. The band gap of the calcium bismuthate nanoflakes is 2.21 eV. The photocatalytic activity of the calcium bismuthate nanoflakes is high enough to completely degrade GV under solar light irradiation for 6 h. Conclusion: The photocatalytic performance for the removal of GV is dependent on the irradiation time, dosage of the calcium bismuthate nanoflakes and initial GV concentration. The calcium bismuthate nanoflakes exhibit great promising activity for the removal of organic pollutants.

Adsorption and photocatalytic performance of Au nanoparticles decorated porous Cu2O nanospheres under simulated solar light irradiation

In this work, pristine Cu2O and Au nanoparticle modified Cu2O (Au/Cu2O) spherical nanocomposites were prepared by a simple redox method at room temperature. The as-prepared Cu2O nanospheres with diameters of 150–200 nm show relatively large surface area. The dye removal abilities of the pure Cu2O and the Au/Cu2O nanocomposites were tested by evaluating their adsorption and photocatalytic activities towards different aromatic molecules (e.g., Congo red (CR), Methyl orange (MO), Methyl blue (MB), Rhodamine B (RhB)). The experimental results indicate that the Au/Cu2O nanocomposites exhibit much superior adsorption and photocatalytic properties to the pristine Cu2O nanospheres. Among the catalysts, 1 wt% Au/Cu2O nanocomposite shows the best removal abilities to various dyes. Besides, the removal abilities towards these dyes are quite different from each other. For deep understanding of the adsorption mechanism, molecular dynamics (MD) caculations were conducted to investigate the adsorption energy of the Cu2O spheres by simulating the porous structure and Au modification. The calculation results indicate that CR and MO are chemically adsorbed on the Cu2O materials while the adsorption of MB and RhB are physical adsorption, which are well consistent with the experimental results. This study demonstrates the porous Cu2O based nanocomposites are promising materials with high adsorption and solar light-photocatalytic performance. In the meanwhile, the underlying mechanism on the superior dye removal abilities of Au modified Cu2O nanospheres were systematically discussed.

A simple approach for controlling the morphology of g-C3N4 nanosheets with enhanced photocatalytic properties

In this work, we focus on synthesizing g-C3N4 nanosheets with a large surface area for enhanced solar light photocatalytic performance via a simple thermal polymerization of a low-cost urea precursor in enclosed conditions. The effects of annealing duration on the phase formation, structure, and optical and photocatalytic properties of the g-C3N4 nanosheets were investigated. The characterization analysis revealed that g-C3N4 nanosheets with different textures, including stacked-layer, porous and ultrathin morphologies, were obtained by controlling the annealing time. The prepared g-C3N4 samples offer a large specific surface area, narrow band gap and efficient separation of photogenerated electron-hole pairs with increasing annealing duration. The photocatalytic properties of the as-synthesized g-C3N4 samples were examined by measuring the degradation of rhodamine B (RhB) under simulated solar irradiation. With a 100% RhB solution (10 ppm) decomposed by exposure to solar irradiation for 60 min, ultrathin g-C3N4 shows considerable potential in practical applications concerning environmental remediation, especially in large-scale applications in industry.

Structural elucidation of core–shell TiO2 nanomaterials for environmental pollutants removal: A focused mini review

Abstract Recently, core–shell structured titania (CS TiO2) nanomaterials has garnered enormous research interest due to its improved visible light absorption capability and performance for various applications. While CS TiO2 nanomaterials have shown satisfactory performance in other applications, its solar light photocatalytic performance is still far from excellent for environmental pollutants removal. This might be due to the poor understanding of mismatch between the various structural properties of CS TiO2 and the contaminant we target for or scarcity of information about the atomic, nanocrystalline and electronic structure of CS TiO2 and its correlation with photocatalytic performance. The present review provides an in-depth understanding of property–performance​ relationship, specifically for the removal of organic pollutants from environmental media, which will help further understand and optimize the photocatalytic properties of CS TiO2 for enhancing its solar driven photocatalytic activity. The formation mechanism, structural properties, and photocatalytic performance of CS TiO2 for environmental pollutants removal were reviewed, and it is established that an inclusive strategy is needed to address the key challenges in designing CS TiO2 for environmental pollutants removal. The key challenges are the management of the location and concentration of defects states, optimization of surface to bulk defects ratio, and controlling the thickness of the shell. Conclusive prospective research needs for tuning the nanocrystalline structure and associated properties of CS TiO2 are suggested accordingly.

Two-photon induced NIR active core-shell structured WO3/CdS for enhanced solar light photocatalytic performance

Near-infrared (NIR) light utilization in the photoreduction of water to H2 remains a great challenge. Here we show an interesting design of NIR-driven photocatalyst via a two-photon absorption process by exploiting the electron-storage peculiarity of oxygen-deficient WO3. In the core-shell structured WO3/CdS, the WO3 core absorbs ultraviolet (UV)-visible and NIR photons successively and transfer excited electrons to the UV-visible light activated CdS shell for H2 generation. The core-shell structure effectively hinders the consumption of the photo-generated charges on the surface of WO3. With the absence of cocatalyst, the WO3/CdS heterojunction presents an unprecedented H2 generation rate of 65.98 and 14.84 mmol g–1 h–1 under solar light irradiation and in the NIR region, respectively. The solar-to-hydrogen conversion efficiency under simulated solar light irradiation reaches as high as 3.00 %. This work proposes a new approach to profiting the electron-storing WO3-like materials for designing solar light activated photocatalysts.

Enhanced solar light photocatalytic performance based on a novel Au-WO3@TiO2 ternary core–shell nanostructures

Based on difference in work function, novel Au nanoparticle-decorated WO3@TiO2 ternary core–shell rod-like nanocomposites (Au-WO3@TiO2) are designed and constructed as solar-light-driven photocatalysts. The photocatalytic activities were evaluated by monitoring the concentration change of methylene blue (MB) under simulated solar light irradiation. The results show that the Au-WO3@TiO2 ternary core–shell nanocomposites exhibited higher photocatalytic performance than the pure WO3 nanorods, the Au decorated WO3 nanorods and the WO3@TiO2 core–shell nanorods. The highest photocatalytic activity was found in the 1 wt% Au-WO3@TiO2 ternary core–shell nanocomposites, whose degradation efficiency and apparent rate constant (k) are 94.5% in 240 min under simulated solar light irradiation and 0.0295 min−1, respectively. The high performance of the ternary composites can be attributed to high specific area by coating of TiO2, the high utilization of solar light achieved by the surface plasmon resonance (SPR) effect of Au nanoparticles, and the low recombination rate of electrons and holes caused by electron transfer from TiO2 to Au and WO3. This study may offer a demonstration to make use of WO3 based ternary structure to help suppress the recombination of photo-induced electrons and holes in TiO2 and ultimately improve the photocatalytic efficiencies for multiple energy and environmental application.

One-step synthesis of OH-TiO2/TiOF2 nanohybrids and their enhanced solar light photocatalytic performance.

TiO2/TiOF2 nanohybrids were quickly synthesized through a hydrothermal process using titanium n-butoxide (TBOT), ethanol (C2H5OH) and hydrofluoric acid as precursors. The prepared nanohybrids underwent additional NaOH treatment (OH-TiO2/TiOF2) to enhance their photocatalytic performance. In this paper, the mechanism of NaOH affecting the pathway of transformation from TBOT (Ti precursor) to TiO2 nanosheets was discussed. The synthesized TiO2/TiOF2 and OH-TiO2/TiOF2 were characterized by field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction pattern (XRD), Fourier infrared spectroscopic analysis (FT-IR), Photoluminescence (PL) emission spectra and UV–visible diffuse reflection spectra (UV–vis DRS). The photocatalytic activity and stability of synthesized samples were evaluated by degradation of methylene blue (MB) under the simulated solar light. The results showed that a larger ratio of TiO2 to TiOF2 in TiO2/TiOF2 and OH-TiO2/TiOF2 nanohybrids could allow for even higher MB conversion compared with only TiO2 nanosheets. NaOH treatment can wash off the F ions from TiOF2 and induce this larger ratio. The highest efficiency of MB removal was just above 90% in 1 h. Lower electron–hole pairs recombination rate is the dominant factor that induces the photocatalytic performance enhancement of TiO2/TiOF2 nanohybrids. The synthesized OH-TiO2/TiOF2 nanohybrids exhibit great potential in the abatement of organic pollutants.

Solar Light Photocatalytic Performance for Gentian Violet Using Aluminium Bismuthate Nanorods

Solar Light Photocatalytic Performance for Gentian Violet Using Aluminium Bismuthate Nanorods

Uniform Gold-Nanoparticle-Decorated {001}-Faceted Anatase TiO2 Nanosheets for Enhanced Solar-Light Photocatalytic Reactions.

The {001}-faceted anatase TiO2 micro-/nanocrystals have been widely investigated for enhancing the photocatalysis and photoelectrochemical performance of TiO2 nanostructures, but their practical applications still require improved energy conversion efficiency under solar-light and enhanced cycling stability. In this work, we demonstrate the controlled growth of ultrathin {001}-faceted anatase TiO2 nanosheets on flexible carbon cloth for enhancing the cycling stability, and the solar-light photocatalytic performance of the synthesized TiO2 nanosheets can be significantly improved by decorating with vapor-phase-deposited uniformly distributed plasmonic gold nanoparticles. The fabricated Au-TiO2 hybrid system shows an 8-fold solar-light photocatalysis enhancement factor in photodegrading Rhodamine B, a high photocurrent density of 300 μA cm-2 under the illumination of AM 1.5G, and 100% recyclability under a consecutive long-term cycling measurement. Combined with electromagnetic simulations and systematic control experiments, it is believed that the tandem-type separation and transition of plasmon-induced hot electrons from Au nanoparticles to the {001} facet of anatase TiO2, and then to the neighboring {101} facet, is responsible for the enhanced solar-light photochemical performance of the hybrid system. The Au-TiO2 nanosheet system addresses well the problems of the limited solar-light response of anatase TiO2 and fast recombination of photogenerated electron-hole pairs, representing a promising high-performance recyclable solar-light-responding system for practical photocatalytic reactions.

Fabrication of Ag 2 O/TiO 2 -Zeolite composite and its enhanced solar light photocatalytic performance and mechanism for degradation of norfloxacin

Abstract Norfloxacin, as an antimicrobial drug, has frequently been detected in municipal plants, which is predicted to be potential risk on human beings and the environment. In the present study, zeolite immobilizes silver oxide decorated titanium dioxide (Ag2O/TiO2-Zeolite) composite has been fabricated through modified sol-gel method. Afterwards, physicochemical properties of the as-fabricated Ag2O/TiO2-Zeolite sample are systematically studied by scanning electron microscope, X-ray diffraction, X-ray photoelectron microscopy, ultraviolet visible diffuse reflectance spectroscopy and surface photovoltage spectra measurements. Besides these, photocatalytic (PC) performance of Ag2O/TiO2-Zeolite composite is evaluated by photodecomposition of norfloxacin under simulated solar light illumination and generation of active hydroxyl ( OH) radicals. Results indicate that the decorated Ag species exists in the form of Ag2O, which can greatly enhance the visible light absorbance and charge separation efficiency. Furthermore, Ag2O/TiO2-Zeolite composite displays superior PC performance, which is mainly ascribed to the intense light absorbance in visible region, narrow band gap level and high charge separation efficiency. In addition, the solar light PC degradation pathways of norfloxacin are proposed according to the HPLC-MS/MS measurements, including hydroxylation addition to parent compound, decarboxylation and defluorination of side chain from the norfloxacin. Moreover, the as-fabricated Ag2O/TiO2-Zeolite composite exhibits high stability after consecutive utilization for seven times.

Sulfur nanoparticles in situ growth on TiO2 mesoporous single crystals with enhanced solar light photocatalytic performance

Sulfur nanoparticles in situ growth on TiO2 mesoporous single crystals with the narrowed band gap, and the coupling effect between sulfur and TiO2 is responsible for the enhancement of solar light photocatalytic performance.

Fabrication of ZnO nanorods/Fe3O4 quantum dots nanocomposites and their solar light photocatalytic performance

ZnO nanorods (NRs)/Fe3O4 quantum dots (QDs) nanocomposites were successfully synthesized via an easy electrostatic self-assembly method. The results showed that Fe3O4 QDs with an average diameter of 4–5 nm were well dispersed on the surface of the ZnO NRs with an average diameter of 118 nm, forming ZnO NRs/Fe3O4 QDs nanocomposites. The ZnO NRs/Fe3O4 QDs nanocomposites were used as photocatalysts for the degradation of Rhodamine B under solar light irradiation. The kinetic rate constant of the ZnO NRs/Fe3O4 QDs nanocomposites was two times higher than that of the ZnO NRs. The enhanced photocatalytic property was attributed to the extended absorption spectrum of the nanocomposites.

Room-temperature solid state synthesis of ZnO/Bi2O3 heterojunction and their solar light photocatalytic performance

ZnO/Bi2O3 heterojunction was prepared by solid state reaction method at room temperature. The as-prepared nanostructures were characterized as the assembled nanosheets of ZnO on which Bi2O3 nanoparticles were well dispersed. Further studies revealed that the morphology and photocatalytic property could be regulated by tuning the amount of Bi2O3. The introduction of Bi2O3 can lead to the enhancement of solar light absorption, and the 5% ZnO/Bi2O3 samples exhibited the best photocatalytic activity under the solar light irradiation. The excellent photocatalytic performances could be ascribed to the synergistic effects of the hierarchical nanostructures and the effective separation of photogenerated carriers. Moreover, the hydroxyl radicals (OH) are found to be the main active species generated in the oxidation reaction of RhB over ZnO/Bi2O3 photocatalyst. Therefore, our work demonstrated a facile way to prepare hierarchical nanostructures with excellent photocatalytic performance using solid state method at room temperature.

Fabrication of Dy-doped BiVO4 with Enhanced Solar Light Photocatalytic Performance

BiVO4 and Dy-doped BiVO4 photocatalysts with different molar ratio of Dy/Bi (1%, 2%, 3%, and 4%) were prepared by a sol–gel method and characterized by Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), UV/Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopic (XPS) techniques, and surface photovoltage spectroscopy (SPS), respectively. The photocatalytic performance for decolorization of rhodamine B (RhB) aqueous solution under solar light was evaluated, the results show that Dy-doped BiVO4 with about 2%Dy possesses the best photocatalytic activity and the underlying mechanism is suggested.