Visible Light Photocatalytic Activity Research Articles

Facile fabrication of a SnS2/Ag3VO4 Z-scheme heterojunction for boosting visible-light photocatalytic activity

A SnS2/Ag3VO4 Z-scheme heterojunction was prepared for the first time. The SnS2/Ag3VO4 hybrid photocatalyst can efficiently degrade MB, and it possessed higher photoactivity and better stability than the single catalyst.

Synergy of adsorption-photocatalysis and enriched surface oxygen vacancies over lignin-biochar/Bi2MoO6 nanocomposites for organic pollutant removal and bamboo ECF bleaching effluent treatment

LC/Bi 2 MoO 6 composites were successfully fabricated and applied to the effective degradation of methylene blue (MB) under visible light illumination. The composition, morphology and photoelectrochemical properties of prepared samples were characterized by various techniques. EPR analysis reveals that the density of surface oxygen vacancies was enhanced after lignin-biochar addition. Under optimal conditions, the degradation efficiency of MB over LC/Bi 2 MoO 6 was 95.34 % at 1 h under visible light irradiation, and the reaction rate constant ( k ) was 18.96 folds higher than that of pristine Bi 2 MoO 6 . The enhanced photocatalytic performance of LC/Bi 2 MoO 6 was due to the synergistic effect between adsorption-photocatalysis and enriched surface oxygen vacancies, which greatly promotes the separation of photogenerated charge carriers. Moreover, the MB degradation removal with LC/Bi 2 MoO 6 decreased by 3.84 % at 1 h under visible light irradiation after four cycles, illustrating excellent stability and reusability in the photocatalytic recycling process. Notably, the bandgap of Bi 2 MoO 6 decreased from 2.66 eV to 2.26 eV with the addition of lignin-biochar. Radical capture experiment and ESR characterization demonstrate that •OH radicals were the main active radical in the photocatalytic process, which increases the radical concentration during the combination of lignin-biochar. Furthermore, the LC/Bi 2 MoO 6 composites were also applied to the degradation of bamboo ECF bleaching effluent, with a higher COD Cr and AOX removal of 75.72 % and 69.64 %, respectively. Herein, this work provides a novel insight for constructing economic and efficient photocatalysts for wastewater remediation and biomass utilization. • A novel LC/Bi 2 MoO 6 composites with enriched oxygen vacancies was prepared. • LC/Bi 2 MoO 6 composites exhibits superior adsorption and visible-light photocatalytic activity for MB and bamboo ECF bleaching effluent degradation. • The photocatalytic mechanism of LC/Bi 2 MoO 6 was proposed.

119Sn Mössbauer spectroscopic insight into the effect of surface-located tin dopant cations on the visible-light photocatalytic activity of anatase TiO2

The presence of Sn4+ dopant ions on the surfaces of titania crystallites results in a nearly fourfold increase in the rate constant of a white-light photocatalytic bleaching reaction of methyl orange. Thus, the positive effect of a SnII electronic lone pair, which was theoretically predicted in 2013 by Iwaszuk and Nolan for a SnO-nanocluster modified anatase model, can be experimentally revealed using catalyst powders containing surface-located oxidized Sn4+ species.

Kilogram-scale fabrication of TiO2 nanoparticles modified with carbon dots with enhanced visible-light photocatalytic activity.

Incorrect discharge of dye wastewater will cause environment pollution and be very harmful to human health. Visible-light photocatalysis over large-scale synthesized semiconductor materials can become one of the feasible solutions for the practical application of purifying dye wastewater. As a new candidate, carbon dots (CDs) with unique fluorescence were fabricated on a tens of grams scale and then further applied to the kilogram-scale synthesis of a CDs/TiO2 composite by one-step heat treatment. Compared with single TiO2 nanoparticles (NPs), the CDs/TiO2 composite with a large specific surface area exhibits enhanced photo-degradation performance for methyl orange (MO). This phenomenon can be attributed to the loading of CDs in the TiO2 NPs, which is conducive to broadening the light absorption spectrum and improving absorption intensity, narrowing the band gap, charge carrier trapping, up-converting properties, and charge separation. The kilogram-scale synthesis of the CDs/TiO2 photocatalyst does not affect the morphology, structure, optical properties and photocatalytic performance of the composite, which opens up a new avenue to construct elaborate heterostructures for enhanced photocatalytic performance using visible light as the light source.

Construction of 2-aminobenzothiazole (ABT)-g-C3N4/WO3 composites with enhanced visible-light photocatalytic activity and properties

ABT doping improves the band gap and electron–hole separation efficiency of g-C3N4, and ethanol enhances the photocatalytic activity of ABT/CN/W composites.

Facile one-pot synthesis of a BiOBr/Bi2WO6 heterojunction with enhanced visible-light photocatalytic activity for tetracycline degradation

Photocatalytic removal of tetracycline (TC) from the wastewater is of great value in the chemical and environmental engineering field. Here, we introduced a facile one-step method for the synthesis of BiOBr/Bi 2 WO 6 heterojunctions by using cheap CTAB as the Br source. We showed the possibility of our method to fine-tune the content of BiOBr in the produced BiOBr/Bi 2 WO 6 through by simply changing the dosage of CTAB, providing a platform for the delicate tuning of the visible-light absorbance ability of the composites. With a suitable heterojunction structure of BiOBr/Bi 2 WO 6 -0.2, it exhibited an ultrarapid photocatalytic activity towards TC (20 mg·L −1 ), with a competitive removal efficiency of 88.1% within 60 min and an ultrahigh removal rate of 0.0349 min −1 . It could also be robustly recycled for at least 5 cycles with slight removal efficiency loss. We demonstrated that this exciting photocatalytic performance was due to the highly decreased recombination of photoinduced electrons and holes on our composites by constructing this heterojunction structure, and the resulting ·OH and · O 2 - contributed to the effective degradation of TC to CO 2 .

Strontium-induced phase, energy band and microstructure regulation in Ba1−xSrxTiO3photocatalysts for boosting visible-light photocatalytic activity

The polyacrylamide gel method has been developed for fabrication of Ba1−xSrxTiO3(BST) photocatalysts. The structure, surface morphology, band gap and photocatalytic activity of BST photocatalysts can be regulated by adjusting thexvalue.

Efficient doping to synthesize high-performance Co/Fe-BiOCl photocatalyst assisted by the ion release from novel CoFe2O4 nanofiber reservoir

Metal ion doping is an efficient method to achieve high photocatalytic performance of semiconductors. However, the current synthetic methods by using inorganic salts as doped sources in the precursor reaction system might suffer from ion waste and second pollution. Herein, we developed a novel method by employing electrospun nanofibers as ion reservoir to release metal ions for the synthesis of ion-doped semiconductors with high photocatalytic activity. As demonstrated, Co/Fe co-doped BiOCl photocatalyst (Co/Fe-BOC) was facilely prepared in the presence of CoFe2O4 nanofibers as Co and Fe ion reservoir via a simple solvothermal method. Compared with BiOCl, the resulted Co/Fe-BOC shows increased specific surface area, visible light response as well as separation and transportation efficiencies of photogenerated carriers. Thus, the Co/Fe-BOC exhibits significantly enhanced visible light photocatalytic activity to degrade 99.4% rhodamine B (RhB) within 4 min. This new doping approach not only avoids the ion waste and pollution during the reaction process but also facilitates the separation of the photocatalyst. Moreover, the CoFe2O4 nanofibers could be repeatedly used as ion reservoir to prepare high-performance Co/Fe-BOC. This nanofiber-based ion doping approach provides a novel, universal and promising insight to obtain doped semiconductors with high photocatalytic activity.

Polypyrrole/cadmium sulfide/nickel hollow fiber as an enhanced and recyclable intrinsic photocatalyst for pollutant removal and high-effective hydrogen evolution

The photocatalysis for environment purification and clean energy production has attracted widespread attention, however, traditional powder-form photocatalysts cannot meet the practical application due to their poor recyclability, especially in slurry system. Here, polypyrrole/cadmium sulfide/nickel (PPy/CdS/Ni) multi-layer hollow fibrous photocatalyst with favorable photocatalytic activity for pollutants removal and hydrogen (H2) evolution was successfully fabricated, which possesses a narrow band gap of ∼1.87 eV and enhanced visible-light photocatalytic activity. The removal efficiency of methylene blue (MB) and tetracycline can reach up to ∼94.76% and ∼76.1%, respectively. Simultaneously, the TOC removal efficiency with regard to MB can reach up to 78.1% and Cd2+ leakage is extremely low (<3 mg⋅L−1). More interestingly, H2 evolution rate of PPy/CdS/Ni hollow fiber is up to as high as 665.7 μmol⋅g−1⋅h−1, which is about 1.43 and 1.86 folds higher than the PPy/CdS/Ni/PET fiber (466.3 μmol⋅g−1⋅h−1) and CdS/Ni/PET fiber (357.1 μmol⋅g−1⋅h−1), respectively. As a fiber-form intrinsic photocatalyst, our catalytic fiber shows great promise for pollutants removal and hydrogen energy production due to its easy-handling and recyclement.

Synergetic interfacial charge transfer with Z-scheme heterostructure and S–Mo–S linkage in one-pot synthesized SnIn4S8/MoS2 for efficient photocatalytic activity

Construction of high-efficiency scheme towards interfacial charge transfer is of great value to suppress the spatial carrier recombination and thus to develop advanced heterogeneous photocatalysts for environmental remediation. Herein, a novel Z-scheme SnIn4S8/MoS2 with interfacial S–Mo–S bond was synthesized by a facile one-step hydrothermal method. The prepared optimal SnIn4S8/MoS2 heterostructure (SIS/MS-24) exhibited significantly enhanced visible-light photocatalytic activities for crystal violet degradation and Cr(VI) reduction compared with individual materials. The boosted photocatalytic performance was primarily attributed to the Z-scheme charge transfer mechanism certificated by the trapping experiments, ESR (electron spin resonance) test, and DFT (density functional theory) calculation. What’s more, the formation of S–Mo–S bond between SnIn4S8 and MoS2 acted as a specific bridge to further promote the Z-scheme channel for charge transport at the interface. This synergy of Z-scheme heterostructure and covalent S–Mo–S linkage greatly accelerated the separation of electron-hole pairs. Additionally, the SIS/MS-24 composite also displayed good stability even after five cycles of testing experiments. This work provides a novel way to design and fabricate efficient Z-scheme photocatalysts for water purification.

Ag–TiO2 mesocrystal-coupled g-C3N4 nanosheets with enhanced visible-light photocatalytic activity

Ag–TiO2 mesocrystal-coupled g-C3N4 nanosheets with enhanced visible-light photocatalytic activity

Novel La3+/Sm3+ co-doped Bi5O7I with efficient visible-light photocatalytic activity for advanced treatment of wastewater: Internal mechanism, TC degradation pathway, and toxicity analysis

Controlling semiconductor photocatalysts by doping rare-earth ions is an effective strategy to improve photocatalytic performance. Simple solvothermal and calcination methods were used to prepare La3+ and Sm3+ modified Bi5O7I nanomaterials. Some characterizations such as XRD, XPS, SEM, TEM, UV–vis, etc. were carried out to explore its structural composition and photoelectrochemical properties. The photocatalytic activity was investigated by simulating the degradation of TC and RhB under visible-light irradiation. The degradation results showed that the photocatalytic efficiency of 4S4L-Bi5O7I was the best among the samples with the 100% degradation rate of TC (Tetracycline hydrochloride) and 93% of RhB (Rhodamine B). The capture experiment and ESR test proved that the active substances that play a role in the photocatalytic degradation of pollutants were ·O2−, 1O2 and h+, and on this basis, the possible degradation mechanism was proposed. The final results showed that La/Sm co-doping expanded the light absorption range of Bi5O7I and improved the charge separation efficiency and the specific surface area. Besides, the surface defects were formed on the surface of Bi5O7I due to ion-doping, which could catch e− to promote the separation and transfer of carriers and improve the photocatalytic activity. LC-MS was used to analyze the possible degradation pathways of TC. And the toxicity of TC was also analyzed via T.E.S.T and Toxtree. The results showed comprehensive toxicity of TC was decreased by 4S4L-Bi5O7I so that the overall water pollution was reduced. This work can provide a reference for the subsequent development of bismuth-based photocatalysts.

Hydrolysis‐Induced InOx on ZnIn2S4 Promotes Selective CO2 Photoreduction over H2 Evolution

AbstractMetal sulfides generally show high visible light photocatalytic activity, but lower selectivity in the CO2 photoreduction due to the competitive hydrogen evolution. Here, a partial hydrolysis method is reported to promote the selective photocatalytic CO2 reduction over ZnIn2S4. The ZnIn2S4 was post‐hydrolyzed in an aqueous ammonia solution to form oxide species (ZIS‐[InOx]). Detailed experiment and DFT calculation demonstrated that the post‐hydrolysis treatment facilely prohibits the recombination of photogenerated charge carriers and benefits CO2 activation. Under visible light irradiation, the ZIS‐[InOx] photocatalyst shows enhanced CO2‐to‐CO conversion activity with a CO‐evolving rate of 1771 μmol g−1 h−1, which is about 8 times higher than that over pristine ZIS and 3.5 times higher than that over bulk ZIS/In2O3. More importantly, the post hydrolysis treatment significantly prohibits the hydrogen evolution and increases the CO/H2 ratio from 0.08 over ZIS to 1.8 over ZIS‐[InOx]. This work provides a new strategy to prepare catalysts for photocatalytic CO2 reduction.

Modified BiFeO3/rGO nanocomposite by controlled synthesis to enhance adsorption and visible-light photocatalytic activity

In this study, a sol-gel process is used to synthesize a bismuth ferrite (BiFeO3, or BFO for short)/reduced graphene oxide (rGO) nanocomposite (BGO). The structural, morphological, and optical characteristics of the BiFeO3 nanopowder are modified by controlling heat treatment parameters and rGO contents. The semi-spherical BFO nanoparticles possess rhombohedral distorted perovskite crystal structure and are grafted on rGO nanosheets of various sizes which are attributed to the existence of rGO content during the sol-gel process. The observed interface between rGO nanosheets and BFO nanoparticles assists in the efficient charge separation and transfer of photogenerated BFO charge carriers through rGO nanosheets. Compared to BFO, BGO has a narrower band gap energy of 1.8 eV, a lower rate of charge carrier recombination, and stronger magnetic characteristics. The adsorption performance and photocatalytic activity mechanisms have been thoroughly examined. By adding rGO, the adsorption isotherm of methylene blue (MB) on the BFO photocatalyst changed from the Freundlich to the Langmuir. Also, the adsorption kinetics were investigated using a pseudo-second-order model. Furthermore, the degradation of MB is used to evaluate the visible light photocatalytic activity whereby 98% degradation was reached after 300 min. The Mott-Schottky test and the active species scavenger experiment are used to assess the potential mechanisms of MB photodegradation. The findings showed that the primary active species in photodegradation were hydroxyl radicals. Also, the nanocomposite was reasonably stable, and it could be magnetically removed from aqueous environments and utilized again for subsequent usage.

Heterostructured BiOCl–LaOCl S-scheme composites with improved visible-light photocatalytic activity on Rhodamine B dye

In this work, we report the synthesis of heterostructured BiOCl–LaOCl composites by using KCl as a source of chlorine and varying contents of LaOCl as raw materials in the presence of ethylene glycol at a temperature of 100 °C by using the solvothermal method. The prepared composites were characterized by X-ray diffraction, UV–Visible NIR spectroscopy, photoluminescence spectroscopy, SEM, TEM, EDX mapping, BET, and XPS analysis. TEM analysis revealed that the LaOCl particles were deposited on the surface of the BiOCl microspheres. The photo-efficiency of the BiOCl–LaOCl composite as photocatalyst was assessed by decomposing the Rhodamine B dye in an aqueous solution under irradiation from sunlight. The composite was found to have a higher rate of degradation of the dye solution than those of pure BiOCl and LaOCl semiconductors. The BiOCl–LaOCl‐1 composite exhibited the maximum catalytic activity of all the synthesized materials. The ability of the composite to degrade the dye was studied by using UV–Vis spectroscopy. The apparent rate of reaction of BiOCl–LaOCl‐1 was 0.1209 min−1, four and six times higher than those of BiOCl–LaOCl-2 and BiOCl, respectively. The results of the scavenger test revealed that the superoxide and hole radicals were mainly responsible for photodegradation. The high BET surface area of the composite also indicated enhanced photocatalytic activity.

In Situ Fabrication of N-Doped ZnS/ZnO Composition for Enhanced Visible-Light Photocatalytic H2 Evolution Activity.

For achieving the goal of peaking carbon dioxide emissions and achieving carbon neutrality, developing hydrogen energy, the green and clean energy, shows a promising perspective for solving the energy and ecological issues. Herein, firstly, we used the hydrothermal method to synthesize the ZnS(en)0.5 as the precursor. Then, ZnS/ZnO composite was obtained by the in situ transformation of ZnS(en)0.5 with heat treatment under air atmosphere. The composition, optical property, morphology, and structural properties of the composite were characterized by X-ray photoemission spectroscopy (XPS), Ultraviolet-visible absorption spectra (Uv-vis Abs), Scanning electron microscopy (SEM) and Transmission electron microscopy image (TEM). Moreover, the content of ZnO in ZnS/ZnO was controlled via adjustment of the calcination times. The visible-light response of ZnS/ZnO originated from the in situ doping of N during the transformation of ZnS(en)0.5 to ZnS/ZnO under heat treatment, which was verified well by XPS. Photocatalytic hydrogen evolution experiments demonstrated that the sample of ZnS/ZnO-0.5 h with 6.9 wt% of ZnO had the best H2 evolution activity (1790 μmol/h/g) under visible light irradiation (λ > 400 nm), about 7.0 and 12.3 times that of the pure ZnS and ZnO, respectively. The enhanced activities of the ZnS/ZnO composites were ascribed to the intimated hetero-interface between components and efficient transfer of photo-generated electrons from ZnS to ZnO.

Nano TiO2 and Molybdenum/Tungsten Iodide Octahedral Clusters: Synergism in UV/Visible-Light Driven Degradation of Organic Pollutants.

Emissions of various organic pollutants in the environment becomes a more and more acute problem in the modern world as they can lead to an ecological disaster in foreseeable future. The current situation forces scientists to develop numerous methods for the treatment of polluted water. Among these methods, advanced photocatalytic oxidation is a promising approach for removing organic pollutants from wastewater. In this work, one of the most common photocatalysts-titanium dioxide-was obtained by direct aqueous hydrolysis of titanium (IV) isopropoxide and impregnated with aqueous solutions of octahedral cluster complexes [{M6I8}(DMSO)6](NO3)4 (M = Mo, W) to overcome visible light absorption issues and increase overall photocatalytic activity. XRPD analysis showed that the titania is formed as anatase-brookite mixed-phase nanoparticles and cluster impregnation does not affect the morphology of the particles. Complex deposition resulted in the expansion of the absorption up to ~500 nm and in the appearance of an additional cluster-related band gap value of 1.8 eV. Both types of materials showed high activity in the photocatalytic decomposition of RhB under UV- and sunlight irradiation with effective rate constants 4-5 times higher than those of pure TiO2. The stability of the catalysts is preserved for up to 5 cycles of photodegradation. Scavengers' experiments revealed high impact of all of the active species in photocatalytic process indicating the formation of an S-scheme heterojunction photocatalyst.

Synthesis and enhanced visible-light photocatalytic activity of anatase TiO2/sludge-derived activated carbon composite for degradation of methylene blue

Synthesis and enhanced visible-light photocatalytic activity of anatase TiO2/sludge-derived activated carbon composite for degradation of methylene blue

Novel core–shell heterojunction photocatalytic wire mesh for efficient ciprofloxacin degradation under visible light

In order to solve the problems of easy recombination of electron–hole pairs, low solar energy utilization efficiency and difficult reuse of catalyst, a core–shell α–Fe2O3/Bi2MoO6@304SS heterojunction photocatalytic was synthesized and successfully immobilized on the 304 stainless steel (304SS) wire mesh. The result featured a flower–like particles assembled by a nanosheet catalyst uniformly distributed on the surface of the α–Fe2O3 shell, and showed high adsorption and visible–light photocatalytic activity towards ciprofloxacin (CIP). The CIP degradation efficiencies of 96 % and 92 % in the presence of visible light from a 40 W LED lamp and direct sunlight, respectively. Moreover, the photocatalytic mesh exhibited good structure stability and recycling performance. As determined, a built–in the electric field generated by the heterojunction reduced the recombination probability of electron–hole pairs, and significantly improved photocatalytic activity. Additionally, the possible electron migration mode in the heterojunction interface is proposed, the photocatalytic mechanism is elucidated, and possible degradation pathways of CIP are analyzed. With these unique features, the synthesis of photocatalytic mesh could be easily applied in water environment restoration and wastewater treatment systems.

Effect of Ni doping on the adsorption and visible light photocatalytic activity of ZnO hexagonal nanorods

Pristine and 1, 1.5, 2, 2.5 and 3 wt% Ni doped ZnO nanorods are prepared by hydrothermal technique as an effective photocatalyst for the removal of Malachite Green (MG) dye from aqueous media. Kinetic modelling of photocatalytic degradation and adsorption properties of the catalysts are done by pseudo first order (PFO), pseudo second order (PSO), fractal like psuedo first order (FPFO), fractal like psuedo second order (FPSO), elovich, exponential and intra particle diffusion (IPD) models. In contrary to the general trend, adsorption efficiency of ZnO is decreased while photocatalytic property got enhanced with doping. As-prepared catalysts are well characterised using XRD, FESEM, XPS, EDS, BET, UV and PL. This study points out the effect of Ni doping on the adsorption and visible light photocatalytic properties of ZnO nanostrutures via detailed kinetic modelling and explanation through various characterisation techniques and show cases their practical application in the field of waste water management. Water quality analysis was done post to degradation studies and the purified water samples have pH in the permissible range of drinking water which shows the efficient removal of dye molecules from the solution.