Visible light induced photocatalytic activity of MnO2/BiVO4 for the degradation of organic dye and tetracycline

In this work, α-MnO₂/BiVO₄ nanocomposites with varying MnO₂ contents (0–7 wt%) were successfully prepared via the simple chemical method. The structure, morphology, and optical properties of prepared nanocomposites were studied by various analytical techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible absorption spectroscopy, and photoluminescence (PL) spectroscopy. The photocatalytic efficiency of α-MnO₂/BiVO₄ nanocomposites was studied via decomposition of rhodamine B (RhB) and tetracycline (TC) under exposure to visible light (λ ≥ 420 nm). Due to good structure and composite advantages, 5%MnO₂/BiVO₄ (MnBV-5) photocatalyst exhibited superior RhB and TC degradation efficiency to all other samples. In addition, the MnBV-5 photocatalyst showed good stability, and no apparent reduction in photocatalysis efficiency was noted after five testing cycles. Therefore, the MnO₂/BiVO₄ nanocomposite demonstrated a good potential for photocatalytic decomposition of new water contaminants.     

Fabrication and characterization of CdS/BiVO4 nanocomposites with efficient visible light driven photocatalytic activities

Novel CdS/BiVO₄ nanocomposites were synthesized by simple solvothermal method. The as-prepared samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Raman spectroscopy, UV–vis diffuse reflectance spectra (DRS), Fourier transform infrared spectra (FT-IR) and photoluminescence (PL). In the nanocomposites, CdS particles were deposited on the surface of the BiVO₄. The photocatalytic tests showed that the CdS/BiVO₄ nanocomposites possessed a higher rate for degradation of malachite green (MG) than the pure BiVO₄ under visible light irradiation. The 1.5-CdS/BiVO₄ nanocomposite photocatalyst was found to degrade 98.3% of MG under visible light irradiation. Moreover, the photocatalytic mechanism of CdS/BiVO₄ nanocomposites was also discussed. The results showed that the nanocomposite construction between CdS and BiVO₄ played a very important role in their photocatalytic properties, which has the potential application in solving environmental pollution issues utilizing solar energy effectively.     

A unique Cu2O/TiO2 nanocomposite with enhanced photocatalytic performance under visible light irradiation

A unique Cu₂O/TiO₂ nanocomposite with high photocatalytic activity was synthesized via a two-step chemical solution method and used for the photocatalytic degradation of organic dye. The structure, morphology, composition, optical and photocatalytic properties of the as-prepared samples were investigated in detail. The results suggested that the Cu₂O/TiO₂ nanocomposite is composed of hierarchical TiO₂ hollow microstructure coated by a great many Cu₂O nanoparticles. The photocatalytic performance of Cu₂O/TiO₂ nanocomposite was evaluated by the photodegradation of methylene blue (MB) under visible light, and compared with those of the pure TiO₂ and Cu₂O photocatalysts synthesized by the identical synthetic route. Within 120 min of reaction time, nearly 100% decolorization efficiency of MB was achieved by Cu₂O/TiO₂ photocatalyst, which is much higher than that of pure TiO₂ (26%) or Cu₂O (32%). The outstanding photocatalytic efficiency was mainly ascribed to the unique architecture, the extended photoresponse range and efficient separation of the electron-hole pairs in the Cu₂O/TiO₂ heterojunction. In addition, the Cu₂O/TiO₂ nanocomposite also retains good cycling stability in the photodegradation of MB.     

Insight into the adsorption and photocatalytic properties of in-situ synthesized g-C3N4/SnS2 nanocomposite

In this paper, a novel g-C₃N₄/2 wt% SnS₂ nanocomposite was successfully synthesized using an in-situ growth of SnS₂ on g-C₃N₄. X-ray diffraction (XRD), atomic force microscopy (AFM), Brunauer-Emmett-Teller (BET) method, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectrometer were used to characterize the photocatalysts. Exploring adsorption behavior, as an importatnt stage during photocatalytic reactions, is of great importance. Hence, both adsorption and photocatalytic performance of the synthesized photocatalysts have been investigated in detail. The adsorption isotherm fittings exhibited that Freundlich and Langmuir-Freundlich models can be applied to the methylene blue (MB) adsorption on the photocatalysts, indicating surface heterogeneity should be considered. A pseudo-second-order model was fitted to explore the adsorption kinetics. According to the observed redshift in the Fourier transform infrared spectroscopy (FTIR) result of g-C₃N₄/SnS₂ nanocomposite, π-π interaction was dominant during MB adsorption. Also, a slight redshift and significant PL intensity reduction in g-C₃N₄/SnS₂ nanocomposite led to 96% photocatalytic efficiency after 180 min under visible light radiation. The kinetics of photodegradation over g-C₃N₄/SnS₂ was about 9 and 3 times higher than those of g-C₃N₄ and SnS₂ photocatalysts, respectively. The superoxide and hydroxyl radicals were the main reactive species in the photocatalytic degradation with a Z-scheme charge transfer mechanism. The g-C₃N₄/SnS₂ nanocomposite was found to be remarkably stable after three consecutive cycles of MB degradation.     

Mn1-xCuxO2/ reduced graphene oxide nanocomposites: Synthesis,characterization, and evaluation of visible light mediated catalytic studies

The narrow optical band gap, higher electrical conductivity, and wider-absorption range are three key features that a good photocatalyst must possess. Herein, we have fabricated Cu-doped MnO₂ (Mn_1-xCu_xO₂) nanostructure by facile wet chemical approach and formed its nanocomposite with r-GO (Mn_1-xCu_xO₂/r-GO) via ultra-sonication approach. The successful replacement of host metal ions (Mn⁴⁺) with the dopant metal ions (Cu²⁺) was supported with the PXRD, FT-IR, and EDX characterizations. The effect of Cu-doping on the band gap and r-GO matrix on the conductivity of the fabricated nanocomposite was also evaluated via Tauc plots and I–V tests, respectively. The photocatalytic efficiency of the fabricated photocatalysts was tested and compared against the methylene blue (MB) under visible light irradiation. The photocatalytic experiments revealed that Mn_1-xCu_xO₂/r-GO photocatalyst exhibited superior photocatalytic aptitude than that of pristine MnO₂ and Mn_1-xCu_xO₂ photocatalysts. More precisely, the Mn_1-xCu_xO₂ photocatalysts degraded 86.89% MB dye at the rate of 0.021 min^?1 after a 90-min exposure to the visible light. Observed superior catalytic activity of the nanocomposite can be attributed to the synergistic effects between the Cu doped MnO₂ and r-GO nanosheets that resulted in its narrow band-gap (2.19 eV) and excellent conductivity (2.217 × 10^?2 Scm^?1).     

Preparation of Cu2O/exfoliated graphite composites with high visible light photocatalytic performance and stability

Cu₂O/exfoliated graphite composites (Cu₂O/EG (1 wt%), Cu₂O/EG (4 wt%), Cu₂O/EG (7 wt%), Cu₂O/EG (10 wt%), and Cu₂O/EG (15 wt%)) were prepared by the precipitation method. The photocatalytic activity of the material was evaluated using the decolorization of methyl orange (MO) solution as model reaction. Results showed that Cu₂O deposited on the worm-like flakes of EG in the form of nanocrystals. The EG provided a three-dimensional environment for photocatalytic reaction and endowed a high adsorption capacity for the sample. Under optimal conditions, the decolorization efficiencies of MO for 60 min reached 96.7%. Recycling of the catalyst showed Cu₂O/EG composites (10 wt%) to possess high photocatalytic efficiency even when repeatedly used for five times.     

Innovative synthesis of a novel ZnO/ZnBi2O4/graphene ternary heterojunction nanocomposite photocatalyst in the presence of tragacanth mucilage as natural surfactant

Developing interfacial connections is one of the breakthrough strategies to improve the photocatalytic activity of graphene/p-n heterojunction systems. Herein, natural tragacanth mucilage, for the first time, was employed as cost-effective and ecofriendly surfactant to prepare highly efficient ZnO–ZnBi₂O₄/graphene hybrid photocatalyst. The results indicated that the methylene blue (MB) photocatalytic degradation efficiency of ZnO–ZnBi₂O₄/graphene-mucilage heterojunction, containing 10 wt% ZnBi₂O₄ and 1 wt% graphene, was ～1.2, 1.4, 3.1 and 8.3 times higher than that of ZnO–ZnBi₂O₄/graphene, ZnO–ZnBi₂O₄, ZnBi₂O₄ and ZnO samples, respectively. This significant improvement in the photocatalytic performance could be mainly ascribed to the desirable advantages of using natural mucilage as surfactant, including uniform distribution of ZnO–ZnBi₂O₄ nanoparticles on the surface of graphene sheets, increasing of the effective surface area, and improving of the charge carriers separation. Based on the trapping experiments, electron spin resonance and photoelectrochemical Mott-Schottky tests, direct Z-Scheme charge transfer mechanism with hydroxyl radicals as main active species was suggested for photocatalytic degradation of MB on the ZnO–ZnBi₂O₄/graphene-mucilage nanocomposite. This study provides a new insight to fabricate more homogeneous and close contact interfaces in graphene-based hybrid photocatalytic systems for environmental remediation.     

Hydrothermal synthesis and visible-light photocatalytic activity of porous peanut-like BiVO4 and BiVO4/Fe3O4 submicron structures

Porous peanut-like BiVO₄ and BiVO₄/Fe₃O₄ submicron structures were synthesized by a template-free hydrothermal process at 160 °C for 24 h. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM) and UV–vis spectroscopy. The photocatalytic activity of BiVO₄ and BiVO₄/Fe₃O₄ submicron structures were evaluated for the degradation of Rhodamine B (RhB) and methylene blue (MB) under visible light irradiation with and without the assistance of H₂O₂. According to the experimental results obtained, porous peanut-like BiVO₄/Fe₃O₄ composite photocatalyst shows higher photocatalytic activity in the H₂O₂-assisted system under visible light irradiation compared to BiVO₄. Recycling test on the BiVO₄/Fe₃O₄ composite photocatalyst for the degradation of RhB under visible light irradiation indicates that the composite photocatalyst is stable in the H₂O₂-assisted system in five cycles. Therefore, this composite photocatalyst will be beneficial for efficient degradation of organic pollutants present in water and air under solar light.     

Investigation of g-C3N4/ZnAl2O4 and ZnO/ZnAl2O4 nanocomposites: From synthesis to photocatalytic activity of pollutant dye model

The fabrication of nanocomposite photocatalytsts with excellent photocatalytic activity is an important step in the improved degradation of organic dyes. A series of nanocomposite photocatalysts was synthesized with g-C₃N₄ and ZnO loading contents of 10, 20 and 30%. The nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). The optical band gaps of g-C₃N₄, ZnO and ZnAl₂O₄ were about 2.79, 3.21 and 3.55 eV, respectively. Methylene blue (MB) was degraded over the prepared photocatalysts under UV irradiation. Photocatalytic activity was about 9.1 and 9.6 times higher, respectively, on 20%g-C₃N₄/ZnAl₂O₄ and 20%ZnO/ZnAl₂O₄ nanocomposite photocatalysts than on pure ZnAl₂O₄ spinel powders. Recycling experiments showed that 20%g-C₃N₄/ZnAl₂O₄ and 20%ZnO/ZnAl₂O₄ nanocomposite photocatalysts exhibited good stability after five cycles of use.     

Synthesis and photocatalytic behavior of BiVO4 with decahedral structure

Decahedral BiVO₄ was successfully synthesized with Tween-80 as a template by the microwave hydrothermal method. The effects of hydrothermal temperature and Tween-80 on crystal phase and morphology of the obtained BiVO₄ were investigated. The crystal phase and morphology were characterized by X-ray diffraction, field emission scanning electron microscopy and UV–vis diffuse reflectance spectroscopy. The results indicated that the as-prepared decahedral BiVO₄ was monoclinic. The photocatalytic behavior for methylene blue (MB) degradation was enhanced with the assistance of an appropriate amount of hydrogen peroxide (H₂O₂) under visible light irradiation. The photocatalytic tests indicated that the photocatalytic efficiency of decahedral BiVO₄ synthesized at 180 °C was 63.5%. However, BiVO₄ sample synthesized at 160 °C showed the highest photocatalytic degradation rate, up to 81.6%, due to its small size and crystal defects.     

Preparation, characterization and activity evaluation of p–n junction photocatalyst p-CaFe2O4/n-ZnO

p–n junction photocatalyst p-CaFe₂O₄/n-ZnO was prepared by ball milling of ZnO in H₂O doped with p-type CaFe₂O₄. The structural and optical properties of the p–n junction photocatalyst p-CaFe₂O₄/n-ZnO were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflection spectrum (DRS) and fluorescence emission spectra. The photocatalytic activity of the photocatalyst was evaluated by photocatalytic degradation of methylene blue (MB). The results showed that the photocatalytic activity of the p-CaFe₂O₄/n-ZnO was higher than that of ZnO. When the amounts of doped p-CaFe₂O₄ were 0.0 wt.% and 1.0 wt.%, the photocatalytic degradation efficiencies were 50.1 and 73.4%, respectively. Effect of ball milling time on the photocatalytic activity of the photocatalyst was also investigated. The mechanisms of influence on the photocatalytic activity were also discussed by the p–n junction principle.     

Fabrication of titanium doped BiVO4 as a novel visible light driven photocatalyst for degradation of residual tetracycline pollutant

In this study, titanium (Ti) was used as an active dopant to incorporate into BiVO₄ lattice using the hydrothermal method. The synthesized BiVO₄ and Ti–BiVO₄ with 1, 5 and 10 wt% of Ti dopants have been applied for photocatalytic decomposition of Tetracycline under visible light irradiation. The characterized results showed that this synthesized BiVO₄ and Ti–BiVO₄ materials existed in a form of spherical particles. The particle sizes of the Ti–BiVO₄ were much bigger than that of the BiVO₄. However, Ti dopants effectively enhanced visible light absorption, decreased band gap energy as well as prevented electron-hole recombination of the BiVO₄ leading to increase in photocatalytic activities of the doped materials. The obtained results from photocatalytic experiments indicated that the 5Ti–BiVO₄, whose weight ratio of Ti was 5%, was the best material for TC degradation (78.49%). Recycling tests were consecutively carried out in 4 runs to demonstrate the stability of the BiVO₄ photocatalyst with 5 wt% of Ti dopant.     

Design and fabrication of ternary BiVO4/FeVO4/Cu2O nanorod array photoelectrode for boosting photoelectrochemical water oxidation

In this study, we demonstrate for the first time the construction of a ternary BiVO₄/FeVO₄/Cu₂O nanorod array (NRA) photoelectrode via seed-assisted refluxing, hydrothermal and successive ionic-layer adsorption and reaction (SILAR) method and its photoelectrochemical (PEC) water oxidation performance. The energy band structures of the BiVO₄, FeVO₄ and Cu₂O show that two type-II band alignments with a ladder-like structure are formed in the constructed ternary BiVO₄/FeVO₄/Cu₂O NRA photoelectrode, enabling the photoelectrode to display substantially enhanced PEC performance. The constructed ternary photoelectrode loaded with the optimized Cu₂O nanoparticles achieves a zero-bias photocurrent density of 50 μA cm^?2, 5 times higher than that of the pure BiVO₄ NRA photoelectrode. The measurements of optical property reveal that the constructed BiVO₄/FeVO₄/Cu₂O nanorod arrays (NRAs) demonstrate improved light absorption capability. The electrochemical impedance and photoluminescence measurements confirm that the charge carriers of the BiVO₄/FeVO₄/Cu₂O heterojunction NRAs are transferred and separated effectively. The substantially boosted PEC water oxidation activity of the constructed ternary BiVO₄/FeVO₄/Cu₂O heterojunction NRA photoelectrode is ascribed to the improved light harvesting and effective charge separation.     

Solvothermal synthesis and characterizations of graphene-ZnBi12O20 nanocomposites for visible-light driven photocatalytic applications

The Bismuth based Zinc metal oxide (ZnBi₁₂O₂₀) nanorods were synthesized via single step solvothermal approach. The characterization of synthesized hybridized structure was done by several analysis such as X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UVvis–DRS), Fourier transform-infrared spectroscopy (FT–IR), Thermogravimetric analysis (TGA), Raman spectroscopy, Field-Emission scanning electron microscopy (FESEM), Energy dispersive analysis of X-rays (EDX), High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy. The photocatalytic activity of ZnBi₁₂O₂₀ and an incorporation of varying weight percentages of GO (1–4 wt %) into ZnBi₁₂O₂₀ catalyst (GZBC) were analyzed under visible light irradiation by the degradation of an aqueous solution of Methylene blue (MB) and Methyl orange (MO) dye. Among various developed nanocomposites, 3 wt% GZBC reduced graphene oxide exfoliated nanocomposites has revealed the degradation efficiency as 96.04, 94.52% at 100 and 120 min for MB and MO respectively with enriched visible light absorption range. The photocatalytic property of 3 wt % reduced graphene oxide exhibits higher degradation behavior than that of other synthesized nano-composites.     

Microwave fabrication of Cu2ZnSnS4 nanoparticle and its visible light photocatalytic properties

Cu₂ZnSnS₄ nanoparticle with an average diameter of approximately 31 nm has been successfully synthesized by a time effective microwave fabrication method. The crystal structure, surface morphology, and microstructure of the Cu₂ZnSnS₄ nanoparticle were characterized. Moreover, the visible light photocatalytic ability of the Cu₂ZnSnS₄ nanoparticle toward degradation of methylene blue (MB) was also studied. About 30% of MB was degraded after 240 min irradiation when employing Cu₂ZnSnS₄ nanoparticle as a photocatalyst. However, almost all MB was decomposed after 90 min irradiation when introducing a small amount of H₂O₂ as a co-photocatalyst. The enhancement of the photocatalytic performance was attributed to the synergetic effect between the Cu₂ZnSnS₄ nanoparticle and H₂O₂. The detailed photocatalytic degradation mechanism of MB by the Cu₂ZnSnS₄ was further proposed.     

Transparent zinc silicate/ zinc oxide crystallized glass-ceramics for water remediation application under visible light

The present study focuses on taking advantage of both Zinc Silicate (Zn₂SiO₄) and Zinc Oxide (ZnO) crystals in the glass matrix for enhancing photocatalytic activity. The fabricated samples were used as a photocatalyst for degrading ～ 5 mg/L concentrated “Methylene Blue” (MB) and “Rhodamine B” (RB) dye separately under visible light. For this, 44 SiO₂:11 Al₂O₃:35 ZnO:10 K₂O compositions were prepared via the traditional melt quench process followed by heat treating at a temperature of 750 °C at 2, 4, and 6 h. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) was employed to characterize the fabricated samples. The bandgap measured from Differential reflectance spectroscopy (DRS) was found to decrease with an increase in the heat treatment duration. 44 SiO₂:11 Al₂O₃:35 ZnO:10 K₂O composition heat-treated at 750 °C for 2 h degraded ～59% and ～71% of Rhodamine B (RB) dye and Methylene Blue (MB) dye under visible light in 4 h.     

MOF assisted synthesis of a Ho2O3/CNT nanocomposite photocatalyst for organic pollutants degradation

In this work, a holmium oxide (Ho₂O₃/CNT) photocatalysts were successfully synthesized through a MOF assisted route for the first time. The effects of the morphology and purity on the photocatalytic behavior of the products, were investigated by determining various physicochemical properties. The Ho₂O₃/CNT nanocomposite was systematically analyzed by powder X-ray diffraction (P-XRD), transmission electron microscopy (TEM), ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy studies. The Ho₂O₃ derived from a MOF assisted synthetic route using Ho(NO₃)₃·5H₂O and terephthalic acid with a 1:1 M ratio at a temperature of 750 °C for 3 h prove the most advantageous, 98% degradation of 20 mg/L aqueous tetracycline pollutant was observed within 60 min. The elevated photocatalytic activity was mainly attributable to the unique synthetic route, improved crystallinity, wide UV-light absorption rate and excellent adsorption capabilities of CNT, as well as enhanced oxygen deficiency. The photocatalytic results confirm that the Ho₂O₃/CNT nanocomposite is an efficient photocatalyst for the degradation of toxic tetracycline pollutant and is thus suitable for use in environmental remediation.     

Facile mechano-chemical synthesis and enhanced photocatalytic performance of Cu2ZnSnS4 nanopowder

In the present study, Cu₂ZnSnS₄ (CZTS) powder was synthesized by the mechano-chemical method from its elemental constituents. X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and diffusion reflectance spectroscopy (DRS) were used for characterization of structural, morphological and optical properties. XRD result confirmed that a highly crystalline CZTS phase corresponding to the kesterite structure was formed after 50 h ball milling. Raman analysis confirmed the existence of single phase CZTS without any other phases. FESEM and TEM images reveal the irregular CZTS nanoparticles with an average size of 90 nm. The elemental mapping of the CZTS nanopowder showed the uniform distribution in agreement with the stoichiometry. DRS result showed a band gap value of 1.53 eV. XPS result revealed the oxidation states as Cu⁺, Zn²⁺, Sn⁴⁺ and S²⁻. The photocatalytic activity of CZTS has been investigated through photodegradation of methylene blue (MB) and methyl orange (MO) dyes solution with different concentrations under visible light irradiation. Although the CZTS decomposed MO only 81% until 210 min, the MB solution was completely photodegraded after 100 min. A kinetic study by Langmuir-Hinshelwood (L-H) model indicated about 3.7 times faster degradation of MB than MO and also higher adsorption capacity for MB by CZTS. Furthermore, the prepared CZTS was reusable and can be repeatedly used for the removal of dyes from aqueous solutions.     

Magnetically recyclable Ni1-xCdxCeyFe2-yO4-rGO nanocomposite photocatalyst for visible light driven photocatalysis

In this study, a magnetically recyclable Ni_1-xCd_xCe_yFe_2-yO₄-rGO (x, y = 0.05) (NCCF-rGO) nanocomposite photocatalyst has been prepared by following a facile in-situ co-precipitation method combined with ultra-sonication means. The as-synthesized magnetically separable NCCF-rGO nanocomposite photocatalyst efficiently degrades methylene blue (MB) dye in comparison to bare Ni_1-xCd_xCe_yFe_2-yO₄ (x, y = 0.05) (NCCF) nanoparticles (NPs) under visible light irradiation. The photo-degradation rate of MB with NCCF-rGO was ~9 times higher than NCCF nanoparticles (NPs). This enhanced photocatalytic performance of NCCF-rGO photocatalyst was due to the presence of reduced graphene oxide, which greatly help in production of photoactive species by reducing the rate of electro-hole pair recombination. The role of photoactive species that were responsible for the photocatalytic degradation of methylene blue has also been investigated. The as-synthesized NCCF-rGO photocatalyst expressed superb chemical stability and photocatalytic activity even after seven cycle runs. Moreover, the NCCF-rGO nanocomposite worked at all pH values and showed good acid resistance. In particular, the as-synthesized NCCF-rGO photocatalyst could be collected for the next cycle run by simply applying an external magnetic field. Hence, the NCCF-rGO nanocomposite could have potential use in organic dyes contained wastewater treatment.     

Visible light-activated degradation of microcystin-LR by ultrathin g-C3N4 nanosheets-based heterojunction photocatalyst

Microcystins (MCs) is a harmful toxin generated by blue-green algae in water, which has seriously threatened the ecological safety of water and human body. It is urgent to develop new catalysts and techniques for the degradation of MCs. A feasible electrostatic self-assembly method was carried out to synthesize BiVO₄/g-C₃N₄ heterojunction photocatalyst with highly efficient photocatalytic ability, where BiVO₄ nanoplates with exposed {010} facets anchored to the g-C₃N₄ ultrathin nanosheets. The morphology and microstructure of the heterojunction photocatalysts were identified by XRD, SEM, TEM, XPS, and BET. The g-C₃N₄ nanosheets have huge surface area over 200 m²/g and abundant mesoporous ranging from 2-20 nm, which provides tremendous contact area for BiVO₄ nanoplates. Meanwhile, the introduction of BiVO₄ led to red-shift of the absorption spectrum of photocatalyst, which was characterized by UV-vis diffuse reflection spectroscopy (DRS). Compared with pure BiVO₄ and g-C₃N₄, the BiVO₄/g-C₃N₄ heterojunction shows a drastically enhanced photocatalytic activity in degradation of microcystin-LR (MC-LR) in water. The MC-LR could be removed within 15 minutes under the optimal ratio of BiVO₄/g-C₃N₄. The outstanding performance of the photocatalyst is attributed to synergetic effect of interface Z-scheme heterojunction and high active facets {010} of BiVO₄ nanoplates, which provides an efficient transfer pathway to separate photoinduced carriers meanwhile endows the photocatalysts with strong redox ability.