Visible-light Photocatalytic Activity For Degradation Research Articles

Efficient charge carrier separation over carbon-rich graphitic carbon nitride for remarkably improved photocatalytic performance in emerging organic micropollutant degradation and H2 production

Graphitic carbon nitride (g-C3N4) shows great potentials in visible-light-driven catalytic oxidation of organic micropollutants to harmless products and reduction of water to H2 but suffers from drawback of sluggish charge carrier separation and transfer dynamics. To overcome this drawback, here a novel point defect engineering strategy, by a nicotinic acid or barbituric acid-assisted supramolecule self-assembly of dicyandiamide followed by thermal polymerization, is designed to prepare pyridine unit-incorporated g-C3N4 (CPyr-CNx) and carbon atom self-doped g-C3N4 (C-CNx). The strategy leads to well-regulated chemical structures of CPyr-CNx and C-CNx and thus the precisely controlled electronic structures. The CPyr-CNx and C-CNx both exhibit remarkably improved visible-light photocatalytic activity in degradation of emerging organic micropollutants (methylparaben, acetaminophen and bisphenol A) and water-splitting to H2 production in comparison of bulk g-C3N4 and carbon-rich g-C3N4 prepared by a direct thermal copolymerization of nicotinic acid or barbituric acid with dicyandiamide, and their photocatalytic redox activity depends on carbon doping level. Experimental results combined with theoretical simulations reveal that the superior photocatalytic redox performance of CPyr-CNx and C-CNx is mainly dominated by the significantly boosted charge carrier separation and transfer dynamics driven by carbon doping induced-local electric field and -midgap states, which finally generates abundant reactive oxidation species including •O2− anion radicals, •OH radicals and 1O2 for the deep oxidation of target organic micropollutants to significantly reduce their ecotoxicity; additionally, such efficient charge carrier separation and transfer also favors high mobility for free electron-involved photocatalytic H2 evolution reaction.

PREPARATION AND PHOTOCATALYTIC PERFORMANCE OF AG3PO4/MOS2 COMPOSITE PHOTOCATALYST

Ag3PO4 and MoS2 semiconductor materials were synthesized by hydrothermal method. The composite materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), and UV–vis diffuse reflectance spectroscopy (UV–VIS DRS), and the photocatalytic degradation of organic dyes by rhodamine B was studied. The results showed that: Ag3PO4/MoS2 composite photocatalyst is formed by using MoS2 microspheres as the matrix and Ag3PO4 nanoparticles coated on its surface or embedded in its lamellar structure. When the molar fraction of Ag3PO4 in the composite product is 75%, the composite photocatalyst has better light absorption capacity and lower photogenerated carrier recombination rate (optical band gap is 1.24 eV), and shows better visible light photocatalytic degradation activity in the photocatalytic degradation of RhB experiment, the catalytic degradation rate is as high as 95.0%. At the same time, the degradation mechanism showed that H+ and O2− were the main active substances for RhB degradation. The photocatalyst has excellent performance and simple preparation method. It has broad application prospects in the field of photocatalysis.

Construction of g/C3N4-ZnO composites with enhanced visible-light photocatalytic activity for degradation of amoxicillin

Construction of g/C3N4-ZnO composites with enhanced visible-light photocatalytic activity for degradation of amoxicillin

Composition-dependent structure evolution of FeVO4 nano-oxide and its visible-light photocatalytic activity for degradation of methylene blue

This work report on the synthesis of the iron orthovanadate oxide (FeVO4) catalysts with various vanadium (V) loading amounts of 10% (FeV-1); 20 wt% (FeV-2); 30 wt% (FeV-3) and 40 wt% (FeV-4). The structure evolution of FeVO4 was studied by using XRD, UV–vis, PL, FTIR, XPS, SEM, EDX, TEM, EIS, Raman and BET surface area techniques. XRD analysis showed that crystal structure and phase formation of FeVO4 to depend on V-metal loadings, and that the various Fe:V ratio showed peaks shifting, which were related to the transformation of Fe2O3 and V2O5 interface into FeVO4 phase with respect to increasing V-metal loadings. The XPS results showed the significant influence of the V-metal loadings on inducing various electronic, redox oxidation states of V3+/V4+/V5+ and Fe2+/Fe3+ and oxygen vacancy defects structure properties of FeVO4 catalysts. The physical structure changes confirmed by XRD, XPS and FTIR manifested the tailoring of the optical properties as evidenced by PL and UV–vis with FeV-3 catalyst showing the desirable optics properties. This were determined to give the properties for the efficient photodegradation activity of methylene blue model organic dye of wastewater with its near complete removal with 30 min reaction time. The enhanced productivity photodegradation performance of the hetero-mixed FeVO4 catalysts is ascribed to their enriched visible-light harvesting range and efficient suppression of electrons/holes (e-/h+) recombination manifested by the effect of Fe:V composition ratio. Moreover, the presence of small quantity of Fe2O3 in predominant FeVO4 could allow efficient e-/h+ separation and transfer by creation of Fe2O3/FeVO4 heterojunction interface. The FeVO4 catalyst showed excellent recyclability and its stable photoactivity under aqueous degradation conditions.

NiFe-Layered Double Hydroxides as a Novel Hole Repository Layer for Reinforced Visible-Light Photocatalytic Activity for Degradation of Refractory Pollutants

NiFe-Layered Double Hydroxides as a Novel Hole Repository Layer for Reinforced Visible-Light Photocatalytic Activity for Degradation of Refractory Pollutants

Fabrication of ternary Ag/La-black TiO2−x photocatalyst with enhanced visible-light photocatalytic activity for tetracycline degradation

The ternary Ag/La-TiO2−x heterojunctions were prepared successfully and was used for the photocatalytic degradation of tetracycline (TC) under visible light irradiation. Using numerous techniques, the factors affecting the structure, morphology and optoelectronic properties of Ag/La-TiO2−x composites were systematically discussed. Due to the higher photoinduced charge separation efficiency, the as-prepared composites possessed the excellent visible-light photocatalytic degradation activity of TC. The ·O2- was the primary active species as well as the h+ and •OH were the essential active species during the process of photocatalytic degradation. Moreover, the mechanism of photocatalytic degradation of TC by Ag/La-TiO2−x composites was given, and the degradation pathways of TC during the process of photocatalytic were also considered. Based on the synergism of the introduction of Ti3+ and Ov, the inhibition charges recombination caused of La and the SPR effect of Ag nanoparticles, the photocatalytic performance of the Ag/La-TiO2−x composite observably improved. Due to the excellent photocatalytic properties and stability, the Ag/La-TiO2−x hybrid composites are expected to have significant potential applications in energy conversion and environmental remediation.

Enhanced visible-light photocatalytic degradation activity of Ti3C2/PDIsm via π–π interaction and interfacial charge separation: Experimental and theoretical investigations

Herein, Ti3C2 MXene nanosheets and perylene diimide supramolecular (PDIsm) were successfully combined via a facile self-assembly method. The apparent rate constant of photodegradation for tetracycline hydrochloride (TCH) and Rhodamine B (RhB) of 1%-Ti3C2/PDIsm (0.079 min−1 and 0.082 min−1) were 2.5 times and 7.2 times higher than that of pure PDIsm, respectively. The introduction of Ti3C2 MXene nanosheets is beneficial to the stacking degree of PDIsm and the adsorption capacity of PDIsm for organic pollutants. Moreover, the excellent electrical conductivity of Ti3C2 also promotes the charge separation, which contributes to more photoelectrons participated in the photodegradation reaction of pollutants and thereby the enhanced photocatalytic performance. Additionally, the density functional theory (DFT) calculation also provides strong evidence for the enhanced photocatalytic degradation activity of Ti3C2/PDIsm structure. Meanwhile, the mechanism exploration indicates that h+, ∙O2– and 1O2 play leading roles in the photocatalytic process. This work provides a new insight into using 2D MXenes as co-catalysts to enhance the activity of self-assembled organic materials for environmental remediation.

Interfacial and electronic band structure optimization for the adsorption and visible-light photocatalytic activity of macroscopic ZnSnO3/graphene aerogel

A macroscopic monolithic ZnSnO3/reduced graphene oxide aerogel (ZGA) composite was prepared and showed excellent adsorption and visible-light photocatalytic degradation activity for ciprofloxacin (CIP) wastewater. Especially, when the mass ratio of ZnSn(OH)6 to graphene oxide (GO) is 1:2 (ZGA-4), the removal efficiency of CIP is almost reach 100%. The enhanced photoactivity of ZGA can be attributed to the optimized interfacial and electronic band structure reducing the recombination of photogenerated e−-h+ pairs to produce more ·O2− and ·OH active species, which were confirmed by series of characterization techniques combine with density functional theory (DFT) calculations. Moreover, ZGA also exhibits satisfactory photostability, 98% CIP and the biological toxicity of CIP to Escherichia coli DH5a have been basically eliminated after four-cycle photocatalytic degradation.

WITHDRAWN: g-C3N4-nanosheet/ZnCr2O4 S-scheme heterojunction photocatalyst with enhanced visible-light photocatalytic activity for degradation of phenol and tetracycline [Sep. Purif. Technol. (2021) 118511

Abstract Photocatalytic processes based on semiconductors have been regarded as an efficient environmental purification technology to remove different contaminants from wastewater, and summon for impressive photocatalysts is incessant. Herein, a new step-scheme nanocomposite constructed of g-C3N4-nanosheet/ZnCr2O4 heterojunction is synthesized for effective degradation of phenol and tetracycline. The prepared g-C3N4-nanosheet/ZnCr2O4 nanocomposite exhibits photocatalytic performance for phenol and tetracycline degradation more than 5.8 and 22.5-folds greater than bare g-C3N4-nanosheet and 6.2 and 34.2-times larger than pure ZnCr2O4, respectively. The recycling tests also display that about 88.2% and 89.7% of phenol and tetracycline can be photo-degraded by binary g-C3N4-nanosheet/ZnCr2O4 photocatalyst even after five cycles. The prepared binary photocatalyst pursues a step-scheme charge transfer mechanism that leads to the significant photocatalytic activity under visible illumination. The superior photoability is assigned to the excellent visible light-harvesting capability and fast charge separation and transportation characteristics. The present research serves as a principle route to design and extend striking step-scheme g-C3N4-based nanocomposites with promising environmental purification and solar fuel generation usage.

The study of visible-light photocatalytic degradation activity of Ag doped g-C3N4 obtained by heating process

In this paper, Ag nanoparticles (Ag NPs) were loaded on pure g-C3N4 (CN) via two different methods of direct heating and indirect heating to form g-C3N4/Ag-DX and g-C3N4/Ag-IDX photocatalysts, respectively. Using methylene blue as the degradation dye, the photocatalytic performance of g-C3N4/Ag-DX and g-C3N4/Ag-IDX was studied through visible light photocatalysis experiments. The results demonstrated that the photocatalytic performance of g-C3N4/Ag-DX and g-C3N4/Ag-IDX both increases with the increase in content of Ag nanoparticles. It is obvious that g-C3N4/Ag-ID8 has the optimal photocatalytic activity. Meanwhile, the g-C3N4/Ag-ID8 has excellent stability and can be reused in photocatalysis experiments.

Construction of DyVO4/nitrogen deficient g-C3N4 composite for enhanced visible-light photocatalytic activity for tetracycline degradation

The defects engineering takes effects on regulating the electronic structure to enhance the optical absorption, and acting as the capture centers of charge carriers to hinder the recombination of electron hole pairs. In this work, DyVO4/nitrogen deficient g-C3N4 (DVO/CNx) composite photocatalysts were successfully synthesized by a simple precipitation-calcination method, which showed excellent visible-light photocatalytic activity for the degradation of tetracycline (TC). Among them, 10 % DVO/CNx (with the mass ratio of 10 % DVO in the composites) exhibited the optimum photocatalytic performance (within 1 h, 92 % degradation of TC), which was higher than pure phase materials (CN, CNx and DVO) and DVO/CN heterojunction photocatalyst. The dramatically enhanced photocatalytic activity of DVO/CNx composite can be ascribed to its defect structure and the construction of heterojunction, which can simultaneously improve the visible-light absorption and separation efficiency of photo-generated electron-hole pairs. More importantly, the DVO/CNx photocatalyst exhibits high stability and reusability.

Ultrasonic-assisted preparation of ZrO2/g-C3N4 nanocomposites with high visible-light photocatalytic activity for degradation of 4-chlorophenol in water

Various methods including photocatalysis have been used for degradation and removal of phenolic compounds, which classified as hazardous materials in the environment. Nanomaterials exhibited significant advantages for photocatalytic degradation of phenolic compounds compared to the conventional oxidation approaches such as traditional biological and physical methods. In this study, zirconia (ZrO2)/graphitic carbon nitride (g-C3N4) nanocomposites were successfully synthesized using ultrasonication method and used for photodegradation of 4-chlorophenol (4-CP) in water under visible light. The g-C3N4 nanosheets, ZrO2 nanoparticles (NPs), and ZrO2/g-C3N4 nanocomposite were characterized by N2 adsorption, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), photoelectrochemical (PEC) measurements, and photoluminescence spectroscopy (PL). The incorporation of ZrO2 NPs enhanced the surface area and light absorption capacity of pristine g-C3N4. The photocatalytic activity of ZrO2/g-C3N4 nanocomposite sample was evaluated by the degradation of 4-CP in aqueous medium. Results exhibited an increase in photocatalytic activity of ZrO2/g-C3N4 nanocomposite compared to unmodified ZrO2 NPs and pristine g-C3N4. In addition, reusability experiment of ZrO2/g-C3N4 nanocomposite for photo-catalytic degradation, as well as for 4-CP adsorption showed the ZrO2/g-C3N4 nanocomposites can be effectively used for several cycles.

Facile synthesis of multi-type carbon doped and modified nano-TiO2 for enhanced visible-light photocatalysis.

Nano-TiO2 is a type of environment-friendly and inexpensive substance that could be used for photocatalytic degradation processes. In this study, the multi-type carbon species doped and modified anatase nano-TiO2 was innovatively synthesized and developed to overcome the deficiency of common nano-TiO2 photocatalysts. The multi-type carbon species were derived from tetrabutyl titanate and ethanol as the internal and external carbon sources, respectively. Meanwhile, diverse characterization methods were applied to investigate the morphology and surface properties of the photocatalyst. Finally, the visible-light photocatalytic degradation activity of the collected samples was evaluated by using methyl orange as a model pollutant. The promotion mechanism of multi-type carbon species in the photocatalytic process was also discussed and reported. The results in this work show that the doping and modification of multi-type carbon species successfully narrows the bandgap of nano-TiO2 to expand the light absorption range, reduces the valence band position to improve the oxidation ability of photogenerated holes, and promotes the separation of photogenerated charge carriers to improve quantum efficiency. In addition, the further modification of the external carbon source can promote the surface adsorption of MO and stabilize the multi-type carbon species on the surface of nano-TiO2.

3D graphene aerogel composite of 1D-2D Nb2O5-g-C3N4 heterojunction with excellent adsorption and visible-light photocatalytic performance

A novel three-dimensional graphene aerogel composite Nb2O5-g-C3N4/rGA was prepared, with a composition of nanorods-nanosheets Nb2O5-g-C3N4 (NbNR-CN) heterojunction and graphene aerogel (rGA). The 1D-2D NbNR-CN heterojunction was first prepared by a simple grinding and calcination method. Afterwards, different amounts of NbNR-CN (30%, 60%, 90%) were loaded onto graphene nanosheets by chemical reduction self-assembly method to obtain the 3D composites Nb2O5-g-C3N4/rGA (NbNR-CN/rGA). The compositions, morphologies, and optical properties of all materials were characterized. The results showed that the obtained 1D-2D heterojunctions were uniformly loaded onto rGA and the NbNR-CN/rGA composites had good visible light response. Compared with g-C3N4, NbNR and NbNR-CN, NbNR-CN/rGA showed the lowest charge transfer resistance and the highest photocurrent density. Photodegradation experiments indicated that the NbNR-CN/rGA composites exhibited remarkably enhanced visible-light photocatalytic activity for degradation of Rhodamine B (RhB). The removal rate for the 60%NbNR-CN/rGA composite was 94.8% within 100 min. The enhanced photoactivity could be explained by prolonged lifetime of photogenerated carriers due to the formation of heterojunction as well as the good electron transfer ability of rGA. Our research demonstrated that the NbNR-CN/rGA composite is a promising candidate for visible-light photocatalyst.

Synthesis and degradation kinetics of TiO2/GO composites with highly efficient activity for adsorption and photocatalytic degradation of MB

Poriferous TiO2/GO (denoted as TGO-x%) photocatalysts with ultrathin grapheme oxide (GO) layer were prepared by a hydrothermal method, the adsorption and photocatalytic degradation and its kinetics about Methylene blue(MB) were studied systematically. All the TGO-x% showed improved adsorption and photodegradation performance. TGO-25% had excellent adsorptivity while TGO-20% exhibit the highest visible light photocatalytic degradation activity. The adsorption capacity for TGO-25% was 20.25 mg/gcatalyst along with the k1 was about 0.03393 min·gcatalyst/mg, this enhancement was mainly owing to the strong adsorption capacity of GO and the stacking structure of sheets and nanoparticles. GO sheets prevented the agglomeration of TiO2 particles and TiO2 nanoparticles also prevented the agglomeration of GO sheets, which could provides greater surface area. Besides, the remarkably superior photodegradation activity of TiO2/GO composites is mainly attribute to the strong absorption of visible light and the effective charge separation revealed by the photoluminescence, the total removal rate of MB is 97.5% after 35 min adsorption and 140 min degradation, which is 3.5 times higher than that of TiO2.

In-situ fabrication of g-C3N4/MIL-68(In)-NH2 heterojunction composites with enhanced visible-light photocatalytic activity for degradation of ibuprofen

For the first time, visible-light-driven g-C3N4/MIL-68(In)-NH2 heterojunction composites with high photocatalytic activity were prepared for the degradation of ibuprofen (IBP) using an in-situ solvothermal synthesis method assisted with ultrasonication. The composites achieved intensive visible-light absorption, enhanced separation efficiency of photogenerated carriers, and high adsorption capacity, thus achieving excellent photocatalytic degradation for IBP. Among all the composites, 10 wt% g-C3N4/MIL-68(In)-NH2 exhibited the maximum photocatalytic rate (0.01739 min−1), 19.28 and 2.00 times higher than those of g-C3N4 and MIL-68(In)-NH2, respectively. Moreover, the pH, ibuprofen concentration, and catalyst dosages played important roles both in photodegradation and adsorption. In addition, the photocatalytic mechanism was also elucidated, demonstrating that h+ was the main reactive species, followed by OH and O2− radicals, responsible for the degradation of IBP. Finally, seven aromatic intermediates of IBP were identified, and five possible degradation pathways were proposed, mainly involving hydroxylation, aldehyde oxidation, decarboxylation, and dehydrogenization reactions.

Three-dimensional Z-Scheme Ag3PO4/Co3(PO4)2@Ag heterojunction for improved visible-light photocatalytic degradation activity of tetracycline

Constructing Z-scheme photocatalyst is paramount to improve the photocatalytic activity of single semiconductor materials by the efficient separation of photo-generated carriers. Herein, a novel Z-scheme photocatalyst Ag3PO4/Co3(PO4)2@Ag was successfully synthesized, which has the distinctive three dimensional (3D) structure with the Ag3PO4 rhombic dodecahedrons on the flower-like Co3(PO4)2. The ternary Ag3PO4/Co3(PO4)2@Ag heterostructure photocatalyst exhibits the highest photocatalytic activity in comparison with Ag3PO4, Co3(PO4)2 and Ag3PO4/Co3(PO4)2, which can be up to 91.2% at 60 min for the degradation of tetracycline (TC) under visible light irradiation. This enhanced photocatalytic performance is attributed to the surface plasmon resonance (SPR) of Ag to effectively broaden the absorption of visible light in composites, which is proved by the finite-difference time domain (FDTD) simulation. Moreover, the results of electron spin resonance (ESR) confirmed that the introduction of Ag nanoparticles can further facilitate the charge transfer of heterostructure Ag3PO4/Co3(PO4)2 through the route of the Z-scheme, fully retaining prominent redox ability of Ag3PO4 and Co3(PO4)2. Finally, the possible photocatalytic degradation mechanism over Ag3PO4/Co3(PO4)2@Ag was proposed and discussed in detail.

Three-dimensional network structure assembled by g-C3N4 nanorods for improving visible-light photocatalytic performance

Bulk g-C3N4 has suffered from its low specific surface area and high recombination of photogenerated electron-hole pairs. Herein, three-dimensional network structure g-C3N4 assembled by nanorods (3D g-C3N4 NR) was successfully fabricated via a chemical tailoring route. The as-prepared 3D g-C3N4 NR exhibits lager specific surface areas (6.7 times of bulk g-C3N4) and faster charge carrier transfer kinetics. Hence, the visible-light photocatalytic activities for degradation of phenol and hydrogen evolution over 3D g-C3N4 NR are evidently enhanced, 4.3 and 5.9 times as high as that of bulk g-C3N4, respectively. Briefly, this work throws light on structural tuning of carbon nitride polymer photocatalysts for improved solar energy capture and conversion.

Fabrication of Z-scheme photocatalyst, Er3+:Y3Al5O12@NiGa2O4-MWCNTs-WO3, and visible-light photocatalytic activity for degradation of organic pollutant with simultaneous hydrogen evolution

Three new visible-light-induced Z-scheme photocatalytic systems, Er3+:Y3Al5O12@NiGa2O4-WO3, Er3+:Y3Al5O12@NiGa2O4-MWCNTs (10–20 nm)-WO3 and Er3+:Y3Al5O12@NiGa2O4-MWCNTs (40–60 nm)-WO3, are successfully prepared via hydrothermal method. The prepared photocatalysts are characterized by X-ray diffractometer (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) and photoluminescence (PL) spectra. UV–vis absorption and PL spectra were also determined to explore luminescence effect of the Er3+:Y3Al5O12. The photocatalytic activities of prepared photocatalysts are evaluated and compared under simulated solar-light irradiation in degradation of organic pollutant with simultaneous hydrogen evolution. The influence factors such as simulated solar-light irradiation time and photocatalyst amount on the photocatalytic activities of prepared photocatalysts are investigated. The results show that the Er3+:Y3Al5O12@NiGa2O4-MWCNTs (40–60 nm)-WO3 is the best one of three prepared photocatalysts in the degradation of methylene blue with simultaneous hydrogen evolution under simulated solar-light irradiation. In addition, the Er3+:Y3Al5O12@NiGa2O4-MWCNTs (40–60 nm)-WO3 also displays high performance in five repeated experiments. At last, the process of photocatalytic degradation of organic pollutant with simultaneous hydrogen evolution caused by Er3+:Y3Al5O12@NiGa2O4-MWCNTs (40–60 nm)-WO3 is proposed.

A facile synthesis method for fabrication of LaFeO3/g-C3N4nanocomposite as efficient visible-light-driven photocatalyst for photodegradation of RhB and 4-CP

A solid state method for the large scale synthesis of LaFeO3/g-C3N4nanocomposite with enhanced visible-light photocatalytic degradation activity.