Visible Light Photocatalyst For Degradation Research Articles

Solution combustion synthesis and exploration of chromium reduction and organic dyes degradation of cobalt tungstate (CoWO4) nanoparticles

Facile preparation route for cobalt tungstate (CoWO4) via cost effective, time saving, easy and solution combustion approach is described in the present paper. The structural, morphological properties of cobalt tungstate characterized by different physiochemical techniques which include X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray absorption (EDS). The optical properties assessed by UV–visible spectroscopy (DRS) and photoluminescence spectroscopy (PL). Using these methods, it was discovered that CoWO4 which has been synthesized displayed a monoclinic phase of Wolframite with great crystallinity and purity. The average crystallite size of prepared CoWO4 was 22 nm and band gap obtained was 2.84 eV due to which it can be used as visible light photocatalyst in aqueous medium. As a result, in this study, the photocatalytic degradation ability of CoWO4 was assessed by observing the aqueous phase degradation of the most widely used dyes, methylene blue (MB) and Rhodamine-B as well as Cr(VI) reduction under visible light. Almost all MB degraded in 90 min whereas 69 % degradation of RhB takes place in 240 min under visible light irradation. The different aspects for low rate of photodegradation of RhB dye than MB dye was also discussed in this report. The present study deals advanced approach that CoWO4 can also be used as capable visible light photocatalyst for degradation of dangerous contaminants and for reduction of carcinogenic Cr(VI) into nontoxic Cr(III) from waste water.

Sol-gel Pechini preparation of CuEr2TiO6 nanoparticles as highly efficient photocatalyst for visible light degradation of acid red 88

This study reports preparation of CuEr2TiO6 nanoparticles using Pechini sol-gel method. The characterization of nanoparticles was carried out using FESEM, EDX, XRD, PL, DRS, Raman, and FTIR. DRS analysis shows that the prepared nanoparticles can serve as an effective visible light photocatalyst. Photocatalytic activity of the prepared nanoparticles was investigated toward degradation of aqueous solution of acid red 88 (AR88) under visible light irradiation. The highest photoactivity (91.2 %) was achieved after 150 min illumination using 40 mg of the photocatalyst. Effect of some contributing factors was studied on degradation rate of AR 88, including amount of photocatalyst and H2O2 concentration. Also, in order to examine stability of the prepared nanoparticles for long-time applications, the recyclability experiments were conducted at 7 successive reaction cycles which confirm the great stability of the prepared nanoparticles. Also, radical scavenging experiments reveal that the dominant species in photocatalytic reactions are hydroxyl radicals.

Decoration of ZnFe2O4 and UiO-66 over g-C3N4 as magnetically novel reusable visible light photocatalyst for degradation of Rh–B

In this research, a unique nanohybrid ternary g-C3N4/ZnFe2O4/UiO-66 (g-C3N4/ZnF/UiO) was successfully prepared applying a hydrothermal synthesis technique. The characteristic properties of the prepared nanocomposite were specified using different characterization methods such as FT-IR, XRD, EDX, SEM, TEM, VSM, GTA, DRS, and BET analysis. The use of zirconium-based (UiO-66) as metal-organic framework has resulted in an expansion in the total surface area of photocatalyst compared to the pure g-C3N4 sample, which has a significant effect on improving Rhodamine B (Rh–B) dye degradation. Maximum efficiency of photocatalytic achievement of the prepared g-C3N4/ZnF/UiO for photodegradation of Rh–B was obtained by using 10 wt% of UiO-66 expose to visible light irradiation for 60 min. The detailed analysis of the structural and degradation outcomes confirmed that the amended photocatalytic degradation performance could be credited to the extremely impressive spatial separation of the charge carriers between suggested materials. The results are also shown that the magnetic property of the synthesized nanocomposites to be enough and useful for separation and collection of the photocatalyst. The nanohybrid ternary can be good recyclability reused for sixth runs without apparent loss of its photocatalytic performance in degrading Rh–B pollutant. Consequently, the ternary g-C3N4/ZnFe2O4/UiO-66 (g-C3N4/ZnF-UiO) prepared nanocomposite can be a favorable replacement for the treatment of dye pollutants in wastewater.

Development of Ag0.04ZrO2/rGO heterojunction, as an efficient visible light photocatalyst for degradation of methyl orange

Methyl orange (MO) is mutagenic, poisonous, and carcinogenic in nature, hence, effective methods are required for its degradation. We have synthesized pure ZrO2, Ag-doped ZrO2, and Ag-doped ZrO2/rGO as hybrid photocatalysts by facile hydrothermal method. These photocatalysts were characterized by powder XRD, scanning electron microscopy, EDX, FTIR, photoluminescence, UV–Vis diffuse reflectance (DRS), and Raman spectroscopy. The photodegradation of MO (10 ppm) was studied with pure ZrO2, Ag-doped ZrO2, and Ag-doped ZrO2/rGO (10 mg/100 mL catalyst dosage) photocatalysts at 100 min irradiation time under UV–Visible light. The pH effect and catalyst dosage on photodegradation of MO was investigated. Ag0.04ZrO2/rGO photocatalyst exhibited the maximum photocatalytic degradation of MO (87%) as compared to Ag0.04ZrO2 (60%) and pure ZrO2 (26%). Reusability experiments ensured the excellent stability of photocatalyst after five consecutive experiments. To the best of our knowledge, this is the first report on the facile hydrothermal synthesis of Ag0.04ZrO2/rGO photocatalyst for photocatalytic degradation of methyl orange.

Sol–gel method synthesized Ce‐doped TiO2 visible light photocatalyst for degradation of organic pollutants

The Ce‐doped TiO2 nanoparticles were prepared by the sol–gel method. The prepared nanoparticles were characterized by sophisticated analytical techniques such as XRD, FESEM with EDX, HR‐TEM, XPS, FTIR, TGA, and UV–visible spectroscopy, which gives structural features, morphology, elemental composition, and thermal stability of prepared nanoparticles. Based on the analysis, we conclude that increasing the dopant content of cerium in TiO2 results in a decrease in particle size, increase in thermal stability, and decrease in band gap. Further, on increasing the dopant content of cerium, there is an increase in photocatalytic activity due to changes in structural features due to doping, and 5 mol% Ce‐doped TiO2 has shown nearly four times higher photocatalytic activity than pure TiO2 for degradation of tetracycline. In this study, the photocatalytic activity and kinetics of photocatalytic degradation of antibacterial agent tetracycline have been studied by using these prepared catalysts. Further, effects of different parameters such as change in pH and change in concentration of tetracycline and amount of catalyst loading have been studied for the degradation of tetracycline. Also, Ce‐doped TiO2 has shown good photocatalytic efficiency for degradation of a mixture of textile dyes (methylene blue, rhodamine B, and brilliant green) and for degradation of a mixture of emerging contaminants (tetracycline, diclofenac, and triclosan).

TiO2/graphene nanocomposite supported on clinoptilolite nanoplate and its enhanced visible light photocatalytic activity

In this work, TiO2/graphene nanocomposite supported on clinoptilolite (CLP) nanoplate was prepared for the first time by hydrothermal method and was used as efficient visible light photocatalyst for degradation of nitenpyram insecticide. The results indicated that the photocatalytic degradation efficiency of TiO2/CLP/graphene nanocomposite, containing 30 wt% CLP and 1 wt% graphene, was remarkably higher than that of pure TiO2. This significantly improved photocatalytic performance could be mainly ascribed to the desirable advantages of CLP and graphene, including microporous structure, increasing of the effective surface area, enhancement of the visible light harvesting and improving of the charge carriers separation. Based on the radical rapping experiments, the hydroxyl radicals were identified as main active species responsible for the photocatalytic degradation of nitenpyram on the prepared photocatalyst. This study provides a new insight to fabricate more effective zeolite and graphene-based nanocomposite photocatalysts for environmental remediation.

Waste plastic-derived NiO-MWCNT composite as visible light photocatalyst for degradation of methylene blue dye

Waste plastic-derived NiO-MWCNT composite as visible light photocatalyst for degradation of methylene blue dye

Graphene oxide–ZnO nanocomposite: an efficient visible light photocatalyst for degradation of rhodamine B

Lignin-based graphene oxide (L-GO), zinc oxide (ZnO), and modified L-GO–ZnO nanocomposites are prepared to explore the photocatalytic efficiency of the catalysts under UV–visible light irradiation. The absorbance of dye’s solution (rhodamine B) at regular intervals has been recorded at λmax = 553 nm using a UV–Vis spectrophotometer. The kinetics parameters, viz. half-life (t1/2), time constant τ (Tau), and rate constant (k), have been evaluated by integrated rate expression to predict the order of the reaction. The rate constant for the reactions has been evaluated to be k_L-GO–ZnO = 1.46 × 10–1, k_ZnO = 2.23 × 10–2, and k_L-GO = 1.740 × 10–2 min−1. The degradation reaction is predicted to follow the first-order kinetics when the data are fitted to the integrated rate expression, kt = -ln(D/D0). The interactions of the dye and the catalyst have been probed by FTIR spectroscopy. The percent degradation efficiency of ZnO, L-GO, and L-GO–ZnO catalyst is 85.96, 83.15, and 91.75, respectively.

Copper-Doped ZnO Visible Light Photocatalyst for Degradation of Methylene Blue.

Water pollution due to uncontrolled liberation of industrial toxic chemicals, materials, drugs and dyes is one of the major causes of environmental contamination. Solar energy is one of the natural energy sources that can degrade toxic dyes in the presence of suitable active catalysts. Despite of having several advanced semiconductor-based photocatalysts, there is an open domain for the preparation of economical, cheap and high effective photocatalysts for the degradation of toxic dyes. In this study, we have prepared nanosized Cu-doped ZnO photocatalysts containing different amounts of Cu (0.1, 0.2, and 0.3 wt%) by a hydrothermal process followed by calcination at 500 °C for methylene blue (MB) degradation. The incorporation of Cu into the ZnO lattice and the crystal structure stability of the prepared catalysts are confirmed by X-ray photoelectron spectroscopy and powder X-ray diffraction. Our study shows that the photocatalytic activity of ZnO toward MB degradation under visible light can be effectively enhanced by doping it with Cu.

Novel reduced graphene oxide/ZnBi2O4 hybrid photocatalyst for visible light degradation of 2,4-dichlorophenoxyacetic acid.

A new highly efficient rGO/ZnBi2O4 hybrid catalyst has been successfully synthesized through oxidation-reduction and co-precipitation methods, followed by heating at 450°C. The obtained rGO/ZnBi2O4 catalyst was characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The catalytic activity of rGO/ZnBi2O4 under visible light irradiation was tested using 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution. The rGO/ZnBi2O4 hybrid catalyst containing 2% rGO (2.0rGO/ZnBi2O4) showed the best catalytic performance. More than 90% of 2,4-D in a 30mg/L solution was degraded after 120min of visible light irradiation using 2.0rGO/ZnBi2O4 at 1.0g/L concentration. Moreover, the 2.0rGO/ZnBi2O4 catalyst showed excellent stability over four consecutive cycles, with no significant changes in the photocatalytic degradation rate. This study demonstrated that rGO/ZnBi2O4 may be a promising, low-cost, and green photocatalyst for environmental remediation applications.

Sulfur-doping polyoxometallate-metal-organic intercalation compound with PPy coating as highly efficient photocatalyst for visible light degradation

A new sulfur-doping Keggin polyoxometalates (POMs) based metal organic intercalation compound (S-POM-MOIC) has been synthesized, namely, H[Ag(BPTD)2]2[PMo12O40] (BPTD = 2,5-bis(3-pyridyl)-1,3,4-thiadiazole). Single crystal X-ray analysis reveals that the Keggin-type POMs as a template embedded a 2D graphite-like intercalation framework, and all the sulfur atoms have been exposed into the inner cavity of empty channels. Which means the S-POM-MOIC framework can not only give full play to the catalytic ability of POMs, but also endow the synergistic catalytic effect of sulfur. Finally, we successfully obtained the visible light photocatalyst with excellent catalytic activity by using the ternary composite nanomaterials synthesis strategy.

Retraction: Ni/Ti layered double hydroxide: synthesis, characterization and application as a photocatalyst for visible light degradation of aqueous methylene blue.

Retraction of 'Ni/Ti layered double hydroxide: synthesis, characterization and application as a photocatalyst for visible light degradation of aqueous methylene blue' by Priyadarshi Roy Chowdhury and Krishna G. Bhattacharyya, Dalton Trans., 2015, 44, 6809-6824.

Synthesis of AgI/2D-La2Ti2O7 hybrids as a visible light photocatalyst for degradation of rhodamine B

The AgI/2D-La2Ti2O7 hybrids were obtained via a facile method at room temperature. Rhodamine B, as an organic dye, was used to determine the photocatalytic activity of the samples. The photocatalytic degradation mechanism was also analyzed. Experimental results display that AgI can broaden the light absorption of La2Ti2O7 under the visible light irradiation. The photocatalytic degradation efficiency of the as-synthesized hybrids appears the tendency of first increasing and then decreasing with increasing the usage of La2Ti2O7. When the usage of La2Ti2O7 is 10%, within 60 min, the as-synthesized hybrids possess the maximum of 93.1%. This is higher than 2.1% of La2Ti2O7 and 80.9% of AgI. Moreover, the improved photocatalytic activity can be attributed to AgI particles conjugating with 2D-La2Ti2O7 nanosheets via chemical-bonds, which can enhance the separation and transformation of the photo-generated holes and electrons. In addition, the dominating role is superoxide radicals during the photocatalytic process.

Metal-Free Organic Optoelectronic Molecule as a Highly Efficient Photocatalyst for the Degradation of Organic Pollutants.

With the increasing consumption of natural resources, photocatalysis converting solar energy to chemical energy has attracted extensive attention of researchers owing to the advantages of developing energy-saving and environmentally benign processes. In this work, a facile and simple method was developed to synthesize a metal-free organic optoelectronic molecule (denoted as DPPRD), which is composed of a central diketopyrrolopyrrole moiety and two terminal units of a rhodanine (RD) moiety. This is a first green strategy toward the synthesis of DPPRD. Because of good thermal stability, narrow band gap, and excellent visible light absorption of solar spectrum, DPPRD exhibited to be an efficient and chemically stable photocatalyst for visible light degradation of organic pollutants such as bisphenol A (BPA) and methyl orange (MO) in aqueous solution. The control experiments with different types of radical scavengers implied that the hole (h+) and hydroxyl radicals (•OH) were the key reactive species during the photodegradation processes. The photodegradation pathways of BPA and MO were thus proposed based on the identified intermediates. This improved method for DPPRD synthesis is expected to widen its applications to industrial production, whereas its excellent visible light photocatalytic activity would be utilized potentially in the field of environmental and industrial applications.

Novel indigo-dye-doped graphene-supported Mn/WO3 nanocomposite as visible light photocatalyst for degradation of methylene blue dye

Tungsten Trioxide based novel photocatalyst was fabricated through the simple one-pot hydrothermal process by constructing its composite with Mn, Indigo and reduced Graphene Oxide. The synthesized products were characterized by XRD, FT-IR and SEM analysis. Photocatalytic activity was observed from UV–vis absorption results under visible light irradiation. The catalytic proficiency in sunlight was boosted by synergistic association between the Tungsten Trioxide and RGO which increased the rate of charge transfer and also halted the reunion of electrons and holes in the nanosized composite. This photocatalyst has ability to degrade the dyes in waste water into their respective components.

Synthesis of Ag2CrO4/SnO2 n–n type heterojunction as a visible light photocatalyst for degradation of rhodamine B

The Ag2CrO4/SnO2 n–n type heterojunction has been fabricated by coupling Ag2CrO4 particles with SnO2 nanorods via an in situ synthetic method. The photocatalytic degradation mechanism of the as-prepared heterojunction has also been discussed. Characterization results revealed that the as-fabricated Ag2CrO4/SnO2 composites could reinforce the photo-degradation competencies for rhodamine B dilute solution compared to pure Ag2CrO4 and SnO2 samples. As the increase in the molar ratios of Ag2CrO4–SnO2, the photocatalytic degradation efficiency appeared to the tendency of first increasing and then decreasing. When it was 4:10, in 90 min, the as-obtained samples possessed the vintage photocatalytic degradation efficiency of 95.8% among of pure SnO2, Ag2CrO4 and the as-prepared composites with various molar ratios, respectively. Furthermore, the Ag2CrO4 and SnO2 were connected via chemical bonds to form the homogenous heterojunction. It could boost the separation and transfer of the photogenerated holes and electrons. In addition, the holes, hydroxyl and superoxide radicals played a major role during the photodegradation process.

Formation of one-dimensional CeVO4 nanobelts as an enhanced photoelectrocatalyst and density functional study

The rationally designed one-dimensional (1D) porous CeVO4 nanobelts have been prepared by electrospinning process and the band structure and density of states are simulated by DFT method. As an excellent photocatalyst for visible light degradation of methylene blue (MB) solution, 1D porous CeVO4 nanobelts possess the stable crystal structure, which contributes to the enhanced photocatalytic stability. Accordingly, the 1D belt structures are beneficial to promoting the separation and migration of charge carriers, reducing diffusion length, and providing rich catalytically active sites for photoeletrochemical reactions. Benefiting from these structural and compositional features, CeVO4 nanobelts exhibit the excellent photocatalytic performance and recycling ability, compared with individual CeVO4 powders upon simulated sunlight irradiation.

BFO thin film on the stainless steel mesh by anodic EPD: A visible light photocatalyst for degradation of Rhodamin B

Bismuth ferrite thin film as an active visible light photocatalyst was synthesized by anodic electrophoretic deposition on the stainless steel mesh. The stability of suspension was studied in the presence of dispersant under different conditions through the sediment percentage measurements. The effect of various dispersants was also evaluated on the stabilization of BFO aqueous suspension. The films were characterized by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and magnetic force microscopy (MFM). Electrochemical impedance spectroscopy (EIS) was applied to evaluate the separation of photogenerated electron-hole by measured resistance and capacity of films under visible light irradiation. The visible light photocatalytic activity of thin films was investigated by degradation of Rhodamin B subjected to direct solar irradiation in a designed photocatalytic reactor. The film illustrated a better photocatalytic efficiency than slurry state. High efficiency in immobilized film can be attributed to the conductive substrate (stainless steel mesh) that makes better separation of photogenerated electrons and holes. In addition, the fractal dimension measurement indicated that films with high surface roughness improve the light adsorption capacity and leads to enhance the photocatalytic reaction rate. The photocatalytic activity of films was also investigated in the presence of some common anions in Rhodamin B solution. It can be highlighted that the thin film completely removed the dye from aqueous solution and COD reached to near zero.

TiO2-Bi2O3/(BiO)2CO3-reduced graphene oxide composite as an effective visible light photocatalyst for degradation of aqueous bisphenol A solutions

TiO2 nanorods (T) were combined with a narrow band gap semiconductor β-Bi2O3 (B) to form a heterojunction, which makes it possible for TiO2 to become active as a photocatalyst also under visible light illumination. To further increase the photocatalytic activity of TiO2 + Bi2O3/(BiO)2CO3 (TB) composite, we used a hydrothermal procedure to link it with reduced graphene oxide (rGO). Structural, surface and electronic properties of the obtained catalysts were analyzed and correlated to their performance in photocatalytic oxidation of aqueous bisphenol A (BPA) solution conducted in a batch reactor under visible light illumination. XRD, FTIR, UV–vis DR spectroscopy and photocurrent measurements of visible light illuminated TB composite catalyst clearly showed that (i) β-Bi2O3 acts as a photosensitizer for TiO2 and (BiO)2CO3 present in the TB composite, (ii) holes (h+) are photo-generated in valence band (VB) of β-Bi2O3 and due to the β-Bi2O3/TiO2 heterojunction transferred into VB of TiO2, (iii) p-n junction between β-Bi2O3 and TiO2 allows the photo-generated electrons (e−) in the conduction band (CB) of β-Bi2O3 to transfer to TiO2, and (iv) p-n junction between β-Bi2O3 and (BiO)2CO3 allows the photo-generated electrons in the conduction band of β-Bi2O3 to transfer to (BiO)2CO3. This means that more charge carriers are available to participate in the catalytic visible-light triggered oxidation process for the degradation of organic pollutants dissolved in water. The highest photocurrent density was measured for multi-phase TBR (TB + rGO) composite, which indicates that visible-light generated charge carriers in TB composite are injected into the reduced graphene oxide. The latter acts as a web for charge carrier percolation and suppresses the recombination of electron-hole pairs, thus resulting in improved catalytic activity of TBR. The results of UV–vis DR spectroscopy and photocurrent density measurements were entirely in line with the results of photocatalytic oxidation of water dissolved bisphenol A (BPA) in batch reactor under visible light illumination.

Active and recyclable ordered mesoporous magnetic organometallic catalyst as high‐performance visible light photocatalyst for degradation of organic pollutants

A novel light‐active magnetic Pd complex as a photocatalyst was prepared through bonding organometallics to mesoporous silica channels formed on the surface of silica‐coated iron oxide nanoparticles. The nanocomposite (denoted as Fe3O4@SiO2@m‐SiO2@PDA‐Pd(0); PDA = 1,10‐phenanthroline‐2,9‐dicarbaldehyde) is more efficient and has higher photocatalytic capability in the degradation of 2,4‐dichlorophenol under visible light irradiation compared with virgin Pd complex (PDA‐Pd). This noteworthy photodegradation activity can be due to the high dispersion of Pd nanoparticles. High yield, low reaction time and non‐toxicity of the catalyst are the main merits of this protocol. Also magnetic separation is an environmentally friendly alternative method for the separation and recovery of the catalyst, since it minimizes the use of solvents and auxiliary materials, reduces operation time and minimizes catalyst loss by preventing mass loss and oxidation. The produced Pd catalyst was characterised using various techniques. Furthermore, transmission electron microscopy characterization was used for determining the structural properties of the Pd nanocatalyst.