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Cellulose plays a significant role in designing efficient and stable cellulose-based metallic catalysts, owing to its surface functionalities. Its hydroxyl groups are used as anchor sites for the nucleation and growth of metallic nanoparticles and, as a result, improve the stability and catalytic activity. Meanwhile, cellulose is also amenable to surface modifications to be more suitable for incorporating and stabilizing metallic nanoparticles. Herein, the Ag-/Bi-doped Mo(S,O)3 trimetallic sulfo-oxide anchored on B and N codoped cellulose (B-N-C) synthesized by a facile approach showed excellent stability and catalytic activity for PHER at 573.28 µmol/h H2 with 25 mg of catalyst under visible light, and 92.3% of the 4-nitrophenol (4-NP) reduction was achieved within 135 min by in situ-generated protons. In addition to B and N codoping, our use of the calcination method for B-N-C preparation further increases the structural disorders and defects, which act as anchoring sites for Ag-/Bi-doped Mo(S,O)3 nanoparticles. The Ag-/Bi-doped Mo(S,O)3@B-N-C surface active site also stimulates H2O molecule adsorption and activation kinetics and reduces the photogenerated charge carrier's recombination rate. The Mo4+ â Mo6+ electron hopping transport and the O 2p and Bi 6s orbital overlap facilitate the fast electron transfer by enhancing the electron's lifetime and photoinduced charge carrier mobility, respectively. In addition to acting as a support, B-N-C provides a highly conductive network that enhances charge transport, and the relocated electron in B-N-C activates the H2O molecule, which enables Ag-/Bi-doped Mo(S,O)3@B-N-C to have appreciable PHER performance.
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Herein, we design to synthesize a novel Cu2O/ZnO/kaolinite composite catalyst by co-precipitation method. The synthesized composite catalysts were labeled as 5CZK, 10CZK, 15CZK, and 20CZK which represent 5, 10, 15, and 20% of Cu2O, respectively, on ZnO/kaolinite. The photocatalyst samples were characterized with different instruments. Moreover, the methylene blue (MB) dye was used as a target organic pollutant and the degradation was evaluated under visible light irradiation. The highest performance for the degradation of MB was achieved by 10CZK catalyst and degrades 93% within 105 min. However, ZnO (Z), Cu2O/ZnO (CZ), 5CZK, 15CZK, and 20CZK composite catalysts, degrades 28, 66, 76, 71, and 68% of MB dye, respectively. The enhanced degradation efficiency of 10CZK composites catalyst could be due to the higher adsorption properties from metakaolinite and the light-responsive properties of the Cu2O/ZnO samples under visible light. Hence, the resulting composite catalyst could be applicable for environmental remediation.
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The oxy-sulfide based V2O5@(In,Ga)2(O,S)3 nanocomposite catalyst, at different weight percentages of V2O5, was successfully synthesized via a simplistic procedural route for the detoxification of hazardous Cr(VI). The two pure catalysts were intimately allied and used for visible light-driven reduction of hazardous Cr(VI). The nanocomposite catalysts were characterized to observe the effects of V2O5 on crystal phase, morphology, light absorption, catalytic activity, and electrical properties. Compared to all, 40% V2O5 loaded nanocomposite catalyst, designated as VOS-2, exhibited the best-reducing capability. It completely reduced toxic Cr(VI) at 2â¯min under visible light illumination. From the kinetics, it was found that the rate constant of the nanocomposite catalyst was improved by a factor of 3.6 compared to the host nanoflower catalyst. The plausible mechanism of charge transfer process across the interfacial region indicates the diminished recombination probability of photogenerated charge carriers. Therefore, the nanocomposite catalyst is promising for enhanced reduction of Cr(VI) in the Cr-based industrial activities, which is significantly relevant for environmental remediation.
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Cromo , Nanocompostos , Sulfetos , Catálise , Técnicas de Química Analítica , Cromo/química , Recuperação e Remediação Ambiental , Nanocompostos/química , Sulfetos/síntese químicaRESUMO
Vertically aligned undoped and Sb-doped ZnO (ZnSbO) nanorods were grown by the vapor-phase oxidation process on sapphire substrates at 700 °C using Fe as the catalyst. The effect of Sb doping on surface morphology, structural and optical properties of ZnO were studied. The grown undoped and Sb-doped ZnO nanorods have a hexagonal wurtzite structure with preferential c-axis orientation. The as-grown nanorods morphology has shown length of 2-5 µm and a diameter of 100-250 nm. An elongated nanorods and high aspect ratio was observed in Sb-doped ZnO. The undoped ZnO nanorods showed a strong and sharp ultraviolet (UV) emission centered at ~381 nm, whereas Sb-doped ZnO nanorods exhibited two defect related emissions centered at ~530 nm (green) and ~630 nm (red) with a suppressed UV emission. The dominance of the red emission in the nanorods indicates that it exhibits a much higher defect caused by the Sb doping.
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The n-type TiO2 semiconductor nanoparticles were coated on the p-type Ag2O nanoparticles deposited on SiO2 spherical particles through a simple sol-gel method for catalytic reduction of 4-nitrophenol. The as-prepared spherical composite abbreviated as SiO2/Ag2O@TiO2 was characterized by different techniques and tested as a catalyst towards 4-nitrophenol (4-NP) reduction into 4-aminophenol (4-AP) with NaBH4 as a reducing agent at room temperature. This work combines an interesting design with the n-type TiO2 rich in electrons outward and the p-type Ag2O rich in electronic holes inward to form the p/n junction for the purpose of efficiently separating the charge carrier to have a longer lifetime of outward electrons for catalytic reduction reactions. The SiO2/Ag2O@TiO2 composite catalyst showed the best performance in the reduction of 4-NP to 4-AP within 30 seconds. Our results reveal that the p-n junction combined composite sphere was superior and efficient in reduction of 4-nitrophenol without using the light source. The conversion mechanism is proposed here. Overall, the SiO2/Ag2O@TiO2 composite can be used as a cost-effective reduction catalyst for converting the toxic 4-NP into useful 4-AP, an industrial organic intermediate compound.
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The global concern over water pollution caused by organic pollutants such as methylene blue (MB) and other dyes has reached a critical level. Herein, the Allium cepa L. peel extract was utilized to fabricate copper oxide (CuO) nanoparticles. The CuO was combined with MgAl-layered double hydroxides (MgAl-LDHs) via a co-precipitation method with varying weight ratios of the CuO/LDHs. The composite catalysts were characterized and tested for the degradation of MB dye. The CuO/MgAl-LDH (1:2) showed the highest photocatalytic performance and achieved 99.20% MB degradation. However, only 90.03, 85.30, 71.87, and 35.53% MB dye was degraded with CuO/MgAl-LDHs (1:1), CuO/MgAl-LDHs (2:1), CuO, and MgAl-LDHs catalysts, respectively. Furthermore, a pseudo-first-order rate constant of the CuO/MgAl-LDHs (1:2) was 0.03141 min-1 while the rate constants for CuO and MgAl-LDHs were 0.0156 and 0.0052 min-1, respectively. The results demonstrated that the composite catalysts exhibited an improved catalytic performance than the pristine CuO and MgAl-LDHs. The higher photocatalytic performances of composite catalysts may be due to the uniform distribution of CuO nanoparticles into the LDH matrix, the higher surface area, and the lower electron and hole recombination rates. Therefore, the CuO/MgAl-LDHs composite catalyst can be one of the candidates used in environmental remediation.
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Nitrogen fixation reaction via photocatalysis offers a green and promising strategy for renewable NH3 synthesis, and catalysts with high-efficiency photocatalytic properties are essential to the process. Herein, we demonstrate a W-doped Sb2OS2 bimetal oxysulfide catalyst (labeled as SbWOS) with abundant oxygen vacancies, heterovalent metal states, and hydrophilic surfaces for nitrogen photoreduction to ammonia. The SbWOS-3 with suitable W-doping exhibited excellent nitrogen fixation activity of 408.08 µmol·g-1·h-1 and an apparent quantum efficiency (AQE) of 1.88% at 420 nm and a solar-to-ammonia (STA) conversion efficiency of 0.082% in pure water under AM1.5G light irradiation. The W-doping not only transforms hydrophobic Sb2OS2 into a hydrophilic catalyst, making it easier for H2O molecules adsorbed on the SbWOS surface and catalyzed into protons, but also endows the SbWOS catalyst with rich oxygen vacancies, acting as the active sites for trapping and activating the N2 molecule, and for trapping and activating H2O to produce the protons for the N2 photocatalytic reduction reaction. The hydrazine drives the SbWOS catalyst with the heterovalent metal states, which acts as the photogenerate electrons quickly hopping between W5+ and W6+ to transfer for the N2 reduction reaction. This study provides a feasible scheme for applying oxygen vacancy defects, heterovalent metal states, and surface hydrophobic-to-hydrophilic wetting engineering in bimetal oxysulfide for N2 photoreduction to ammonia.
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The development of new carbon-based materials using natural biowaste for biomedical applications has remained a significant challenge in the past decades. In this study, we successfully synthesized and characterized composite materials made from peanut shell-derived carbon (PNS-C) decorated on ZnO that formed star-shaped particles via a simple hydrothermal technique. The as-prepared composites possess several advantages, including unique optical properties and high photostability. We evaluate the antibacterial performance against Escherichia coli, a gram-negative bacterium and Staphylococcus aureus, a gram-positive bacterium, under irradiated and non-irradiated conditions. Interestingly, the photo-antibacterial activities of ZnO/PNS-C composites showed great inhibition of bacterial growth as compared to pure ZnO. Moreover, significant disruptions in cellular activities occur when the composites make direct contact with the bacterial cell wall. The electrons and holes produced by excitation in composites provide a pronounced deactivating effect on bacterial activity. In addition, ZnO/PNS-C composites are highly biocompatible with normal cells. Thus, these newly developed composites made from a natural biowaste system with an affordable price, abundance, and non-toxicity could provide a potentially environmentally friendly and fruitful route for antibacterial therapy in future applications.
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Herein, Cellulose-templated Zn1-XCuXO/Ag2O nanocomposites were prepared using biological renewable cellulose extracted from water hyacinth (Eichhornia crassipes). Cellulose-templated Cu-doped ZnO catalysts with different amounts of Cu as the dopants (1, 2, 3, and 4%) were prepared and denoted CZ-1, CZ-2, CZ-3, and CZ-4, respectively, for simplicity. The prepared catalysts were tested for the degradation of methylene blue (MB), and 2% Cu-doped ZnO (CZ-2) showed the best catalytic performance (82%), while the pure ZnO, CZ-1, CZ-3, and CZ-4 catalysts exhibited MB dye degradation efficiencies of 54, 63, 65, and 60%, respectively. The best catalyst (CZ-2) was chosen to further improve the degradation efficiency. Different amounts of AgNO3 (10, 15, 30, and 45 mg) were used for the deposition of Ag2O on the surface of CZ-2 and denoted CZA-10, CZA-15, CZA-30, and CZA-45, respectively. Among the composite catalysts, CZA-15 showed remarkable degradation efficiency and degraded 94% of MB, while the CZA-10, CZA-30, and CZA-45 catalysts showed 90, 81, and 79% degradation efficiencies, respectively, under visible light within 100 min of irradiation. The enhanced catalytic performance could be due to the smaller particle size, the higher electron and hole separation and charge transfer efficiencies, and the lower agglomeration in the composite catalyst system. The results also demonstrated that the Cu-doped ZnO prepared with cellulose as a template, followed by the optimum amount of Ag2O deposition, could have promising applications in the degradation of organic pollutants.
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The increasing demand for an alternative to traditional fuel has motivated intensive research and drawn more attention. H2O2 has emerged as an alternative due to its high capabilities, relatively safer nature as a fuel, and ease of transportation. The photocatalytic method is adopted to generate H2O2 using sustainable light energy to achieve an entire green system for a completely environmentally friendly process. Herein, the synthesized microsphere carbon-assisted hierarchical two-dimensional (2D) indium sulfide (In2S3) nanoflakes have been characterized thoroughly by various techniques such as X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectra (DRS), photoluminescence (PL), and electron paramagnetic resonance (EPR). The photocatalytic performance of the In2S3-based photocatalysts can be promoted with the carbon layer assisting in facilitating the transfer of the photogenerated electrons and narrowing their band gaps. Optimized In2S3 successfully yielded 31.2 mM g-1 h-1 in the photocatalytic oxygen reduction reaction (ORR) process. Based on the results of different radical trapping experiments and different reaction conditions, the catalytic ORR process is proposed to be a two-step one-electron pathway.
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A novel and nonstoichiometric Mn1-xMo(S,O)4-y oxysulfide catalyst with oxygen vacancies and a partial Mo6+-to-Mo4+ transition after the substitution of sulfur was synthesized for an efficient photocatalytic hydrogen evolution reaction (PHER). With appropriate sulfur substitution, a MnMoO4 semiconductor with a wide band gap was converted to Mn1-xMo(S,O)4-y with a narrow gap and a suitable band position for PHER. MnMo oxysulfide of 50 mg achieved a high PHER rate of 415.8 µmol/h under visible light, an apparent quantum efficiency (AQE) of 4.31% at 420 nm, and a solar-to-hydrogen (STH) conversion efficiency of 1.28%. Oxygen vacancies (VO) surrounded by low coordination metal atoms act as active reaction sites, which strengthen water adsorption and activation. Here, we demonstrate that sulfur substitution of MnMoO4 for lowering its wide band gap can not only disturb the strict periodicity of the lattice but also the valence states of Mn and Mo for enhancing PHER via material design.
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The increasing global crisis considers energy as the fundamental cause to conduct extensive research work to find clean alternative methods with high capabilities such as H2O2 synthesis. Photocatalytic H2O2 production can tackle this growing issue by maintaining environmental remediation. In this work, dysprosium oxide (Dy-oxide)-integrated g-C3N4 has been synthesized and characterized with XRD, SEM, TEM, XPS, EPR, DRS, PL, and electrochemical analyses. Simulated solar light irradiation implemented photocatalytic H2O2 production using the as-prepared catalysts. The facile preparation technique in the Ar atmosphere raises more N deficiency in the g-C3N4 matrix. N-deficient g-C3N4 nanosheets with an exceptionally high photocatalytic performance can be further enhanced by integrating well-dispersed Dysprosium oxide (Dy2O3) particles onto g-C3N4. This study reports bandgap narrowing and various surface defects on g-C3N4 with trace amounts of Dy2O3. Undoped g-C3N4 (Dy0) yielded 20.27 mMâ g-1â h-1, while the optimized photocatalyst Dy15 showed high performance of H2O2 production up to 48.36 mMâ g-1â h-1. It is approximately 2.4 times higher than the pristine g-C3N4. Dy15 proves the positive impact of Dy-oxide on enhancing the N-deficient g-C3N4 performance towards photocatalytic H2O2 production. This work highlights the oxygen reduction reaction (ORR) through a mixed pathway of well-known two-step one-electron and one-step two-electron processes in H2O2 generation.
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Defect engineering and heterojunction are promising strategies to improve the photocatalytic performance of particular catalyst through effective charge carrier separation and transport. Herein, we developed Z-scheme MgO/TiO2/g-C3N4 ternary heterojunction photocatalyst with surface defects and effective charge separation for reduction of recalcitrant dinitrobenzene isomers under simulated solar light irradiation. Mott-Schottky (MS) plot analysis and electron spin resonance (ESR) radical trapping experiment suggested the formation of Z-scheme heterojunction at the interface of TiO2/g-C3N4, which played a crucial role in the electron-hole separation. Incorporating MgO into the structure further enhances charge separation via Ti3+ and oxygen vacancy (OV) defects formation at the TiO2/MgO interface as confirmed by electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analyses. Besides, the surface basicity of MgO enhanced conversion of dinitrobenzene (DNB) isomers through formation of nitrophenylhydroxylamine intermediate which can easily be reduced to phenylenediamines (PDAs). As confirmed by high performance liquid chromatography (HPLC) analysis, excellent selectivity for PDAs (95-98%) was achieved in 90 min with ternary MgO/TiO2/g-C3N4 composite compared to the binary MgO/TiO2 and TiO2/g-C3N4. A possible reaction pathway and photocatalytic reduction mechanism were proposed and elucidated. This work demonstrated an effective strategy to reduce recalcitrant dinitrobenzene isomers using efficient, low-cost, and environmental benign photocatalyst with a facile identification of reaction intermediates.
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Dinitrobenzenos , Poluentes Ambientais , Óxido de Magnésio , Oxigênio , Fenilenodiaminas , TitânioRESUMO
Due to the sluggish kinetic reaction, the electrolytic oxygen evolution reaction (OER) is one of the obstacles in driving overall water splitting for green hydrogen production. In this study, we demonstrate a strategy to improve the OER performance of Ni3S2. The effect of addition of different FeCl2 contents during the hydrothermal process on the OER activity is systematically evaluated. We found that all samples upon the addition of FeCl2 produced Fe-doped Ni3S2 and FeS2 to form a nanocomposite. Their OER performances strongly depend on the amount of FeCl2, where the NSF-0.25 catalyst with 0.25 mmol FeCl2 added during the hydrothermal synthesis shows the best OER performance. Its overpotential was 230 mV versus RHE and it achieves a high current density of 100 mA·cm-2, which was much lower than that of pristine Ni3S2 (320 mV) or RuO2 (370 mV) as the benchmark OER catalyst. The postcharacterizations reveal that NSF-0.25 has gone through an in situ phase transformation into an Fe-NiOOH phase during the OER test. This study presents a simple method and a low-cost material to improve the OER performance with in situ formation of oxyhydroxide.
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The Cu-doped ZnO photocatalysts were prepared with a green and coprecipitation approach by using water hyacinth (Eichhornia crassipes) aquatic plant extract. In the preparation process, different amount of copper precursors such as 1, 2, 3, 4, and 5% of molar ratio were added to zinc nitrate precursors and abbreviated as Cu-ZnO (1%), Cu-ZnO (2%), Cu-ZnO (3%), Cu-ZnO (4%), and Cu-ZnO (5%), respectively. The characterization of the obtained samples was carried out, and the removal of the methylene blue (MB) dye was examined. Out of all catalysts, Cu-ZnO (3%) had the best photocatalytic performance and 89% of the MB dye was degraded. However, the degradation performances of blank (without catalysts), ZnO, Cu-ZnO (1%), Cu-ZnO (2%), Cu-ZnO (4%), and Cu-ZnO (5%) catalysts were 6, 54, 69, 83, 80, and 73%, respectively. Therefore, the use of water hyacinth plant extract with the optimum amount of Cu added to ZnO during the preparation of the catalyst could have a promising application in the degradation of organic pollutants.
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Photocatalysis is extensively investigated as a green, efficient and promising technique for environmental remediation. In this study, a series of template free In-doped BiOBrxI1-x photocatalysts have been successfully prepared at room temperature and characterized by various methods. Complete degradation of negatively charged methyl Orange, positively charged Rhodamine B and Methylene Blue organic dyes, and neutral and colorless non-dye organic compound of furfural was attained. The flat band potential offered the possibility of reduction of dissolved O2 to O2.- in the conduction band while the trapping experiment identified the (O2.-)is the main radical species followed by h+ for the photodegradation. In-BiOBrI-0.4 had an excellent photocatalytic degradation activity which could be due to the synergetic effect between metal ion doping and solid solution formation. It further promotes visible light-harvesting ability and photoinduced charge carrier separation efficiency. The order of the reaction rate was determined and the mechanism was proposed. This work can lay a base for the design of effective photocatalyst toward environmental remediation.
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Bismuto/química , Corantes/análise , Poluentes Ambientais/análise , Recuperação e Remediação Ambiental/métodos , Índio/química , Compostos de Iodo/química , Nanoestruturas/química , Fotólise , Compostos Azo/análise , Catálise , Luz , Azul de Metileno/análise , Rodaminas/análise , Propriedades de Superfície , TemperaturaRESUMO
The active edge site, surface defect, and noble-metal nanoparticle have been engineered to improve the electrocatalytic activity of earth-abundant and layered MoS2, but there was no single and facile process to achieve all yet. Here, basal-plane-defected Ag/MoSx lamellae with different Ag contents were deposited by one-step, single-cermet target (ceramic + metal) magnetron sputtering for the electrocatalytic hydrogen evolution reaction (HER). Ag/MoSx (10 vol %) showed a current density of 10 mA/cm2 at an overpotential of 120 mV with a Tafel slope of 42 mV/dec in a 0.5 M H2SO4 solution. The HER performance of Ag-MoSx lamellae was higher than that of the Ag-free one due to the activated basal antisite defects and the decorated Ag for enhancing electron transport. The green magnetron sputtering technique together with the target design has achieved Ag/MoSx lamellae with the film grown using the advantages of active edge-up lamella, S vacancy-type basal sites, and electron transport-enhanced Ag interconnect for enhancing hydrogen evolution.
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Zn(O,S) has been successfully doped with different amounts of Ho and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and transient photocurrent (TPC). The as-prepared Ho-doped Zn(O,S) catalysts with different Ho amounts are evaluated for hydrogen evolution reaction. The catalyst with the best performance in evolving hydrogen is further utilized to hydrogenate 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). It is found that doping with Ho obviously enhanced charge transfer and photoresponse properties of the catalyst. Therefore, the modified Zn(O,S) can optimally evolve hydrogen by 18â¯624 µmol/g, which is 20% higher than that of pristine Zn(O,S). Subsequently, the in situ generated hydrogen ions on catalyst surfaces also play an important role as a hydrogen source to hydrogenate 4-NP to 4-AP without any reducing agents such as NaBH4, which is commonly used as a hydrogen source. As Ho is doped in the lattices of Zn(O,S), it acts not only to separate photocarriers and to enhance the charge transfer but also to shorten the diffusion time of nitrophenolate ions to catalyst surfaces for further photocatalytic hydrogenation reaction (PHR) process. A plausible PHR mechanism has been provided to elucidate the great performance of Ho-modified Zn(O,S) for photocatalytic hydrogenation.
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Environmentally toxic organic pollutants, namely methylene blue (MB), neutral red (NR), Rhodamine B (RhB), and methyl orange (MO) dyes contain highly toxic, carcinogenic, non-biodegradable, and colored pigments which cause harm for humans and aquatic organisms even at low concentrations. To detoxify these toxic organic pollutants from the wastewater, the bimetallic solid solution-typed In-Mo(O,S)2 catalyst with various indium (In) contents were synthesized at low temperature through a simple precipitation method. The morphological, structural, chemical compositions, electrochemical and optical properties of the catalysts were thoroughly characterized. The photodegradation performance of the In-Mo(O,S)2 catalysts over the cationic, anionic and neutral dyes were studied under visible light irradiation. It has been observed that the photocatalytic activity was enhanced as In was added to the Mo(O,S)2 catalyst, and In-Mo(O,S)2-20 was found to be the best composition to completely degrade four organic dyes. The dye degradation had rate constant values of 9.5 × 10-2 min-1, 6.3 × 10-2 min-1, 4.4 × 10-2 min-1, and 15.7 × 10-1 min-1 for MB (20 ppm), NR (20 ppm), RhB (10 ppm), and MO (10 ppm) dyes, respectively. The active species for degradation of MB is different from those for RhB and MO. Single phase In-Mo(O,S)2-20 capable to degrade four kinds of dyes at a fast rate is a good photocatalyst.