Biological Renewable Cellulose-Templated Zn1-XCuXO/Ag2O Nanocomposite Photocatalysts for the Degradation of Methylene Blue.

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.

Photocatalytic activity of the biogenic mediated green synthesized CuO nanoparticles confined into MgAl LDH matrix.

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.

Photocatalytic H2O2 Generation over Microsphere Carbon-Assisted Hierarchical Indium Sulfide Nanoflakes via a Two-Step One-Electron Pathway.

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.

Sulfur Substitution and Defect Engineering in an Unfavored MnMoO4 Catalyst for Efficient Hydrogen Evolution under Visible Light.

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.

Highly efficient photocatalytic H2O2 generation over dysprosium oxide-integrated g-C3N4 nanosheets with nitrogen deficiency.

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 mM⋅g-1⋅h-1, while the optimized photocatalyst Dy15 showed high performance of H2O2 production up to 48.36 mM⋅g-1⋅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.

Solar-light-driven ternary MgO/TiO2/g-C3N4 heterojunction photocatalyst with surface defects for dinitrobenzene pollutant reduction.

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.

Single-Step Synthesis of Fe-Doped Ni3S2/FeS2 Nanocomposites for Highly Efficient Oxygen Evolution Reaction.

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.

Biogenic Synthesis of Cu-Doped ZnO Photocatalyst for the Removal of Organic Dye.

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.

Visible light-driven photocatalytic activity of Cu2O/ZnO/Kaolinite-based composite catalyst for the degradation of organic pollutant.

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.

Self-Protonated Ho-Doped Zn(O,S) as a Green Chemical-Conversion Catalyst to Hydrogenate Nitro to Amino Compounds.

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 18 624 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.

Ag-Decorated MoSx Laminar-Film Electrocatalyst Made with Simple and Scalable Magnetron Sputtering Technique for Hydrogen Evolution: A Defect Model to Explain the Enhanced Electron Transport.

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.

Room-temperature synthesized In-BiOBr1-xIx nanosheets with visible-light-driven superior photocatalytic activity: Degradation of dye/non-dye organic pollutants for environmental remediation.

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.

Highly efficient In-Mo(O,S)2 oxy-sulfide for degradation of organic pollutants under visible light irradiation: An example of photocatalyst on its dye selectivity.

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.

Effects of Tin in La-Sn-Codoped Zn(O,S) Photocatalyst to Strongly Cleave the Azo Bond in Azobenzene with in Situ Generated Hydrogen.

La-Sn-codoped Zn(O,S) catalysts were synthesized with different amounts (0%, 2.5%, 5%, and 10%) of Sn and a constant amount (10%) of La to improve the photocatalytic hydrogenation reaction (PHR) of azobenzene to aniline. The as-prepared catalysts were carefully characterized and tested for a hydrogenation reaction. The incorporation of Sn significantly enhanced the PHR activities since the incorporated Sn in the Zn(O,S) lattices could increase the conductivity of the catalysts to improve the charge transfer during the catalytic reaction as indicated with EIS measurement. Further measurement with a photoresponse of La-Sn-codoped Zn(O,S) catalysts also exhibited relatively higher intensities as compared to those of La-doped Zn(O,S) and Sn-doped Zn(O,S) catalysts. On the basis of the measurement results of EIS and transient photo current, the La-Sn-codoped Zn(O,S) with the best properties was further utilized for PHR to convert azobenzene to aniline. GC-MS measurement confirmed that 15 ppm azobenzene could be totally converted to aniline in only 60 min which was achieved with a catalyst that was prepared with 5%-Sn and 10%-La doping. The relatively short reaction time indicated that the as-prepared catalyst had a strong reduction capability able to cleave the strong bonding of N═N in azobenzene. The reaction kinetic of the N═N bond cleavage was elucidated based on solvation, adsorption, pinning, and photocatalytic hydrogenation processes on the catalyst surfaces.

Synthesis and application of V2O5-CeO2 nanocomposite catalyst for enhanced degradation of methylene blue under visible light illumination.

Methylene blue dye is among the toxic, mutagenic, and carcinogenic pollutants. Hence, its treatment via photocatalytic degradation is an important remediation method for the sake of a healthy environment. Herein, the V2O5-CeO2 nanocomposite catalysts were synthesized via a simple precipitation-thermal decomposition approach and used for the photodegradation of methylene blue in the presence of H2O2 as an effective electron scavenger under visible light illumination. The nanocomposite catalysts were systematically characterized to investigate the effects of V2O5 with the aids of X-ray, morphology, light absorption, catalytic activity, and charge transfer properties of the nanocomposite catalysts. The VC-2 nanocomposite prepared with NH4VO3:CeO2 molar ratios at 0.15:1 was found to be the best efficient catalyst where ≥98% of methylene blue was degraded within 25 min irradiation time. From the kinetics analysis, its rate constant was found to be higher than those of the pure V2O5 and CeO2 catalysts by a factor of 12.0 and 13.5, respectively. The plausibly mechanistic elucidation of charge transfer and utilization of reactive species are conspicuous allegations of the combined effects of the nanocomposite catalyst, H2O2 sacrificial agent, and visible light for the photodegradation of the dye.

Concept of Stagnant Capillarity Water in the Nanoporous SiO2@(Zn,Ni)(O,S) Nanocomposite Photocatalyst as a Strategy to Improve Hydrogen Evolution.

(Zn,Ni)(O,S) nanoparticles were uniformly deposited on nanoporous SiO2 spheres to form SiO2@(Zn,Ni)(O,S) nanocomposites (NCs). To obtain optimum deposition of (Zn,Ni)(O,S) on the SiO2 spheres for the hydrogen evolution reaction (HER), different amounts of 0.25, 0.5, 1, and 1.5 mmol zinc precursor for (Zn,Ni)(O,S) were deposited on SiO2 to obtain different SiO2@(Zn,Ni)(O,S) NCs. All the as-prepared catalysts were examined with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, photocurrent response, photoluminescence spectral studies. Finally, the HER performance was evaluated with SiO2@(Zn,Ni)(O,S). The best SiO2@(Zn,Ni)(O,S)-0.5 surprisingly reached 41.1 mmol/gh for generating H2, which was about a 840% increase as compared to that of the SiO2 sphere-free one. The great improvement in the HER rate was due to the utilization of nanoporous SiO2 spheres. The concept of stagnant capillarity water, adopted from the leaf vein system, was applied to explain the enhanced HER reaction.

Synthesis of oxy-sulfide based nanocomposite catalyst for visible light-driven reduction of Cr(VI).

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 2 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.

A noble bimetal oxysulfide CuVOS catalyst for highly efficient catalytic reduction of 4-nitrophenol and organic dyes.

A novel copper-vanadium bimetallic oxysulfide (CuVOS) nanoparticle catalyst was successfully synthesized by a facile method. The samples were characterized by X-ray photoelectron spectrometry (XPS), X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), UV-Vis diffuse spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), and N2 adsorption-desorption isotherms. In order to check the catalytic efficiencies toward reduction reaction, 4-nitrophenol (4-NP) and other organic dyes such as rhodamine-B (RhB), methylene blue (MB), and methyl orange (MO) were used. The results showed that the CuVOS prepared in the presence of a suitable amount of N2H4 during the synthesis of the nanoparticles exhibited the fastest reduction capabilities by using NaBH4 as a reducing agent. It was demonstrated that a 100 mL 4-NP (20 ppm) solution was completely reduced by 5 mg CuVOS-3 within 2 min. Moreover, the complete reduction of 100 mL of MO, RhB, and MB solutions of 100 ppm was also achieved by 5 mg CuVOS-3 within 2 min, 6 min, and 5 min, respectively. Hence, the CuVOS is an efficient catalyst for reducing 4-NP and organic dyes and can have great potential for industrial application.

Synthesis and characterization of La-doped Zn(O,S) photocatalyst for green chemical detoxification of 4-nitrophenol.

La-doped Zn(O,S) nanoparticles (NPs) with different contents of lanthanum have been synthesized with a simple sol-gel method at low temperature (90 ℃) for 4-nitrophenol (4-NP) detoxification. The as-prepared catalysts were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), photoluminescence (PL) and UV-vis absorbance spectroscopy, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and photoresponsivity. In this work, it is considered that the detoxification of 4-NP to 4-aminophenol (4-AP) without NaBH4 by using photocatalytic method is a green chemical conversion. The experimental data showed 30 ppm toxic 4-NP had been totally converted to useful 4-aminophenol (4-AP) with lower toxicity in 2 h, which was confirmed with a specific peak shift as indicated with UV-vis absorbance spectra and high performance liquid chromatography (HPLC) measurement. The lower amount of evolved hydrogen from photocatalytic process on La-doped Zn(O,S) NPs in the presence of 4-NP confirmed the produced hydrogen was consumed as a reducing agent during the 4-NP-to-4-AP conversion. The photocatalytic detoxification of 4-NP to 4-AP had been demonstrated and an appropriate mechanism based on the experimental data had been proposed and elucidated in this work.

Facile synthesis of bimetallic (In,Ga)2(O,S)3 oxy-sulfide nanoflower and its enhanced photocatalytic activity for reduction of Cr(VI).

Hexavalent chromium is one of the most chronic and harmful to human beings, animals, and environmental well-being, and hence needs a high attention to detoxify it. For this purpose, bimetallic (In,Ga)2(O,S)3 oxy-sulfide nanoflower catalyst with different Ga contents was successfully synthesized at a low temperature of 150 °C via a facile method. It was systematically characterized and the visible light-driven photocatalytic reduction of toxic Cr(VI) was 100% completed at 4 min. The Cr(VI) reduction reaction rate constant was 13.8 fold higher than that of Ga-free In2(O,S)3 catalyst. It also showed lower recombination of photogenerated charge carriers, faster interfacial reaction rate, and higher electrical conductivity. The photoexcited electrons and H+ ions played crucial roles in the reduction of Cr(VI). The Cr(III) composition was 12.0% of the total atomic composition. The as-synthesized catalyst showed a tremendously fast Cr(VI) reduction activity and hence, it is promising for detoxification of hazardous Cr(VI).