Degradation Of Indigo Carmine Research Articles

Degradation of indigo carmine in water induced by non-thermal plasma, ozone and hydrogen peroxide: A comparative study and by-product identification.

The non-thermal plasma (NTP) technique is an advanced oxidation technology (AOT) applied to the degradation of organic compounds in water. In this study, the degradation kinetics of indigo carmine was investigated systematically, applying N2-NTP, O2-NTP, ozonolysis and hydrogen peroxide and the results were compared. The transient species (OH, O and NO radicals) formed with the NTP discharge at the gas-liquid interface and their products (NO3-, NO2-, H2O2) stabilized by the water, were identified and quantified. These species contribute to the effects on the chemical characteristics of the water, such as a decrease in the pH and increase in the conductivity and redox potential. Additionally, the stabilization of the oxidative species was estimated from the degradation reactions induced by the post-discharge effect, which was significant in the case of N2-NTP, due to the presence of long-lived species, such as nitrite and nitrate. The kinetics study revealed first-order kinetics for IC color removal and the rate constant values followed the order: O2-NTP (3.0×10-1 min-1)>O3 (1.4×10-1 min-1)>N2-NTP (2.2×10-2 min-1)>H2O2 (negligible). Also the main by-products of N2-NTP, O2-NTP and ozonolysis degradation reaction were identified by ultra-fast liquid chromatography coupled with mass spectrometry. The route fragmentation showed the formation of indole intermediates, such as isatin, which is an important precursor in organic synthesis.

Preparation and photocatalytic activity of hematite from iron sand modified ZnO for indigo carmine degradation

Modification of hematite (α-Fe2O3) with ZnO to produce ZnO/α-Fe2O3 composites by sol gel method and their photocatalytic activity testing on the degradation of indigo carmine (IC) dye has been done. The hematite was extracted from iron sand using hydrochloric acid and precipitated using aqueous ammonia. The ZnO/α-Fe2O3 composites were prepared with the mole ratio of ZnO to α-Fe2O3 1:1, 1:5 and 5:1. XRD pattern analysis showed that the average crystallite size of ZnO/α-Fe2O3 composites were greater than that of α-Fe2O3. The result of photocatalytic activity test showed that composite with the mole ratio of ZnO to α-Fe2O3 1:5 has the highest photocatalytic activity under the optimized conditions, with the maximum degradation efficiency of IC are 91.75 % and 93.18 % under UV light and sunlight irradiation, respectively. These highest of photocatalytic activity was reached at the initial pH of dye solution = 1, photocatalyst dosage of 300 mg, initial dye concentration 15 ppm and irradiation time 120 minutes under UV light and 90 minutes under sunlight irradiation.

Synthesis of an environmental nano-polyoxometalate (α2P2W17CoO61)8− as catalyst for dyes degradation: A comparative study oxidation of indigoid and azo dyes

A nanopolyoxometalate (nano-POM) compound consisting of saturated Dawson anions (α2P2W17CoO61)8− has been synthesized and characterized by various analytical methods, UV–vis spectroscopy, FT-IR spectroscopy, single crystal X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray analysis (EDX).The separately oxidative degradation of indigo carmine and methyl orange dyes in aqueous solution by KMnO4 using (α2P2W17CoO61)8− as catalyst was investigated. The full Decolorization was attained during the first minutes of oxidation process by this new homogeneous system (dye/KMnO4/α2P2W17O61Co). The experimental results showed that the catalyst greatly affected the discoloration efficiency; it was up to 75.4 % and 66.1 % respectively for IC and MO under these optimum conditions: an initial potassium permanganate concentration of 0.02 mM, a catalyst concentration of 0.2 mM and initial concentration dyes of 5 mg/L at pH 3 and room temperature (25 °C).The effect of other Dawson type polyoxometalates on the dyes oxidation under the same conditions was evaluated. After four consecutive reaction cycles, the catalyst (α2P2W17CoO61)8− exhibited a good recyclability and reusability without significant loss of activity. The precedents analytical methods indicated that this recovered catalyst has effectively a good stability. This nano-POM function as a recyclable efficient catalyst for the rapid removal of various anionic textile dyes from aqueous solutions.

High photocatalytic activity of TiO2/Fe2O3 nanocomposite prepared by impregnation method for degradation of indigo carmine

The photocatalytic degradation of indigo carmine (IC) dye was carried out by using TiO2/Fe2O3 nanocomposite prepared by impregnation method under UV light irradiation. The effect of TiO2 to Fe2O3 mole ratio on the properties and photocatalytic activity of TiO2/Fe2O3 nanocomposite was studied by the prepared three series of TiO2/Fe2O3 nanocomposites with TiO2 to Fe2O3 mole ratio of 1:3, 1:1 and 3:1. The characterization of TiO2/Fe2O3 nanocomposite by XRD showed that the iron (III) oxide extracted from iron ore and calcined at 700°C was in hematite phase (a-Fe2O3). The photocatalytic activity of TiO2/Fe2O3 nanocomposites was determined by using 6 W UV lamps with the wavelength 365 nm and the degradation efficiency of indigo carmine was determined based on UV-Vis spectrophotometer data. The TiO2/Fe2O3 nanocomposite with the the mole ratio of TiO2 to Fe2O3 1:3 showed higher photocatalytic activity than other mole ratio and bare Fe2O3. Degradation efficiency also was highly affected by the initial pH of IC solution, photocatalyst dosage and initial IC concentration. The maximum experimental degradation efficiency of IC was achived at pH value 1 using 0.35 g of photocatalyst and at 20 ppm of initial IC concentration after being irradiated by UV light for 120.

Visible light driven Ni–BaMo3O10 photocatalyst for Indigo Carmine degradation: Mechanism and pathways

The microwave hydrothermal method was employed for the synthesis of Ni doped Barium trimolybdate (Ni–BaMo3O10) tripod microcrystals. The photocatalyst, BaMo3O10 and Ni–BaMo3O10 have tendency to degrade the Indigo Carmine (IC) about 40 and 98% under visible light irradiation, respectively in 180 min. The photocatalyst revealed the excellent photodegradation stability up to five cycles. The active species (OH•, O2•-, and h+) were responsible for IC degradation on the basis of scavenger test. Effect of pH on IC degradation was also investigated. The enhancement of photocatalytic efficiency for IC degradation is related to increase in visible light absorption/oxygen vacancy and efficient separation of electron-hole pairs on the surface of photocatalyst. The suppression of charge recombination explained by transient photocurrent response and EIS measurements. The IC degradation was analyzed by ultra-performance liquid chromatography-photodiode array (UPLC-PDA) and high resolution-quadruple time of flight electrospray ionization mass spectroscopy (HR-QTOF ESI/MS). The four degradation pathways of IC in water were proposed on the basis of degraded products. Hydroxylation, oxidation, methylation, decarboxylation, and desulfonation reactions were observed during IC degradation. The efficient mineralization of IC occurred according to total organic carbon (TOC) investigation. Therefore, this research article presents removal of dyes pollutants from polluted water and in-depth analysis of IC pathways.

Comparison of the photoactivity of TiO2 coatings using a flat panel reactor and FTIR to monitor the CO2 evolution rate

A system designed to continuously monitor the gas phase for the UV irradiation of flat panels of organic coatings has been modified to compare the photocatalytic degradation of organic pollutants using TiO2 functional coatings. TiO2 was formulated into pastes and was coated onto various stainless steel and glass fibre meshes. The photoactivity was determined by monitoring the photodegradation of acetone and following the rate of CO2 evolution using FTIR spectroscopy. The kinetics were compared to the photoinduced degradation of indigo carmine, followed by UV–vis spectroscopy to determine whether the CO2 evolution method is a viable, rapid alternative to photodegradation monitoring. A correlation was established between the two methods by determining the rate constants of the decolourisation of indigo carmine and CO2 evolution, demonstrating that such a method can be used as a rapid assessment of the photoactivity of photocatalytic coatings.

Supported growth of inorganic-organic nanoflowers on 3D hierarchically porous nanofibrous membrane for enhanced enzymatic water treatment

Organic-inorganic nanoflower is a new type of functional material that can effectively immobilize a wide range of enzymes to form flower-like structures for various enzymatic applications with enhanced catalytic performance and stability. In order to avoid the processing inconvenience and flower structure damage caused by the particular form of these hybrid nanoflowers during material fabrication and catalytic application, different substrates have been used to carry out supported growth of hybrid nanoflowers. However, all previously used substrates have only 2-dimensional feature and only incorporate hybrid nanoflowers on surface with limited nanoflower loading. In this study, three-dimensional (3D) hierarchically porous nanofibrous PVA-co-PE membranes (HPNM) are prepared by a simple template method for effectively immobilizing laccase-Cu2(PO4)3•3H2O hybrid nanoflowers. Compared with dense nanofibre membrane with only small sized pores (<1 micron), the coexistence of both small and large sized (30–80 microns) pores of HPNM could significantly increase the nanoflower density and allow the penetrated growth of hybrid nanoflowers into the inner structure of the membrane. The hybrid nanoflower containing hierarchically porous nanofibrous membranes (HNF-HPNM) show excellent catalytic performance in degrading different types of textile dyes (reactive blue 2, acid blue 25, acid yellow 76 and indigo carmine), with a degradation efficiency of ˜99.5% for indigo carmine. In addition, the HNF-HPNM could be reused at least 14 times for indigo carmine degradation, with a negligible degradation efficiency drop from 99.48% to 98.52%. These results indicate that hierarchically porous nanofibrous membrane can be a promising type of materials for supported hybrid nanoflower growth for practical applications such as waste water treatment, dye degradation and biosensing.

The Synthesis of Copper-doped Hematite Nanoparticles of Iron Ore through Impregnation Method for Photodegradation of Textile Dyes

Copper-doped hematite (Cu-doped α-Fe2O3) nanoparticles have been synthesized by the impregnation method using iron ore as the hematite source. The structural and morphological properties of the prepared samples were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption-desorption. The XRD results showed that the hematite extracted from iron ore was in the hematite phase. The average crystallite size of copper-doped hematite was slightly smaller than that of hematite. The copper-doped hematite nanoparticles exhibited high photocatalytic activity on degradation of indigo carmine (IC) dye with the degradation percentage of 98.21 % and 99.78%, respectively under UV and solar light irradiation. The highest photocatalytic activity was obtained at the experimental condition namely initial pH of IC solution 1.0, photocatalyst mass of 400 mg, initial concentration dye solution of 15 mg/L, and 90 minutes of irradiation times. The copper-doped hematite nanoparticles could also remove dyes found in batik wastewater with a percentage of the degradation up to 77.56 % and 97.83% under UV and solar light irradiation, respectively.

Photocatalytic degradation of indigo carmine dye using α-Fe2O3/bentonite nanocomposite prepared by mechanochemical synthesis

Preparation of α-Fe2O3/bentonite nanocomposite has been successfully conducted by mechanochemical synthesis using iron sand from Syiah Kuala Beach, Banda Aceh and bentonite from Kuala Dewa, North Aceh as raw materials. The α-Fe2O3 was extracted using hydrochloric acid and precipitated using ammonium hydroxide as precipitation agent at pH 6 followed by calcination at high temperature in order to obtained α-Fe2O3. The α-Fe2O3/bentonite nanocomposite was prepared by milling the mixture of α-Fe2O3 and bentonite at 4:1 ratio in a planetary mill for 2 hours without any solvent. The XRD results showed that the main component of iron sand was magnetite (Fe3O4), while in α-Fe2O3/bentonite nanocomposite the main component was α-Fe2O3 and SiO2. The photocatalytic activity of α-Fe2O3/bentonite nanocomposite was investigated on degradation of indigo carmine (IC) dye at various conditions of pH, photocatalyst mass, initial dye concentration and irradiation time. The results showed that the highest photocatalytic activity of α-Fe2O3/bentonite nanocomposite was obtained at the initial pH value of IC solution 1, 250 mg photocatalyst mass and initial concentration of IC 10 mg/L after irradiated for 90 minutes under ultra violet and solar light, respectively. The photocatalytic activity of α-Fe2O3/bentonite nanocomposite using UV light was almost the same as that of by solar light.

ZnO-Bi2O3/graphitic carbon nitride photocatalytic system with H2O2-assisted enhanced degradation of Indigo carmine under visible light

Indigo carmine in aqueous solution was effectively degraded using ZnO-Bi2O3/Graphitic Carbon Nitride heterojunction structure by visible light/H2O2 system. The mechanism of photocatalytic degradation of Indigo carmine shows the responsible species for the degradation of Indigo carmine in the ZnO-Bi2O3-xC3N4/H2O2/visible light system (x = 0, 1, 2, and 3) is the hydroxyl radicals which were generated from the reaction of e− and h+ with H2O2. Under optimal conditions, ZnO-Bi2O3-2C3N4/H2O2/Vis system degraded more than 93% of Indigo carmine in 180 min. Besides, the kinetic of the photocatalytic process was detailed. These results demonstrate that the ZnO-Bi2O3-2C3N4/H2O2/visible light system may become a promising approach to achieve efficient environmental remediation as an environmentally friendly oxidant.

Synthesis, Characterization and Photocatalytic Activity of α-Fe2O3/Bentonite Composite Prepared by Mechanical Milling

Preparation of α-Fe2O3/bentonite composite has been carried out by solid state reaction method by using iron ore from Aceh Besar district, Aceh as hematite source and bentonite from Kuala Dewa, North Aceh. The α-Fe2O3 was extracted from iron ore using hydrochloric acid and precipitated using ammonium hydroxide. The α-Fe2O3/bentonite composite was prepared by mixing α-Fe2O3 and bentonite at 4: 1 ratio using ball mill for 2 h. The XRD results showed that the dominant phase of iron ore was magnetite (Fe2O3) and was converted to α-Fe2O3 after extracting and calcined at 700 °C. The photocatalytic activity of α-Fe2O3/bentonit composite was evaluated on degradation of indigo carmine (IC) dye at various condition of pH, photocatalyst mass, initial dye concentration and irradiation time. The results showed that the highest photocatalytic activity of α-Fe2O3/bentonite composite was obtained at an initial pH of 1, a photocatalyst mass of 250 mg and an initial dye concentration of 5 mg/L with UV irradiation time for 2 h. The photocatalytic activity of α-Fe2O3/bentonite composite using solar light was higher than that of UV light.

Visible light driven mesoporous Mn and S co-doped TiO2 nano material: Characterization and applications in photocatalytic degradation of indigocarmine dye and antibacterial activity

The present study explored the Photocatalytic & antibacterial activity of Mesoporous Mn and S co-doped TiO2 nano material synthesized by sol-gel method. As prepared samples were characterized by X-ray diffraction (XRD), X-ray photo electron spectroscopy (XPS), Scanning electron microscopy (SEM), Energy dispersive X-ray Spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), UV–vis Diffused Reflectance Spectroscopy (UV–vis-DRS), Transmission electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) and Photoluminescence (PL). The Characterization results revealed that all the co-doped and undoped samples shows anatase phase. The Frequency shift of Ti-O-Ti in the catalyst samples was observed in FT-IR due to substitutional doping of Mn and S by replacing Ti and O, Further the catalyst shows smooth spherically shaped small particle size (7.6 nm) with high surface area (155.87 m2/g) and having less band gap energy (2.58 eV). The most reactive •OH are produced during the progress of reaction was determined by using Photo luminescence (PL) technique. The photocatalytic efficiency and antibacterial activity was evaluated by degradation of Indigo carmine(IC), Bacillus coagulans and klebsiella pneumonia respectively. The complete degradation of IC was achieved at optimum reaction parameters such as 0.150 g of the catalyst dosage, solution pH = 4 and initial dye concentration 20 ppm with the catalyst of 1.0 Wt% of Mn-0.25 Wt% of S co-doped Titania with in 90 min. The zone of inhibition bacterial growth was observed (24 mm and 23 mm) compared to control value (Chloramphenicol) 25 mm and 24 mm.

Visible-light assisted CdO nanowires photocatalyst for toxic dye degradation studies

In the present work, CdO nanowires (NWs) as a visible-light assisted photocatalyst was developed and studied for photocatalytic degradation of representative hazardous colour dyes, which are often exposed to water sources by the textile industries. The uniform CdO NWs were synthesized using the simple soft chemical route. Further, the CdO NWs were annealed in air from 350 to 450 °C with an interval of 50 °C and were characterized to understand their physical and optical properties. Structural analysis showed that the crystallinity increases with annealing temperature till 400 °C. FESEM study of CdO thin films revealed the transformation of NWs into earthworm-like chain NWs after thermal annealing. The optical absorption study revealed the presence of direct band-to-band transition with band-gap ranging from 2.17 to 1.55 eV for as-deposited to annealed films, respectively. The photocatalytic activity of the CdO NWs annealed at 400 °C was tested by visible-light-induced degradation of Indigo carmine (IC), Ponceau-S (PS), and Congo red (CR) dyes. In the presence of CdO NWs photocatalyst, the efficiency was found to be 30% for IC, 39% for PS and 57% for CR dyes. The CdO NWs photocatalyst showed enhanced photodegradation i.e., ∼ 1.9 times and ∼1.4 times higher for CR in comparison to IC and PS, respectively.

MnO2 efficiently removes indigo carmine dyes from polluted water

MnO2 is identified as a highly efficient sonocatalyst and sonophotocatalyst for the complete removal of even very small concentration of Indigo carmine (IC) dye pollutant from water. The effect of various reaction parameters, viz. dosage of the catalyst, concentration of pollutant, volume of reaction system, pH, dissolved gases, presence of anions/salts and oxidants etc. on the rate of degradation is evaluated and optimum parameters are identified. The degradation follows variable kinetics depending on the concentration of the substrate. The rate of degradation is facilitated by acidic pH. Classic oxidants H2O2 and S2O82− behave differently, with the former inhibiting and the latter enhancing the degradation. The effect of anions/salts on the degradation is complex and ranges from ‘inhibition’ (PO43−, CO32−, HCO3−) and ‘no effect’ (SO42−, Cl−) to ‘enhancement’ (NO3−, CH3COO−). The high affinity of MnO2 for O2 and its extremely efficient adsorption of H2O2 and the substrate play key roles in the efficiency of the process. Participation of lattice oxygen from MnO2 in the reaction, whenever the dissolved or adsorbed oxygen is deficient, is an important highlight of the process. Major transient intermediates formed during the process are identified by LC–MS. Combination of sonocatalysis with UV photolysis (sonophotocatalysis) enhances the efficiency of degradation and mineralization of IC.

Ag/Ag2CrO4 nanoparticles modified on ZnO nanorods as an efficient plasmonic photocatalyst under visible light

The highly efficient plasmonic photocatalysts have drawn attention with their effective charge carrier separation capabilities and visible light absorption features, which makes them immensely favorable material in the organic contaminants eliminating for wastewater treatment. Thus, the goal of this study is to improve visible light driven plasmonic photocatalysts using Ag/Ag2CrO4 and ZnO. A highly efficient nanoheterojunction structured Ag/Ag2CrO4/ZnO has been prepared by precipitation-photoreduction method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (ATR-FTIR), electrochemical measurements and UV–vis diffuse reflectance/absorbance spectroscopy (DRS). When photocatalytic efficiencies of ZnO, Ag2CrO4, Ag/Ag2CrO4, Ag2CrO4/ZnO and Ag/Ag2CrO4/ZnO are compared, Ag/Ag2CrO4/ZnO exhibits the best efficiency for the degradation of indigo carmine (IC) under visible-light. The reasons for the highly increased performance of Ag/Ag2CrO4/ZnO may be related to the synergistic effect of Ag/Ag2CrO4 doped on ZnO surface. Thus, the visible light absorption capability of ZnO can be increased and the recombination of charge carriers can be effectively hindered. The nano photocatalyst also showed high stability even after five cycles. Therefore, the Ag/Ag2CrO4/ZnO can be effectively used as active plasmonic photocatalysts under visible light and it exhibits a great potential in removing environmental contamination.

Mechanism of Visible‐Light Photocatalytic Mineralization of Indigo Carmine Using ZnBi2O4‐Bi2S3 Composites

AbstractNovel highly visible‐light active ZnBi2O4‐Bi2S3 photocatalysts with various weight percentages of Bi2S3 have been synthesized by a simple two‐step co‐precipitation and hydrothermal method. The efficacy of the as‐prepared ZnBi2O4‐Bi2S3 composites was evaluated for the degradation of Indigo carmine in aqueous solutions under visible light irradiation. It was found that the as‐prepared ZnBi2O4‐Bi2S3 composites showed was greatly enhanced photocatalytic activities as compared to that of pristine ZnBi2O4 under visible light, which could be attributed to synergetic effects, charge transfer between ZnBi2O4 and Bi2S3, as well as the separation efficiency of the photogenerated electrons and holes. The superoxide anion radical was the major active species responsible for the photodegradation process, whereas the contributions of the photoinduced h+ and hydroxyl radicals were moderate and minor, respectively. These results demonstrate the feasibility of utilizing ZnBi2O4‐Bi2S3 as potential heterogeneous photocatalysts for environmental remediation.

Fast decolourization of Indigo Carmine and Crystal Violet in aqueous environments through micellar catalysis

Abstract Herein we report the modulating effect of sodium dodecyl sulphate (SDS), hexadecyl-pyridinium chloride (HDPC) and octylphenol ethoxylate (Triton X100) on the degradation of indigo carmine (IC) and crystal violet (CV) in bicarbonate-activated peroxide (BAP) system. Upon the addition of surfactant/BAP “surfoxidant”, the decolourization degrees of both dyes were above 60% after 5 min, and the total organic carbon removal after 15 min varied within 44–50%. While SDS has shown rather an inhibitory effect during the oxidation of CV, HDPC and Triton promoted the oxidation of both CV and IC, particularly HDPC when a 10-fold increase of the decolourization rate was obtained. This behaviour suggests the formation of active entities –kinetic micelles- acting as nano-reactors by “enclosing” reactants in small-sized aggregates with volumes ranging from 30 to 720 nm3.

Fabrication of novel carbon quantum dots modified bismuth oxide (α-Bi2O3/C-dots): Material properties and catalytic applications

The present work reports the facile and the template free sonochemical synthesis of a novel catalyst, α-Bi2O3/C-dots, for the degradation of indigo carmine (IC) dye, its simulated dyebath effluent and levofloxacin under visible light catalysis. The compositional, structural, optical and morphological analysis of α-Bi2O3/C-dots was studied using analytical, spectroscopic and microscopic techniques. X-ray diffraction (XRD) results confirmed the presence of a monoclinic phase of α-Bi2O3 in the nanocomposite and crystallite size of 28.75 nm. Photoluminescence (PL) and UV–vis diffuse reflectance spectra (UV-DRS) studies showed good optical properties and a band gap of 2.49 eV. The synthesized photocatalyst showed superior visible-light driven photocatalytic activity for the degradation of indigo carmine dye (86% dye degradation in 120 min) compared to pure α-Bi2O3 (57%). α-Bi2O3/C-dots also exhibited 79% degradation of antibiotic drug levofloxacin within 120 min, under optimized conditions of pH, catalyst dose and initial dye concentration. Scavenger studies revealed that hydroxyl radicals and electrons played predominant roles in the photocatalytic degradation of IC dye. With respect to total organic carbon (TOC) analysis, 68.8% total organic carbon reduction of the IC dye (10 mg/L) was observed under the same experimental conditions. The catalytic efficiency of C-dots in the photocatalytic process is explained by proposing a degradation mechanism.

Graphene oxide–nano‐titania composites for efficient photocatalytic degradation of indigo carmine

Nano‐titania composites assembled with variable weight percentages (wt%) of graphene oxide (GO) were synthesized, and their effectiveness as photocatalysts was investigated for the degradation of indigo carmine under visible light irradiation. Controlled hydrolysis of titanium tetrachloride (TiCl4) was performed in aqueous medium, and 1% aqueous solution of GO was added under ultrasonication. Depending on the wt% of GO, the materials were designated as 1, 2, 5, 10, 15 wt%GO–nano‐titania (GO–NT) composites. Their morphology and structural properties were characterized using X‐ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), high‐resolution transmission electron microscopy (HRTEM), and field‐emission scanning electron microscopy (FE‐SEM). Excellent photocatalytic activity was demonstrated by the NT composite containing 10%GO in 60 min, and the required optimum conditions were established.

Green synthesis of earth-abundant metal sulfides (FeS2, CuS, and NiS2) and their use as visible-light active photocatalysts for H2 generation and dye removal

Earth-abundant metal sulfides (for example, FeS2, CuS, and NiS2) are promising materials to be used as photocatalysts due to their suitable electronic and optical properties. In this work, we present a fast and low-cost hydrothermal method to synthesize these materials. They are integrally characterized and evaluated as photocatalysts for the H2 evolution reaction and the degradation of indigo carmine (IC). FeS2 exhibits the highest photocatalytic efficiency (32 µmol g−1 h−1 of H2 evolution and 88% of indigo carmine degradation) under visible light, and this activity is attributed to a larger crystallite size, smaller particle size, and lower recombination, compared to CuS and NiS2. Moreover, three different sacrificial reagents are studied for the H2 evolution reaction, including Na2S/Na2SO3, EDTA, and ethanol. Na2S/Na2SO3 shows the highest enhancement in the activity, increasing the rate of H2 production more than 15 times. This behavior is related to the lower oxidation potential of Na2S/Na2SO3. Moreover, we evaluate the activity of the materials for the electrochemical hydrogen evolution reaction (HER). In summary, this work provides valuable information for effective applications of these earth-abundant metal sulfides for energy and environmental photocatalytic processes.