Visible-light Activity Research Articles

Visible-Light Photoredox Catalyzed Regioselective 1,4-Hydroalkylation of 1,3-enyne.

Described herein is a visible-light photoredox-catalyzed regioselective 1,4-hydroalkylation of 1,3-enynes. Various of di- and tri-substituent allenes were really accessible under the present reaction conditions. The visible-light photoredox activation of the carbon nucleophile to generate its radical species, allowing the addition with un-activated enynes. The synthetic utility for the present protocol was demonstrated by a large-scale reaction, as well as the derivatization of the allene product.

A novel tungsten diselenide nanoparticles for enhanced photocatalytic performance of Cr (VI) reduction and ciprofloxacin (CIP)

Nanoparticles (NPs) fabrication is a significant approach to enhance the visible light response of photocatalysts, to realize inexpensive and more harmful compound removal, at larger scale. The poor electrons and holes separation capability and low light activity of bulk materials can be notably enhanced through developing NPs. From photocatalytic investigation, better performance was received in the tungsten diselenide (WSe2) NPs than that in bare WSe2, exhibiting the action of restrained recombination of charge carriers in the NPs. The photocatalytic Cr(VI) reduction efficiency of WSe2 NPs is 2.7 folds greater than that by bare WSe2. On the other hand, the photocatalytic efficiency follows the order of nano WSe2-3 > nano WSe2-2 > nano WSe2-1 > bare WSe2, nano WSe2-3 is nearly 2.7 folds greater than that of bare WSe2. The results imply the fabrication of WSe2 NPs and it possesses improved visible light utilization. The proposed WSe2 NPs have merged with the three aspects of photocatalytic capability including the visible light activity, the valid separation of photo-response charge carriers and enough surface active sites owing to the nanoscale formed. This research endows conduct on the potential style of NPs for photo-response water environmental remediation.

Porous Graphitic phase carbon nitride/graphene oxide hydrogel microspheres for efficient and recyclable degradation of aflatoxin B1 in peanut oil.

Removal of aflatoxin is an urgent issue in agricultural products. A porous graphitic carbon nitride/graphene oxide hydrogel microsphere (CN/GO/SA) was synthesized and used to degrade AFB1 in peanut oil. CN/GO/SA was characterized by scanning electron micrograph (SEM), X-ray diffraction (XRD) and FT-IR. The introduction of GO significantly improved the adsorption capacity and visible light activity of photocatalysts. About 98.4% AFB1 in peanut oil was removed by 20% CN/GO/SA under visible light for 120min. ‧O2- and h+ were the main active species during photoreaction, and five degradation products were identified by UPLC-Q-Orbitrap MS analysis. At the same time, the quality of treated peanut oil was still acceptable. More importantly, CN/GO/SA showed excellent cycle stability, and the degradation rate of AFB1 in peanut oil remained above 95% after five-time recycling. This work provides a practical way for developing efficient and sustainable photocatalysts to degrade mycotoxins in edible oil.

Chiral Perovskite Nanocrystals for Asymmetric Reactions: A Highly Enantioselective Strategy for Photocatalytic Synthesis of N-C Axially Chiral Heterocycles.

Catalytic approaches to generate enantiospecific chiral centers are the major premise of modern organic chemistry. Heterogeneous catalysis is responsible for the vast majority of chemical transformations, yet the direct employment of chiral solid catalysts for asymmetric synthesis is mostly overlooked. Here, we demonstrated that a heterogeneous metal-halide perovskite nanocrystal (NC) catalyst is active for asymmetric organic synthesis under visible-light activation. Chiral 1-phenylethylamine (PEA)-hybridized perovskite PEA/CsPbBr3 NC photocatalysts exhibit an enantioselective (up to 99% enantiomer excess, ee) avenue to produce N-C axially chiral N-heterocycles, i.e., N-arylindoles from N-arylamine photo-oxidation. Mechanistic investigation indicated a discriminated prochiral binding of the N-arylamine substrates onto the chiral-NC surface with ca. -2.4 kcal/mol enantiodifferentiation. Our perovskite NC heterogeneous catalytic system not only demonstrates a promising strategy to address the long-term challenges in atroposelective pharmaceutical scaffold synthesis but also paves the road to directly employ chiral solids for asymmetric synthesis.

A visible light-sensitive argentous oxide/calcium aluminate nanocomposite photocatalyst

A photo-deposition method was developed to synthesise argentous oxide/calcium aluminate nanocomposites (Ag2O-CAONCS) with orthorhombic Ca5Al6O14 and cubic Ag2O phases. Micro-morphology, micro-structure, optical, and visible-light catalytic properties were investigated via different techniques. Ag2O enhances visible-light absorption performance and decreases the band gap of the Ag2O-CAONCS. About 20 mL crystal violet (CV) dye (10 mgL–1) is totally degraded using 20 mg Ag2O-CAONCS under sunlight irradiation for 20 min. The enhanced photocatalytic activity of the Ag2O-CAONCS towards CV under sunlight irradiation is ascribed to the reduction of the band gap, improvement in visible-light absorption and inhibitation role of carriers recombination by Ag2O. The high, stable visible-light catalytic activity makes Ag2O-CAONCS promising photocatalysts for removing organic pollutants.

Fabrication of Au@α-Fe2O3 particles with an enhanced visible-light photocatalysis activity

Au nanoparticles deposited α-Fe2O3 (Au@α-Fe2O3) particles with a well-defined structure were fabricated by the hydrothermal and the magnetron sputtering methods. After deposited 4.6% Au, Au@α-Fe2O3 shows a new absorption peak at 550 nm in the UV–Vis spectrum, and its bandgap narrows from 2.20 to 1.93 eV. Moreover, the fluorescence intensity and electrochemical impedance of 4.6% Au@α-Fe2O3 decrease significantly, while the photocurrent increases from 0.20 to 0.56 μA cm−2. Au nanoparticles extend the visible-light absorption performance and inhibit the recombination of electron-hole pairs of Au@α-Fe2O3 particles. The photocatalytic property of Au@α-Fe2O3 particles becomes more stable, and the photocatalytic efficiency of Au@α-Fe2O3 particles is about 1 time higher than that of α-Fe2O3 particles.

Postsynthetic Annulation of Three-Dimensional Covalent Organic Frameworks for Boosting CO2 Photoreduction.

Three-dimensional covalent organic frameworks (3D COFs), with interconnected pores and exposed functional groups, provide new opportunities for the design of advanced functional materials through postsynthetic modification. Herein, we demonstrate the successful postsynthetic annulation of 3D COFs to construct efficient CO2 reduction photocatalysts. Two 3D COFs, NJU-318 and NJU-319Fe, were initially constructed by connecting hexaphenyl-triphenylene units with pyrene- or Fe-porphyrin-based linkers. Subsequently, the hexaphenyl-triphenylene moieties within the COFs were postsynthetically transformed into π-conjugated hexabenzo-trinaphthylene (pNJU-318 and pNJU-319Fe) to enhance visible light absorption and CO2 photoreduction activity. The optimized photocatalyst, pNJU-319Fe, shows a CO yield of 688 μmol g-1, representing a 2.5-fold increase compared to that of unmodified NJU-319Fe. Notably, the direct synthesis of hexabenzo-trinaphthylene-based COF catalysts was unsuccessful due to the low solubility of conjugated linkers. This study not only provides an effective method to construct photocatalysts but also highlights the unlimited tunability of 3D COFs through structural design and postsynthetic modification.

Visible light-assisted efficient degradation of Rhodamine B by N-TiO2/Mn-HPMo/Ag ternary composites

In this paper, Ag nanoparticles were deposited on the surface of nitrogen-doped titanium dioxide coupled with manganese-substituted phosphomolybdic acid composites (N-TiO2/Mn-HPMo) using photoreduction method to construct ternary photocatalysis-Fenton composite catalyst (N-TiO2/Mn-HPMo/Ag), and the degradation performance of the catalyst was evaluated with Rhodamine B (RhB) as the target pollutant. The results showed that the N-TiO2/Mn-HPMo/Ag ternary composite catalyst had remarkable visible light activity, and the degradation efficiency of RhB could reach 96.3% in 20 min under visible light. Meanwhile, UV–vis diffuse reflectance spectroscopy illustrated the promotion effect of Ag deposition on the visible light response of N-TiO2/Mn-HPMo. The behavior of photogenerated charges was also characterized by Surface Photovoltage Technique, which further demonstrated that Ag deposition not only extended the light absorption range but also enhanced the separation efficiency of photogenerated charges. This work provides favorable information for the construction of efficient catalysts with high activity under visible light.

Fiberglass cloth coated by coffee ground waste-derived carbon quantum dots/titanium dioxide composite for removal of caffeine and other pharmaceuticals from water

Coffee ground waste from the coffee beverage preparation is mainly discarded and consequently ends up in landfill, which cause the contamination of caffeine in various environmental compartments. This study focuses on the upcycling of coffee-ground waste to carbon quantum dots (CQDs) for use as a modifying material to improve the visible light activity of titanium dioxide (TiO2). The CQD solution was synthesized by hydrothermal method, which has an average size of 2.80 ± 0.63 nm. The CQDs/TiO2 photocatalysts were prepared by combining CQD solutions at various amounts with sol-gel TiO2 and then coated on the fiberglass cloths (FGCs). The photocatalytic application mainly focuses on the removal of caffeine from the water. The photocatalytic experiment was preliminary run in a simple batch reactor under visible light. The 5CQDs/TiO2 coated FGC (5 mL of CQD solution/g of Ti-based on sol-gel) showed the best performance, and it was selected for the removal of caffeine and other pharmaceuticals (i.e., carbamazepine and ibuprofen) in the recirculating reactor. The removals of caffeine, carbamazepine, and ibuprofen after irradiation for 9 h were 82%, 88%, and 84%, respectively. The residual concentrations were significantly lower than the reported toxicity levels based on specific species. The changes in total organic carbon were observed, indicating the mineralization of pharmaceuticals in water. The 5CQDs/TiO2 coated FGC showed good flexible performance. No obvious loss of activity was observed for five runs. The actual wastewater from the coffee pot cleaning process was also tested. The removal was 80% for caffeine and 86% for color in the unit of the American Dye Manufacturers Institute (ADMI).

Yttrium vanadate coupled with cobalt ferrite nanocrystals for enhanced photocatalytic H2 production under visible light irradiation

Yttrium vanadate (YVO4) nanocrystals are synthesized by a modified sol-gel route followed by coupling with 4.0–16.0 wt% of cobalt ferrite (CoFe2O4) nanoparticles. The synthesized heterostructures were laboured for photocatalytic H2 generation in a water/glycerol system below visible light in the presence of platinum cocatalyst traces. The addition of CoFe2O4 nanoparticles has improved the physicochemical characteristics of YVO4 in terms of light harvesting and photoinduced charge separation. The 12.0 wt% CoFe2O4/YVO4 indicates the narrowest bandgap of 2.5 eV and the highest visible-light activity with a slight reduction of its surface area from 185 to 168 m2 g−1. Moreover, the H2 evolution rate has augmented utilizing this photocatalyst at 2.557 mmol g−1h−1 compared to 0.044 mmol g−1h−1 over the pure YVO4. Furthermore, the dose optimization of 12% CoFe2O4/YVO4 at 2.0 gL−1 has endorsed the photocatalytic generation of H2 to 3.389 mmol g−1h−1 with recyclability of 97% after the fifth cycle.

Conjugated Polymer Modifying TiO2 Performance for Visible-Light Photodegradation of Organics.

Up to now, the use of TiO2 has been considered a promising advanced technology for organic pollutants removal from air or water, since it has high biological and chemical stability, high photoactivity, low toxicity, and low-cost production. However, there are issues to be addressed in enhancing TiO2 performance, and one of the current key issues is redesigning UV-active photocatalysts and making them active in the visible region of the electromagnetic spectrum. This way, solar light absorption will be insured, and thus, a more efficient photocatalyst could be obtained. For this reason, conjugated polymers and their derivatives are considered to act as photosensitizers, being able to shift the TiO2 activity from the UV to the visible region. Therefore, this study focuses on the synthesis of TiO2/conjugated polymer systems, which was accomplished by the deposition of poly-3,4-ethylene-dioxy-thiophene (PEDOT [-C6H4O2S-]n), a low-band semiconductor with an excellent stability due to its extending π-conjugated electron system, on titania nanoarchitecture. First of all, a TiO2 nanoarchitecture was synthesized by an ultrasound-assisted sol-gel method. Then, TiO2/PEDOT systems were obtained and characterized by using different techniques such as X-ray diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, UV-Vis diffuse reflectance, and N2 sorption measurements. The synthesized composites confirmed their mesoporosity and lower band gap values compared to bare titania, which clearly shows the ability to work as photocatalysts under visible-light activity. Further, we demonstrated that an organic pollutant, Congo Red dye, used as a model molecule could be photodegraded with the synthesized TiO2/PEDOT systems, with efficiencies of up to 95% in the case of TconvPEDOT under UV light and up to 99% for TconvPEDOT under visible-light irradiation, accomplishing in this way a successful synthesis of visible-light-activated titania photocatalyst.

Controlled Architectures in Supported Photocatalysis: Exploring the Potential of Cold Plasma Discharge, Additive Manufacturing, and Fractal Geometry to Form Hierarchically Immobilized Ni-MOF/BiOI/AgVO3.

Herein, we explore the potential of innovative manufacturing techniques based on green chemistry principles, for the fabrication of convenient, performant, and stable supported photocatalysts to be used for water depollution. After giving some insight into the use of fractal geometry for the fabrication of tunable polymer supports for photocatalysts, we investigated the use of liquid crystal display (LCD) 3D printing to generate the fractal resin substrates to be used for the immobilization of semiconductor photocatalysts. Notably, confocal laser imaging was used as a first attempt for assessing the surface area of the fractal substrate. Immobilization methods based on cold plasma discharge (CPD) were employed to modify the surface of the polymer substrates and permanently anchor three different phases, namely, nickel-based metal-organic framework (Ni-MOF), BiOI, and AgVO3, in a hierarchical configuration. Herein, for the first time, we developed a plasma-initiated condensed in situ complexation-assisted precipitation (c-ISCAP) method that allowed 2D Ni-MOF to be synthesized directly onto the surface of a polymer substrate, in a single step. Not only this MOF coating was found to be strongly bound to the surface of the polymer substrate but also very uniform and fully functional, even when other inorganic phases were immobilized on the top of this layer. This chemical approach opens the way for the fabrication of hybrid materials with complex polymer substrates and MOF coatings that could be used in a range of possible applications, for instance as chemical sensors, electrodes, adsorbents, optical devices, etc. Our hybrid photocatalysts were tested via photodegradation of Rhodamine B (RhB) dye upon visible light activation, with recycling runs to assess their durability. It was found that the hierarchical heterojunction Ni-MOF/BiOI/AgVO3 showed an outstanding ability for the removal of RhB dye, owing to the activity of the Ni-MOF layer in terms of charge transfer, and also partly because of its adsorbing potential. The three photoactive phases demonstrated a strong synergistic effect through coupling. However, more importantly, our findings show that their immobilization itself, regardless of the method used, significantly modified their optoelectronic properties, hence most likely changing the overall mechanism of charge transfer in the heterojunction. The Ni-MOF phase, notably, was found to display a reduced bandgap when obtained by c-ISCAP, which contributed to enhance its activation by visible light irradiation. Finally, it was established that the fractal geometry had a significant impact on the efficiency of the supported catalysts, probably thanks to an increased immobilization ratio of photocatalyst mostly, owing to the larger surface area available.

Study on the interaction of anions and cations in the synthesis of nanoflower bismuth silicate and its photocatalytic removal of dyes and antibiotics

It is challenging to construct photocatalysts with excellent adsorption-photocatalytic synergy and multi-system pollutant degradation by utilizing double heterostructure with unique nanoflower structure and energy band modulation. Here, a nanoflower-like double-heterojunction composite photocatalyst with high visible light activity is prepared in situ by ion exchange, namely BOSBM (M=I, B, C, K, L; the modified ions are I-, Br-, Cl-, K- and Li-). On the other hand, surface-charged ions provide multiple adsorption sites for pollutants. In BOSBC-6 (the ion is Cl-, the concentration is 1.05 mol/L) photocatalyst, the photocatalytic performance (10 min, degradation rate of 98 %) is 4 times that of BOS. It still has excellent catalytic stability (30 min, 98 % degradation rate) even after 3 cycles of testing. Meanwhile, BOSBM exhibited high degradation efficiency for dye (RhB) and various antibiotics (norfloxacin, ciprofloxacin, and tetracycline hydrochloride). Due to its upward shifting structure (Vo level), BOSBM plays an important role in the degradation of multi-system pollutants. In particular, the formation of Bi2O2SiO3-BiOCl and Si2Bi24O40-BiOCl double heterojunctions in BOSBC-6, which significantly improves the separation efficiency and increases the redox capacity of the sample. Therefore, this work broadens the application range of bismuth silicate photocatalysts and provides a new strategy for obtaining photocatalysts with excellent adsorption-photocatalytic synergistic effect by utilizing the heterojunction structure for modification purposes.

Construction of Pt@BiFeO3 Xerogel-Supported O-g-C3N4 Heterojunction System for Enhanced Visible-Light Activity towards Photocatalytic Degradation of Rhodamine B

Synthetic organic pigments from the direct discharge of textile effluents are considered as colossal global concern and attract the attention of scholars. The efficient construction of heterojunction systems involving precious metal co-catalysis is an effective strategy for obtaining highly efficient photocatalytic materials. Herein, we report the construction of a Pt-doped BiFeO3/O-g-C3N4 (Pt@BFO/O-CN) S-scheme heterojunction system for photocatalytic degradation of aqueous rhodamine B (RhB) under visible-light irradiation. The photocatalytic performances of Pt@BFO/O-CN and BFO/O-CN composites and pristine BiFeO3 and O-g-C3N4 were compared, and the photocatalytic process of the Pt@BFO/O-CN system was optimized. The results exhibit that the S-scheme Pt@BFO/O-CN heterojunction has superior photocatalytic performance compared to its fellow catalysts, which is due to the asymmetric nature of the as-constructed heterojunction. The as-constructed Pt@BFO/O-CN heterojunction reveals high performance in photocatalytic degradation of RhB with a degradation efficiency of 100% achieved after 50 min of visible-light irradiation. The photodegradation fitted well with pseudo-first-order kinetics proceeding with a rate constant of 4.63 × 10−2 min−1. The radical trapping test reveals that h+ and •O2− take the leading role in the reaction, while the stability test reveals a 98% efficiency after the fourth cycle. As established from various interpretations, the considerably enhanced photocatalytic performance of the heterojunction system can be attributed to the promoted charge carrier separation and transfer of photoexcited carriers, as well as the strong photo-redox ability established. Hence, the S-scheme Pt@BFO/O-CN heterojunction is a good candidate in the treatment of industrial wastewater for the mineralization of organic micropollutants, which pose a grievous threat to the environment.

Oxygen vacancies in the Spotlight: On the engineering of intrinsic defects in highly defective TiO2 photocatalysts

Nanostructured oxide semiconductors are widely used in energy conversion, catalysis, sensing and environmental applications, due to their high stability, commercial availability, efficiency and low cost. Despite its crucial importance for the design of more efficient materials, the interplay between intrinsic and extrinsic defects is yet to be clarified. For example, oxygen vacancies (VO’s) can be either beneficial or detrimental to the desired performances, depending on a variety of factors. Here, we synthesize TiO2-x samples by the addition of three different N chemical sources (NH3, triethylamine, urea). X-ray absorption spectroscopy, confocal microscopy, UV–vis absorbance and fluorescence, are employed to explore the occurrence and location of VO’s both in real and energy spaces. High–grade bulk DFT simulations complement the experimental picture. Synergy between theory and experiment, on the one hand, estimates the relative VO’s content in the different samples from local structural information. On the other hand, a sharp optical transition at ≈2.7 eV serves an unequivocal spectral signature of bulk VO’s, allowing a semi-quantitative analysis by confocal microscopy. Surface oxygen vacancies do not display fluorescence features under UV pumping, possibly due to the reaction of surface defects with atmospheric O2. Thus, the comparison between local structure and confocal microscopy can discriminate surface-localized and bulk VO’s. Concurrently, UV-induced photochromism and visible light photodegradation shed light on the most effective reactive defects. Eventually, surface-localized oxygen vacancies are predominant where actual N substitutional doping occurs, leading to materials exhibiting visible-light activity and characteristic photochromic behaviour. Implications on strategies for concomitant VO engineering and extrinsic doping are discussed.

Influence of Bi co-catalyst particle size on the photocatalytic activity of BiOI microflowers in Bi/BiOI junctions – A mechanistic study of charge carrier behaviour

Herein, we investigate the effect of Bi particle size in BiOI/Bi junctions on their photocatalytic function towards NO gas. BiOI microflowers (BiOI) and BiOI microflowers decorated with micron-sized Bi particles (BiOI/Bi MPs) were produced by a solvothermal method. BiOI decorated with nano-sized Bi particles (BiOI/Bi NPs) were produced by a reduction process. All samples were physically characterised by XRD, FT-IR, SEM, HR-TEM coupled with EDX analysis, DR-UV–visible and PL spectroscopy and functionally characterised by photocatalytic testing towards NO gas, TAS and EPR spectroscopy.Their photocatalytic activity towards NO gas was measured following ISO protocol (ISO 22197–1:2016). The best performing BiOI-based sample was BiOI/Bi NPs, showing NO and NOx conversion efficiencies of ∼33 and ∼11% under UVA light, and ∼26 and ∼8.1% under visible light, respectively. The BiOI and BiOI/Bi MPs samples showed significantly lower activities, displaying overall NOx conversion efficiencies of ∼3.5 and ∼0.8% under UVA light, respectively. Importantly, the best performing BiOI/Bi NPs samples showed visible light activity that was at least 6 times higher than that of a commercial TiO2 benchmark (CristalACTiVTM PC-S7). TAS measurements showed that charge carriers were significantly longer lived in the BiOI/Bi NPs sample (t50% from 10 μs of ∼90 μs) than the BiOI and BiOI/Bi MPs samples (t50% from 10 μs of ∼50 μs). This was attributed to the significant degree of interfacial contact formed between Bi and BiOI in the BiOI/Bi NPs sample, which enhanced charge carrier separation. EPR studies showed that this interfacial contact between BiOI and Bi likely promoted the formation of VO, which may have contributed to enhancement seen in photocatalytic activity in the BiOI/Bi junction.

Rational design of high temperature processed TbVO4/Nb2O5/carbon aerogel photocatalyst for prompt degradation of emerging pollutants

This present study investigates the construction of novel ternary heterojunction photocatalysts using terbium vanadate (TbVO4), niobium pentoxide (Nb2O5), and carbon aerogel (CG), to increase the photocatalytic performances under visible light. The X-ray diffraction (XRD) outcomes confirmed that the TbVO4 and Nb2O5 present themselves in a highly crystalline nature due to the high-temperature synthesis process. The successful combination of carbon aerogel and Nb2O5 into the TbVO4 lattice is further established by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) studies. The UV-DRS results confirmed that the materials comprising of both carbon aerogel and Nb2O5 present an expressive improvement in visible light activity, which leads to a drop-in band gap energy of the ternary TbVO4/Nb2O5/carbon aerogel photocatalyst. The improved charge separation in the ternary system was further confirmed by the electron spin resonance (ESR) and photoluminescence (PL) studies. The experimental results reveal that Nb2O5 and carbon aerogel were successfully incorporated in the TbVO4, increasing its surface area and structural photostability, thereby increasing its photocatalytic performance in the removal of pollutants under visible light. Compared with TbVO4 and Nb2O5, the outcomes illustrate that the TbVO4/Nb2O5/carbon aerogel displays the optimum photocatalytic removal rate and outstanding chemical stability in the removal of sulfamethoxazole. It shows a degradation efficiency of 92.3 in 90 min, which is 5 and 7 times as high as TbVO4 and Nb2O5, respectively. Based on the trapping experiments, h+, OH, and O2− improved the sulfamethoxazole photodegradation process. Finally, a novel, recyclable photocatalyst was made, which underwent a brand-new pathway for the degradation of various emerging pollutants.

Facile green synthesis of ZnO/AC nanocomposites using Pontederia crassipes leaf extract and their photocatalytic properties based on visible light activation

Facile green synthesis of ZnO/AC nanocomposites using Pontederia crassipes leaf extract and their photocatalytic properties based on visible light activation

Potential of novel dual Z-scheme carbon quantum dots decorated MnIn2S4/CdS/Bi2S3 heterojunction for environmental applications.

In this work, CQDs decorated MnIn2S4/CdS/Bi2S3 heterojunction was prepared successfully by hydrothermal technique for photocatalytic disinfection of Escherichia coli (E. coli) and mineralization of methyl orange (MO) dye. The charge transferal route and mineralization process in CQDs-MnIn2S4/CdS/Bi2S3 heterojunction were comprehensively investigated by advanced spectroscopic techniques. The improved visible-light activity and enhanced photo-generated charge transferal efficacy caused dual Z-scheme CQDs-MnIn2S4/CdS/Bi2S3 heterojunction to achieve boosted photodegradation ability. The catalytic degradation trend was followed as CQDs-MnIn2S4/CdS/Bi2S3 > MnIn2S4 > CdS > Bi2S3. The dye was mineralized within 180min under visible light irradiation. The effect of reaction parameters, pH effect, catalyst dosage, and H2O2 addition on MO degradation was also investigated. The degradation rate was maximal at pH 4 with a pseudo-first-order rate constant, 0.0438min-1. The assessment of antibacterial properties revealed that CQDs-MnIn2S4/CdS/Bi2S3 composite effectively inactivated E. coli under visible light. Scavenging experiments, transient photocurrent response, and electron spin resonance spectroscopy suggested that •[Formula: see text] and holes were the dominant reactive species. The Z-scheme heterojunction is recyclable up to ten photocatalytic cycles according to recycling experiments. This research indicates the importance of dual Z-scheme CQDs decorated MnIn2S4/CdS/Bi2S3 heterojunction in wastewater remediation.

Laser flash photolysis study of Nb2O5/g-C3N4 heterostructures as efficient photocatalyst for molecular H2 evolution

Improvements of visible light activity, slow recombination rate, stability, and efficiency are major challenges facing photocatalyst technologies today. Utilizing heterostructures of g-C3N4 (bandgap ∼2.7eV) with Nb2O5 (bandgap ∼3.4eV) as an alternative materials for the first time, we tried to overcome such challenges in this work. Heterostructures of Nb2O5/g-C3N4 have been synthesized via hydrothermal technique. And then a time-resolved laser flash photolysis of those heterostructures has been analyzed, focusing on seeking how to improve photocatalytic efficiency for molecular hydrogen (H2) evolution. The transient absorption spectra and the lifetime of charge carriers at different wavelengths have been observed for Nb2O5/g-C3N4, where g-C3N4 was used for a control. The role of hole scavenger (methanol) has also been investigated for the purpose of boosting charge trapping and H2 evolution. The long lifetime of Nb2O5/g-C3N4 heterostructures (6.54165 μs) compared to g-C3N4 (3.1651897 μs) has successfully supported the increased H2 evolution of 75 mmol/h.g. An enhancement in the rate of H2 evolution (160 mmol/h.g) in the presence of methanol has been confirmed. This study not only deepens our understanding of the role of scavenger, but also enables a rigorous quantification of the recombination rate crucial for photocatalytic applications in relation with efficient H2 production.