Superior Visible Light Photocatalytic Performance Research Articles

Perylene diimide covalent organic frameworks super-reductant for visible light-driven reduction of aryl halides

In recent years, there has been a growing interest in the utilization of molecular photocatalysts in their radical ionic forms, especially as visible-light super-reductants. These catalysts exhibit remarkable capabilities in facilitating otherwise inert high-potential organic reactions, such as the reduction of aryl halides to aryl radicals. However, the development of heterogeneous super-reductants has lagged behind due to the deactivation effect caused by molecular aggregation. This study presents a novel approach to address this limitation by heterogenizing perylene diimides (PDIs) super-reductants with a consecutive photo-induced electron transfer mechanism into two-dimensional donor-acceptor (D-A) covalent organic frameworks (COFs). Both COFs, possessing D-A electronic structures and photothermal effects, demonstrated superior visible-light photocatalytic performance compared to their homogeneous counterparts. They achieved up to 99% conversion in the dehalogenation of aryl halides, primarily through a hydrogen atom trapping aryl radical mechanism. Additionally, we conducted a comparative investigation of the excited states of radical anionic D-A-type COFs and DPPDI using femtosecond transient absorption spectroscopy. Notably, the lifetimes of COFs were significantly prolonged, measuring 210 and 260 ps, respectively, compared to the 150 ps lifetime of (DPPDI•−). This study offers valuable insights into the design of efficient free radical ion-type photocatalysts, with potential applications in various chemical transformations.

Daul Z-scheme heterojunction BiOBr/Bi2O2.33/g-C3N4 for enhanced visible-light-driven tetracycline hydrochloride degradation

The construction of heterojunction photocatalysts with superior visible light photocatalytic performance is an effective strategy to addressing antibiotic pollution. A dual Z-scheme heterojunction BiOBr/Bi2O2.33/g-C3N4 was synthesized via hydrothermal and calcination methods, exhibiting exceptional degradation TC-HCL efficiency under visible light irradiation. The well-designed heterojunction was comprehensively supported by SEM, XPS, XRD and other series of characterization. Moreover, the BBCN50 heterojunction demonstrated an optimal degradation efficiency of 97.0% in 60 min compared to BB and CN with efficiencies of 90.8% and 70 respectively. The superior photocatalytic performance is attributed to the significantly broadened visible light absorption region and enhanced migration and separation of photogenerated electron-hole pairs facilitated by the fabricated heterojunction. Moreover, cyclic interpretation and free radical capture research have confirmed both the high stability of catalyst and its Z-type charge transfer mechanism.

Mussel Shell-Supported Yttrium-Doped Bi2MoO6 Composite with Superior Visible-Light Photocatalytic Performance

Mussel Shell-Supported Yttrium-Doped Bi2MoO6 Composite with Superior Visible-Light Photocatalytic Performance

Facile fabrication of three-dimensional nanofibrous foams of cellulose@g-C3N4@Cu2O with superior visible-light photocatalytic performance

In this work, a unique three-dimensional nanofibrous foam of cellulose@g-C3N4@Cu2O was prepared via electrospinning followed by a foaming process. A cellulose solution in DMAc/LiCl containing g-C3N4 and CuSO4 was applied for electrospinning, while aqueous alkali was used as the coagulation bath. The solidification of electrospun cellulose/g-C3N4 nanofibers would be accompanied with in-situ formation of Cu(OH)2 nanoparticles. Interestingly, the hydrogen gas (H2) generated from NaBH4 could transform the two-dimensional membrane into a three-dimensional foam, leading to the increased specific surface area and porosity of the material. Meanwhile, the Cu(OH)2 nanoparticles attached on the electrospun nanofibers were reduced to Cu2O to form a p-n heterostructure between Cu2O and g-C3N4. The as-prepared cellulose@g-C3N4@Cu2O foam exhibited a high degradation efficiency (99.5 %) for the dye of Congo Red under visible light radiation. And ·O2− was discovered to be the dominant reactive species responsive for dye degradation. Moreover, the cellulose@g-C3N4@Cu2O could maintain its initial degradation efficiency even after seven cycles of reuse, suggesting the excellent stability and cycling performance.

Facile in-situ fabrication of ZnO2/CQD composites with promoted visible-light photocatalytic activities for organic degradation and bacterial inactivation

Herein, the novel zinc peroxide/carbon quantum dots (ZnO2/CQD) composites were synthesized by an in-situ composite process for visible-light photocatalytic tetracycline (TC) degradation and Escherichia coli (E. coli) inactivation. It was found that 0.1 g/L ZnO2/CQD composite could degrade over 80 % of 50 mg/L TC and inactivate around 7-log E. coli cells after 2 h and 50 min of irradiation, respectively. The as-obtained ZnO2/CQD composites exhibited superior visible-light photocatalytic performance to individual ZnO2, and superoxide radical (•O2−) and singlet oxygen (1O2) were identified to be the main reactive oxygen species (ROSs) for TC degradation and E. coli inactivation. The introduction of CQD reduced the particle size and increased specific surface area, benefiting for adsorption. Meanwhile, it promoted visible-light absorption and accelerated the separation of photogenerated electron-hole pairs with a 3-fold increase in photocurrent, thus producing more ROSs under visible-light irradiation. Moreover, the ZnO2/CQD composites exhibited a high adaptability towards initial solution pH, common coexisting anions, oxygen-deficientenvironment, diverse water sources and organic pollutants. This study not only provided highly adaptable visible-light-driven photocatalysts for organic degradation and bacterial inactivation, but also shed light on the multifunctional roles of CQD in boosting visible-light photocatalytic performance.

Designing oxygen vacancy mediated bismuth molybdate (Bi2MoO6)/N-rich carbon nitride (C3N5) S-scheme heterojunctions for boosted photocatalytic removal of tetracycline antibiotic and Cr(VI): Intermediate toxicity and mechanism insight

Polymeric N-rich carbon nitride of C3N5 is being utilized as a new visible-light-driven catalyst due to its narrower bandgap (∼2.0 eV). Building step-scheme (S-scheme) heterojunction by coupling with other semiconductors especially those own oxygen vacancies (OVs) can further upgrade the photocatalytic performance of C3N5-based photocatalysts. Herein, a novel S-scheme heterojunction of OVs mediated Bi2MoO6/C3N5 was fabricated by in-situ growing Bi2MoO6 nanoparticles with OVs on C3N5 nanosheets. Benefiting from the efficient separation and transfer of high energetic charge carriers by S-scheme charge migration, enriched structural defects, as well as the close contact by the in-situ growth, the heterojunction exhibited superior visible-light photocatalytic performance toward the removal of tetracycline (TC) and Cr(VI) than C3N5, Bi2MoO6, and their mechanical mixture under visible light. The TC degradation routes and the bio-toxicity evolution of TC were explored. Moreover, the photocatalytic mechanism for TC decomposition and Cr(VI) reduction over Bi2MoO6/C3N5 with OVs were elucidated. This work presents a newfangled vision for designing promising C3N5-based S-scheme heterojunction photocatalysts for pollution control.

Triptycene incorporated carbon nitride based donor-acceptor conjugated polymers with superior visible-light photocatalytic activities

Polymeric carbon nitride (CN) has evoked considerable attention in photocatalysis, however, its π-deficiency conjugated frameworks engendering weak visible-light absorption and rapid charge recombination hinder the practical utilizations. Herein, a novel donor–acceptor (D-A) conjugated polymer based on triptycene incorporated carbon nitride (T-CN) has been facilely prepared by thermal copolymerization of melamine and 2,6,14-triaminotriptycene. Combined with the density functional theory (DFT) calculations, it is found that the formation of intramolecular charge transfer and the extended π-conjugative effect in the D-A structure contribute to a broadened light-harvesting spectral range, a higher charge separation/transfer efficiency and more active sites of T-CN for photoredox reactions. The T-CN catalyst accomplished superior visible-light photocatalytic performance in both hydrogen evolving and carbon dioxide reduction. The optimal T-CN catalyst exhibited the highest hydrogen evolution rate of 80.9 ± 1.3 μmol·h−1 and carbon monoxide production rate of 8.1 ± 0.2 μmol·h−1, which are ca. 8-fold and 20-fold of bulk CN, respectively. The convenient strategy of constructing D-A conjugated structure opens up a new intriguing avenue toward the rational creation of efficient polymeric nanomaterials for versatile applications of solar fuel production.

Nd3+-doped β-Bi2O3/Bi2O2CO3 composite nanoplates fabricated via phase transformation and their superior visible light photocatalytic performance for removing phenols and dyes

Nd3+-doped β-Bi2O3/Bi2O2CO3 composite nanoplates fabricated via phase transformation and their superior visible light photocatalytic performance for removing phenols and dyes

In situ decoration of SnS quantum dots on the α-SnWO4 nanosheets for superior visible-light photocatalytic performance

A novel heterostructure consisting of SnS quantum dots (QDs) and α-SnWO4 nanosheets was constructed through the crystallization of amorphous precursor using a one-pot hydrothermal method. The formation of SnS/α-SnWO4 heterostructure was confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques: the SnS QDs with the average particle size of 2.2 nm were uniformly anchored on the surface of α-SnWO4 nanosheets. The amorphous α-SnWO4 precursor with negative charge can attract the excessive Sn2+ ions and further react with S2- to form SnS/α-SnWO4 heterojunction. The intimate contact between SnS QDs and α-SnWO4 nanosheets was beneficial to the effective separation of photo-created electron-hole pairs. Thus, the SnS/α-SnWO4 nanocomposites exhibited the enhanced photocatalytic activity in the degradation of methyl orange (MO), Rhodamine B (RhB) and tetracycline (TC). The optimal amount of SnS QDs on the α-SnWO4 surface was 2 mol%, whose photodegradation efficiency was about 95.56% for MO removal after 90 min visible-light illumination and its degradation rate (0.0338 min−1) was 8.7 times higher than that of pure α-SnWO4 (0.0039 min−1). The trapping experiments evidenced that the ·O2–, h+ and ·OH play important roles in the photocatalysis process. The superior photocatalytic performance of SnS/α-SnWO4 nanocomposite would be ascribed to the Z-scheme photocatalytic reaction mechanism.

Rigorous design of outermost surface of TiO2 via one-step single-mode magnetic microwave field toward highly efficient visible-light photocatalyst

Among numerous efforts toward preparation of visible-light TiO2, recently design and control for chemical structure of TiO2 outermost surface have been paid strong attention to enhance photocatalytic performance. We have previously succeeded in direct synthesis of structurally well-controlled TiO2 with highly concentrated Ti3+ from metal titanium particle via single-mode magnetic microwave (SMMW)-assisted reactions. Here, we demonstrate synthesis of Ti3+ and interstitial nitrogen (Nint) co-doped TiO2 in Ar/O2/N2 system during one-step SMMW-assisted reactions, where chemical structure of outermost surface is rigorously controlled. In addition, such one-step-generated TiO2 shows significant thermal stability which has not been achieved in previously reported deficient TiO2 even through several step reactions. Additionally, the synthesized co-doped TiO2 with specific surface structures shows superior visible-light photocatalytic performance for photo-degradation of rhodamine B. The mechanism of outermost surface formation is systematically investigated by characterizations of XRD, XPS, UV–Vis absorption and PL. It demonstrates that the specific TiO2 surface including highly concentrated Ti3+ and Nint can be attributed to the rapid heat-dynamics during the reaction, which enhance the efficiency for separation of photo-excited carriers. The one-step SMMW-assisted reactions on metallic particle as bottom-up process will open new strategy for material design of functional metal oxides.

Facile synthesis of Bi5O7Br/BiOBr 2D/3D heterojunction as efficient visible-light-driven photocatalyst for pharmaceutical organic degradation

BiOBr-based composite photocatalysts had attracted extensive attention for efficient photocatalytic degradation aqueous organic pollutants in the past decade. However, the catalysis ability of photocatalyst is greatly limited by their intrinsic high recombination rate of photo-generated charge carriers. Herein, we solve this problem by constructing a novel 2D/3D Bi5O7Br/BiOBr heterojunction photocatalyst that was prepared via one-step facile hydrolysis process. The pure Bi5O7Br and pure BiOBr photocatalysts were also obtained by only adjusting the pH value of the mixed solution. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical and electric property analysis and etc. The results suggested that 2D Bi5O7Br nanosheets tightly attached to the surface of BiOBr 3D structure with nanoflakes self-assembled microsphere, which could increase the transfer and separation efficiency of photogenerated charges. Furthermore, the 2D/3D Bi5O7Br/BiOBr heterojunction exhibited superior visible light photocatalytic performance for carbamazepine (CBZ) degradation than pure BiOBr and pure Bi5O7Br, which owing to the enhanced separation of photoinduced electrons and holes. At last, the underlying photocatalytic mechanism is elucidated based on the band structure and radical scavenging experiments. This work provided a feasible design idea to one-step construct 2D/3D nanocomposite for pharmaceutical wastewater purification.

One pot milling route to fabricate step-scheme AgI/I-BiOAc photocatalyst: Energy band structure optimized by the formation of solid solution

Abstract Given that the construction of step-scheme (S-scheme) system could prolong the lifetime of more reactive charge carriers, a novel S-scheme photocatalyst AgI/BiO(CH3COO)xI1-x (denoted as AgI/I-BiOAc) was constructed via a facile and green one-pot milling method. The as-prepared AgI/I-BiOAc S-scheme photocatalyst with the optimized ratio of Ag/Bi at 0.8 exhibited superior visible-light photocatalytic performance for the degradation of methyl violet (MV), methyl orange (MO), malachite green (MG), and colorless bisphenol A (BPA), which was better than AgI, BiOAc, I-BiOAc-0.4, and even AgI/BiOAc heterojunction. Mott-Schottky analysis indicated that the formation of I-BiOAc solid solutions with suitable I content could optimize energy band structure, which transformed type-I AgI/BiOAc heterojunction to typical S-scheme AgI/I-BiOAc photocatalyst. Furthermore, owing to in situ preparation of AgI/I-BiOAc, the as-prepared S-scheme photocatalyst possessed closely contacted interfaces, which is beneficial to the transfer and recombination of electrons and holes with low redox ability, thus maintaining charge carriers with high redox capacity. The S-scheme mechanism was further verified by electron spin resonance (ESR) and the radicals trapping experiments. This work provides a facile way to design S-scheme system by modulating the composition of the solid solutions.

Photodegradation of 2,4-dichlorophenol and rhodamine B over n-type ZnO/p-type BiFeO3 heterojunctions: detailed reaction pathway and mechanism.

The development of new technologies for efficient degradation of pollutant has been an increasing demand in the globe due to the serious environmental issues. Herein, we report n-type ZnO/p-type BiFeO3 composites as highly efficient visible light nanophotocatalysts prepared via a wet chemical solution method. Based on the measurements of •OH-related fluorescence (FL) spectra, photoluminescence (PL) spectra, photoelectrochemical I-V curves, and electrochemical impedance spectra (EIS), it is demonstrated that the photo-induced charge carrier (electron-hole pairs) in the as-prepared n-type ZnO/p-type BiFeO3 composites with proper amount of the coupled ZnO (10% by mass) exhibits high separation compared with the bare BiFeO3 (BFO) nanoparticles. This is well responsible for the superior visible light photocatalytic performance of the composites for 2,4-dichlorophenol (2,4-DCP) and rhodamine B (RhB) degradation. It is confirmed by means of scavenger test and liquid chromatography-tandem mass spectrometry (LC/MS) analysis of the intermediate products that •OH is the pre-dominant oxidant involved in the degradation of 2,4-DCP. A detailed reaction pathway for 2,4-dichlorophenol degradation over the amount-optimized ZnO/BFO composite is proposed mainly based on the LC/MS product ions. This work will provide a feasible route to design and develop BFO-based highly efficient visible light-active photocatalysts for environmental purification and could be extended to other visible light-active semiconductor materials.

A high-performance photocatalyst of ZnTCPP sensitized porous graphitic carbon nitride for antibiotic degradation under visible light irradiation

In this paper, a highly efficient photocatalyst of ZnTCPP sensitized g-C3N4 was successfully constructed via a facile thermal polycondensation method. The FT-IR and XRD data indicated that ZnTCPP molecules were successfully condensed on the surface of g-C3N4 through amide groups as the bridging units. The optimum 10%ZnTCPP/g-C3N4 composites exhibits excellent enhanced photocatalytic activity for decomposing both methylene blue (MB) and tetracycline (TC) under visible light with long-term reusability and elimination rates of 96% and 80.3%, respectively. The superior visible light photocatalytic performance was mainly attributed to the highly efficient separation of electron-hole pairs and the enhanced solar light utilization, as demonstrated by photoluminescence (PL), electrochemical impedance spectra (EIS), photocurrent responses, and UV–vis diffuse reflectance spectroscopy (DRS). The active species trapping and terephthalic acid (TA) fluorescence experiments indicated that OH was the dominating reactive oxidizing species for TC degradation. Furthermore, the possible photocatalytic degradation pathways for MB and TC have been proposed based on the UPLC-MS spectrometry. The excellent degradation efficiency of ZnTCPP/g-C3N4 reveals that it has great potential as photocatalysts for practical application to eliminate recalcitrant organic contaminants.

Gaseous bubble-assisted in-situ construction of worm-like porous g-C3N4 with superior visible light photocatalytic performance

Metal-free graphitic carbon nitride (g-C3N4) displays benign photocatalytic properties for contaminants photodegradation under visible photoirradiation. Devising a simple modification strategy for the improved photocatalytic activity of g-C3N4 has always been desired. Herein, we report a spherical worm-like g-C3N4 nanostructure via facile ammonium lauryl sulfate (ALS) gaseous bubbles templating approach. This strategy employing ALS as gaseous bubbles templating agent bestowed not only g-C3N4 with improved specific surface areas, a porous structure with more exposed photocatalytic reactive sites and mass diffusion of reactants molecules, but also rendered extended optical absorption range and suppression of the photoinduced charge carriers recombination. As a result, the ALS-mediated g-C3N4 photocatalysts unfolded excellent photocatalytic performance regarding photodegradation of rhodamine B (RhB) and phenol under visible photoirradiation. Additionally, the quenching effects of various scavengers proved that the holes (h+) and superoxide anions (O2−) radicals were the main active species responsible for ameliorated photocatalytic performance for rhodamine B and phenol photodegradation. Our work offers a straightforward approach for developing high-performance metal free photocatalysts with great potential for environmental remediation.

Construction of 2D SnS2/g-C3N4 Z-scheme composite with superior visible-light photocatalytic performance

Constructing efficient materials for photocatalytic removal of organic pollutant is very important for environment purification. Herein, the hexagonal SnS2 is selected to couple with ultrathin graphitic carbon nitride nanosheet (2D g-C3N4) forming a 2D/2D Z-scheme photocatalyst. The obtained composites possess enhanced photodegradation activities in comparison with the single component. The 5% 2D SnS2/g-C3N4 exhibits the best performance, 94.8% rhodamine B (RhB) removed after 60 min irradiation, reaching a 42.1% improvement compared to the pure 2D g-C3N4. The 2D/2D Z-scheme structure can provide sufficient interfacial contact for charge migration, and remain relatively stronger redox potentials, thereby enhancing the photocatalytic activity. Such design strategy for photocatalytic materials may provide insights for the development of other Z-scheme photocatalysts.

Synthesis of nano-Ag-assisted attapulgite/g-C3N4 composites with superior visible light photocatalytic performance

Abstract Graphitic carbon nitride (g-C3N4) based hybrid photocatalysts have recently emerged as a new class of functional materials for solar energy conversion. Here, we synthesized a novel visible-light-responsive Ag-assisted attapulgite/g-C3N4 composite photocatalyst (ATP/g-C3N4-Ag) by depositing Ag nanoparticles onto the surface of ATP/g-C3N4, which is fabricated by introducing a thin layer of g-C3N4 onto the ATP surface (pre-grafted by (3-glycidyloxypropyl) trimethoxysilane (KH560)). The products were fully characterized by XRD, FT-IR, BET, XPS, UV–vis, TEM and Raman techniques. Results show that g-C3N4 thin layer is uniformly loaded onto the ATP surface by forming a new chemical bond (Si-O-C), which results from the bimolecular nucleophilic substitution reaction (SN2) between KH560 and melamine. Comparing with g-C3N4 and ATP/g-C3N4, ATP/g-C3N4-Ag exhibits remarkably enhanced visible light photocatalytic activity in degradation of methyl orange (MO). The highest decomposition rate of MO reaches 96.70% within 20 min, which remains unchanged after 4 cycles. The possible photocatalytic mechanism is investigated by photoluminescence, electrochemical impedance spectroscopy analysis, and radical trapping experiments. Results suggest that OH and O2− are the main active species, and numerous electrons on the Ag surface will be utilized to generate considerable amount of O2− and OH for the degradation of MO.

Fabrication of Fe3O4/CaCO3/CuWO4 heterostructures for enhanced photocatalytic activities for the degradation of organic dyes

Novel magnetically recoverable Fe3O4/CaCO3/CuWO4 heterostructures photocatalysts, with superior visible-light photocatalytic performance, were successfully fabricated by a simple method in presence of different surfactants. The materials were characterized by X-ray diffraction, field emission scanning electron microscopy, vibrating sample magnetometer, photoluminescence emission spectra, and UV–vis diffuse reflectance spectroscopy. This coupled semiconductor system has also been examined for the photocatalytic application. In addition, methylene blue was chosen as a dye water pollution to evaluate its degradation by as-synthesized Fe3O4/CaCO3/CuWO4 under visible light irradiation. Furthermore, the photocatalysis results reveal that the maximum decolorization of 99% for MB occurred at 180 min. Fe3O4/CaCO3/CuWO4 heterostructures photocatalysts exhibited superior photocatalytic activity.

π–π Interaction between self-assembled perylene diimide and 3D graphene for excellent visible-light photocatalytic activity

A three-dimensional (3D) graphene/self-assembled perylene imide (rGO/PDI) aerogel composite has been successfully constructed via a simple low-temperature hydrothermal method in this work. The 3D rGO/PDI composite exhibited superior visible-light photocatalytic performance. The removal rate was respectively 2.46 times and 3.33 times higher than that of PDI in static and dynamic catalytic systems. The satisfactory activity is mainly attributed to the more effective separation of electron–hole pairs. To be specific, the self-assembled PDI nanofibers and graphene are effectively combined via non-covalent π-π interaction. The π-π interaction enhances the long-range π-electrons delocalization and electron coupling effects, which is beneficial for the carrier mobility and the separation of electron–hole pairs. Meanwhile, the three-dimensional structure of graphene provides a fast multidimensional channel for electron transfer and effectively improves the adsorption capacity of PDI due to the large specific surface area. What’s more, the rGO/PDI composite exhibits great stability than the pure PDI. Overall, this work provides a new insight into improving the photocatalytic activity of self-assembled organic materials.

Enhanced photocatalytic activity of Bi12O17Cl2 preferentially oriented growth along [200] with various surfactants

In this study, Bi12O17Cl2 nanosheets preferentially oriented growth along [200] were successfully synthesized through a facile hydrothermal method in the presence of various surfactants, including PVP, CTAB and CTAC. The crystallization behavior, band gap structure and morphology of Bi12O17Cl2 could be modulated by the addition of surfactants. Bi12O17Cl2 with surfactants displays superior visible light photocatalytic performance than pristine sample for photodegrading RhB and 2-chlorophenol. Moreover, Bi12O17Cl2 preferentially oriented growth along [200] maintained stable and recyclable in the photocatalytic process, demonstrating their promising application in environment remediation.