Visible Light Absorption Range Research Articles

Reasonable regulation of carbon/nitride ratio in carbon nitride for efficient photocatalytic reforming of biomass-derived feedstocks to lactic acid

Photocatalysis provides a promising opportunity for selective oxidation of biomass to high-value chemicals under mild conditions. The key to realize this transformation is to design a cost-effective and environmentally friendly photocatalyst. Here, we report the preparation of a carbon nitride photocatalyst with controllable carbon/nitride (C/N) ratio and its application in the selective photocatalytic synthesis of lactic acid from biomass-derived monosaccharides. Reasonable C/N ratio in the catalyst can significantly enhance the visible light absorption range and accelerate the mobility of photogenerated carriers. The obtained photocatalyst exhibited excellent photocatalytic activity, yielding 76.8% lactic acid. All of the h+,·O2-,·OH and 1O2 are beneficial for lactic acid production, and the·O2- plays a major role. Furthermore, the photocatalyst exhibited excellent reusability and universality. The 1000-fold scale-up experiments indicated that the system has potential for industrial production of lactic acid. Therefore, the present work offers a promising example for photocatalytic reforming of biomass.

Semiconducting nanomaterials for photocatalytic desulfurization of liquid fuel under sunlight irradiation

Abstract Nanomaterials have fascinated the interest of researchers due to their unique electronic, optical, magnetic, and several other properties. Tin sulfide (SnS2) and Zinc oxide (ZnO) have emerged as promising materials for pharmaceutical, textile, environmental remediation, energy conversion, and storage device design. These two compounds were widely used in waste-water treatment for photocatalytic destruction of organic contaminants. However, the degradation of organic sulfur compounds in the liquid fuel desulfurization process has rarely been investigated using such materials. We hereby, present a hydrothermal method for developing the hexagonal lattice structure of SnS2 and ZnO for the deep desulfurization of model liquid fuel. These materials were further characterized through powder X-ray diffraction for phase purity and crystalline, FTIR analysis to validate functional groups, N2 adsorption-desorption isotherm to study surface properties, UV–vis diffuse reflectance spectroscopy for band gap analysis, scanning and transmission electron microscopy for morphology analysis. The optical behavior reveals that the energy gap for SnS2 and ZnO is 2.09 and 3.21 eV, respectively which corresponds to the visible light absorption range. The photocatalysis experiment was carried out in direct sunlight to degrade 10 ppm DBT in iso-octane. The obtained results show that 60% of the DBT degrade with SnS2 and 15% of the DBT degraded with ZnO in 120 min, with a first-order kinetics rate constant of 0.009 and 0.001 min−1 respectively.

Structure evolution of thiophene-containing conjugated polymer photocatalysts for high-efficiency photocatalytic hydrogen production

Conjugated polymer photocatalysts have received extensive attention in the field of photocatalytic hydrogen evolution owing to their tunable molecular structures and electronic properties. Herein, we developed three donor-acceptor (D-A) type thiophene-containing narrow-band-gap conjugated polymers with pyrene as a donor and different fused-thiophene derivatives as acceptors via direct C-H arylation coupling polymerization. It was found that the band gap of the polymers can be tuned by adjusting the number of the fused-thiophene rings. The visible light absorption range can be extended by increasing the number of the thiophene rings, the planar molecular structure for both donor and acceptor units facilitates the charge transmission along the polymer skeleton, and the D-A type polymer structure promotes the dissociation of photo-induced electrons and holes. As a result, a high photocatalytic hydrogen evolution rate of 33.07 mmolh−1 g−1 was obtained by PyTP-2 with an optimized molecular structure under visible light irradiation (λ > 420 nm) without the aid of Pt co-catalyst. In addition, PyTP-2 also shows a photocatalytic activity for oxygen evolution with an average oxygen evolution rate of 58.37 µmolh−1 g−1.

Photocatalytic H2 production with simultaneous wastewater purification over flower-like 1T/2H-MoS2-decorated CNT/CNU isotype heterojunction photocatalyst

Exploring low-cost and earth-abundant photocatalysts to efficiently release H2 from wastewater is an appealing solution for global energy and environmental issues. Here, we successfully prepared flower-like 1T/2H-MoS2-decorated g-C3N4 (thiourea)/g-C3N4 (urea) (denoted as CNT/CNU) isotype heterojunction photocatalysts via a facile ultrasonic dispersion method and researched the photocatalytic H2 generation and pollutant degradation performance in oxalic acid (OA) simulated wastewater. The results displayed that 20% 1T/2H-MoS2@CNT/CNU sample exhibited the highest photoreactivity, and the H2 release rate was 1563.32 μmolg-1h−1, which was about 96 times higher than the CNT/CNU. Meanwhile, it also showed the highest total organic carbon (TOC) removal rate of 67.5%. The increased photoreactivity of nanocomposites can be ascribed to the double-interface system to effectually improve the separation of photoinduced charges. Additionally, the experimental results further confirmed that the loading of flower-like 1T/2H-MoS2 could provide abundant active sites as well as expand the visible-light absorption range. Significantly, photoelectrochemistry measurements and density functional theory (DFT) calculations also confirmed that 1T/2H-MoS2 cocatalysts accelerated the charge migration. On this basis, the mechanism of 1T/2H-MoS2@CNT/CNU promoting hydrogen production and synergistic OA degradation was proposed. This research presents a prospective idea for the utilization of waste water and the simultaneous production of clean energy.

The first principle screening and design of the high-performance organic photosensitizers based on EY2− dye in homogeneous non-noble metal photocatalytic hydrogen production system

Photocatalytic hydrogen production, capable of dissociating water to make hydrogen using sunlight as abundant and clean energy, provides a promising solution for energy crisis. However, currently dominated metal complexes photosensitizers are based on precious and rare metal elements, which prohibits large scale applications. Herein, based on the experimental dye Eosin Y (EY2−), we report a series of metal-free organic dyes EY2-1- EY2-18 and present a systematic study on their ground-state geometry, electrochemistry, energy gap, reduction potential and driving force by using density functional theory (DFT) and time-dependent DFT (TDDFT). The calculated results show that compared to other dyes, the dye EY2-11 has a large visible light absorption range, a higher reduction potential and greater driving force, which indicates that EY2-11 is a promising candidate for the visible-light-driven hydrogen production. Our theoretical researches are expected to provide valuable insights for designing efficient metal-free organic photosensitizers.

Electrospinning visible light response Bi2MoO6/Ag3PO4 composite photocatalytic nanofibers with enhanced photocatalytic and antibacterial activity

Due to its significant biocompatibility and environmental friendliness, the composite of heterojunction photocatalyst and natural protein is a promising material in the field of photocatalysis. For the first time, direct Z-scheme Bi2MoO6/Ag3PO4 composites with different concentrations of Ag3PO4 were successfully fabricated by an in-situ deposition method, and Bi2MoO6/Ag3PO4@silk fibroin (BMO/APO@SF) films were further constructed by electrospinning technology to explore the photocatalytic activity of heterojunction photocatalysts. The results of various characterizations confirmed that improved photocatalytic performance, including efficient charge separation, and a widened visible light absorption range, could be attributed to the formation of a heterojunction structure between Bi2MoO6 and Ag3PO4, which considerably promoted photocatalytic activity for ciprofloxacin (CIP) degradation. According to the analysis of degradation products measured by Q-TOF, possible CIP degradation pathways were proposed. Density functional theory (DFT) calculation and Laplacian bond order (LBO) analysis were consistent with the results of Q-TOF. Through trapping experiments, the significant contribution of O2– to BMO/APO@SF was demonstrated. Moreover, the antibacterial rates of Bi2MoO6/15Ag3PO4@SF (BMO/15APO@SF) against Escherichia coli and Staphylococcus aureus were greater than 94.36% and 95.72%, respectively, indicating that BMO/15APO@SF had excellent antibacterial performance.

Visible-Light-Mediated Alkylation of Thiophenols via Electron Donor-Acceptor Complexes Formed between Two Reactants.

A metal-free, photocatalyst-free, photochemical system was developed for the direct alkylation of thiophenols via electron donor-acceptor (EDA) complexes (KEDA = 145 M-1) between two reactants, N-hydroxyphthalimide esters as acceptors and thiophenol anions as donors, in the presence of a tertiary amine. The EDA complexes in the reaction system have a broad range of visible-light absorption (400-650 nm) and can trigger the reaction effectively under sunlight.

Novel fumed silica/g‐C3N4 composites for highly efficient removal of rhodamine B under visible light emitting diodes light irradiation

AbstractGraphitic carbon nitride (g‐C3N4) is a fascinating nonmetallic photocatalyst for the removal of environmental pollutants. The fumed silica/g‐C3N4 (gCN‐FS) composite photocatalysts were successfully fabricated by a combination of solvent volatilization and post‐annealing methods. The introduction of SiO2 not only widens the absorption range of visible light, but also enhances the specific surface area of g‐C3N4. The gCN‐FS‐3 composite has a BET surface area of 129.89 m2/g, which is ~3.3 times as much as that of g‐C3N4 (39.54 m2/g). The gCN‐FS composites have markedly improved rhodamine B (RhB) photodegradation activity in comparison to pure g‐C3N4, bulk g‐C3N4 and P25 under 557 nm yellow‐green light emitting diode light irradiation. The gCN‐FS‐3 has the highest RhB photodegradation rate, which is ~9.67‐, 11.81‐folds as compared to bare g‐C3N4 and bulk g‐C3N4, respectively. The coupling effect between the increase in specific surface areas and the inhibition effect of SiO2 on photogenerated electron/hole pairs recombination is responsible for the enhanced visible light photocatalytic activity of gCN‐FS composite. Superoxide and holes are responsible for the RhB photocatalytic degradation. Furthermore, no apparent loss of photocatalytic activity over five cycles is observed, which indicates that the gCN‐FS composites have considerable stability and reusability in the photodegradation process. The gCN‐FS composites show great promise in visible light driven photocatalysis for environmental applications.

CdS/BiOBr heterojunction photocatalyst with high performance for solar-light-driven degradation of ciprofloxacin and norfloxacin antibiotics

Sunlight active CdS/BiOBr heterojunction photocatalyst was fabricated by a solvothermal route. To the best of our knowledge, the novelty of the research is based on the decoration of the hexagonal CdS nanoparticles on the surface of the tetragonal BiOBr microflowers for the creation of a heterostructure photocatalyst used for the removal of the antibiotics. The CdS/BiOBr-1:3 heterojunction exhibited 100% removal of norfloxacin and ciprofloxacin under simulated visible light. In addition, complete degradation of the antibiotics under natural sunlight was also achieved. Construction of the CdS/BiOBr heterojunction is a promising strategy for the improvement of photocatalytic performance due to a decrease in the charge carrier recombination rate at the interface, an increase in the visible light absorption range, and an enhancement of the surface area of the resultant product. The removal of the pollutants fit very well with the first-order reaction. The photogenerated hole played a crucial role in the removal of the antibiotics. Confirmation of the stability of the CdS/BiOBr heterojunction was also elucidated. The photoactivity of the photocatalyst remained the same after the fifth cycle implying the excellent cycling ability of the sample. This research demonstrates the promising potential of the CdS/BiOBr heterojunction for degradation of toxic antibiotics presented in water.

Tunable electronic and optical properties of new two-dimensional CuCl/GaSe van der Waals heterostructures with the potential for photocatalysis applications

The construction of a heterojunction photocatalyst can enhance the absorption of visible light and reduce the recombination of electrons and holes, which greatly improves the photocatalytic performance, which is also a current research hotspot in the energy field. In this paper, the first-principles calculation method is used to systematically study the electronic structure and photocatalytic mechanism of the new CuCl/GaSe van der Waals (vdW) heterojunction. The main research contents are summarized as follows: CuCl/GaSe vdW heterojunction is a direct band gap semiconductor material with a lattice mismatch rate of less than 1.5%, and a stable structure. The band gap of the heterojunction is 1.143 e V, which corresponds to a wider visible light absorption range. And it shows direct energy band alignment. The photo-generated holes are transferred from the GaSe layer to the CuCl layer, while the electrons are on the contrary, indicating that the electrons and holes are well separated in space. All these indicate that the CuCl/GaSe vdW heterojunction has good photocatalytic performance and is a new type of photocatalytic material with excellent performance.

A novel Z‐scheme Er3+:Yb0.5Y2.5Al5N0.01F0.01O11.98/g‐C3N4–Pt–BiPO4 photocatalyst for enhanced photocatalytic degradation of azofuchsin and ciprofloxacin

AbstractIn this paper, a novel Z‐scheme photocatalyst Er3+:Yb0.5Y2.5Al5N0.01F0.01O11.98/g‐C3N4–Pt–BiPO4 was synthesized by sol‐hydrothermal and calcination methods. The prepared samples were characterized by XRD, SEM, TEM, EDS mappings, XPS, PL, and DRS. In addition, the optimal hydrothermal conditions for the preparation of BiPO4 were explored with the azofuchsin solution and ciprofloxacin(CIP) solutions as the target pollutants. At the same time, the best calcination temperature and the best calcination time of the Er3+:YbnY3−nAl5NxFyO12−x−y and BiPO4 were investigated. The results showed that the Z‐scheme Er3+:Yb0.5Y2.5Al5N0.01F0.01O11.98/g‐C3N4–Pt–BiPO4 photocatalyst has strong redox ability, wide absorption range of visible light, and excellent separation effect of electron–hole pairs, which can efficiently degrade organic pollutants and antibiotic.

AIEgen-loaded nanofibrous membrane as photodynamic/photothermal antimicrobial surface for sunlight-triggered bioprotection

The outbreak of infectious diseases such as COVID-19 causes an urgent need for abundant personal protective equipment (PPE) which leads to a huge shortage of raw materials. Additionally, the inappropriate disposal and sterilization of PPE may result in a high risk of cross-contamination. Therefore, the exploration of antimicrobial materials possessing both microbe interception and self-decontamination effects to develop reusable and easy-to-sterilize PPE is of great importance. Herein, an aggregation-induced emission (AIE)-active luminogen-loaded nanofibrous membrane (TTVB@NM) sharing sunlight-triggered photodynamic/photothermal anti-pathogen functions are prepared using the electrospinning technique. Thanks to its porous nanostructure, TTVB@NM shows excellent interception effects toward ultrafine particles and pathogenic aerosols. Benefiting from the superior photophysical properties of the AIE-active dopants, TTVB@NM exhibits integrated properties of wide absorption in visible light range, efficient ROS generation, and moderate photothermal conversion performance. A series of antimicrobial evaluations reveal that TTVB@NM could effectively inactivate pathogenic aerosols containing bacteria (inhibition rate: >99%), fungi (~88%), and viruses (>99%) within only 10 min sunlight irradiation. This study represents a new strategy to construct reusable and easy-to-sterilize hybrid materials for potential bioprotective applications.

Fabrication of new MIL-53(Fe)@TiO2 visible-light responsive adsorptive photocatalysts for efficient elimination of tetracycline

Novel semiconductor–MOFs composites based on TiO2 and MIL-53(Fe) were constructed using a facile one-pot solvothermal process and acted as effective visible-light responsive adsorptive photocatalysts for the removal of tetracycline (TC). The resultant MIL-53(Fe)@TiO2 composites were characterized by comprehensive analyses, ESR, and photoelectrochemical measurements. Experimental results showed that the synthesized MIL-53(Fe)@TiO2 composites possessed enhanced adsorption and excellent photocatalytic activity for TC solution under visible light irradiation. Among all the composites, the MIL-53(Fe)@TiO2 = 1:2 exhibited optimal removal performance compared with pristine MIL-53(Fe) and TiO2. The results of UV–vis DRS verified the visible light absorption range of the prepared composite was improved, and the results of the Nyquist plot illustrated that the transfer ability of photo-generated charge carriers was boosted. More importantly, the ESR results showed that the •O2− and •OH active species played a crucial role in photocatalytic reactions. The enhanced photocatalytic ability was due to not only the fabrication of the n-n type heterojunction photocatalysts, which could provide more active species, but also the synergy between MIL-53(Fe) and TiO2 in the composites. A possible reaction mechanism was proposed to elucidate the reason for the photocatalytic performance enhancement. Our findings may open up a new field for Fe-MOF and semiconductor composite materials in removing TC in visible light.

Linkage Dependence of Interfacial Charge-Transfer Transitions in ZnO: Carboxylate versus Sulfur Linker.

Interfacial charge-transfer transitions (ICTTs) between organic compounds and inorganic semiconductors have recently attracted much attention due to the unique features of a wide range of visible light absorption with colorless organic molecules and direct interfacial charge separation for their potential applications in photoenergy conversions and chemical sensing. As the research on ICTT has almost been limited to titanium oxide semiconductors such as TiO2, the exploration of ICTT in other inorganic semiconductors is a high-priority issue. Recently, we demonstrated that ICTT is strongly induced by chemisorption of aromatic thiols on ZnO nanoparticles via the sulfur atom. Here, we report on ICTT in ZnO nanoparticles adsorbed with benzoic acid derivatives and the linkage dependence of ICTT in ZnO. We observed ICTT bands in the visible region upon adsorption of 4-(dimethylamino)benzoic acid (4-DMABA) and 3,4-dimethoxybenzoic acid (3,4-DMOBA) on ZnO nanoparticles via the carboxylate group. Notably, the ICTT absorption intensities are about 1 order of magnitude lower than those in the ZnO surface complexes with aromatic thiol compounds. Time-dependence density functional theory (TD-DFT) calculations well reproduce the linkage dependence of ICTT. This characteristic linkage dependence of ICTT in ZnO is attributed to the difference in the valence orbital of bridging atoms. The sulfur bridging atom with the larger 3p valence orbitals gives rise to strong electronic couplings between ZnO and adsorbates for ICTT, in contrast to very weak electronic couplings via the smaller 2p valence orbitals of the oxygen bridging atoms in the carboxylate linkage. Our research reveals the important linkage dependence of ICTT in ZnO and elucidates the mechanism.

Preparation, Characterization of Graphitic Carbon Nitride Photo-Catalytic Nanocomposites and Their Application in Wastewater Remediation: A Review

Energy crisis and environmental pollution are the major problems of human survival and development. Photocatalytic technology can effectively use solar energy and is prospective to solve the above-mentioned problems. Carbon nitride is a two-dimensional polymer material with a graphite-like structure. It has good physical and chemical stabilities, unique chemical and electronic energy band structures, and is widely used in the field of photocatalysis. Graphitic carbon nitride has a conjugated large π bond structure, which is easier to be modified with other compounds. thereby the surface area and visible light absorption range of carbon nitride-based photocatalytic composites can be insignificantly increased, and interface electron transmission and corresponding photogenerated carriers separation of streams are simultaneously promoted. Therefore, the present study systematically introduced the basic catalytic principles, preparation and modification methods, characterization and calculation simulation of carbon nitride-based photocatalytic composite materials, and their application in wastewater treatment. We also summarized their application in wastewater treatment with the aid of artificial intelligence tools. This review summarized the frontier technology and future development prospects of graphite phase carbon nitride photocatalytic composites, which provide a theoretical reference for wastewater purification.

Graphene quantum dots with a Stone-Wales defect as a topologically tunable platform for visible-light harvesting

In this work, we report for the first time the crucial role of topological anomalies like Stone-Wales (SW) type bond rotations in tuning the optical properties of graphene quantum dots (GQDs). By means of first-principles calculations, we first show that the structural stability of GQDs strongly depends on position of SW defects. Optical absorption spectra is then computed using electron-correlated methodology to demonstrate that SW type reconstruction is responsible for the appearance of new defect-induced peaks below the optical gap and dramatically modifies the optical absorption profile. In addition, our investigations signify that electron correlation effects become more dominant for SW-defected GQDs. We finally establish that the introduction of SW defects at specific locations strongly enhances light absorption in visible range, which is of prime importance for designing light harvesting, photocatalytic and optoelectronic devices.

0D, 1D, 2D molybdenum disulfide functionalized by 2D polymeric carbon nitride for photocatalytic water splitting

Photocatalytic activity of molybdenum disulfide structures with different dimensions (0D, 1D and 2D) functionalized with polymeric carbon nitride (PCN) is presented. MoS2 nanotubes (1D), nanoflakes (2D) and quantum dots (0D, QDs) were used, respectively, as co-catalysts of PCN in photocatalytic water splitting reaction to evolve hydrogen. Although, 2D-PCN showed the highest light absorption in visible range and the most enhanced photocurrent response after irradiation with light from 460 to 727 nm, QDs-PCN showed the highest photocatalytic efficiency. The detailed analysis revealed that the superior photocatalytic activity of QDs-PCN in comparison with other structures of MoS2 arose from (i) the most effective separation of photoexcited electron–hole pairs, (ii) the most enhanced up-converted photoluminescence (UCPL), (iii) the highest reactivity of electrons in conduction band. Moreover, a narrowed size of QDs affected shorter diffusion path of charge carriers to active reaction sites, higher number of the sites and higher interfacial area between molybdenum disulfide and PCN.

Highly sensitive detection of chromium (VI) by photoelectrochemical sensor based on p-n heterojunction of carbon nitride-modified BiOI

In this study, bismuth oxyiodide (BiOI) was synthesized by one-step solvothermal method firstly. Then it was combined with different mass ratio of carbon nitride (CN) to obtain the BiOI/CN-X (X is the mass ratio of CN to BiOI, X = 11%, 34%, 56%). The chemical composition and morphology of these samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). Furthermore, through the photoelectrochemical (PEC) measurements, UV-Visible diffuse reflectance spectra (UV-Vis DRS) and photoluminescence (PL) spectra confirmed that the synthesized materials (BiOI/CN-34%) exhibit the highest PEC activity, wider visible light absorption range and increased carrier lifetime. Subsequently, the PEC sensor based on BiOI/CN-34% was designed to detect hexavalent chromium (Cr (VI)) under visible light irradiation. The prepared sensor shows a lower detection limit of 0.1 µM (the signal to noise ratio (S/N = 3)), with a wider linear range from 0.5 µM to 190 µM. Meanwhile, the PEC sensor of BiOI/CN-34% can be applied to the real sample detection with good stability, reproducibility, and selectivity. Thus, BiOI/CN-34% has potential application in Cr (VI) detection.

Preparation and properties of Al3+-doped BiVO4 semiconductor photocatalyst

The xAl3+/BiVO4 (x = 0, 1%, 2%, 5%, 10%) photocatalysts were successfully prepared by hydrothermal method, and the removal efficiency of organic pollutants was improved in different degrees under the conditions of visible light irradiation. The results showed that proper Al3+-doping could improve the morphology of BiVO4, narrow the band gap and expand the absorption range of visible light. Meanwhile, Al3+ acted as a capture center for photogenerated electrons, reducing the recombination rate of the photogenerated electron-hole pair. When the doping amount of Al3+ was 1%, the photocatalytic activity was maximized, and the removal rate of RhB within 90 min was as high as 96%, this was an improvement of about 43% compared to pure BiVO4. In the whole reaction system, O2−, h+ and OH were the main active species, contributing 72.4%, 18.4% and 5.9% to the degradation of RhB, respectively.

Double Free: A Promising Route toward Moisture-Stable Hypotoxic Hybrid Perovskites

Double Free: A Promising Route toward Moisture-Stable Hypotoxic Hybrid Perovskites