Enhancement Of Photocatalytic Activity Research Articles

Enhancing Photocatalytic Redox Activity of Polymeric Carbon Nitride for Valuable Fluorinated Heterocycles through Fast-Track Electron Highways

Enhancing Photocatalytic Redox Activity of Polymeric Carbon Nitride for Valuable Fluorinated Heterocycles through Fast-Track Electron Highways

Enhanced degradation of rhodamine B under visible light by BiOCl@COF-1n-n type heterojunction photocatalysts

A novel n-n type heterojunction BiOCl@COF-1 was synthesized by a facile one-step solvothermal method and used for the degradation of rhodamine B(RhB) in water. The structure, morphology, composition, optical and electrochemical properties of the prepared composite were characterized through various techniques. Compared with the pure BiOCl, the BiOCl@COF-1 composite demonstrated significantly enhanced efficiency and durability for degradation of RhB under visible light. The observed enhancement in photocatalytic activity can be attributed to the synergistic effect of the n-n type heterojunction, which notably improve the visible light absorption efficiency, and the efficient charge separation. Additionally, the possible photodegradation mechanism of RhB was explores based on the characterization results. This work not only offers a promising strategy for the purification of organic wastewater, but also provides an effective approach for the construction of other COF-based n-n type heterojunction.

Enhanced degradation of rhodamine B under visible light by BiOCl@COF-1n-n type heterojunction photocatalysts

A novel n-n type heterojunction BiOCl@COF-1 was synthesized by a facile one-step solvothermal method and used for the degradation of rhodamine B(RhB) in water. The structure, morphology, composition, optical and electrochemical properties of the prepared composite were characterized through various techniques. Compared with the pure BiOCl, the BiOCl@COF-1 composite demonstrated significantly enhanced efficiency and durability for degradation of RhB under visible light. The observed enhancement in photocatalytic activity can be attributed to the synergistic effect of the n-n type heterojunction, which notably improve the visible light absorption efficiency, and the efficient charge separation. Additionally, the possible photodegradation mechanism of RhB was explores based on the characterization results. This work not only offers a promising strategy for the purification of organic wastewater, but also provides an effective approach for the construction of other COF-based n-n type heterojunction.

The synergistic enhancement of photocatalytic activity by Fe3O4–TiO2 nanosheets for rhodamine B degradation

As an advanced oxidation material, Fe3O4-TiO2 nanocomposites have been widely used in wastewater treatment. However, conventional Fe3O4 nanoparticles suffer from drawbacks such as carrier recombination and aggregation, which seriously affect the catalytic activity. In this study, Fe3O4-TiO2 nanosheets with different TiO2 loading rates were synthesized by sol-gel method and solvothermal method. The unique two-dimensional nanostructure of Fe3O4 nanosheets facilitated the deposition of TiO2 nanoparticles, resulting in Fe3O4-TiO2 nanosheets with a high BET specific surface area of 121.67 m2·g−1. Under optimal experimental conditions, the degradation rate of RhB dye in the photocatalytic synergistic Fenton-like system constructed with Fe3O4-TiO2 nanosheets reached 98.12 % within 120 min, significantly surpassing that of single photocatalysis and Fenton-like systems. It was attributed to the unique surface structure of Fe3O4 nanosheets, which provided a larger contact area for TiO2 nanoparticles. It facilitated the effective reduction of Fe3+ to Fe2+ by photogenerated electrons in TiO2, inhibited the recombination of photogenerated electron-hole pairs, and consequently enhanced the degradation rate of RhB dye. Furthermore, Fe3O4-TiO2 magnetic nanosheets exhibited excellent reusability and stability, with the recovery rate and degradation rate of RhB dye remaining above 90 % even after five cycles. More importantly, the catalytic mechanism of Fe3O4-TiO2 nanosheets was elucidated, and •OH identified as the primary reactive species responsible for degrading RhB dye. This work provides a novel research direction for designing and preparing advanced catalytic degradation materials, offering a practical solution to the challenging issue of wastewater treatment.

Boosting visible-light response for the complete decomposition of volatile organic compounds on the Cu-oxide deposited WO3 photocatalyst by the synergistic effects of TiO2

The degradation of volatile organic compounds (VOCs) by photocatalytic systems is the most practical strategy due to its cost performance, simplicity, and environmental sustainability. To address such issues, the photocatalytic activities of tungsten trioxide (WO3) were developed by the deposition of various cocatalysts. In particular, the Cu-oxide (CuO/Cu2O)-deposited WO3 (Cu-WO3) photocatalyst could efficiently decompose acetic acid and acetaldehyde into CO2 under visible-light irradiation, although it exhibited low activity for the decomposition of benzene, toluene and xylene (BTX). Furthermore, a composite Cu-WO3/TiO2 photocatalytic system, which was fabricated by the simple physical mixing of Cu-WO3 with TiO2, was found to exhibit unprecedented reactivity for the complete decomposition of persistent BTX pollutants into CO2 under visible light irradiation. The synergistic effects of Cu-WO3 and the interfacial surface complex (ISC) formed by toluene-adsorbed TiO2 contribute to the efficient visible light response by excitation up to around 600nm. The reaction mechanism for the enhancement of photocatalytic activity by the Cu-WO3/TiO2 composite photocatalyst is examined in this study.

Effect of Yttrium doping on enhancing the Photocatalytic performance of TiO2/GO nanocomposite

Pure and yttrium doped Titania/Graphene oxide (YTGO) nanocomposites were synthesized by hydrothermal method. XRD analysis confirmed the crystal structure and anatase phase of TiO2 nanoparticles. The anatase phase of TiO2 has been retained in the composite as confirmed from the XRD pattern. SEM and TEM images revealed that the spherical TiO2 nanoparticles are embedded into sheet like structures of GO. The size of the spherical nanoparticles in the composites is relatively smaller than that of pure sample due to anchoring on the GO sheets. The photocatalytic performance of TiO2 has significantly increased in the Y-doped TiO2 with GO compared to pure TiO2 and TiO2/GO. Moreover, 0.7 % Y-doped TGO nanocomposite exhibited superior photocatalytic performance with overall efficiency of 97 % compared to other samples. The 0.7 % Y-doped TGO nanocomposite shows higher rate constant and shorter half life time compared to other samples. The enhancement of photocatalytic activity of YTGO composites attributed to the combination of increased absorption due to the absorption edge shift and effective separation of photo generated carriers.

Synthesis and characterisation of Ag-Cu-co-Doped WO3 @Carbeneous materials composites for waste water treatment

Nanoparticles of tungsten oxide are widely used in advanced chemical processes but the application of tungsten oxide (WO3) in photocatalysis is limited. To increase their application in photocatalysis, nanostructured tungsten oxide (W-1) is co-doped with silver and copper (W-2), and nanocomposites with g-C3N4 (W-3) and CNTs (W-4) are synthesized. Structural, elemental, and morphological analyses of prepared samples were carried out using different characterization techniques like XRD, SEM, FTIR, EDX, and Mott-Schottky. The bandgap of WO3 is 2.75 eV which is reduced to 2.32 eV by doping and composite formation. The degradation of crystal violet and chlorpyrifos is done to check the photocatalytic performance of prepared materials under the light bulb energy. Photodegradation experiment shows 83.33 % and 41 % degradation of CV and chlorpyrifos respectively. The higher degradation ability is shown by CNTs composites because they have smaller crystallite size (12.81 nm) as compared to other photocatalysts. In the presence of CNTs, the rate of recombination of holes and electrons decreases, resulting in the enhancement of photocatalytic activity. The research reveals that W-4 exhibits promising potential for applications in the photodegradation of organic wastes.

Highly efficient CdS/SbVO4 composites for visible-light-driven Cr(VI) reduction

Heavy metal contamination is a grave environmental concern due to its severe implications for human health and ecosystems, causing carcinogenic and teratogenic effects. This study addresses this pressing issue by exploring the synthesis and application of CdS/SbVO4 composites as effective photocatalysts. These composites were synthesized by a streamlined two-step hydrothermal method, with investigations conducted on varying molar ratios. The composite with a molar ratio of 0.2:1 demonstrated superior Cr(VI) photoreduction properties under visible light irradiation, exhibiting an efficiency quadruple that of pure SbVO4. This enhancement in photocatalytic activity is credited to the augmented separation of electrons and holes facilitated by the integration of narrow band gap materials within the composite. Electrochemical tests indicated the electron transfer mechanism and identified the primary active centers of the samples. The detailed photocatalytic mechanism of the composite was further discussed, grounded on insights derived from free radical trapping experiments and electron spin resonance analyses.

Photochromic radical states in 3D covalent organic frameworks with zyg topology for enhanced photocatalysis.

Covalent-organic frameworks (COFs) with photoinduced donor-acceptor (D-A) radical pairs show enhanced photocatalytic activity in principle. However, achieving long-lived charge separation in COFs proves challenging due to the rapid charge recombination. Here, we develop a novel strategy by combining [6+4] nodes to construct zyg-type 3D COFs, first reported in COF chemistry. This structure type exhibits a fused Olympic-rings-like shape, which provides a platform for stabilizing the photoinduced D-A radical pairs. The zyg-type COFs containing catalytically active moieties such as triphenylamine and phenothiazine (PTZ) show superior photocatalytic production rates of hydrogen peroxide (H2O2). Significantly, the photochromic radical states of these COFs show up to 400% enhancement in photocatalytic activity compared to the parent states, achieving a remarkable H2O2 synthesis rate of 3324 μmol g-1 h-1, which makes the PTZ-COF one of the best crystalline porous photocatalysts in H2O2 production. This work will shed light on the synthesis of efficient 3D COF photocatalysts built on topologies that can facilitate photogenerating D-A radical pairs for enhanced photocatalysis.

Significant enhancement of piezoelectric photocatalytic activity in Mn-doped BiFeO3

Ultrasonic vibration and light irradiation can be used together to slow down the rapid recombination of light-induced charges during the catalytic process. One way to enhance the catalytic performance is by introducing different elements into the structure. In this study, pure bismuth ferrite (BiFeO3) and manganese (Mn)-doped bismuth ferrite (BFMO) nanomaterials were successfully synthesized by electrostatic spinning. These materials were then tested for their ability to degrade rhodamine B (RhB). The best-performing material was BiFe0.85Mn0.15O3, which achieved almost complete removal of RhB within 100 min. The degradation rate of this material was 3.3 times higher than that of pristine BiFeO3. This enhanced catalytic activity can be attributed to the wider range of light absorption and the synergistic enhancement of the piezoelectric response, which promotes the movement of free carriers. In addition, the synthesized catalysts have good stability and reusability, with little metal leaching after multiple uses. Free radical scavenging experiments tests showed that ·OH and holes are the main active species in the catalytic process. This work paves a new approach for creating highly efficient piezoelectric catalysts and expands the application of BiFeO3-based materials for wastewater purification.

Precise structure-tailoring of multicomponent nanocatalysts enabled by continuous flow-controlled flash nanoprecipitation technique

Nanostructured catalysts with diverse compositions offer an exciting prospect for various catalytic applications. The precise control of nanostructures allows to tune the physicochemical properties of nanocatalysts and improve their performance. However, most preparative methods rely on conventional batch systems, which require tedious procedures and cause low productivity. Herein, we reported a novel engineered flash nanoprecipitation (FNP) technique to synthesize well-structured nanocatalysts in a continuous-flow procedure with intelligent operation and high productivity, in which a series of multicomponent bismuth oxyhalides (BiOClxBr1-x) were demonstrated as the model catalysts. This method was established on the uninterrupted continuous synthesis of BiOClxBr1-x with precisely controlled microstructure by simply altering the flow rate ratio of precursor fluids in the reactor. The computational fluid dynamics (CFD) simulation showed that the automized flow setup could achieve the accurate control over the intensified fluid mixing. Significantly, a volcano relationship between the halogen compositions and catalytic activities toward photodegradation of tetracycline (TC) was observed, which indicated that the structural changes enabled band structure-dependent regulation. The FNP-processed BiOCl0.75Br0.25 possessed a balanced redox ability and light absorption, thus located at the peak of volcano with a five-fold enhancement of intrinsic photocatalytic activity. Overall, this work provides a promising prospect of continuous-flow technique in the engineered manufacturing of the advanced nanomaterials, offering fine-tuning of the nanostructures of materials with low cost and high productivity.

Polyvinyl alcohol/polyethyleneimine grafted carbon oxynitride composite nanofiber membranes with the synergistical enhanced photocatalytic degradation and bactericidal performance

AbstractGraphitic carbon nitride (g‐C3N4) has received much attention as a metal‐free photocatalyst for dye degradation and sterilization. However, the low photocatalytic bactericidal activity and the difficulty in recycling have limited its applications. Here, oxidatively modified g‐C3N4 grafted with polyethyleneimine (PEI) nanofiber membranes (PVA/PEI‐OCN) was reported to enhance the photocatalytic activity. The modification by PEI grafting could reduce the recombination rate of photogenerated carriers and lead to more electrons for the photocatalytic reaction. In addition, electron spin resonance (ESR) results showed that the generation of reactive oxygen species (˙OH, ˙O2− and 1O2) were significantly enhanced in photocatalysis, leading to the significant enhancement of photocatalytic bactericidal activity and dye degradation. Furthermore, the PVA/PEI‐OCN nanofiber membranes prepared by electrospinning had smooth surfaces and uniform fiber formation, with an average diameter of 380 ± 60 nm. The tensile strength was about 73.5% higher than that of PVA nanofiber membranes. The inhibition diameter of PVA/PEI‐OCN‐4 against Escherichisa coli (E. coil) could reach 20 ± 0.2 mm, and the maximum degradation efficiency of methylene blue solution (10 mg/L) could reach 92.8% within 120 min. This work provided an effective paradigm for the rational design of metal‐free photocatalytic materials for elimination of bacterial and dye contamination.

Fabrication of black phosphorus/CdS heterostructure with enhancement photocatalytic degradation activity for tetrabromobisphenol A and toxicity prediction of intermediates

Black phosphorus nanosheets (BPNs)/CdS heterostructure was successfully synthesized via hydrothermal method. The experimental results indicated that BPNs modified the surface of CdS nanoparticles uniformly. Meanwhile, the BPNs/CdS heterostructure exhibited a distinguished high rate of photocatalytic activity for Tetrabromobisphenol A (TBBPA) degradation under visible light irradiation (λ > 420 nm), the kinetic constant of TBBPA degradation reached 0.0261 min−1 was approximately 5.68 and 9.67 times higher than that of CdS and P25, respectively. Moreover, superoxide radical (•O2−) is the main active component in the degradation process of TBBPA (the relative contribution is 91.57%). The photocatalytic mechanism and intermediates of the TBBPA was clarified, and a suitable model and pathway for the degradation of TBBPA were proposed. The results indicated that the toxicities of some intermediates were higher than the parent pollutant. This research provided an efficient approach by a novel photocatalyst for the removal of TBBPA from wastewater, and the appraisal methods for the latent risks from the intermediates were reported in this paper.

Enhancement photocatalytic activity of CeO2 infused CA@Gelatin nanocomposites for the degradation of organic dyes under UV-light irradiation

In the present study, facile 100 % recoverable handpicked CeO2/CA@GEL (CA; Cellulose acetate, GEL; Gelatine) nanocomposite thin film photocatalyst were successfully synthesized by simple solution cast method. The efficacy of the CeO2/CA@GEL was tested against the photodegradation of organic dyes viz Crystal violet (CV) and Rhodamine-B (RhB) under visible light irradiation. The CeO2/CA@GEL exhibited excellent photocatalytic activity, durability and utmost 80.52 % (CV) and 82.65 % (RhB) degradation of the dye solution was achieved within 60 min. The CeO2/CA@GEL showed the excellent degradation efficiency compared to pure CeO2 Nanoparticles. The reactive oxidative species involved in the photocatalytic reaction is superoxide radical anion (O2 radical) and OH radical under visible light irradiation by trapping experiments. The 100 % recovery of the photocatalyst was achieved by simple handpicking process and stable unto its 3rd usage.

Electric field driven tourmaline/hematite dual mineral photocatalysis for efficient antibiotic removal

Hematite (Fe2O3) has garnered attention due to its stability, economic viability, and non-toxic nature. However, the rapid recombination of charge carriers hampers its practical application. On the other hand, tourmaline's inherent surface electric field facilitates the rapid separation of photogenerated electrons and holes. In this study, two directly mined natural minerals, tourmaline and hematite (TFO), were successfully combined. Characterization and experiments indicate that the pronounced enhancement of photocatalytic activity in Fe2O3 is attributed to the electric field effect on the surface of tourmaline. TFO successfully removes 93% of tetracycline (TC, 50 ppm) within 60 min. The reaction rate constant for TFO composite material (0.0410 min−1) is 8.5 times that of tourmaline (0.0048 min−1) and 14.1 times that of hematite (0.0029 min−1). Simultaneously, it markedly improves light absorption and charge carrier separation capabilities. Through simulations of various natural environmental factors, TFO demonstrates excellent practicality. Analyzing and detecting active species revealed the involvement of four types of active species, with ·OH radicals making the most significant contribution. The photocatalytic mechanism was proposed. Furthermore, the degradation pathway of tetracycline and the toxicity of its metabolites were investigated. This work provides additional inspirations and insights for photocatalytic materials performance enhancement and natural resources green governance environment.

Phase transition influenced photocatalytic dye degradation capability of pure and Eu-doped CoMoO4 polymorphic nanostructures

ABSTRACT The efficient degradation of organic dyes via photocatalysis presents a critical environmental challenge, necessitating advancements in catalyst design and performance. This study investigates the potential of pure and Eu doped CoMoO4 polymorphic nanostructures in addressing this challenge. Our primary focus is on enhancing the efficiency and stability of photocatalysts under diverse condition by performing sol–gel synthesis. Characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible (UV-visible) analysis and Raman analysis was employed to elucidate structural and morphological changes. Our results highlight the significant enhancement in photocatalytic activity achieved through phase transitions induced by Eu doping. This enhancement is attributed to the creation defect sites and the establishment of improved charge transfer pathways within the CoMoO4 nanostructures. By shedding light on the role of phase transition in photocatalysis, this study contributes valuable insights for the design of efficient and durable photocatalysts for environmental remediation application.

Effect of multi-walled carbon nanotubes properties on the photocatalytic activity of bismuth-based composites synthesised via an imidazolium ionic liquid

The use of various types of multi-walled carbon nanotubes in the synthesis of bismuth oxybromide semiconductors via imidazolium ionic liquid was studied in detail. The effect of the MWCNT shape, specific surface area, and various diameters on the morphology, surface properties and photoactivity of the Bi-based composites has been investigated for the first time. So far, the literature has only shown the enhancement of photocatalytic activity of composites containing MWCNT; however, our research shows a broader view of the issue. The photocatalytic activity of the individual composites under UV–Vis irradiation was assessed by the degradation of various micropollutants, showing the diversity of properties of the obtained composites. It is also significant that in the composite system, the imidazolium ionic liquid played a crucial role in the formation of microspheres and acted as a dispersing agent, leading to an even distribution of MWCNTs on the surface of the spherical bismuth oxybromide.

Interface Regulation of Bi3TiNbO9/Rh Photocatalysts by Introducing Ultrathin Heterolayer to Enhance Overall Water Splitting

AbstractAurivillius compounds‐based photocatalysts have attracted extensive interest largely due to their ferroelectric properties and modifiable characteristics arising from the alternate stacking of structural units. However, the interfacial Schottky barrier between such semiconducting compounds as light absorbers and metallic cocatalysts for hydrogen evolution restrains the transfer of photogenerated electrons, resulting in low photocatalytic overall water splitting activity and stability. Here, an anions‐induced surface structure transformation strategy is employed to modulate the interface structure between Bi3TiNbO9 as a typical Aurivillius compound and the cocatalyst Rh by in situ growing ultrathin Bi2MoO6 heterolayer on the surface of Bi3TiNbO9 nanosheets. The introduction of Bi2MoO6 heterolayer lowers the energy barrier near the Bi3TiNbO9 surface, which can facilitate the transfer of the photogenerated electrons from bulk to surface and thus the reduction of Rh cocatalyst for highly active hydrogen production. Compared with the Bi3TiNbO9‐Rh photocatalyst, the proportion of low‐valence metallic Rh0 in Bi2MoO6 heterolayer‐modified Bi3TiNbO9‐Rh (Bi3TiNbO9‐Bi2MoO6‐Rh) is improved by 7.76%, giving rise to a photocatalytic overall water splitting activity enhancement by a factor of 4.74. This strategy emphasizes the importance of interface regulation in promoting the transfer of photogenerated charge carriers in Aurivillius‐type photocatalysts, providing an effective pathway for designing and fabricating high‐performance photocatalysts.

Ligand modulation of active center to promote lead-free Cs2AgInCl6 photocatalytic CO2 reduction

Metal halide perovskites (MHP) are potential candidates for the photocatalytic reduction of CO2 due to their long photogenerated carrier lifetime and charge diffusion length. However, the conventional long-chain ligand impedes the adsorption and activation of CO2 molecules in practical applications. Here, a ligand modulation technology is employed to enhance the photocatalytic CO2 reduction activity of lead-free Cs2AgInCl6 microcrystals (MCs). The Cs2AgInCl6 MCs passivated by Oleic acid (OLA) and Octanoic acid (OCA) are used for photocatalytic CO2 reduction. The results show that the surface defects and electronic properties of Cs2AgInCl6 MCs can be adjusted through ligand modulation. Compared with the OLA-Cs2AgInCl6, the OCA-Cs2AgInCl6 catalyst demonstrated a significant improvement in the catalytic yield of CO and CH4. The CO and CH4 catalytic yields of OCA-Cs2AgInCl6 reached 171.88 and 34.15 µmol g−1 h−1 which were 2.03 and 12.98 times higher than those of OLA- Cs2AgInCl6, and the total electron consumption rate of OCA-Cs2AgInCl6 was 615.2 µmol g−1 h−1 which was 3.25 times higher than that of OLA-Cs2AgInCl6. Furthermore, in situ diffuse reflectance infrared Fourier transform spectra revealed the enhancement of photocatalytic activity in Cs2AgInCl6 MCs induced by ligand modulation. This study illustrates the potential of lead-free Cs2AgInCl6 MCs for efficient photocatalytic CO2 reduction and provides a ligand modulation strategy for the active promotion of MHP photocatalysts.

Synthesis of a novel biomass waste-based photocatalyst for degradation of high concentration organic pollutants under visible light: Optimization of synthesis condition and operational parameters via RSM-CCD

Reducing electron-hole pair recombination rate under visible light and preventing α-Fe2O3/WO3 nanoparticle aggregation enhances the photocatalytic efficiency. Herein, a novel heterojunction-activated carbon-based photocatalyst (α-Fe2O3/WO3/AC) was successfully synthesized from Rosa Canina seeds and characterized by PL, EIS, Photocurrent, ESR, XPS, LC-MS, FTIR, XRD, SEM, EDS-map, TEM, and BET analyses. Investigating the influence of significant parameters, including impregnation ratio (1–5), activation temperature (400–600 °C), and α-Fe2O3/WO3 loading (10–90 wt.%) by RSM method resulted in optimal photocatalyst synthesis (50 wt.%: FeW/AC3–500) evidenced by its capability for doxycycline degradation. The maximum doxycycline degradation (98.01 %) was achieved under optimal conditions with a degradation rate constant of 0.03 min−1. Trapping experiments revealed that •OH and •O2− played crucial roles in photocatalysis. The possible doxycycline degradation pathway of (50 wt.%: FeW/AC3–500) photocatalyst is proposed. Based on the transient photocurrent measurements and EIS results, the 50 wt.% FeW/AC3–500 composite exhibited a significant enhancement in photocatalytic activity, which can be attributed to the efficient speed of electron-hole separation. Overall, an innovative approach was introduced to design an efficient AC-based photocatalytic process, which enhances the performance of wastewater treatment and environmental remediation.