High Photocatalytic Efficiency Research Articles

Enhancing membrane performance for oily wastewater treatment: comparison of PVDF composite membranes prepared by coating, blending, and grafting methods using TiO2, BiVO4, CNT, and PVP.

This comparative study investigates the modification of polyvinylidene fluoride (PVDF) membranes with different nanoparticles (TiO2 or TiO2-based composites containing BiVO4 and/or CNT), using three distinct methods (blending, coating, and grafting) and polyvinylpyrrolidone (PVP). The objective was to enhance the photocatalytic and filtration performance for the separation of oil-in-water emulsions. Regarding the UV activity, the PVDF-TiO2/CNT/PVP-coated membrane presented the best performance. Overall, the addition of 2 wt.% CNT to the TiO2 notably enhanced the photocatalytic activity of the membranes for both UV and visible irradiations. Meanwhile, the presence of 2 wt.% BiVO4 was beneficial only for photocatalysis under visible light irradiation. Regarding the filtration of the oil-in-water emulsions, 2 wt.% CNT or BiVO4 addition resulted in the highest fluxes in the series of the PVDF-TiO2-grafted membranes. The presence of pore former PVP led to relatively high fluxes and photocatalytic activities for all series. Regarding the modification methods, coated membranes showed the highest photocatalytic efficiency and lowest fluxes. Grafted membranes showed relatively high photocatalytic efficiencies and the best filtration performances.

Enhanced photocatalytic activity of BB41 and ROM2R dyes using green synthesized NiO nanoparticles: A response surface methodology approach

BackgroundNiO NPs are recognized for their potential in catalysis, energy storage, and environmental remediation. Green synthesis using plant extracts, such as Cucumis maderaspatanus L. (CmL.) leaves, offers an eco-friendly approach. This study focuses on synthesizing and analyzing the structural, optical, and photocatalytic properties of Cm-NiO NPs. MethodologyCm-NiO NPs were synthesized using CmL. leaf extract and calcinated at 300, 500, and 700 °C. XRD confirmed a face-centered cubic structure. Band gap values were 3.36 eV at 300 °C, 2.98 eV at 500 °C, and 3.15 eV at 700 °C. TEM showed spherical particles of 17.81 nm. The point of zero charge (pHpzc) was pH 7.95. The photocatalytic activity was tested on BB41 and ROM2R dyes under varying pH (4 – 10), dye concentrations (10 – 50 ppm), catalyst amounts (0.1 – 1.0 mg/mL), and light sources. Scavenger studies identified reactive compounds. Response surface methodology (RSM) optimized the degradation process. LC-MS analyzed degradation products, and ECOSAR software estimated their toxicity. Significant FindingsCm-NiO NPs showed high photocatalytic efficiency, degrading 93.60 % of BB41 and 88.76 % of ROM2R under UV light (250 W, 365 nm). The nanoparticles demonstrated a face-centered cubic structure and a pHpzc of 7.95. RSM effectively optimized the process, and toxicity analysis suggested a potential for environmental applications.

A portable bifunctional platform of aluminum/alkalized carbon nitride/silver for sensitive SERS detection and efficient photocatalytic degradation of malachite green

It is necessary to construct a portable bifunctional substrate with high-repeatability and low-cost for detection and degradation of pollutants in practical applications. Herein, the alkalized carbon nitride (ACN) is assembled onto the etched aluminum sheet (EAl) by hydrogen bonding self-assembly which induces the porous structure of EAl/ACN. Subsequently, Ag nanoparticles (AgNPs) are mainly in-situ embedded in the cavities of EAl/ACN, and finally a portable bifunctional substrate of EAl/ACN/Ag is constructed. The surface-enhanced Raman scattering (SERS) response of the EAl/ACN/Ag is highly sensitive and selective for detection of malachite green (MG), and the limit for MG can reach 5.53 × 10-13 mol/L with an enhancement factor (EF) of 2.95 × 105. In addition, the EAl/ACN/Ag substrate shows excellent homogeneity, stability, recyclability and reproducibility. Moreover, the EAl/ACN/Ag substrate displays a high photocatalytic degradation efficiency of 96.4 % for MG within 50 mins even if it is reused for five cycles. Therefore, the developed portable bifunctional substrate shows bright prospects for the detection and removal of organic pollutants in the fields of industrial wastewater analysis.

Polymer-grafted metal–organic framework with carbon nanocomposite for photocatalytic dye degradation

Wastewater effluent threatens the environment. Creating eco-friendly materials for its treatment is crucial. We have created an eco-friendly material to treat wastewater effluent. Our trinary nanocomposite combines ZIF-8, Ppy, and AC to degrade organic dyes. We used sugar as the carbon source and changed the pH from acidic to basic to develop Zn/Ppy/AC nanocomposite material. A trinary hybrid named Zn/Ppy/AC was employed to break apart organic dyes, notably methylene blue (MB). The combined material possesses high photocatalytic efficiency when combined with polypyrrole as it is a conductive material that excites electrons more easily and transfers them towards ZIF-8 MOF. The control studies show that the nanomaterial photocatalytic efficiency increased by 98.32 % under UV visible light conditions for 30 min of exposure containing 50 mg nanocomposite with 50 ppm of 50 ml dye solution at room temperature and having neutral pH. Through several cycles, it was discovered that the newly developed hybrid nanocomposite had boosted reusability. The chemical oxygen demand for the nanocomposite was 124 mg/L, revealing that (MB) has been photocatalytically degraded. The in-situ synthesis of the Zn/Ppy/AC nanocomposite was the main objective of this work to synthesize it in large amounts at an affordable price for use in the breakdown of organic pollutants and other applications.

Template-synthesized CdWO4/Cd0.5Zn0.5S hollow microsphere photocatalyst for high-efficient hydrogen evolution under visible light

Photocatalytic water splitting for hydrogen production is a promising strategy for renewable energy. While Cd1-XZnXS catalysts display high photocatalytic hydrogen evolution efficiency in pure water, they are limited by severe photocorrosion and rapid recombination of electron–hole pairs. In this study, HGM (hollow glass microspheres) was used as the support template, Cd0.5Zn0.5S and CdWO4 were successively coated on the template by hydrothermal method. The tightly packed heterojunction interface between the coatings ensures efficient electron transport and suppresses the recombination of electron-hole pairs. Under visible light irradiation, when the theoretical mass ratio of Cd0.5Zn0.5S to CdWO4 is 4:1, the Cd0.5Zn0.5S/CdWO4-25% hollow microsphere photocatalyst exhibits the highest hydrogen evolution rate, reaching 41.40 mmol g−1 h−1, which is approximately 3.4 times higher than the hydrogen evolution rate of pure Cd0.5Zn0.5S (12.31 mmol g−1 h−1). This research provides a novel approach for the design and synthesis of efficient and stable photocatalysts.

Solar driven highly efficient photocatalyst based on Dy2O3 nanorods deposited on reduced graphene oxide nanocomposite for methylene blue dye degradation.

In recent years, the demand for rare earth elements has surged due to their unique characteristics and diverse applications. This investigation focuses on utilizing the rare earth element dysprosium oxide (Dy2O3) for the photocatalytic oxidation of model pollutants under solar light irradiation. A novel RGO-Dy2O3 nanocomposite photocatalyst was developed using a solvothermal approach, Dy2O3 nanorods uniformly deposited onto reduced graphene oxide (RGO) nanosheets. Comprehensive characterization techniques, including Brunner-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), Raman spectroscopy, high resolution - transmittance electron microscopy (HR-TEM), field emission-electron scanning microscopy (FE-SEM), atomic force microscopy (AFM), electron paramagnetic resonance spectroscopy (EPR), photoluminescence spectroscopy (PL), and electrochemical impedance spectroscopy EIS techniques. The UV-visible diffusive reflectance spectroscopy (UV-Vis-DRS) studies revealed a band gap energy of 3.18eV and a specific surface area of 114 m2/g for the fabricated RGO-Dy2O3 nanocomposite. The RGO-Dy2O3 nanocomposite demonstrated a high photocatalytic degradation efficiency of 98.1% at neutral pH for methylene blue (MB) dye for the dye concentration of 10ppm. The remarkable photocatalytic performance was achieved within 60min under solar light irradiation. Reusability tests demonstrated stability, maintaining over 90% photocatalytic efficiency after three cycles. The EPR spectra and quenching experiments confirmed that photogenerated hydroxyl radicals significantly influence the photodegradation processes. The RGO-Dy2O3 nanocomposite photocatalyst, with its green, easy preparation process and recycling capabilities, presents an ideal choice for various applications. It offers a viable alternative for the photocatalytic degradation of organic dyes in real wastewater, contributing to sustainable environmental remediation.

Nitrogen–oxygen vacancy and S-scheme heterostructure synergistically enhance solar photocatalysis

Introducing vacancies and constructing S-scheme heterojunctions are promising approaches for enhancing photocatalytic activity. However, the application of this synergistic strategy to realize inexpensive and efficient photocatalysts remains challenging. In this study, a straightforward hydrothermal and calcination modification strategy was used to prepare a photocatalyst in which abundant nitrogen–oxygen vacancies were coupled with a Ce-ZnO@C-g-C3N4 composite with an S-scheme heterojunction. Under sunlight irradiation, the prepared composite achieves 98.3% and 86.4% degradation of methylene blue and ciprofloxacin, with degradation rate constants of 0.3464 and 0.0893 min−1, respectively. Compared with ZnO and g-C3N4, the degradation rates of methylene blue over the composite catalyst are 34.8 and 22.7 times higher, respectively, and those of ciprofloxacin are 2.4 and 4.9 times higher, respectively. Based on a detailed examination of the catalyst structure and photoelectric properties, the high photocatalytic efficiency is attributed to nitrogen–oxygen vacancies, an enhanced surface area, and synergistic S-scheme heterojunction effects. These factors broaden the spectral range, increase the number of active sites, and facilitate efficient charge transfer, thereby enhancing the photocatalytic reaction. This system demonstrates the feasibility of integrating doping and heterojunction formation to enhance photocatalytic performance synergistically.

Influence of Sulfur Addition on The Physical and Photocatalytic Properties Biosynthesized Se-doped ZnO Nanoparticles

Abstract The objective of this study was to investigate the influence of Sulfur (S) addition to selenium-doped zinc oxide (Se-ZnO) nanoparticles on their physical properties and photocatalytic activity. S,Se-ZnO sample was prepared by adding 1wt% sulfur onto 4%Se-ZnO nanoparticles. In the synthesis procedure, microwave irradiation was used as heating power and matoa leaf extract was used as a bioreductor. The nanoparticles were characterized using UV-Vis Spectroscopy, X-ray diffraction (XRD), and Field Emission Scanning Electron Microscopy (FESEM). The calculated band gap energies of Se-ZnO and 1% S,Se-ZnO are 2.38 eV and 2.62 eV, respectively. Both samples exhibit a hexagonal wurtzite structure. FESEM image of addition S reveals flower petal flake formations and decrease particle size of 187 nm. The photocatalytic activity of nanoparticles was evaluated through 4-nitrophenol (4-NP) degradation under UV-C irradiation. 1% S,Se-ZnO exhibits high photocatalytic efficiency compared to Se-ZnO, with a degradation percentage of 85.09% after 60 min and a reaction rate of -0.0315 min−1. Based on these results, the addition of S on Se-ZnO biosynthesized shows improve physical properties and efficient photocatalytic materials for pollutant removal.

Enhanced performance of photocatalytic oxidation of indoor toluene over Pd/TiO2 catalyst by tuning surface defect concentrations

An effective approach for the elimination of indoor gaseous toluene through photocatalytic oxidation involves the engineering of surface defects on catalysts. In this study, the concentrations of surface oxygen defects in PdTi-xN (x = 10, 30) catalysts were controlled using the sodium borohydride solid-phase reduction method, and their performances in the photocatalytic oxidation of indoor gaseous toluene were evaluated. PdTi–10 N demonstrated high photocatalytic efficiency for toluene oxidation, achieving 84% toluene conversion and approximately 75% CO2 mineralization. Characterization results indicated that surface oxygen defects can enhance the separation of photo-generated electrons and holes, facilitating their interaction with Pd0 species to form Ti3+ species. More reactive oxygen species (·OH-and ·O2−) were generated on PdTi–10 N due to the synergistic effect of surface oxygen defect and Ti3+ species, which played a significant role as the toluene oxidation. This work provides a new insight for the design and development of high-performance Pd/TiO2 catalysts in the field of indoor VOCs treatment.

Fabrication of temperature-regulated sorbitol/mannitol-doped copper oxides derived from a Cu complex and their photocatalytic properties

In this study, a series of composites containing copper oxide (CuxO) particles doped with sorbitol/mannitol, namely Cu/CuxO@C (x = 1 or 2), was successfully derived from a novel copper complex ([Cu(IPZ)2Cl2] (Cu-Complex), where IPZ = 4-Iodopyrazole) by pyrolysis method and exploiting the stability and modulation of the coordination sites of sorbitol/mannitol, which exhibited excellent photocatalytic properties. The results showed that Cu/CuxO@C possessed high efficiency in degrading rhodamine B (RhB), gentian violet (GV), methyl orange (MO) and Congo red (CR) dyes under UV irradiation, and the degradation effect was gradually enhanced with the increase of calcination temperature. The structural and chemical states of the materials were characterised in detail. Furthermore, the effects of experimental factors such as catalyst dose, solution pH, and inorganic anions on dye degradation efficiency were investigated. The photocatalytic mechanism study demonstrated that the primary oxygen-active substance was superoxide radical (·O2-). The electron transport hypothesis explains the effective separation of electrons and holes within a substance. The Cu/CuxO@C composite was regarded as a potential photocatalyst for dye wastewater treatment due to its high photocatalytic efficiency, reusability, and universality, offering a novel solution to environmental and energy issues.

Recent Developments in Immobilized Photocatalyst for Hydrogen Production

AbstractSolar‐driven water splitting for hydrogen production has emerged as one of the most promising methods for addressing environmental and energy crises. The utilization of immobilized photocatalyst for hydrogen production has attracted significant attention in recent years due to its excellent stability, high photocatalytic efficiency, and ease of recovery and reuse. Hence, a comprehensive review of the development of immobilized photocatalyst appears exceedingly significant. Herein, we initially analyze the advantages of the immobilized photocatalytic system in aspects such as light absorption, photon utilization, and charge separation. Subsequently, we introduce various assembly techniques for immobilized photocatalyst and elaborate on some representative characteristics of this immobilized system. Furthermore, we cite the examples of the application of immobilized photocatalyst in large‐scale hydrogen production to envision its future prospects. Finally, we discuss the remaining issues in this field and outline future directions of development and challenges therein. This review holds great promise for prompting the advancement of immobilized photocatalyst in the field of photocatalysis.

Integration of Perylene Diimide into a Covalent Organic Framework for Photocatalytic Oxidation.

Perylene diimides (PDIs) have garnered considerable attention due to its immense potential in photocatalysis. However, manipulating the molecular packing within their aggregates and enhancing the efficiency of photogenerated carrier recombination remain significant challenges. In this study, we demonstrate the incorporation of a PDI unit into a covalent organic framework (COF), named PDI-PDA, by linking an ortho-substituted PDI with p-phenylenediamine (PDA) to control its intermolecular aggregation. The incorporation enables precise modulation of electron transfer dynamics, leading to a ten-fold increase in the efficiency of photocatalytic oxidation of thioether to sulfoxide with PDI-PDA compared to the PDI molecular counterpart, achieving yields exceeding 90%. Electron property studies and density functional theory calculations show that the PDI-PDA with its well-defined crystal structure, enhances π-π stacking and lowers the electron transition barrier. Moreover, the strong electron-withdrawing ability of the PDI unit promotes the spatial separation of the valency band maximum and conduction band minimum of PDI-PDA suppressing the rapid recombination of photogenerated electron-hole pairs and improving charge separation efficiency to give high photocatalytic efficiency. This study provides a brief yet effective way for the improvement of the photocatalytic efficiency of commonly used PDI-based dyes by integrating them into a framework skeleton.

Integration of Perylene Diimide into a Covalent Organic Framework for Photocatalytic Oxidation

AbstractPerylene diimides (PDIs) have garnered considerable attention due to their immense potential in photocatalysis. However, manipulating the molecular packing within their aggregates and enhancing the efficiency of photogenerated carrier recombination remain significant challenges. In this study, we demonstrate the incorporation of a PDI unit into a covalent organic framework (COF), named PDI‐PDA, by linking an ortho‐substituted PDI with p‐phenylenediamine (PDA) to control its intermolecular aggregation. The incorporation enables precise modulation of electron‐transfer dynamics, leading to a ten‐fold increase in the efficiency of photocatalytic oxidation of thioether to sulfoxide with PDI‐PDA compared to the PDI molecular counterpart, with yields exceeding 90 %. Electron property studies and density functional theory calculations show that the PDI‐PDA with its well‐defined crystal structure, enhances π–π stacking and lowers the electron transition barrier. Moreover, the strong electron‐withdrawing ability of the PDI unit promotes the spatial separation of the valency band maximum and conduction band minimum of PDI‐PDA, suppressing the rapid recombination of photogenerated electron‐hole pairs and improving the charge‐separation efficiency to give high photocatalytic efficiency. This study provides a brief but effective way for improving the photocatalytic efficiency of commonly used PDI‐based dyes by integrating them into a framework skeleton.

Effect of Calcination Temperature on the Surface of Prepared ZnO Nanocatalysts

ZnO nanoparticles (NPs) having nsemiconducting properties are important nanocatalysts for many surface reactions. Because of their extensive use as heterogeneous nanocatalyst for energy production and environmental cleaning, it is essential to understand their surface properties to design better chemical and photochemical nanocatalysts. Here, we used the sol-gel method to develop numerous ZnO NPs at various calcination temperatures (300 - 800 oC) and analyzed by different surface characterization techniques such as FTIR, SEM, XRD and UV-visible absorption spectroscopy. To investigate the catalytic activity a series of photooxidation studies on Remazol Red RR (RRR) were carried out at different conditions. From the surface characteristic analysis, it is found that the crystalline ZnO NPs are formed at above 400 oC temperature. The highest photocatalytic efficiency is found at 500 oC which might be related to the lowest particle size (35.4 ± 5.2 nm) and surface heterogeneity. The experimental results suggest that temperature-controlled growth rate and intra/inter-particle heterogeneity of ZnO nanoparticles have a great impact on the surface properties and photocatalytic activity. In addition to surface area, surface defects and crystal deformation may have a considerable impact on the photocatalytic activity by ZnO NPs. Finally, this study will help to understand what type of surface properties need to optimize to design industrial suit ZnO nanocatalysts. Journal of Engineering Science 15(1), 2024, 75-81

Manganese-doped Zinc Oxide recycled from spent alkaline batteries for photocatalysis and supercapacitor applications

In a sustainable future, recycling e-waste will offer an adequate solution to control the raw materials and energy crisis. Our study aims to obtain ZnO-based materials by recycling the alkaline batteries using mild and cost-effective methods. Manganese-doped ZnO materials were obtained through anodic paste annealing at different temperatures. In terms of morphology and structure, particles with rod shape, high crystallinity, and hexagonal symmetry were obtained. The annealing provides an atomic rearrangement ensuring the presence of isolated Mn2+ ions in the ZnO lattice, as evidenced by EPR spectroscopy. The sample defect evolution with the annealing temperature was highlighted by photoluminescence spectroscopy. The photocatalytic and energy storage applications of the obtained sample were investigated. The photocatalytic activity was tested on Rhodamine B and Oxytetracycline under visible light irradiation. The highest photocatalytic efficiency was obtained for Mn-doped ZnO annealed at 700 °C, and the proposed mechanism was based on reactive oxygen species generation correlated with scavengers’ tests, defect’s structure, and pores diameter. Additionally, the samples were used to design symmetric supercapacitors and tested using different electrochemical techniques to prove their energy storage features. As a result, the Mn-doped ZnO particles annealed at 800 °C showed increased specific capacitance of 182 F/g, energy density of 25.2 Wh/kg, and power density of 38.7 kW/Kg without the use of booster materials.

Morphology-Dependent Photocatalytic Activity of Nanostructured Titanium Dioxide Coatings with Silver Nanoparticles.

This study aims to improve the photocatalytic properties of titanium dioxide nanorods (TNRs) and other related nanostructures (dense nanorods, needle-like nanorods, nanoballs, and nanoflowers) by modifying them with silver nanoparticles (AgNPs). This preparation is carried out using a two-step method: sol-gel dip-coating deposition combined with hydrothermal crystal growth. Further modification with AgNPs was achieved through the photoreduction of Ag+ ions under UV illumination. The investigation explores the impact of different growth factors on the morphological development of TiO2 nanostructures by modulating (i) the chemical composition, the water:acid ratio, (ii) the precursor concentration involved in the hydrothermal process, and (iii) the duration of the hydrothermal reaction. Morphological characteristics, including the length, diameter, and nanorod density of the nanostructures, were analyzed using scanning electron microscope (SEM). The chemical states were determined through use of the X-ray photoelectron spectroscopy (XPS) technique, while phase composition and crystalline structure analysis was performed using the Grazing Incidence X-ray Diffraction (GIXRD) method. The results indicate that various nanostructures (dense nanorods, needle-like nanorods, nanoballs, and nanoflowers) can be obtained by modifying these parameters. The photocatalytic efficiency of these nanostructures and Ag-coated nanostructures was assessed by measuring the degradation of the organic dye rhodamine B (RhB) under both ultraviolet (UV) irradiation and visible light. The results clearly show that UV light causes the RhB solution to lose its color, whereas under visible light RhB changes into rhodamine 110, indicating a successful photocatalytic transformation. The nanoball-like structures' modification with the active metal silver (TNRs 4 Ag) exhibited high photocatalytic efficiency under both ultraviolet (UV) and visible light for different chemical composition parameters. The nanorod structure (TNRs 2 Ag) is more efficient under UV, but under visible-light photocatalyst, the TNRs 6 Ag (dense nanorods) sample is more effective.

Optimization of trypan blue and brilliant green dyes photocatalytic degradation and adsorption of lead(II) and chromium (VI) heavy metal ions by copper sulfide nanoparticles

The use of nanoparticles for to remove organic pollutants and heavy metals is a rapidly expanding field in environmental sciences. However, process optimization for practical, real-world applications is still underexplored. In this work, copper sulfide nanoparticles prepared from a single-source precursor were characterized using SEM, TEM, EDX, FTIR, and UV-visible spectroscopy. The copper sulfide nanoparticles demonstrated high photocatalytic degradation efficiency of trypan blue (TB) and brilliant green (BG) dyes. The as-prepared nanoparticles efficiently removed lead(II) (Pb2+) and chromium(VI) (Cr6+) ions. Response surface methodology (RSM) with a Box-Behnken design (BBD) was employed to optimize reaction time, pH, and nanoparticle dosage. The optimal conditions for TB degradation were pH 10.91, 77.46 minutes, and 4.999 g/L, while for BG, they were pH 3, 70 minutes, and 5 g/L. For Pb2+ removal, optimal conditions were pH 7.06, 100.38 minutes, and 0.94 g/L, and for Cr6+ removal, pH 3.03, 168.20 minutes, and 0.98 g/L. Under these optimal conditions, CuS nanoparticles achieved up to 99.35% degradation for TB, 100% for BG, 100% removal for Pb2+, and 98.54% for Cr6+. ANOVA confirmed the models' significance, with high regression coefficients (R²: 0.9852 for BG, 0.9846 for TB, 0.9980 for Pb2+, and 0.9901 for Cr6+). The CuS photocatalyst remained stable over three reuse cycles, with minimal efficiency reduction (8.88% for TB and 19.01% for BG). This study demonstrates the effectiveness of copper sulfide nanoparticles in environmental remediation and highlights the practicality of using RSM to optimize nanoparticles as efficient materials to remove organic dyes and heavy metal-laden wastewater.

Visible-light driven efficient cleavage of Cα–Cβ bond in lignin models and lignin over porous tubular carbon nitride

The photocatalytic selective breaking of recalcitrant Cα–Cβ bond in real lignin to product value-added chemicals under mild conditions is intriguing but remains challenging. Herein, a sustainable strategy for the efficient and selective breakage of Cα–Cβ bond in lignin β-O-4 model compounds and lignin over porous tubular g-C3N4 (PTCN) photocatalyst was designed under ambient conditions. Compared with bulk g-C3N4, the construction of PTCN not only facilitates photogenerated charge separation and transfer, but also provides more exposed interior active sites, which is conductive to reactant adsorption on the surface of PTCN, thereby resulting in the higher photocatalytic efficiency. With this strategy, 2-phenoxy-1-phenylethanol as the typical model substrate was completely converted into aromatic monomers with Cα–Cβ bond cleavage selectivity of 97.2 %. Both mechanistic studies and theoretical calculations revealed that the photogenerated holes, electrons and O2− respectively played an essential role in the Cβ–H dehydrogenation and Cα–Cβ bond breakage. Native lignin samples (alkaline, pine and wheat straw) were applied to these photocatalytic systems and successfully depolymerized with Cα–Cβ bond cleavage under optimal reaction conditions. This work could provide an in-depth insight into photocatalyst design for the economical and efficient valorization of lignin.

MXene quantum dots decorated g-C3N4/BiOI heterojunction photocatalyst for efficient NO deep oxidation and CO2 reduction

The photocatalytic performance of g-C3N4 is greatly limited by the severe charge recombination due to its s-triazine unit structure. Hence, enhancing the separation of photogenerated carriers is the pivotal factor for high-efficiency photocatalysis of g-C3N4. In this work, we construct a MXene quantum dots (MQDs) decorated BiOI/g-C3N4p-n heterojunction photocatalyst. The interfacial charge separation and transfer are substantially promoted, due to the synergistic effect of the internal electric field (IEF) of BiOI/g-C3N4 heterojunction and strong electron-withdrawing capability of MQDs. Furthermore, the introduction of BiOI with a low band gap and MQDs with large specific areas and rich surface terminals lead to enhanced light absorption and active sites. As a result, the ternary g-C3N4/MQDs/BiOI photocatalyst achieves a much higher NO removal rate of 42.23 % and discharges less NO2 intermediate than the individual and binary ones. Meanwhile, the g-C3N4/MQDs/BiOI photocatalyst also exhibits the most effective CO2 photoreduction, with a CO production rate of 57.8 μmol·g−1·h−1 and a CH4 production rate of 3.6 μmol·g−1·h−1, surpassing all other photocatalysts in this study. In addition, the designed composite photocatalyst shows remarkable stability. The photocatalytic mechanisms are studied by the trapping experiment and in-situ Fourier Transform Infrared (FTIR) Spectra. This work paves a new avenue for enhancing charge separation and thus improving performances of g-C3N4-based photocatalysts by integrating a p-n heterojunction and a co-catalyst, which would accelerate commercial deployment of emerging photocatalysts.

Facile Synthesis of Sodium Alginate (SA)-Based Quaternary Bio-Nanocomposite (SA@Co-Zn-Ce) for Antioxidant Activity and Photocatalytic Degradation of Reactive Red 24

This study introduces a new strategy for the environmentally friendly catalytic degradation of Reactive Red 24 (RR24) dye using sunlight. We developed a cost-effective quaternary nanocomposite by immobilizing a sodium alginate biopolymer over bioengineered Co-Zn-Ce nanoparticles, forming an SA@Co–Zn–Ce nanocomposite (where SA means sodium alginate). This composite also demonstrated an exceptional antioxidant potential of approximately 89%, attributed to the synergistic effect of sodium alginate and green-synthesized Co–Zn–Ce nanoparticles (biosynthesized using Ocimum sanctum leaf extract as a reducing agent). Scanning electron microscopy revealed grain sizes of 28.6 nm for Co–Zn–Ce NPs and 25.59 nm for SA@Co–Zn–Ce nanocomposites (NCs). X-ray diffraction showed particle sizes of 16.87 nm and 15.43 nm, respectively. Co–Zn–Ce NPs exhibited a zeta potential of 1.99 mV, whereas the sodium alginate-anchored Co–Zn–Ce showed −7.99 mV. This indicated the entrapment of negatively charged ions from sodium alginate, altering the surface charge characteristics and enhancing the photocatalytic degradation of RR24. Dynamic light scattering revealed an average particle size of approximately 81 nm for SA@Co–Zn–Ce NCs, with the larger size due to the influence of water molecules in the colloidal solution affecting hydrodynamic diameter measurement. The SA@Co–Zn–Ce NCs exhibited a CO2 adsorption capacity of 3.29 mmol/g at 25 °C and 4.76 mmol/g at 40 °C, indicating temperature-dependent variations in adsorption capabilities. The specific surface area of Co–Zn–Ce oxide NPs, measured using Brunauer–Emmett–Teller (BET) analysis, was found to be 167.346 m2/g, whereas the SA@Co–Zn–Ce oxide nanocomposite showed a surface area of 24.14 m2/g. BJH analysis revealed average pore diameters of 34.60 Å for Co–Zn–Ce oxide NPs and 9.26 Å for SA@Co–Zn–Ce oxide NCs. Although the immobilization of sodium alginate on Co–Zn–Ce oxide NPs did not increase the adsorption sites and porosity of the composite, as evidenced by the N2 adsorption–desorption isotherms, the SA@Co–Zn–Ce oxide NCs still demonstrated a high photocatalytic degradation efficiency of RR24.