Stable Photocatalyst Research Articles

Multi-Layer Kesterite-Based Photocathodes for Nh3 Photosynthesis from N2 Reduction Reaction.

The necessity of new methods to substitute the Haber-Bosch process in the NH3 synthesis, generating fewer greenhouse gases, and dispensing less energy, drove the investigation of the photoelectrocatalytic approach in the N2 reduction reaction (N2RR). For that, this work presents the synthesis and characterization of the layered CZTSSe/CdS/TiO2 photocathode decorated with Pt nanoparticles for application in NH3 production using the photoelectrocatalysis technique. The CZTSSe/CdS/TiO2-Pt characterization showed a well-designed and stable photocatalyst synthesized layer by layer with an important contribution of the Pt nanoparticles for the catalyst performance, improving the photocurrent density and the charge transfer. The N2RR in a two-compartment photochemical cell with 0.1 mol L-1 Na2SO3 and 0.05 mol L-1 H2SO4 in the cathodic and anodic chamber, respectively, using CZTSSe/CdS/TiO2-Pt and under 1 sun of light incidence and applied potential of -0.4 VAg/AgCl reached 0.22 mmol L-1 cm-2 NH3, a value 28 folds higher than using the catalyst without Pt modification. The superiority of N2RR under the photoelectrocatalysis technique was demonstrated compared to photocatalytic and electrocatalytic techniques, together with the investigation of the supporting electrolyte influence in the cathodic compartment. Additionally, that is the first time a kesterite-based photocathode has been applied to NH3 photosynthesis, showing excellent photoconversion capability.

Polyhydroxykanoate-Assisted Photocatalytic TiO2 Films for Hydrogen Production.

The photocatalytic production of hydrogen using biopolymer-immobilized titanium dioxide (TiO2) is an innovative and sustainable approach to renewable energy generation. TiO2, a well-known photocatalyst, benefits from immobilization on biopolymers due to its environmental friendliness, abundance, and biodegradability. In another way, to boost the efficiency of TiO2, its surface properties can be modified by incorporating co-catalysts like platinum (Pt) to improve charge separation. In this work, the surface of commercial TiO2 PC500 was modified with Pt nanoparticles (Pt1%@PC500) and then immobilized on glass surfaces using polyhydroxyalkanoate biopolymer poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBH). The as-prepared immobilized Pt-modified TiO2 photocatalysts were fully characterized using various physicochemical techniques. The photocatalytic activity of the photocatalyst film was investigated for photocatalytic hydrogen production through water reduction using ethanol as a sacrificial donor. The impact of the film preparation conditions, e.g., PHBH concentration, PHBH:catalyst ratio, and temperature, on activity and stability was studied in detail. The application of biopolymer PHBH as a binder provides a green alternative to conventional immobilization methods, and with the application of PHBH, a stable and active photocatalyst film that showed lower activity compared to that of the suspended photocatalyst but good recyclability in six runs was prepared. A long-term photocatalytic hydrogen production experiment was carried out. In 98 h of operation, 12 mmol of hydrogen was produced in three consecutive runs with a PHBH/Pt1%@PC500 film having an area of ∼5.3 cm2. A significantly lower hydrogen productivity was observed after the first run, possibly due to a change in film structure, but thereafter, the productivity remained almost constant for the second and third runs. Hydrogen was the main product in the gas phase (90%), but carbon dioxide (4-5%) and methane (4-5%) were obtained as important byproducts. The byproducts are a consequence of the use of the sacrificial reagent ethanol. The results of the film performance are very promising, with regard to large-scale continuous hydrogen production.

Synthesis of TiO2-ZnO n-n Heterojunction with Excellent Visible Light-Driven Photodegradation of Tetracycline.

Zinc oxide-based photocatalysts with non-toxicity and low cost are promising candidates for the degradation of tetracycline. Despite the great success achieved in constructing n-n-type ZnO-based heterojunctions for the degradation of tetracycline under full-spectrum conditions, it is still challenging to realize rapid and efficient degradation of tetracycline under visible light using n-n-type ZnO-based heterojunctions, as they are constrained by the quick recombination of electron-hole pairs in ZnO. Here, we report highly efficient and stable n-n-type ZnO-TiO2 heterojunctions under visible light conditions, with a degradation efficiency reaching 97% at 1 h under visible light, which is 1.2 times higher than that of pure zinc oxide, enabled by constructing an n-n-type heterojunction between ZnO and TiO2 to form a built-in electric field. The photocatalytic degradation mechanism of n-n TiO2-ZnO to tetracycline is also proposed in detail. The demonstration of efficient and stable heterojunction-type ZnO photocatalysts under visible light is an important step toward commercialization and opens up new opportunities beyond conventional ZnO technologies, such as composite ZnO catalysts.

Unveiling new insights into photocatalytic enhancement of p-n BiVO4-OV/NiMoO4 Heterojunctions through oxygen defect engineering

The development of efficient and stable photocatalysts holds vital importance in the fast and effective removal of toxic contaminants from wastewater. In this study, novel 1D/2D BiVO4-OV/NiMoO4 hybrid with enriched oxygen vacancies (BiVO4-OV/NiMoO4) were successfully synthesized by using one step hydrothermal synthesis route. Utilizing the p-n heterojunction and oxygen vacancies, the optimized BiVO4-OV/NiMoO4 composite exhibited exceptional photocatalytic efficiency, achieving a photocatalytic degradation efficiency of 92 % for rhodamine B (RhB) under visible light irradiation within 60 min. The apparent rate constant of value of optimized BiVO4-OV/NiMoO4 composite is 0.02864 min−1, exceeding those of BiVO4 and NiMoO4 by 4.4 times and 5.5 times, respectively. The photocatalytic mechanism and degradation pathways of RhB were investigated through active species trapping experiment. Remarkably, optimized BiVO4-OV/NiMoO4 hybrid demonstrated high stability and recyclability. This study on the development of highly efficient visible-light catalysts through synergistic defect and heterojunction engineering, offering a promising approach for organic pollutant degradation.

Demonstration of Scalable Water Splitting into H2 and O2 by a Flow-Type Photocatalysis-Electrolysis Hybrid System Using a Highly Stable Photocatalyst.

Water splitting via a photocatalysis-electrolysis hybrid system has been investigated as a potentially scalable and economically feasible means of producing renewable H2. However, there are no reports demonstrating a scalable system for stoichiometric water splitting using an efficient and stable photocatalyst, and the key operating conditions for efficiently driving the entire system have not been established. Herein, we address the issues required to efficiently drive the entire system of a Cs+, Fe2+, and H+ ion-modified WO3 (denoted as H-Fe-Cs-WO3) photocatalyst fixed reactor combined with a polymer electrolyte membrane (PEM)-type electrolyzer. In electrochemical H2 production using Fe2+, the current density improved as the concentration of both H+ and Fe2+ increased, and we determined the optimum conditions for a hybrid system using high concentrations of HClO4 and Fe(ClO4)3, which differ from those reported for photocatalysis alone. No performance deterioration of the H-Fe-Cs-WO3 photocatalyst was observed even after light irradiation for more than 10 000 h under strong acidic conditions. The accumulated Fe2+ ions were extremely stable and did not oxidize even when exposed to air for more than two months. As for the stepwise operation that takes advantage of the characteristics of the hybrid system, the contribution factor of the photocatalyst in the photocatalysis-electrolysis hybrid system for H2 evolution (CP@STHap) under an applied bias was estimated to be 0.24%, which is a value comparable to that of the solar-to-chemical (STC) conversion efficiency (0.31%). The efficiency difference (0.07%) corresponds to the overpotential of the electrolytic reaction and indicates that water splitting via the photocatalysis-electrolysis hybrid system proceeds efficiently at a small overpotential of 0.06 V (∼11.6 kJ mol-1).

Robust photocatalytic hydrogen evolution performance of 0D/1D NiO/CdS S-scheme heterojunction

Constructing heterojunction, especially S-scheme heterojunction, is an effective strategy for achieving effective separation of photogenerated electron-hole pairs and obtaining high electrode potential. In this study, a unique 0D/1D NiO/CdS S-scheme heterojunction was constructed by solvent evaporation induced self-assembly method. The loading of NiO was found to greatly enhance the photogenerated carrier separation efficiency of CdS by photoluminescence (PL) spectroscopy, electrochemical impedance spectroscopy (EIS), Kelvin probe force microscopy (KPFM) and transient photocurrent tests. The best photogenerated carrier separation effect was observed at a NiO loading ratio of 15 wt% and the largest photocatalytic hydrogen evolution rate reached 7.89 mmol h-1g−1 under visible light, which was 24.66 times that of pristine CdS. In addition, the cycling experiments showed that the loading of NiO led to the alleviation of the photocorrosion phenomenon of CdS, and the performance remained at 94.2 % after five cycles. This is due to the fact that the formation of S-type heterojunction combines the photogenerated holes of CdS with the photogenerated electrons of NiO, which hinders the oxidation of S2- on the surface of CdS, thus alleviating the photocorrosion phenomenon of CdS and improving the stability of CdS. This work furnishes a new strategy for the development of stable and high-performance photocatalysts with inexpensive co-catalysts.

Tetracycline removal via photo-Fenton processes using Fe-based metal-organic frameworks loaded with Bi2S3: Performance evaluation and insights into the charge-transfer mechanism

Combining photocatalytic technology with the Fenton system may help overcome these technologies’ limitations. Photo-Fenton catalysis is economical and eco-friendly. The Fe based heterogeneous photo-Fenton process appears to be a promising wastewater treatment technology. Herein, an Fe based metal–organic framework (MIL-101 (Fe)) was produced via hydrothermal processing. Subsequently, Bi2S3 was loaded onto the surface of MIL-101 (Fe) to form a composite catalyst. A type-II heterojunction was established between MIL-101 (Fe) and Bi2S3. The 10 % Bi2S3-loaded MIL-101 (Fe) (MBS-10) was effective in the photocatalytic degradation of tetracycline, particularly after H2O2 addition. This outcome was due to the enhanced generation of radical species through the photo-Fenton process. The MBS-10 photocatalyst promoted Fe (II)/Fe (III) cycling in the presence of H2O2 and under visible light irradiation. MBS-10 also showed a higher kinetic rate constant during the photocatalytic reaction compared to MIL-101 (Fe) and Bi2S3, suggesting enhanced activity through greater electron-hole separation. Furthermore, MBS-10 proved to be stable and reusable photocatalyst after four testing cycles. The charge-transfer mechanism was elucidated through radical scavenging experiments which demonstrated that superoxide and hydroxyl radicals are the major charge carriers. Therefore, the Bi2S3-MIL-101 (Fe) composite exhibits great potential for degrading tetracycline antibiotics.

Constructing dual-channel carrier transport in AgBr/BiOBr/Ag3PO4 heterojunctions for enhanced photocatalytic NO removal

Efficient and stable photocatalysts are indispensable for effectively reducing nitrogen oxide (NOx) emissions. This study presents a facile method for synthesizing AgBr/BiOBr/Ag3PO4 composites and investigates their application in photocatalytic NO removal. The optimized composite exhibited notable performance, achieving 54.95 % removal of NO (approximately 568 ppb reduced to 256 ppb) under visible light irradiation, which is about 1.6 and 2.0 times higher than single Ag3PO4 (34.95 %) and BiOBr (28.01 %), respectively. Comprehensive physicochemical characterization highlighted enhancements in light absorption and the generation of reactive radicals within the AgBr/BiOBr/Ag3PO4 composite. The favorable electronic structure, characterized by well-aligned redox band positions, facilitated efficient dual carrier transport routes, thereby promoting the separation of photo-generated charge carriers. Additionally, in-situ DRIFTS analysis revealed that the composite facilitated the conversion of intermediates into nitrates during the NO purification process. This work contributes valuable insights into designing and preparing of ternary heterojunction photocatalysts with dual carrier transport channels, advancing strategies for achieving superior photocatalytic performance.

S-scheme3D/3D Bi0/BiOBr/P Doped g-C3 N4 with Oxygen Vacancies (Ov) for Photodegradation of Pharmaceuticals: In-situ H2O2 Production and Plasmon Induced Stability.

Complications accompanying photocatalyst stability and recombination of exciton charges in pollutants degradation has been addressed through the construction of heterojunctions, especially S-scheme heterojunction with strong and distinctive redox centres. Herein, an S-scheme BiOBr (BOR) and g-C3N4PO4 (CNPO) catalyst (BORCNPO) with oxygen vacancy (Ov) was synthesized for levofloxacin (LVX) and oxytetracycline (OTC) photodegradation under visible light. The 3D/3D BORCNPO catalyst possessed C-O-Br bridging bonds for efficient charge transfer during the fabrication of S-scheme heterojunction. In-situ H2O2 formation affirmed by potassium titanium (IV) oxalate spectrophotometric method improved the mineralization ability of BORCNPO7.5 catalyst. Bi0 surface plasmon resonance (SPR) enhanced formation and involvement of ⋅O2 - and the stability of the catalyst which increased reaction rate with increasing cycling experiments. XPS and radical trapping experiments supported the S-scheme charge transfer mechanism formation with high degradation rate of LVX which was 3 times higher than OTC degradation rate. Mineralization of pollutants and their intermediates were demonstrated with florescence excitation and emission matrix (FEEM) and quadruple time of flight high performance liquid chromatography (QTOF-HPLC). This work advances development of highly stable and efficient catalysts for photodegradation of pollutants through the formation of S-scheme heterostructure.

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.

MgCr2O4/MgIn2S4 Spinel/Spinel S-Scheme Heterojunction: A Robust Catalyst for Photothermal-Assisted Photocatalytic CO2 Reduction.

Photocatalytic CO2 reduction technology has engaged significant attention due to its high efficiency, high selectivity, and environmental friendliness. However, its application is severely restrained by issues such as low separation efficiency of photogenerated carriers and a limited light absorption range. This work proposes an innovative MgCr2O4/MgIn2S4 magnesium-based spinel/spinel heterostructure photocatalyst to improve the photocatalytic CO2 reduction efficiency through the synergistic contributions of S-scheme heterojunction and photothermal effect. On the one hand, the unique S-scheme charge transfer mechanism enables the effective separation of photogenerated carriers. On the other hand, the photothermal effect allows an accelerated charge migration by increasing the reaction center temperature. Moreover, the abundant oxygen vacancies serve as electron traps and CO2 adsorption sites, unifying reaction and adsorption sites and substantially improving catalytic efficiency. Under UV-vis and UV-vis-NIR illumination, the average CO yields of the MgCr2O4/MgIn2S4 composite are 8.03 and 15.62 μmol g-1 h-1, respectively, greatly higher than those of pure MgCr2O4 and MgIn2S4 samples. Furthermore, the fabricated photocatalyst demonstrates excellent performance and structure stability. Therefore, this work may offer a new strategy for designing efficient and stable photocatalysts.

Synthesis of Heteromorphic Bi2WO6 Films With an Interpenetrate 1D/2D Network Structure for Efficient and Stable Photocatalytic Degradation of VOCs.

2D layered Bi2WO6 (BWO) is a widely used attractive photocatalyst for degrading VOCs, but the low visible-light utilization and the easy stacking 2D nanosheets(NSs) limit photocatalysis efficiency and stability. Here, inspired by Eucalyptus, a synergistic strategy of multiscale domain-confinement and electrostatic force action, based on electrospinning is proposed, for fabricating a heteromorphic BWO photocatalyst. It is found that BWO NSs can grow radially in an orderly spaced arrangement along BWO nanofibers (NFs) during sintering, thereby forming 1D/2D BWO junctions like eucalyptus leaves. This interpenetrating 1D/2D network structure not only solves the easy stacking problem of BWO NSs but also selectively exposes the {010} crystal planes that exhibit efficient hole oxidation. In addition, this peculiar structure enriches electrons at the 1D/2D interface to avoid carrier recombination, thus improving the photocatalytic activity. The photocatalyst material with a reduced bandgap width from 2.56 to 2.49eV can rapidly degrade 100% of acetaldehyde under visible light without using sacrificial agents and photosensitizers and shows superior stability for eight cycles without any decay. This study provides a feasible method to synthesize an efficient and stable BWO photocatalyst.

Synergistic Coordination and Surface Plasmon Resonance of Quantum Dots in Enhancing Photocatalytic Hydrogen Evolution.

Recent studies have revealed that the integration of metal nanoparticles (NPs) with photocatalysts allows the metal NPs to serve as cocatalysts, significantly enhancing reactant efficiency near nanostructures through the surface plasmon resonance (SPR) effect. On this basis, we synthesized highly reactive FePt quantum dots (FePt QDs) with tailored configurations, manipulating the Pt coordination environment and combining FePt QDs with ultrathin two-dimensional nickel metal-organic layer (Ni-MOL) nanosheets. X-ray absorption fine spectroscopy (XAFS) confirmed the distinctive Pt-Fe configuration after photoactivation. The optimized loading amount of FePt QDs led to a hydrogen evolution reaction (HER) yield of 113 mmol·g-1·h-1 after activation, with the catalyst remaining stable over five cycles. The improved reaction efficiency stemmed from Pt coordination adjustments and a localized SPR effect, supported by ultraviolet-visible (UV-vis), infrared (IR), Raman, and XAFS characterizations. A comparative analysis was conducted with Ni-MOL deposited with platinum NPs, further underscoring the distinct advantages of FePt QDs and corroborating by density functional theory (DFT) calculations, which revealed favorable d-band center properties. These findings offer a promising avenue for the development of highly efficient and stable nanoalloy photocatalysts.

Lead-Free Cs2AgBiBr6/TiO2 S-Scheme Heterojunction for Efficient Photocatalytic Antibiotic Rifampicin Degradation.

Exploring efficient and stable halide perovskite-based photocatalysts is a great challenge due to the balance between the photocatalytic performance, toxicity, and intrinsic chemical instability of the materials. Here, the environmentally friendly lead-free perovskite Cs2AgBiBr6 confined in the mesoporous TiO2 crystal matrix has been designed to enhance the charge carrier extraction and utilization for efficient photocatalytic rifampicin degradation. The as-prepared Cs2AgBiBr6/TiO2 catalyst was stable in air for over 500 days. An S-scheme heterojunction was formed between the (004) plane of Cs2AgBiBr6 and the (101) plane of TiO2 through the Bi-O-Br bonds. The built-in electric field at the interface efficiently promoted the photoinduced charge separation and carrier extraction. The Cs2AgBiBr6/TiO2-200 showed a 92.83% degradation efficiency of rifampicin within 80 min under simulated sunlight illumination (AM 1.5G 100 mW cm-2). This work offers an effective way for the construction of halide perovskite-based photocatalysts with high photocatalytic performance, good stability, and low toxicity simultaneously.

Rational construction of ZnIn2S4/Co3Se4 with boosted photocatalytic hydrogen production through cooperate with S-scheme heterojunction and photothermal effect

The rational design of excellent visible light photocatalysts that efficiently utilize the solar spectrum is urgently needed. In this work, ZnIn2S4 (ZIS) and Co3Se4 (CS) were coupled by a multistep process involving simple ultrasonic self-assembly and calcination to form ZnIn2S4/Co3Se4 (ZIS/CS) photocatalysts with synergistic S-scheme heterojunctions and photothermal effects, which realized efficient photocatalytic hydrogen (H2) production with optimal H2 yield of 2.46 mmol h−1 g−1, superior to pure ZIS (0.47 mmol h−1 g−1) by a factor of 5.23. The excellent cyclic stability and wide environmental adaptability to the ionic environment of water of ZIS/CS were proved. The positive impaction of photothermal effect on the H2 yield of ZIS/CS was investigated and confirmed by the temperature change of photocatalysts powder or photocatalytic system under light irradiation. In addition, based on a series of characterization analyses and first-principle simulation calculations, a charge transfer pathway for ZIS/CS S-scheme heterojunctions was proposed. This work provides valuable ideas and feasible research methods for the design of stable and practical photocatalysts.

Engineering of visible light-activated ZnIn2S4/N-rGO S-scheme heterojunction photocatalyst for H2 generation

The design of S-scheme heterojunction photocatalysts emerges as high-profile candidates for hydrogen (H2) generation. Herein, by integrating heterojunction creation and heteroatom-doping approaches, ZnIn2S4/N-rGO photocatalyst is synthesized using a hydrothermal process. Crystallinity, morphology, surface area, light absorption, interfacial interaction, and charge separation and migration properties of ZnI2S4/Nitrogen-doped reduced graphene oxide (ZnIn2S4/N-rGO) are analytically explored to authenticate its successful construction. Consequently, the H2 generation performance of ZnIn2S4/N-rGO reached 2847 µmolh-1g-1 under visible light illumination, which is about 9.7 and 1.6 times as high as that of ZnIn2S4 and ZnIn2S4/rGO, respectively, with efficient stability. ZnIn2S4/N-rGO exhibits enhancement in the optical response, promotes the surface area, and improves separation and transport of photoexcited electron/hole pairs, attributing to higher H2 generation activity. The S-scheme charge migration mechanism is authenticated through EPR spectra. The current study not only signifies that ZnIn2S4/N-rGO is an excellent photocatalyst for H2 generation but also offers a route to develop outstanding and stable photocatalysts by combining heterojunction creation and heteroatom-doping approaches.

Simple precipitation synthesis and solar light-driven photocatalytic degradation of Ag3PO4 floating photocatalysts

Abstract A highly efficient and stable photocatalyst, Ag3PO4, was prepared using a simple co-precipitation method at room temperature. The precursors used in this process were AgNO3 and K2HPO4. The resulting Ag3PO4 photocatalyst forms irregularly-shaped spheres with diameters ranging from 300 to 1 μm. The shape of the Ag3PO4 photocatalyst slightly changes when different surfactants (PVA, PVP, PEG) are used. The powdered Ag3PO4 photocatalyst exhibits excellent visible light-driven photocatalytic performance. It is capable of decomposing rhodamine B (RhB) as a model pollutant in just 5 min under visible light irradiation. This performance is quite remarkable. Interestingly, Ag3PO4 floating composite sheets have been achieved using polystyrene (PS) and fumed silica Aerosil 200. After three cycles, the decolorization of RhB dyes remains at 87% with the 30% Ag3PO4@PS/Aerosil 200 sheet. This indicates that the Ag3PO4@PS/Aerosil 200 photocatalyst is highly reusable and stable.

Porous hierarchical sphere g-C3N4 with coordinated Co-ions as an efficient and stable self-Fenton photocatalyst for the removal of antibiotic

Photocatalysis-self-Fenton reaction is a promising antibiotics-contaminated wastewater treatment method, but it is still limited by the leakage and sluggish cycling of metal-ions activating sites. Herein, a novel porous hierarchical sphere g-C3N4 with coordinated Co-ions (HCN-Co) was successfully synthesized by a supramolecular modified calcination strategy. The hierarchical sphere structure and coordinated Co-ions of HCN-Co exhibited a synergistic effect on enhancing visible-light absorption, stabilization of Co-ions, charge transfer and surface reaction, which leaded to increased H2O2 generation and activation under visible-light irradiation. Consequently, HCN-Co displayed remarkable and stable photocatalysis-self-Fenton degradation of ciprofloxacin (CIP) with an optimal removal percentage of 99.9 % under visible-light irradiation for 50 min. In this photocatalysis-self-Fenton reaction, H2O2 was generated from 2-step single-e− oxygen reduction reaction and activated to hydroxyl radical (OH) by Co2+ refreshing from interface charge transfer (IFCT) excitation. This work presents a viable approach and provides valuable insights for developing efficient photocatalysis-self-Fenton system for wastewater remediation.

Z-scheme heterojunction Fe-g-C3N4/MoO3-x photocatalyst can effectively activate peroxymonosulfate to degrade humic acid under visible light irradiation

The photo-Fenton-like process is commonly used to degrade organic pollutants in environmental pollution. In this study, a Z-scheme heterojunction Fe-g-C3N4/MoO3-x photocatalyst was prepared by a calcination-hydrothermal two-step method. The results of photo-Fenton-like degradation of humic acid showed that the FCNM-8/PMS/Vis system achieved a degradation activity of 97.42 % for HA (10 mg/L) within 120 min, which was due to the successful construction of a heterojunction between Fe-g-C3N4 and MoO3-x. The efficient charge separation efficiency and abundant oxygen vacancies on the surface contribute to the Fe3+/Fe2+ cycle, thereby improving the PMS activation efficiency. The results of free radical quenching and trapping experiments showed that the active species that played a major role in the degradation of HA by photo-Fenton-like were 1O2 and h+. In addition, the photocatalyst still maintains a removal rate of about 87 % after 5 cycles of repeated use, which means that the prepared sample has good reusability and stability. This work provides a method for designing efficient and stable photocatalysts by constructing heterojunctions and oxygen vacancy regulation strategies.

Synthesis of 9,9′-Bifluorenylidene-Based Porous Aromatic Frameworks (BF-PAFs) for Photocatalytic Production of Hydrogen Peroxide

AbstractPhotocatalytic technology is considered to be a sustainable strategy to convert H2O and O2 into H2O2. However, constructing photocatalytically active and stable organic photocatalyst remain a challenge. In this study, a new class of porous aromatic framework photocatalysts (BF-PAFs) were designed and synthesized, in which 9,9′-bifluorenylidene (99′-BF) and different alkynes are alternately connected. The BF-PAFs were constructed and served as photocatalysts for H2O2 synthesis. Experimental results show that the introduction of different alkynes can effectively regulate the optical band gap and energy band structure, which may further determine their photocatalytic performance. Upon visible light irradiation, PAF-370 exhibits high efficiency for photosynthesis of H2O2 with a production rate of 730 μmol g–1 h–1 in the presence of sacrificial reagent from water and oxygen via oxygen reduction reaction (ORR) pathway. Furthermore, up to 61 μmol H2O2 could be generated from this photocatalytic system after 14 hours.