Separation Of Electron-hole Pairs Research Articles

Facile Synthesis of a Micro–Nano-Structured FeOOH/BiVO4/WO3 Photoanode with Enhanced Photoelectrochemical Performance

In the realm of photoelectrocatalytic (PEC) water splitting, the BiVO4/WO3 photoanode exhibits high electron–hole pair separation and transport capacity, rendering it a promising avenue for development. However, the charge transport and reaction kinetics at the heterojunction interface are suboptimal. This study uses the hydrothermal–electrodeposition–dip coating–calcination method to prepare a microcrystalline WO3 photoanode thin film as the substrate material and combines it with nanocrystalline BiVO4 to form a micro–nano-structured heterojunction photoanode to enhance the intrinsic and surface/interface charge transport properties of the photoanode. Under the condition of 1.23 V vs. RHE, the photoelectric current density reaches 1.09 mA cm−2, which is twice that of WO3. Furthermore, by using a simple impregnation–mineralization method to load the amorphous FeOOH catalyst, a noncrystalline–crystalline composite structure is formed to increase the number of active sites on the surface and reduce the overpotential of water oxidation, lowering the onset potential from 0.8 V to 0.6 V (vs. RHE). The photoelectric current density is further increased to 2.04 mA cm−2 (at 1.23 V vs. RHE). The micro–nano-structure and noncrystalline–crystalline composite structure proposed in this study will provide valuable insights for the design and synthesis of high-efficiency photoelectrocatalysts.

N-defects and P-doping synergistically promote carbon nitride photocatalytic activation of peroxomonosulfate: Triggering the selective generation of 1O2 to degrade 4-Chlorophenol

Metal-based catalyst could be used for efficient peroxymonosulfate (PMS) activation, but inevitably suffered from metal ion leaching. Metal-free graphitic carbon nitride (g-C3N4) materials that can activate PMS are more conducive for practical water treatment. In this study, g-C3N4 with both N-defects and P-doping (CN-NP) was synthesized, which mainly produce singlet oxygen (1O2), and 97 % of 4-CP (4-Chlorophenol) was removed by CN-NP/PMS/Vis reaction system within 60 min. The active species was identified by quenching experiments and electron spin resonance (ESR) tests, and the origin of mainly active species was further verified by the concentration change of PMS during the reaction. It was verified by experiments and theoretical calculations that the introduction of N-defects led to the separation of photoinduced electron-hole pairs and improved photocatalytic activity. Notably, density functional theory (DFT) revealed that both N-defects and P-doping are electron-deficient sites, and P-doping acts as the main PMS adsorption site to promote the loss of electrons from PMS to generate 1O2. In addition, the catalysts developed in this research were anticipated to be applied in real wastewater treatment, contributing to further comprehend the mechanisms of element doping and defect modification in g-C3N4 activating PMS, and providing new insights for the design of PMS-activating catalysts.

3D-micro-flower like [formula omitted] nanoplate solid solution: A facile and rapid room-temperature synthesis with excellent photocatalytic decomposition of antibiotics in water

This research addresses the environmental threat posed by residual antibiotics in water and explores the potential of the photocatalytic process as an eco-friendly solution for antibiotic wastewater treatment. Here in, a series of BiOBr1−xClx nanoplate solid solutions with varied Br:Cl molar ratios were synthesized through a simple co-precipitation method. These solid solutions exhibited superior visible-light-driven photocatalytic activity compared to pristine BiOCl and BiOBr. Notably, the BiOBr0.25Cl0.75 sample demonstrated exceptional performance, achieving 89 % and 99 % degradation efficiency for ciprofloxacin (CIP) and tetracycline hydrochloride (TCH), respectively, within 20 min under optimum conditions. The outstanding performance is attributed to factors such as a large specific surface area, suitable morphology and band gap, effective separation of photo-generated electron-hole pairs, and the presence of meso-size pores in the structure. Thermodynamic studies confirmed the exothermic and spontaneous nature of the photocatalytic reactions. The proposed degradation pathway of CIP and TCH, along with the photocatalytic mechanism, is elucidated. The solid solution, BiOBr1−xClx, exhibits facile recyclability, robust stability, and excellent adaptability to actual aquatic environments, establishing its potential as a promising eco-friendly photocatalyst for antibiotic pollution control.

Multilayer structured bismuth silicate inverse opal film with improved piezo-photocatalytic performance for wastewater purification and dyes removal

Suppressing the recombination of photogenerated charge carriers is thought to be possible by combining the photocatalytic method with the piezoelectric action of piezoelectric semiconductors. A new piezo-photocatalyst, Bi2SiO5 inverse opal film, was prepared by inverse template method. The introduction of 3D ordered inverse opal structure was favorable for light harvesting. The unique two-dimensional layered structure of Bi2SiO5 facilitates electron-hole (e--h+) pair separation. The degradation efficiency of Bi2SiO5 inverse opal film is 15 times higher than that of planar- Bi2SiO5 film under UV light alone. When co-excited by UV light and mechanical energy (ultrasonic vibration), the Bi2SiO5 inverse opal film demonstrated a significantly accelerated degradation rate of RhB compared with planar Bi2SiO5 film. The enhanced piezo-photocatalytic efficiency resulted from the effective separation of photogenerated electron-hole pairs in the Bi2SiO5 inverse opal under the inherent piezoelectric field. Consequently, our work offers fresh perspective on piezo-photocatalytic materials based on Bi2SiO5 for effective wastewater treatment.

Solvothermal synthesis of a flower-like double Z-scheme PANI/Bi2Sn2O7/BiOBr/Ti photoanode and its performance in photocatalytic fuel cell

Photocatalytic fuel cell (PFC) provides a new method to degrade organic pollutants and recover their energy simultaneously. In this work, a novel flower-like hierarchical photoanode (PANI/Bi2Sn2O7/BiOBr/Ti) was synthesized by solvothermal method and assembled with Cu cathode to form a PFC for rhodamine B (RhB) degradation and simultaneous power generation. The crystal structure, chemical composition, and morphology of the photoanode was characterized by a variety of analysis techniques. The photocatalytic activity of the ternary hierarchical composite photoanode was superior to that of single and binary composite photoanodes. Its maximum photocurrent density, maximum power density, degradation rate and FF were 0.241 mA·cm−2, 21.52μW·cm−2, 92.97 % (90 min) and 0.18, respectively. In addition, it still maintains high photocatalytic activity after five consecutive uses. Based on the analysis results of transient photocurrent (i-t), EIS, DRS spectrum, M-S curve and free radical capture experiments, the improvement of photocatalytic performance of PANI/Bi2Sn2O7/BiOBr/Ti photoanode is attributed to the formation of dual Z-scheme heterojunction between PANI and BiOBr and between Bi2Sn2O7 and BiOBr, which realizes the rapid separation and transfer of electron-hole pairs, and retains the strong oxidation of holes in VB of BiOBr and the strong reduction of electrons in LUMO of PANI and CB of Bi2Sn2O7. This study provides a new research idea for the design and construction of high efficiency photoanode in PFC system.

Giant Colloidal Quantum Dot/α-Ga2O3 Heterojunction for High Performance UV-Vis-IR Broadband Photodetector.

Broadband optoelectronics, which extend from the UV to IR regions, are crucial for imaging, autonomous driving, and object recognition. In particular, photon detection efficiency relies significantly on semiconductor properties, such as absorption coefficients and electron-hole pair generation rate, which can be optimized by designing a suitable p-n junction. In this study, we devise giant PbS colloidal quantum dots (G-PbS CQDs) that exhibit high absorption coefficients and broadband absorption. To leverage these exceptional optical properties, we combine G-PbS CQDs with an ultrawide-bandgap semiconductor, α-Ga2O3, and create an efficient G-PbS CQD/α-Ga2O3 heterojunction photodetector that exhibits high performance across the UVC-vis-NIR spectrum range. The resultant heterojunction facilitates efficient electron-hole pair separation at the G-PbS CQD/α-Ga2O3 heterojunction. Furthermore, we utilize transparent graphene electrodes to overcome the limitations of conventional transistor-type device structures and the substantial optical losses induced by opaque metal electrodes. This strategy maximizes the light-collection area and results in an approximately 3-orders of magnitude higher responsivity (55.5 A/W) and specific detectivity (1.66 × 1013 Jones) compared to devices with opaque metal electrodes.

Synthesis of CuOQDs/g-C3N4/C Composites Via Stem Template Induction and their Photocatalytic Properties

Introduction: The synthesis of bio-templated porous CuOQDs/g-C3N4/C composites with controllable morphology and suitable energy band structure was successfully carried out via a simple thermal condensation and hydrothermal method. Method: Dicyandiamide and cadmium chloride were selected as starting materials, while Hollyhock stem was chosen as the biological template. The results indicated that, in comparison to pure g-C3N4, g-C3N4/C had a rich porous structure and better-photogenerated carrier separation efficiency. The CuOQDs were anchored evenly on the surface of the g-C3N4, thus resulting in the formation of a greater number of reactive sites. Results: The type-Z heterojunction formed between the CuOQDs and g-C3N4/C reduced the energy required for electron transition, thereby facilitating the separation of photo-generated electronhole pairs. The highest photocatalytic degradation efficiency of CuOQDs/g-C3N4/C for tetracycline (TC) was 65.1%, which was 3.3 times that of pure g-C3N4. Conclusion: In the photocatalytic process, the main reactive species is O2−. The CuOQDs/g- C3N4/C synthesized by stem induction in multi-phase heterojunction form has a stable microstructure to improve the charge separation efficiency. Further, it represents practical photocatalytic environmental protection.

Graphene quantum dot modified Bi2MoO6 nanoflower for efficient degradation of BPA under visible light

Graphene quantum dots (GQDs) are a novel type of carbon dot material that has significant application value in the field of catalysis due to their non-toxic, stable, abundant surface functional groups, and quantum confinement effects. A unique composite photocatalyst was constructed by modifying GQDs onto Bi2MoO6 (BMO) microsphere-shaped nano petals using simple hydrothermal and sintering techniques. The structural and morphological characterization results indicate that GQDs with size of 10 ​nm are well dispersed on BMO nanosheets, forming close contacts, which can greatly improve the separation efficiency of photo-generated electron-hole pairs under visible light irradiation. In the evaluation of the catalytic performance of BPA solution (20 ​mg/L) with a catalyst content of 20 ​mg under a simulated light source with a power of 300 ​W, the best degradation performance was achieved by a photocatalyst (G6/BMO) with the GQDs mass ratio of 6 ​%, which degraded over 95 ​% of BPA under visible light within 120 ​min, while pure BMO only degraded about 45 ​% of BPA during the same time period. Even if the 400 ​nm filter is removed and directly exposed to Xe lamp radiation, the degradation performance of the optimal composite catalyst is only slightly improved, indicating that the current GQDs/BMO composite catalyst has extremely strong visible light catalytic activity. The improvement of catalytic performance comes from the effective separation of electron-hole pairs caused by the absorption of electrons by GQDs, and the introduction of GQDs to reduce the band gap and enhance visible light absorption, both of which are beneficial for catalytic reactions. Free radical capture and electron spin resonance (ESR) tests indicate that ·OH and ·O2− are the main active species for BPA degradation. Although the current GQDs/BMO catalysts have a simple structure, their catalytic performance has significantly improved, which will guide the design of other semiconductor based photocatalysts.

Pt loaded CoFe2O4-based nanoparticles for breast cancer treatment with chemodynamic therapy and sonodynamic therapy

Breast cancer is one of the most widespread cancers worldwide in the female population. However, the side effects and toxicity of chemotherapy and radiotherapy are the obstacles to the treatment of breast cancer. Therefore, we developed a Pt loaded CoFe2O4-based nanoparticles (CF@Pt) for breast cancer treatment with chemodynamic therapy (CDT) and sonodynamic therapy (SDT). The Co2+/Co3+ and Fe2+/Fe3+ gave CF@Pt peroxidase-like activity and catalase activity to gain ·OH and O2 in the tumor microenvironment (TME) for CDT. Furthermore, the separation of electron-hole pairs of CF@Pt transferred the O2 into 1O2 in the presence of ultrasound (US) for SDT. The high level of O2 generated by CDT would produce more 1O2 by SDT that promoted the CDT efficiency. Moreover, the addition of Pt limited the recombination of electron-hole pairs and reduced the energy gap to enhance SDT/CDT combination therapy. In addition, CF@Pt could be engulfed by MDA-MB-231 cells and induced the apoptosis while it had good biocompatibility and blood compatibility. This design provided a novel application on the treatment of breast cancer.

Solar-driven induced photoelectron remember effect involved in core–shell NiCo2S4@Ni3V2O8 composite electrode with superior electrochemical energy storage for asymmetric supercapacitor

Photo-assisted supercapacitor systems offer a compelling approach to effectively harnessing both solar and electrical energy. In this study, the core–shell heterostructure NiCo2S4@Ni3V2O8 (NCS@NVO) was successfully synthesized for the development of photosensitive supercapacitor electrodes. NCS@NVO demonstrated a pronounced photoelectron memory effect under illumination, attributed to the solar-driven contributions of both NCS and NVO, as photon absorption facilitated electron-hole pair separation and transport. Compared to the specific capacitance in the dark (2292F g−1 at 1 A g−1), the capacitance of the NCS@NVO composite electrode increased dramatically to 3025F g−1 when exposed to light. Moreover, the capacitance retention rate remained remarkably high at 99.83 % after 10,000 cycles at 20 A g−1. In addition, the NCS@NVO hybrid supercapacitor achieved an outstanding energy density of 63.56 W h kg−1 under illumination, alongside a power density of 789.84 W kg−1. This study thoroughly investigated the solar-induced photoelectron memory effect in the NCS@NVO composite electrode for asymmetric supercapacitors, paving the way for the design of high-performance photosensitive nano-electrodes in advanced electrochemical energy storage applications.

Photoresponse enhanced CsPbBr3 quantum dots quantum-confined in mesoporous PCN-600 single crystal microwires

In this work, the CsPbBr3 quantum dots (QDs) are encapsulated into the mesoporous iron-based metal-organic framework (PCN-600) by using a two-step solvothermal method. The success formation of CsPbBr3@PCN-600 composite is confirmed via SEM, TEM, XRD, FTIR, EDS and other measurements. Besides, the characterization of fluorescence lifetime of CsPbBr3@PCN-600 composite reveals the presence of the electron transfer between PCN-600 and CsPbBr3 QDs. Especially, CsPbBr3@PCN-600 exhibits a prominent emission peak at 473 nm due to the quantum confinement effect, and the photoluminescence quantum yield of CsPbBr3 QDs protected by the mesoporous PCN-600 increases to 71 % compared to 52 % of the pristine CsPbBr3 QDs. Also, the protection of CsPbBr3 QDs by the PCN-600 channel enhances the luminescence stability, thermal stability and blue-light stability of CsPbBr3. In fact, under light illumination, the photogenerated carriers from the encapsulated CsPbBr3 QDs could be captured by catalytically active sites on the inner surface of the PCN-600 channel. This charge capture effect can increase the photocurrent and implies much effective separation of electron-hole pairs of the CsPbBr3@PCN-600 composite. These results make this composite a promising candidate for high-performance photoelectronic devices.

Ambient Air-Synthesized CsPbBr3 Nanocrystals Coupled with TiO2 Film as an Efficient Hybrid Photoanode for Photoelectrochemical Methanol-to-Formaldehyde Conversion.

Due to its exceptional optoelectronic properties in the visible spectrum, cesium lead bromide (CsPbBr3) perovskite has attracted considerable attention in solar-driven organic transformations via photoelectrochemical (PEC) cells. However, the performance of the devices is adversely affected by electron-hole recombination occurring between a transparent conductive substrate, such as fluorine-doped tin dioxide (FTO), and a perovskite layer. Herein, to mitigate this issue, a compact layer of titanium dioxide (TiO2) was employed as both an electron transport layer and a hole blocking layer to diminish charge recombination while facilitating electron transfer in such perovskite material. At the oxidation peak potential of 0.70 V vs Ag/AgNO3, a hybrid photoanode of CsPbBr3/TiO2/FTO exhibited a significant increase in photocurrent density, from 15 to 41 μA/cm2, compared to a configuration without a TiO2 layer. Furthermore, the introduction of methanol as a hole scavenger in the PEC system using the hybrid photoanode facilitated the separation of electron-hole pairs, which led to an enhanced photocurrent density of 60 μA/cm2 and promoted the production of formaldehyde. High-performance liquid chromatography (HPLC) confirmed the generation of formaldehyde at a concentration of 26.69 μM with a Faradaic efficiency of 92% under an applied potential of 0.50 V vs Ag/AgNO3 for 60 min of PEC reaction. In addition to the enhanced PEC performance achieved from this hybrid photoanode, CsPbBr3 nanocrystals (NCs) in this work were synthesized by the modified one-pot method under ambient air, where highly uniform and high-purity NCs were obtained. This work signifies the groundbreaking exploration of CsPbBr3 NCs with TiO2 as a photoelectrode material in the organic-based PEC cells, which efficiently improved the interfacial charge transfer within the photoanode for the conversion of methanol to formaldehyde, marking a significant advancement in the field.

Green Engineered CuO/SnO2/HNT Composites: Illuminating the Photocatalytic Path for Organic Pollutant Remediation and Zebrafish Embryo Toxicity Evaluation.

Photocatalysis stands out as a promising technique for treating organic contaminants, yet the quest for visible light active composite materials, crafted through cost-effective, eco-friendly, and uncomplicated processes, poses formidable challenges. Here, we introduce a successful endeavor, the synthesis of a CuO/SnO2 (CS) composite via a microwave method, employing Carissa edulis fruit extract as a reducing as well as capping agent. Various loadings of CS-HNT composites were prepared by ultrasonically incorporating CS onto nanotubular halloysite (HNT) clay. Employing a suite of types of characterization, including XRD, XPS, FT-IR, FE-SEM, HR-TEM, ζ potential, UV-vis-DRS, TGA, BET, and EIS, we meticulously explored the morphology, structure, stability, surface area, electrochemical, and optical properties of the developed CS-HNT composites. HR-TEM observations unveiled the formation of a heterojunction between cubic CuO and spherical SnO2 on the HNT clay surface. Optical and EIS analysis highlighted that the 20CS-HNT composite displayed significant absorption in the visible region, efficient electron-hole pair separation, and enhanced interfacial charge transport relative to other loadings. Photocatalytic evaluations and optimization studies revealed that the 20CS-HNT photocatalyst achieved notable removal efficiencies, eliminating 85% of Congo red (CR) and 80% of tetracycline (TC) within 90 min and 74% of ATZ in 3 h under visible light conditions. Scavenging investigations, the fluorescence probe method, and a NBT transformation study underscored the pivotal roles of hydroxyl and superoxide radicals in pollutant removal. The reusability trials highlighted the exceptional stability and recyclability of the photocatalyst, even after five cycles. In addition, zebrafish embryo toxicity tests revealed improved survival and hatching rates in photocatalyst-treated samples compared to those of controls. Moderate toxicity was observed in treated TC, while the treated CR sample showed non-lethal toxicity. In essence, this study unveils a straightforward and efficacious approach for developing photocatalysts for large-scale wastewater treatment. Furthermore, it proposes the adoption of safe clay-based bimetal oxide photocatalysts in diverse environmental applications.

Visible-light-driven photocatalytic degradation of HCBD using BP/TiO2/CN: Enhanced mechanisms, ecological risks, and management insights

BPNS have attracted significant attention due to their outstanding photocatalytic performance. However, their practical application is often limited by rapid charge recombination. This study introduces a BP/TiO2/CN ternary heterojunction (P-N) that is constructed by sequentially depositing semiconductor materials with varying band gaps onto a single substrate. The composite consisting of 5 mg BP, 30 %TiO2, and 10 %CN (BTC-1) exhibited remarkable pollutant degradation under visible light, achieving a 95 % removal rate for HCBD (50 ppb, 200 mL) within 150 min. This enhanced performance can be attributed to an increase in adsorption sites, improved light absorption, and the effective separation of electron-hole pairs. The degradation mechanism indicates that the removal of HCBD involves de-chlorination and radical attack on its CC bonds. Electrons from the conduction band of BPNS migrate to CN and subsequently to TiO2, with CN acting as a bridging layer. Simultaneously, holes from the valence band of TiO2 transfer to CN and ultimately reach BPNS, thereby enhancing charge separation. The proposed photocatalytic mechanism suggests that ·OH and ·O2−play crucial roles in HCBD degradation, with ·OH being the primary active species. Using TEST software (QSAR method), it was determined that the intermediate degradation products of HCBD are primarily small molecules and ions, which exhibit significantly reduced toxicity and lower ecological risks. This study highlights the practical application potential of BTC-1 in HCBD removal, emphasizing economic benefits and providing insights into the synergistic effects of non-metallic catalysts. Furthermore, it offers a deeper understanding of the mechanisms underlying HCBD degradation, along with new perspectives on toxicity assessment and environmental management of HCBD.

Efficient visible-light-driven photocatalytic degradation of indoor formaldehyde using an indium-based MOF/graphene oxide composite

Formaldehyde (HCHO) severely degrades indoor air quality, and conventional remediation methods are often inadequate for addressing low concentrations of HCHO indoors. In this study, we synthesized a MIL-68(In)-NH2/graphene oxide (GO) composite using a solvothermal method, aimed specifically at enhancing the photocatalytic degradation of HCHO under visible light. Our results show that the integration of GO enhances visible light absorption and facilitates efficient electron transport, significantly improving photocatalytic performance. The MIL-68(In)-NH2/GO composite achieves a 77 % degradation rate of HCHO, significantly outperforming MIL-68(In)-NH2 (51 %) and GO (22 %) alone. This enhanced activity is attributed to the effective separation of electron-hole pairs and synergistic interactions within the composite. We proposed an enhanced photocatalytic mechanism for the MIL-68(In)-NH2/GO system, identifying h+ and •O2– as the principal active species. Moreover, the MIL-68(In)-NH2/GO composite shows excellent reusability and stability, making it a promising candidate for eco-friendly and efficient indoor air purification using metal–organic frameworks.

Construction of Ag-modified ZnO/g-C3N4 heterostructure for enhanced photocatalysis performance.

ZnO/g-C3N4 heterojunction modified with Ag nanoparticles (ZnO/CN/Ag) was synthesized by depositing ZnO nanorods/Ag nanoparticles onto g-C3N4 nanosheets. Under xenon lamp irradiation, 99% of Rhodamine B (RhB) was degraded by ZnO/CN/Ag-5% composite within 30min, which was much higher than the degradation efficiency of ZnO and ZnO/CN. The synergistic effect of g-C3N4 and ZnO, along with the localized surface plasmon resonance effect of Ag NPs, contributes to the improvement of photocatalytic performance. Ag nanoparticle provides another charge transfer path from g-C3N4 to ZnO, which speeds up the separation of electron-hole pairs. Meanwhile, the catalyst had good stability and recyclability. Finite-difference time-domain method and the density functional theory were used to obtain the charge transfer process. The photodegradation process has been studied in depth.

Reducing Dielectric Confinement Effect Enhances Carrier Separation in Two-Dimensional Hybrid Perovskite Photocatalysts.

Two-dimensional organic-inorganic hybrid perovskites (OIHPs) with alternating structure of the organic and inorganic layers have a natural quantum well structure. The difference of dielectric constants between organic and inorganic layers in this structure results in the enhancement of dielectric confinement effect, which exhibits a large exciton binding energy and hinders the separation of electron-hole pairs. Herein, a strategy to reduce the dielectric confinement effect by narrowing the dielectric difference between organic amine molecule and [PbBr6]4- octahedron is put forward. The Ethanolamine (EOA) contains hydroxyl groups, resulting in the positive and negative charge centers of O and H non-overlapping, which generated a larger polarity and dielectric constant. The reduced dielectric constant produces a smaller exciton binding energy (71.03 meV) of (C2H7NO)2PbBr4 ((EOA)2PbBr4) than (C8H11N)2PbBr4 ((PEA)2PbBr4 (156.07 meV), and promotes the dissociation of electrons and holes. The increasing of lifetime of photogenerated carrier in (EOA)2PbBr4 are proved by femtosecond transient absorption spectra. Density functional theory (DFT) calculations have also indicated that the small energy shift of the total density of states (DOS) between the C/H/N and the Pb/Br in (EOA)2PbBr4 favors the separation of electrons and holes. In addition, this work demonstrates the application of (PEA)2PbBr4 and (EOA)2PbBr4 in the field of photocatalytic CO2 reduction.

Fabrication of novel adsorptive photocatalyst GQDs/Sn3O4 for highly efficient synergistic removal of U(Ⅵ)

Developing economically efficient adsorption-photocatalysis bifunctional uranium-containing wastewater treatment agents is significant for environmental remediation and governance. In this study, a novel adsorptive photocatalyst based on low-cost hybrid GQDs/Sn3O4 nanocomposite (GSO) was fabricated using a one-step hydrothermal method for highly efficient synergistic uranium removal. The batch adsorption experiments revealed that the adsorption process of GSO-15 on U(VI) matched the pseudo-second-order model and Langmuir isotherm, with a maximum Langmuir adsorption capacity (qmax) of 226.51 mg·g−1 at pH 6.0. In addition, U(VI) reduction by GSO-15 under visible light irradiation demonstrated excellent photocatalytic performance, while the optimal removal rate of U(VI) by synergistic adsorption-photoreduction was up to 99.67 %, which was significantly higher than that of physicochemical adsorption. Furthermore, the mechanism of GSO-15 photoreduction of U(VI) was explored through various methods, indicating that the photocatalytic performance was primarily attributed to its strong visible light absorbability, narrow bandgap, and efficient separation and transfer of photoinduced electron-hole pairs. After five cycles of photocatalytic reduction desorption, the removal rate remained above 95 %, indicating excellent structural stability and considerable recyclability. The decrease in the removal rate was negligible in the presence of coexisting metal ions. This study provides novel insights into the design and fabrication of efficient adsorptive photocatalytic materials for treating radioactive uranium-containing wastewater.

Fabrication of pyridine incorporated and O-doped g-C3N4/COF: A type-II heterojunction for enhanced hydrogen production under visible light irradiation

The fabrication of heterojunction photocatalysts is important for achieving highly efficient electron transfer, charge separation, and catalytic activity. In this study, we report the successful creation of a type II heterojunction between pyridine incorporated and O-doped g-C3N4 (POCN) and a covalent organic framework (COF). The heterojunction formation significantly reduced the fluorescence intensity of the POCN/COF, indicating effective separation of electron-hole pairs. Additionally, POCN/COF demonstrated excellent interface charge transfer resistance and photocurrent response. Its hydrogen production rate was remarkably high at 3500 μmol g⁻1 h⁻1, about 1.6 times that of pure COF (2200 μmol g⁻1 h⁻1) and 3.5 times that of the physical mixture (1000 μmol g⁻1 h⁻1), and it also exhibited enhanced stability. This indicates that it can be effectively fabricated into a heterojunction of POCN and COF. The optimal value for adding POCN was approximately 5 wt% of COF. This demonstrates greater activity compared to other composite catalysts made from graphitic carbon nitride and COF. This study presents a valuable approach for fabricating reusable heterojunction photocatalytic systems and efficiently generating hydrogen from natural energy sources.

Efficient Catalytic Production of Reactive Oxygen Species through Piezoelectricity in Bismuth Sulfide Rich in Sulfur Vacancies.

Sulfur (S) vacancies in metal sulfides are of interest in electrocatalysis and photoelectronics, but their effect on the generation of reactive oxygen species (ROS) during mechanical catalysis is unclear. This study investigates the impact of S-vacancies in defective bismuth sulfide (Bi2S3-x) on ROS production under ultrasonic irradiation and organic contaminant decomposition. S-vacancies disrupt the centrosymmetric structure of intrinsic Bi2S3, inducing piezoelectric effects and enhancing the electrical energy in Bi2S3-x. The positively charged S-vacancies in Bi2S3-x promote the separation of ultrasound-activated electron-hole pairs by capturing electrons. As a result, the optimal rate of H2O2 formation and the reaction rate constant for degrading Rhodamine B dye on Bi2S3-x are found to be 1.9 and 37 times higher, respectively, than those on Bi2S3 under ultrasonic irradiation. The nonzero catalytic efficiency in centrosymmetric Bi2S3 is due to the flexoelectric catalytic effect from nonuniform strain. These results guide the piezocatalyst design and elucidate mechanical catalysis mechanisms.