Photocatalytic Process Research Articles

Removal of Cr(VI) by coupled adsorption and photocatalytic degradation based on Ag/ZIF-8/PVDF membrane

In order to reduce the hazard of the heavy metal chromium, the reduction of Cr from Cr(VI) to Cr(III) for further removal was applied in this study. ZIF-8 modified with Ag was used as the photo-catalyst, and adsorption and degradation were further enhanced by deep penetration through in situ growth of Ag/ZIF-8 in the pores of polyvinylidene fluoride (PVDF) membrane. The composite Ag/ZIF-8/PVDF membrane was characterized by XRD, BET, SEM-EDS, UV-Vis and XPS, and the results proved that the nanoparticles of ZIF-8 and Ag were uniformly distributed inside the membrane pores. The removal efficiency of Cr(VI) was enhanced by 78% after modification of Ag nanoparticles on the ZIF-8 surface, and further enhanced by 68% after loading the composite particles (Ag/ZIF-8) into the PVDF membrane. Moreover, the removal mechanism was investigated by free radical trapping experiments, and the results showed that O2·- was the main factor in the photo-catalytic process, followed by ·OH. The results indicated that enhancement of coupled adsorption-degradation process by deep permeation is a feasible approach to improve the heavy metal removal performance due to the dispersive and domain-limiting effects of membrane pores. Ag/ZIF-8/PVDF material is expected to be applied in the field of practical Cr(VI)-containing industrial wastewater treatment.

Construction of a self-floating fabric based on CVD-assisted coating and its application in interfacial evaporation

The discharge of industrial wastewater and the shortage of fresh water resources are increasingly endangering human daily life. In this experiment, bismuth oxychloride with oxygen vacancies was attached to a fabric surface using the solution deposition method, and then perfluoro-trichlorosilane was grafted on the surface to prepare a multifunctional superhydrophobic fabric. After mechanical stability testing, the fabric retained a water contact angle that consistently exceeded 150°, which could realize the selective adsorption of insoluble oil such as cyclohexane. Through a capture experiment of active species, the conclusion drawn was that holes (h+) and superoxide free radicals (·O2−) were primary active species for the photocatalytic degradation process. After 4 cycles of photodegradation, the degradation efficiency could still reach 92.8 %, showing excellent cyclic degradation stability. An interfacial solar steam generator (ISSG) was assembled using the superhydrophobic fabric as the support layer and a polypyrrole sponge as the photothermal layer, whose evaporation efficiency under one sun reached 2.8376 kg·m−2·h−1, with a photothermal conversion efficiency of 92.255 %. This ISSG demonstrates excellent wastewater purification capabilities. Interfacial evaporation devices show promising prospects in solar-powered wastewater purification, which further expand the use of interfacial evaporation to solve the problem of water scarcity.

Effect of surface iodine atom on dissolved oxygen activation for enhanced photocatalytic advanced oxidation processes over Bi2WO6 nanosheet

Effect of surface iodine atom on dissolved oxygen activation for enhanced photocatalytic advanced oxidation processes over Bi2WO6 nanosheet

Advanced environmental remediation using enhanced performance of hollow ZnO@SnIn4S8 core-shell nanorod arrays for hazardous ion and organic pollutant removal.

Herein, novel hollow ZnO and ZnO@SnIn4S8 core-shell nanorods (NRs) with controlled shell thickness were developed via a facile synthesis approach for the efficient photocatalytic remediation of organic as well inorganic water pollutants. The introduction of SnIn4S8 shell layer coating over ZnO enhances visible light absorption, efficient exciton-mediated direct charge transfer, and reduces the band gap of ZnO@SnIn4S8 core-shell nanorods. The ZnO@SnIn4S8 core-shell nanorods show efficient solar-light driven catalytic efficiency for the disintegration of industrial dye (orange G), degradation of tetracycline, and reduction of hazardous Cr (VI) ions in aquatic systems. The measured photocurrent density of ZnO@SnIn4S8 core-shell NRs under illumination of simulated solar light was about nine times higher than ZnO NRs. It has been revealed that charge transfer resistance (RCT) of ZnO@SnIn4S8 core-shell NRs was doubled after the illumination of solar light. The developed ZnO@SnIn4S8 core-shell NRs photocatalyst efficiently decontaminate about 99.8±02, 99.98±0.01, and 99.8% of methyl orange, tetracycline, and Cr(VI), respectively. Notably, under similar conditions, ZnO was able to display efficiencies of 29.3±0.6, 27.08±1.1 and 31.1±6.3 % of methyl orange, tetracycline, and Cr(VI), respectively. It was also noted that •O2‾, •OH radical, and holes were majorly contributed in the photocatalysis process for disintegration of industrial dye (orange G), tetracycline and finally transform to water and carbon dioxide. Overall, this work explores an intense insight and a novel idea for a hollow core-shell nanocomposite for photocatalytic reduction of diverse pollutants.

Recent Progress in Advanced Catalytic Strategies for C─F Bond Cleavage in Waste Refrigerants: A Review

AbstractThe degradation of fluorinated refrigerants, known for their highly stable carbon‐fluorine (C─F) bonds, poses significant environmental and technical challenges. This review addresses these challenges by analyzing two core degradation mechanisms: molecular polarization (MP) and free radical attack (FRA), and exploring their applications in thermal catalytic and photocatalytic processes. MP redistributes electron density to weaken C─F bonds, facilitating adsorption and bond cleavage, while radical attack involves reactive species that directly break chemical bonds. However, both mechanisms have limitations: MP alone may lack the kinetic drive for dissociation, and radical‐based methods often suffer from low selectivity, short radical lifetimes, and the formation of toxic intermediates. The section on thermal catalytic degradation discusses how elevated temperatures enhance bond cleavage through MP, addressing adsorption challenges and accelerating dissociation. The part on photocatalytic degradation focuses on the role of light‐activated processes in generating reactive radicals and facilitating bond breaking, with an emphasis on visible and ultraviolet light‐driven reactions. The review concludes by exploring the potential of hybrid catalytic systems that combine thermal and photocatalytic processes, providing insights into the complementary use of these mechanisms for the degradation of persistent fluorinated compounds.

Three New Multifunctional Supramolecular Compounds Based on Keggin-Type Polyoxoanions and 3,5-di(1H-Imidazol-1-yl)benzoic Acid: Syntheses, Structures, and Properties

Three new inorganic-organic hybrid compounds, (H3DIBA)2·SiMo12O40·H2O (1), (H3DIBA)2·SiW12O40·H2O (2), and [(H2DIBA)(H3DIBA)]·PMo12O40·2H2O (3) (HDIBA = 3,5-di(1H-imidazol-1-yl)benzoic acid) were synthesized by the hydrothermal method. The structures were characterized by single-crystal X-ray diffraction, elemental analysis, powder X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. These three compounds are all 3D supramolecular structures formed by Keggin-type polyoxometalate anions and HDIBA through intermolecular weak interactions, which have been studied via Hirshfeld surface analysis. The electrochemistry properties of 1 and 3 have been studied, including cyclic voltammetric behaviors and electrocatalytic properties. The study on the removal of organic dye pollutants in water showed that compounds 1 and 3 had an adsorption effect on cationic dye RhB, and the adsorption process conforms to the Langmuir isotherm model. Compound 2 can photocatalytically degrade cationic organic dyes RhB, MB, and CV, and the photocatalytic mechanism study indicates that h+ plays a major role in the photocatalytic process.

Fine-tuning d-p hybridization in Ni-Bx cocatalyst for enhanced photocatalytic H2 production

The H2-evolution kinetics play a pivotal role in governing the photocatalytic hydrogen-evolution process. However, achieving precise regulation of the H-adsorption and H-desorption equilibrium (Hads/Hdes) still remains a great challenge. Herein, we propose a fine-tuning d-p hybridization strategy to precisely optimize the Hads/Hdes kinetics in a Ni-Bx modified CdS photocatalyst (Ni-Bx/CdS). X-ray absorption fine-structure spectroscopy and theoretical calculations reveal that increasing B-atom amount in the Ni-Bx cocatalyst gradually strengthens the d-p orbital interaction between Ni3d and B2p, resulting in a consecutive d-band broadening and controllable d-band center on Ni active sites. The above consecutive d-band optimization allows for precise modulation of the Hads/Hdes dynamics in the Ni-Bx/CdS, ultimately demonstrating a remarkable H2-evolution activity of 13.4 mmol g-1 h-1 (AQE = 56.1 %). The femtosecond transient absorption spectroscopy further confirms the rapid electron-transfer dynamics in the Ni-Bx/CdS photocatalyst. This work provides insights into the optimal design of prospective H2-evolution catalysts.

Optimizing photocatalysis via electron spin control.

Solar-driven photocatalytic technology holds significant potential for addressing energy crisis and mitigating global warming, yet is limited by light absorption, charge separation, and surface reaction kinetics. The past several years has witnessed remarkable progress in optimizing photocatalysis via electron spin control. This approach enhances light absorption through energy band tuning, promotes charge separation by spin polarization, and improves surface reaction kinetics via strengthening surface interaction and increasing product selectivity. Nevertheless, the lack of a comprehensive and critical review on this topic is noteworthy. Herein, we provide a summary of the fundamentals of electron spin control and the techniques employed to scrutinize the electron spin state of active sites in photocatalysts. Subsequently, we highlight advanced strategies for manipulating electron spin, including doping design, defect engineering, magnetic field regulation, metal coordination modulation, chiral-induced spin selectivity, and combined strategies. Additionally, we review electron spin control-optimized photocatalytic processes, including photocatalytic water splitting, CO2 reduction, pollutant degradation, and N2 fixation, providing specific examples and detailed discussion on underlying mechanisms. Finally, we outline perspectives on further enhancing photocatalytic activity through electron spin manipulation. This review seeks to offer valuable insights to guide future research on electron spin control for improving photocatalytic applications.

Degradation of Bisphenol A and Pyrocatechol in the Photocatalytic System in the Presence of Fe3O4@SiO2@PAEDTC‐Doped MIL‐101 (Fe) Under Visible and UV and Sunlight Irradiation

ABSTRACTIn this investigation, a novel core‐shell photocatalyst, denoted as Fe3O4@SiO2/PAEDTC (FSP)‐doped MIL‐101 (Fe) (FSPM), was synthesized through the sol–gel method and applied for the degradation of bisphenol A (BPA) and pyrocatechol (PCT) in aqueous solutions. Various analytical techniques were employed to assess the characteristics of the core‐shell photocatalyst. The resultant nanocomposite displayed specific attributes, including a saturation magnetization of 12 emu/g, a pore size of 1.35 nm, and a surface area of 992 m2/g, allowing for facile separation using a magnetic field. The optimal conditions for achieving highest BPA (%94.2) and PCT (%100) degradation efficiencies were found to be a pH of 7, 50 mg/L pollutant, a nanocomposite quantity of 0.8 g/L, and a radiation intensity of 8 W after 1 h. The BOD5/COD (biological oxygen demand during 5 days/chemical oxygen demand) ratio exceeded 0.4, accompanied by total organic carbon (TOC) and COD removal rates surpassing 85%. The tests conducted on scavenging suggested the formation of •OH, hole, and electron in the studied system. Among these, •OH was found to be the foremost species responsible for degrading BPA and PCT. Stability tests revealed that the photocatalyst could be recycled with a minimal reduction of only 7% during five reaction steps. The energy consumed by the system during different reactions ranged from 10.2 to 27.1 kWh/m3 for BPA degradation and from 10.9 to 29.4 kWh/m3 for PCT degradation at time of 10 to 60 min. Finally, the results of this study showed that the use of all three sources of radiation in the photocatalytic process can effectively destroy pollutants.

Efficient Photocatalytic Water Purification Through Novel Janus-Nanomicelles with Long-Lived Charge Separation Properties.

Although the design of photocatalysts incorporating donor-acceptor units has garnered significant attention for its potential to enhance the efficiency of the photocatalysis process, the primary bottleneck lies in the challenge of generating long-lived charge separation states during exciton separation. Therefore, a novel Janus-nanomicelles photocatalyst is developed using carbazole (Cz) as the donor unit, perylene-3,4,9,10-tetracarboxydiimide (PDI) with long-excited state as the acceptor unit and polyethylene glycol (PEG) as the hydrophilic segment through ROMP polymerization. After optimizing the ratio, Cz19-PDI18-PEG10 rapidly adsorbs bisphenol A (BPA) within 10 s through π-π interaction, hydrogen-bonding interaction, and hydrophobic interaction between BPA and hydrophobic blocks when exposed to aqueous humor and efficiently photodegrades BPA (50ppm) within 120min for water purification purposes due to its long-lived charge separation state and achieving the highest reported efficiency so far. Mechanistic studies have shown that this excellent performance of Cz19-PDI18-PEG10 can be attributed to synergistic interactions between highly efficient adsorption capacity and long-lived charge separation states during photocatalysis. This novel Janus-nanomicelles design strategy holds promise as an effective candidate for water purification.

Self-Assembly Strategy for Synthesis of WO3@TCN Heterojunction: Efficient for Photocatalytic Degradation and Hydrogen Production via Water Splitting.

Herein, a WO3@TCN photocatalyst was successfully synthesized using a self-assembly method, which demonstrated effectiveness in degrading organic dyestuffs and photocatalytic evolution of H2. The synergistic effect between WO3 and TCN, along with the porous structure of TCN, facilitated the formation of a heterojunction that promoted the absorption of visible light, accelerated the interfacial charge transfer, and inhibited the recombination of photogenerated electron-hole pairs. This led to excellent photocatalytic performance of 3%WO3@TCN in degrading TC and catalyzing H2 evolution from water splitting under visible-light irradiation. After modulation, the optimal 3%WO3@TCN exhibited a maximal degradation rate constant that was twofold higher than that of TCN alone and showed continuous H2 generation in the photocatalytic hydrogen evolution. Mechanistic studies revealed that •O2- constituted the major active species for the photocatalytic degradation of tetracycline. Experimental and DFT results verified the electronic transmission direction of WO3@TCN heterojunction. Overall, this study facilitates the structural design of green TCN-based heterojunction photocatalysts and expands the application of TCN in the diverse photocatalytic processes. Additionally, this study offers valuable insights into strategically employing acid regulation modulation to enhance the performance of carbon nitride-based photocatalysts by altering the topography of WO3@TCN composite material dramatically.

Electron Push-Pull Effect of Benzotrithiophene-Based Covalent Organic Frameworks on the Photocatalytic Degradation of Pharmaceuticals and Personal Care Products.

A covalent organic framework (COF) has emerged as a promising photocatalyst for the removal of pharmaceutical and personal care product (PPCP) contaminants; however, high-performance COF photocatalysts are still scarce. In this study, three COF photocatalysts were successfully synthesized by the condensation of benzo[1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarbaldehyde (BTT) with 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT), 1,3,5-Tris(4-aminophenyl)benzene (TAPB), and 4,4',4''-nitrilotris(benzenamine) (TAPA), namely, BTT-TAPA, BTT-TAPB, and BTT-TAPT, respectively. The surface areas of BTT-TAPA, BTT-TAPB, and BTT-TAPT were found to be 800.46, 1203.60, and 1413.58 cm2∙g-1, respectively, providing abundant active sites for photocatalytic reactions. Under visible-light irradiation, BTT-TAPT exhibited the highest removal rate of tetracycline (TC), reaching 82.7% after 240 min. The superior photocatalytic performance of BTT-TAPT was attributed to its large specific surface area and the strong electron-acceptor properties of the triazine group. Electron paramagnetic resonance capture experiments and liquid chromatograph mass spectrometer analysis confirmed that superoxide radicals played a pivotal role in the degradation of TC and ciprofloxacin. Moreover, BTT-TAPT exhibited high stability and reproducibility during the photocatalytic degradation process. This study confirms that BTT-based COFs are a class of promising photocatalysts for the degradation of PPCPs in water, and their performance can be further optimized by tuning the structure and composition of the frameworks.

Two Novel Viologen/Polyoxometalate‐Based Compounds for the Efficient Photocatalytic Reduction of Cr (VI) Under Visible Light Irradiation

ABSTRACTDesigning efficient photocatalyst has attracted extensive attention for treating polluted wastewater containing Cr (VI). In this work, two viologen/polyoxometalate (POM)‐based compounds were synthesized, [Ni (mimb)2(H2O)4(β‐Mo8O26)]·4H2O (1) and [Zn (mimb)2(H2O)4(β‐Mo8O26)]·4H2O (2) (mimb = 1‐((3,5‐dimethylisoxazol‐4‐yl)methyl)‐[4,4′‐bipyridin]‐1‐ium), through a hydrothermal method and investigated their ability of photocatalytic reduction of Cr (VI). The structures of compounds 1–2 were characterized by single‐crystal X‐ray diffraction, revealing that both possess a zero‐dimensional (0D) structure and can form one‐dimensional (1D) chain structures through hydrogen bondings. Photocatalytic experiments demonstrate that compound 1 has superior photocatalytic performance compared to compound 2. Under optimal conditions (pH = 2, 15 mg catalysts, and 10 mg L−1 Cr (VI) concentration), compound 1 can completely reduce Cr (VI) within 20 min, while compound 2 requires 30 min. Compounds 1–2 also show good stability after photocatalytic reaction, and maintain high photocatalytic activity after five reaction cycles. Additionally, the photocatalytic reaction mechanism of compounds 1–2 was studied, and the free radical scavenging experiments show that its main active species are e−, h+, and ˙O2−. The nitroblue tetrazolium (NBT) experiments further confirm the crucial role of ˙O2− in the photocatalytic process. The good photocatalytic activity, stability, and recyclability of the viologen/POM‐based compounds suggest their potential application in the treatment of wastewater containing Cr (VI).

The use of green synthesized TiO2/MnO2 nanoparticles in solar power membranes for pulp and paper industry wastewater treatment

The pulp and paper manufacturing wastewater is as complicated as any other industrial effluent. A promising approach to treating water is to combine photocatalysis and membrane processes. This paper demonstrates a novel photocatalytic membrane technique for solar-powered water filtration. The method is based on creating green-prepared TiO2, and MnO2 nanoparticles (NPs) using Pomegranate peels and Seder leaf extracts and incorporation into polyvinylidene chloride to produce a novel water purification system that combines semiconductor photocatalysis with membrane filtration. The prepared heterostructure of the TiO2/MnO2 nanocomposite membrane provides photogenerated charge separation. To ensure chemical bonding at the membrane surface, Raman and Fourier transform infrared spectroscopy (FT-IR) were employed. The modified membrane’s hydrophilicity and roughness increased significantly. Additionally, the modified nanocomposite membrane’s porosity was measured. The integrated process demonstrated much higher removal of humic acid and high efficiency of wastewater treatment for pulp and paper. In sunlight, humic acid removal was 98% from synthetic wastewater. While using the produced membrane on pulp and paper effluent, these studies indicate that: in the dark, the removal was 50%, while in the sunlight, the removal increased to 70%, with a reduction in the COD from 1500 mg/L to 247 mg/L. Additionally, the TDS decreased from 1630 to 452 ppt in the sunlight. This research sheds light on how solar energy can clean wastewater from the pulp and paper industry while improving membrane separation. Also, an alternative source to sunlight was used to manufacture a photocatalytic membrane with high efficiency for wastewater treatment and an inexpensive price.

Mesoporous NiFe2O4@g-C3N4-Based p-n Heterostructures for Boosting Solar-Driven Photocatalytic Dye Degradation and Hydrogen Evolution.

Mass-fraction-optimized heterojunction composites featuring precisely engineered interfaces and mesoporous structures are crucial for improving light absorption, minimizing electron-hole recombination, and boosting overall catalytic efficiency. Herein, highly efficient mesoporous-NiFe2O4@g-C3N4 heterojunctions were developed by embedding p-type NiFe2O4 nanoparticles (NPs) within n-type porous ultrathin g-C3N4 (p-uCN) nanosheets. The optimized NiFe2O4@g-C3N4, loaded with 20 wt % magnetic counterparts, exhibits exceptional photocatalytic methylene blue (MB) degradation, achieving the highest performance in both photocatalytic and photo-Fenton processes with rate constants of 0.062 min-1 and 0.161 min-1, respectively. These performance metrics are 1.3 and 2.55 fold higher than p-uCN (0.048 min-1 and 0.063 min-1) and 51.6 and 17.4 fold higher than NiFO (0.0012 min-1 and 0.009 min-1). Notably, mp-NiF@uCN-20 % with 1.0 wt % of Pt loading achieves the highest H2 evolution rate of 2294 μmolg-1h-1, which is 3.72, 1.52, and 13.49 times higher than that of pure CN, p-uCN, and NiFO, respectively. The enhanced performance is corroborated by increased surface area, improved separation of charge carriers, and effective charge transfer, which enables simultaneous reduction and oxidation processes. Further, the magnetic nanocomposite exhibits remarkable stability even after multiple runs, indicating their reusability. The experimental findings emphasize the importance of p-n heterojunctions, interfacial band alignment, and mesoporous architecture in enhancing the photocatalytic efficiency of NiFe2O4@g-C3N4 nanocomposites.

Enhancing the Built-in Electric Field in Oxygen Vacancies-Enriched I-Doped Bi3O4Cl for Visible Light-Driven Photocatalytic Oxidation.

In semiconductor catalysts, rational doping of nonmetallic elements holds significant scientific and technological importance for enhancing photocatalytic performance. Here, using a one-step hydrothermal technique, we synthesized iodine-doped Bi3O4Cl composite and evaluated the impact of iodine doping on its photocatalytic capability for organic dye degradation under visible light irradiation. In this study, we demonstrate that the introduction of iodide ions not only provides an ideal built-in electric field (BIEF) for Bi3O4Cl but also induces the generation of additional oxygen vacancies (OVs). The significantly enhanced BIEF, along with the collaborative effect of the OVs-induced narrow bandgap in Bi3O4Cl, effectively promotes the separation and transfer efficiency of photogenerated charges while suppressing recombination. Under this driving force, photogenerated electrons transfer to the surface OVs, facilitating the activation of surface oxygen, thereby forming highly active superoxide radicals (•O2). Simultaneously, oxygen vacancy engineering can reduce the reaction energy barrier, thereby facilitating the formation of singlet oxygen (1O2), which contributes significantly to photocatalytic processes. The results indicate that under visible light, the prepared iodine-doped Bi3O4Cl exhibits a 6.5-fold increase in the degradation rate constant for rhodamine B and demonstrates enhanced photocatalytic activity toward methyl orange and methylene blue. This study not only provides strong references for optimizing structural design to enhance photocatalytic performance but also offers profound insights into the synergistic effects of BIEF and OVs on charge transfer mechanisms in photocatalytic systems.

Zeolite Encapsulation to Enhance Interfacial Gas Availability for Photocatalytic Hydrogen Peroxide Production

AbstractThe photocatalytic oxidation of water with gaseous oxygen is environmentally benign for the synthesis of hydrogen peroxide (H2O2), but it is currently constrained by the inadequate supply of gaseous oxygen at the catalyst surface in a solid–liquid–gas triple‐phase reaction system. Herein, we address this challenge by employing the zeolite encapsulated catalysts that efficiently enrich gaseous oxygen and accelerate the H2O2 synthesis in aqueous conditions. We focus on the classical titania photocatalyst, encapsulating it within siliceous MFI zeolite crystals. This encapsulation results in a significant enhancement in H2O2 synthesis efficiency, achieving a yield that is ten times greater than that with unencapsulated TiO2. Mechanism study reveals that gaseous oxygen is notably concentrated within the microporous structure of the zeolite under aqueous conditions, thereby facilitating its interaction with the titania surface at the liquid‐solid interface. In addition, the H2O2 product could swiftly transfer through the micropores, thereby reducing the side reaction of decomposition. This design provides an alternative pathway to address the poor gas solubility of gaseous reactants in water, and paves the way for advancements in various other photocatalytic processes.

Isomer-Effects of Aminophenol Decorated Gold Nanoclusters for H2O2 Photoproduction via Two-Step One-Electron Oxygen Reduction Reaction.

Gold (Au) nanoclustersare promising photocatalysts for biomedicine, sensing, and environmental remediation. However, the short carrier lifetime, inherent instability, and unclear charge transfer mechanism hinder their application. Herein, the Au nanoclusters decorated with three different isomers of o-Aminophenol, m-Aminophenol, and p-Aminophenol are synthesized, namely o-Au, m-Au, and p-Au, which achieve efficient hydrogen peroxide (H2O2) photoproduction through two-step one-electron oxygen reduction reaction (ORR). The interfacial kinetics for the photocatalytic process in this system are investigated in detail, in which, the isomer-effects of aminophenol decorated in Au nanoclusters are definitely elucidated by combining transient photovoltage (TPV), transient potential scanning (TPS), and photo-induced current (TPC) tests. The reaction pathway of o-Au, m-Au, and p-Au is confirmed to be the same through TPC. Although the conduction band values of o-Au, m-Au, and p-Au are essentially the same under working conditions, the values of surface effective charges (ne) for both m-Au and p-Au are higher than that of o-Au. In addition, m-Au has a stronger adsorption capacity for O2 and a faster ORR rate. Thus, the m-Au manifests the highest photocatalytic activity for the H2O2 photoproduction. This work shows a new way for the in-situ study on charge distribution and transfer on photocatalysts.

Synthesis of ZnO semiconductor nanoparticles using extracts of Capsicum annuum L. for photocatalytic activity in degradation of polluting dyes

In this work, ZnO semiconductor nanoparticles were green-synthesized using Capsicum annuum L. var. Caribe pepper extracts at 1%, 2%, and 4% w/v (weight/volume) as stabilizing agents. The nanoparticles were applied in photocatalytic processes for the degradation of Methylene Blue (MB), Methyl Orange (MO), and Rhodamine B (RhB) in aqueous media. Characterization involved Fourier Transform Infrared Spectroscopy (FTIR), identifying the Zn-O bond at 421 cm-1. X-Ray Diffraction (XRD) analysis revealed a hexagonal Wurtzite-type crystalline phase with crystallite sizes ranging from 13 to 23 nm. Scanning Electron Microscopy (SEM) showed hemispherical clusters smaller than 5 micrometers. UV–Visible spectrophotometry determined band gap values between 3.05 and 3.13 eV. These materials exhibited significant photocatalytic degradation efficiency for the tested dyes.

Photocatalytic Oxygen Evolution with Prussian Blue Coated ZnO Origami Core-Shell Nanostructures.

The design and development of particulate photocatalysts have been an attractive strategy to incorporate earth-abundant metal ions to water splitting devices. Herein, we synthesized CoFe-Prussian blue (PB) coated ZnO origami core-shell nanostructures (PB@ZnO) with different massratios of PB components and investigated their photocatalytic water oxidation activities in the presence of an electron scavenger. Photocatalytic experiments reveal that the integration of PB on ZnO boosts the oxygen evolution rate by a factor of ~2.4 compared to bare ZnO origami. We ascribe this increased photocatalytic rate to an improved charge carrier separation and transfer due to the formation of heterojunction at the interface between PB and ZnO. Long-term photocatalytic experiments indicate that the activity and stability of the catalyst was preserved up to 9 h. Our results indicate that the core-shell PB@ZnO particles possess a proper band energy alignment for the photocatalytic water oxidation process.