Photocatalytic Mechanism Research Articles

Rational design of Zn4O(BDC)3 metal organic framework incorporated with NiCr2O4 nanoparticles: An affordable photocatalyst for the degradation of hazardous dyes

In this work, a simple hydrothermal approach was used to make Zn4O(BDC)3-NiCr2O4 nanocomposite. The structural, morphological and photophysical properties of the prepared samples were used to evaluate various characterization approaches. The Zn4O(BDC)3-NiCr2O4 nanocomposite appears to have a large surface area and increased absorption of visible light. When compared to pure Zn4O(BDC)3 and NiCr2O4, the Zn4O(BDC)3-NiCr2O4 nanocomposite displayed more effective catalytic activity for degradation of methyl orange (MO) and Rhodamine (Rh B) dye from aqueous solution when exposed to visible light. The Zn₄O(BDC)₃-NiCr₂O₄ nanocomposite achieved degradation efficiencies of 93.75 % and 89.91 % for MO and Rh B dyes, respectively, after 210 and 150 minutes of visible light irradiation. The degradation rate for MO was 0.016 min⁻¹, which is approximately 6.66 times and 3.13 times higher than that of pure Zn₄O(BDC)₃ or NiCr₂O₄ nanoparticles, respectively. In addition, the Zn4O(BDC)3-NiCr2O4 nanocomposite showed high structural stability after the degradation test, and most of its photocatalytic activity was retained even after the recycling examination. Moreover, the radical trapping experiments demonstrated that the major active species including superoxide and hydroxyl radicals played main roles in the photocatalytic process. Additionally, the photocatalytic mechanism of Zn4O(BDC)3-NiCr2O4 nanocomposite has been examined, and a more plausible path of hazardous dye degradation has been provided.

Influence of carbon content and irradiation modes on the antibiotic removal from water using VIS-activated TiO2/expanded graphite composite photocatalysts

TiO2/expanded graphite (TiO2/EG) composite films were applied to water treatment for sulfadiazine (SDZ) degradation in a continuous flat plate photochemical reactor. The films were synthesized by sol-gel method and deposited on borosilicate glass by airbrush spray coating technique, forming a TiO2/C heterojunction. Increasing the amount of carbon promoted more efficient photocatalytic removal of SDZ under simulated sunlight, which increased from 9.1% in the absence of carbon to 49.8% for the material containing 7.5% C. From the formation of the TiO2/C heterojunction, morphological modifications, changes in the electronic structure and reduction of the band gap energy were observed. Type-II heterojunction formation was observed. Foreground and background irradiation modes were investigated, and a possible photocatalytic mechanism was proposed. TiO2/7.5 %-EG exhibited the best photocatalytic performance, with the possibility of reuse. The films showed good reusability in the SDZ degradation over 4 photocatalytic cycles. The influence of irradiation modes and the role of oxidizing species were discussed. The results showed that TiO2/EG hybrid films are a promising alternative for practical photocatalytic applications under sunlight.

In situ constructing 2D/2D layered BiOBr/Bi2O2CO3 heterostructure for efficient photocatalytic reduction CO2 to CO

Photocatalytic reduction of CO2 to valuable energy materials is necessary for sustainable development. It is a considerable challenge to prepare photocatalysts for CO2 photoreduction with excellent separation capability of carriers by simple way. Herein, the BiOBr/Bi2O2CO3 type-II heterostructure was constructed by in situ conversion at room temperature. Combining the advantages of the 2D/2D layered structure can form a close contact interface and the type-II heterostructure can facilitate the transport of photogenerated charges, the BiOBr/Bi2O2CO3 composite showed significant enhancement in photocatalytic CO2 reduction performance. The most obvious performance enhancement was observed for 2.0-BiOBr/Bi2O2CO3, where CO yield could reach 29.55 μmol·g−1 for 3 h under light irradiation, it is 11 and 4 times higher than Bi2O2CO3 and BiOBr, respectively. And the sample exhibits excellent cycling stability in photocatalytic tests. In situ Fourier Transform Infrared spectroscopy confirmed that the important intermediates of the reaction are *COOH and *CO. The photocatalytic reduction mechanism of CO2 to CO in the BiOBr/Bi2O2CO3 type-II heterostructure was further analyzed. This study provides feasible solutions for selecting photocatalytic materials and designing facile preparation of efficient 2D/2D catalysts for photocatalytic reduction of CO2.

Sustainable photodegradation of pharmaceuticals: KOH-impregnated palm oil mill effluent sludge biochar-BiOBr nanocomposite for wastewater treatment

Biochar has explored in the search of a cost-effective and environmentally friendly photocatalyst for the efficient degradation of CIP antibiotic pollutants. Biochar (BC) produced from palm oil mill sludge was used as a base to fabricate biochar-based BiOBr composites by varying the mass ratio of biochar and BiOBr via a hydrothermal route. The optimized composites BBC-1:1 has exhibited the formation of crystal struvture as tetragonal BiOBr with a a significant specific surface of 267 m2/g (BBC-1:1) while incorporating different mass ratios of BC with BiOBr. This composite facilitates the band gap of BiOBr from 2.87 to 2.42 eV and is consistent with the decreasing recombination rate of electron-hole pairs as suggested by UV-Vis DRS and photoluminescence (PL), respectively. Consequently, the synergistic effect of biochar BiOBr leads to a higher degradation efficiency of CIP showing the highest efficiency (97.49 %) and that of pure BiOBr being 55.66 % under optimized conditions. The degradation rate of the BBC-1:1 composite which observed to be 0.0156 min−1 is 3.25 times that of BiOBr (0.0048 min−1). Furthermore, the scavenging experiments confirmed the significant contribution of the active radicals h+ and O2- as the main photoactive species in the photocatalytic degradation of CIP. Consequently, the photocatalytic degradation mechanism was discussed and the reusability test confirmed the high stability of the BBC composites up to 77 % for the seventh cycles. These results show that the BBC composite is suitable for large-scale practical applications as a green photocatalyst.

S-scheme 2D/2D B-doped N-deficient g-C3N4/ZnIn2S4 heterojunction for efficient H2 production intergrated with tertracycline degradation under visible-light illumination

A novel S-scheme 2D/2D boron-doped nitrogen-deficient g-C3N4/ZnIn2S4 (BDCNN/ZnIn2S4) heterojunction was successfully fabricated via the in-situ assembly of ZnIn2S4 onto BDCNN in an oil bath. To assess the quality and characteristics of the synthesized photocatalysts, a comprehensive range of characterizations were conducted. The innovative S-scheme 2D/2D BDCNN/ZnIn2S4 heterojunction, equipped with a deliberately established inter-built electric field, facilitates rapid electron transfer and enhanced separation efficiency of photo-induced carriers. Consequently, this heterojunction demonstrates remarkable enhancements in both H2 production and TC degradation under visible-light illumination (λ > 420 nm). The optimized BDCNN/ZnIn2S4 heterojunction exhibited impressive photocatalytic performance, achieving a promising H2 evolution rate of 2378.8 μmolg−1h−1 and a high degradation efficiency exceeding 90 % (k = 0.021 min−1) for TC. This noteworthy improvement in photocatalytic performance is primarily attributed to the synergistic effects of boron-doping and nitrogen-defects within BDCNN, coupled with the unique S-scheme photocatalytic mechanism inherent to the BDCNN/ZnIn2S4 heterojunction. Overall, this study introduces a groundbreaking approach for constructing 2D/2D g-C3N4-based heterojunctions that exhibit exceptional visible-light photocatalytic capabilities, thereby offering significant potential for various photocatalytic applications.

Z-scheme flower-like Ag/AgCl/NiZnAl-LDH for high efficiency removal of Methylene Blue: Performance and mechanism insights

3D flower-like NiZnAl-LDH was prepared, and then the Z-scheme Ag/AgCl/NiZnAl-LDH heterojunctions were further constructed by loading different amounts of AgCl on NiZnAl-LDH surface. The structure, morphology and photoelectric properties were characterized by a variety of advanced techniques, such as XRD, XPS, SEM, HRTEM and EIS. Furthermore, methylene blue, abbreviated MB, was used as the target pollutant, and the photocatalytic degradation activity of Ag/AgCl/NiZnAl-LDH on it was explored. Results displayed that the Ag/AgCl/NiZnAl-LDH photocatalysts displayed excellent photocatalytic degradation activity for MB dye compared with AgCl and NiZnAl-LDH, and the loading of different AgCl on the surface of NiZnAl-LDH has a considerable influence on the photocatalytic performance. The alkaline condition and low concentration of MB are more conducive to the photocatalytic degradation of MB by Ag/AgCl/NiZnAl-LDH. The photocatalytic process conforms to the first-order kinetic model with a rate constant of 0.0082 min−1, which is about 3.4 times that of AgCl and NiZnAl-LDH. Compared with AgCl and NiZnAl-LDH, it is found that Ag/AgCl/NiZnAl-LDH increases the separation rate of photogenerated electrons and holes, the photogenerated carrier recombination is inhibited, and the electrochemically active area is increased. The outstanding photocatalytic activity and stability make Ag/AgCl/NiZnAl-LDH a perfect material to ease the environmental crisis. Besides, combined with free radical trapping experiments, a possible photocatalytic mechanism was raised.

Construction of S/g-C3N4@β-Bi2O3 heterojunction and its photocatalytic degradation of toluene in the gas phase.

In this paper, a modification of g-C3N4 was carried out by combining non-metal doping with the construction of heterojunctions, and a type II heterojunction composite, S/g-C3N4@β-Bi2O3, was prepared. The phase structure, morphology, elemental composition, valence band structure, and light absorption performance of the photocatalyst were analyzed using characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The performance of the composite photocatalyst in the photocatalytic degradation of gaseous toluene, one of the typical volatile organic compounds (VOCs), under simulated solar light was studied. The effects of preparation conditions, toluene concentration, and recycling on the photocatalytic performance of the composite photocatalyst were investigated. The results show that under the optimal preparation conditions, S/g-C3N4@β-Bi2O3 achieved a degradation efficiency of 74.0% for 5ppm toluene after 5h of light irradiation. Although the degradation efficiency decreased to 61.2% after five cycles, it maintained 83% of its initial activity, indicating good stability of the composite photocatalyst. Free radical quenching experiments demonstrated that h+ was the main active species in the photocatalytic degradation of toluene, followed by ·O2-. Based on all experimental results, the migration law of photo-generated charges was analyzed, and a possible photocatalytic mechanism was proposed. In this study, a new material was obtained for the photocatalytic removal of VOCs by improving the photocatalytic properties of g-C3N4.

Anchoring gadolinium oxide nanoparticles onto CuInZnS: Efficient photocatalytic tetracycline degradation and mechanism analysis

Photocatalysis technology is one of the potential methods to remit the growing issues of environmental pollution. It is of great significance to rationally design high performance antibiotic wastewater degradation catalysts in the whole pH range. In this experiment, Gd2O3 nanoparticles (GdO NPs) were successfully grown onto CuInZnS (CIZS) by a simple hydrothermal method. The introduction of GdO has obvious effects on the nanosheet thickness of CIZS, which reduces carrier transport distances and improves the active sites number of CIZS. What’s more, the SO4•- absorption and electron transfer ability are also greatly optimized. Under 300 W Xe light, tetracycline can be efficient degraded more than 93 % in the whole pH range, which presents absolute advantage compared to CIZS and GdO. Based on the combination of experimental characterization and density functional theory calculations, the proposed photocatalytic tetracycline degradation pathway and mechanism have been given. Moreover, the results of toxicity analysis proved that the CIZS-GdO catalyst could successfully reduce the toxicity of tetracycline wastewater. This work has reference value for the application of rare earth oxides in the field of photocatalysis at full pH range.

Synthesis of leek-based N,S self-doped CQDs/TiO2 and its application in the photocatalytic degradation of organic pollutants

In this work, N,S self-doped CQDs (N,S-CQDs/TiO2) were synthesized from leeks via a microwave method, and a new leek-based N,S-CQDs/TiO2 composite photocatalytic material was prepared by roasting. The structural characteristics, optical properties, and electrical properties of the N,S-CQDs/TiO2 composites were characterized by Scanning electron microscope (SEM), Transmission electron microscope (TEM), X-ray powder diffraction (XRD), Solid ultraviolet–visible diffuse reflectance (UV–vis-DRS), Fourier transform infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transient photocurrent response, and Electrochemical impedance spectroscopy (EIS). In addition, the catalytic degradation effect of N,S-CQDs/TiO2 was evaluated by the photocatalytic degradation of Rhodamine B (RhB) and ibuprofen (IBU). The experimental results showed that the photocatalytic degradation effect of leek-based N,S-CQDs/TiO2 was significantly better than that of TiO2, and N,S-CQDs/TiO2 with 1.86 wt% N,S-CQDs (1.86-N,S-CQDs/TiO2), which demonstrated optimal photocatalytic degradation. The photocatalytic degradation rate of RhB (20 mg/L) was 94.65 % within 120 min of high-voltage mercury lamp irradiation, which was 41.15 % higher than that of TiO2(53.50 %), and the degradation rate was 80.10 % after four cycles. After 180 min, the photocatalytic degradation rate of IBU (10 mg/L) was 96.92 %, which was 26.39 % higher than that of TiO2 (70.53 %), and the degradation rate could still reach 78.94 % after four cycles. In this work, the photocatalytic degradation mechanisms of RhB and IBU by N,S-CQDs/TiO2 were explored by free radical capture and ESR free radical detection experiments. This study may serve as an important reference for enhancing the photocatalytic degradation effect by using biomass self-doped CQDs/TiO2 composite photocatalytic materials, and as a reference for the photocatalytic treatment of organic pollutants in water.

A CuBTC/CuS Photocatalyst for Organic Dyes: Degradation Kinetics and Mechanistic Insights

AbstractOrganic dyes derived from industrial processes have harmful potential to aquatic systems and require novel oxidative treatment. Metal‐organic frameworks (MOF) couple high adsorption capacity and photocatalytic action, which can be improved through heterojunctions. In this work, CuBTC (MOF) photocatalyst was synthesized by an electrochemical methodology, and the in situ CuS templated formation by addition of Na2S solution, giving CuBTC/CuS composites. The synthesized CuBTC MOF and CuBTC/CuS composites were characterized by XRD, FTIR, TGA, and EDX. The adsorptive capacity and photocatalytic properties were evaluated by the photocatalytic performance against methylene blue (MB) aqueous solution, under dark and simulated solar irradiation. Under simulated solar irradiation, the CuBTC/CuS achieved 87 % dye photodegradation after 120 min, 1.7 times higher than CuBTC. The photocatalytic action mechanisms were investigated by free‐radical capture experiments. At the equilibrium, the photocatalytic process presented pseudo‐first‐order (PFO) and pseudo‐second‐order (PSO) non‐linear kinetic models, showing a higher correlation with the PFO model, with a rate constant of 94.3×10−3 min−1. The photocatalytic performance of the composite was also evaluated over five cycles, decreasing to 68 %. The proposed strategy showed promise for the developing of highly effective materials to combat water pollution.

Synthesis of CS/Fe3O4/TiO2@MXene nanocomposite photocatalyst with excellent degradation and bacteriostatic properties by one-step hydrothermal method

With the rapid development of global economy and industrialization, the management and protection of water resources have become increasingly important. In this paper, a novel three-dimensional Chitosan/Fe3O4/TiO2@MXene photocatalyst with excellent degradation and bacterial inhibition properties was prepared by a simple one-step hydrothermal method using FeCl3·6H2O, Chitosan (CS) and MXene (Ti3C2) as main raw materials. TiO2 was generated in-situ on the surface of Ti3C2 nanosheets and modified by loading Fe3O4 nanoparticles and CS films. The conformations and band gaps of the composites were modified, and then photocatalytic mechanisms, phase compositions, morphological structures, magnetic properties and photoelectrochemical properties of the photocatalysts were systematically analyzed. The degradation efficiency of the CS/Fe3O4/TiO2@Ti3C2 composite photocatalyst can reach 95.9 % when the ration of CS to FeCl3·6H2O is 1:3 and the hydrothermal temperature is 180 °C, which showing excellent photocatalytic performance. Meanwhile, the inhibition rate of Staphylococcus aureus (S. aureus) is close to 98.91 % under the light condition. This study further reveals that visible light is a cost-effective way to treat pollution in terms of degradation and bacteriostatic inhibition, and the composite photocatalysts can be efficiently recycled and reused under the action of a magnetic field.

Enhanced visible light-assisted photocatalytic activity of g-C3N4 decorated with ZIF-8 and AgI ternary heterojunctions

Fabrication of a suitable photocatalyst system that responds to visible light has become a requirement for photocatalytic environmental remediation processes. For better transfer/separation of photogenerated-charges, successful interfacial engineering to build photocatalytic heterojunctions is essential for improving the photodegradation performance. Herein, ternary composites of zeolitic-imidazolate-framework-8 (ZIF-8) coupled with AgI nanoparticles assembled on g-C3N4 have been fabricated, characterized using XRD, FESEM, EDX, TEM, PL, UV–visible DRS, and N2-adsorption–desorption, and used as visible-light-driven photocatalysts for photocatalytic destruction of methylene blue (MB). The ternary AgI/ZIF-8/g-C3N4 photocatalyst achieved superb photodestruction activity (94.2 %) within 120 min. Besides, the first-order degradation rate constant reached 0.02431 min−1, which was nearly 1.5, 2.5, 4.5, and 5.5 times greater than that reached by ZIF-8/g-C3N4 (0.01628 min−1), g-C3N4 (0.00941 min−1), AgI (0.00542 min−1) and ZIF-8 (0.00441 min−1), respectively. The improved photocatalytic behavior was accredited to the synergistic influence of the photo-charge carrier transfer/separation pathway and the electron mediation assisted by ZIF-8. The trapping tests supported the recommended photocatalytic mechanism, which suggested that the O2− radicals were the main reacting agents in this process. The parameters affecting the photodegradation, including the AgI/ZIF-8/g-C3N4 dose, the solution pH, and the MB concentration were systematically tested in this work. Furthermore, the AgI/ZIF-8/g-C3N4 demonstrated good degradation stability after multi-consecutive rounds (only 1 % deduction in its activity after 5 rounds), and thus, it is projected to be a promising photocatalyst in wastewater treatment.

Direct Z-scheme ZrS2/InP heterostructure as an efficient photocatalyst for overall water-splitting under acidic, alkaline and neutral environments

Photocatalytic water-splitting for hydrogen production by building heterostructure is an efficient approach to resolve the current environmental pollution problem. Here, the ZrS2/InP heterostructure with a direct Z-scheme have been constructed, and the first-principles calculations with Heyd-Scuseria-Ernzerhof (HSE06) hybrid function and density functional dispersion correction (DFT-D3) have been used to study their structural stabilities, electronic properties, photocatalytic mechanisms and optical features. The findings reveal that the ZrS2/InP heterostructure is a direct bandgap semiconductor having a type-II energy band alignment, where electrons mobilize from InP to ZrS2 monolayer at the interface of the heterostructure, leading to the creation of a build-in electric field pointing from InP to ZrS2. The ZrS2/InP heterostructure is competent for photocatalytic water-splitting owing to its advantageous band edge positions. In addition, the ZrS2/InP heterostructure possesses superior visible light absorption properties than the two monolayers structures, with a solar-to-hydrogen (STH) efficiency of 7.11 % and useable in acidic, alkaline and neutral environments. These excellent properties enable ZrS2/InP heterostructure to be an efficient photocatalyst for overall water-splitting. This effort not only proves the possibility of applying heterostructure in photocatalytic water-splitting but also has important implications for designing efficient direct Z-scheme photocatalysts.

Combining rhombohedral dodecahedral ZnO with g-C3N4 nanosheets for enhanced photocatalytic activity

Photocatalysis technology is an effective method to remove pollutants in aquatic environment assisted by solar energy. Herein, the rhombohedral dodecahedral ZnO was dispersed on the g-C3N4 nanosheets for the construction of ZnO/g-C3N4 heterojunction via the combination of solvothermal method and calcination. The obtained ZnO/g-C3N4 heterojunction manifests excellent photocatalytic ability for methyl orange (MO). Especially, the optimal ZnO/g-C3N4 composite with the ZnO content of 10 wt% (ZC-3) exhibits the degradation efficiency of MO as high as 98.0% under visible-light of 60 min. A series of factors were all-around investigated, such as initial pH, photocatalyst dosage, initial MO concentration, organic anions, humic acid and other dyes. The photocatalytic degradation behavior of MO complies with the first-order reaction kinetics, and the apparent rate constant (kapp) of ZC-3 is 2.3 and 13.4 times than that of pure g-C3N4 and pure ZnO. Meanwhile, the ZnO/g-C3N4 heterojunction exhibits satisfactory cyclic stability and its photocatalytic mechanism is postulated. Therefore, the ZnO/g-C3N4 heterojunction possesses great economic utilization value and is expected to be widely used for wastewater remediation.

Solar-driven remediation of antibiotics in synthetic and real reverse osmosis brine: Addressing lattice oxygen demand and electron transfer for improved purification

This study investigated the significance of integrated advanced oxidation process with reverse osmosis (RO) to ensure the purification and elimination of micropollutants, primarily pharmaceuticals prior to the discharge of brine to the environment. To envisage this, TiO2 based solar driven photocatalysis was employed, highlighting the crucial role of oxygen vacancy formation in the lattice of TiO2 for enhancing the purification of antibiotic contaminants from RO brine. The study elucidated how variations in oxygen environments such as oxygen rich yellow TiO2 (Y-TiO2) and oxygen vacancy black TiO2 (B-TiO2) influence photodegradation reaction kinetics taking ofloxacin (OFX) and tetracycline (TC) as model pollutants. The B-TiO2 exhibited 8.5 times higher photodegradation for OFX compared to Y-TiO2, proving significance in tuning of oxygen environment in lattice. The photodegradation efficiency plot showcases B-TiO2′s efficacy, demonstrating 99.8 % and 99.4 % for OFX and TC, respectively. Additionally, the study investigated the photocatalytic degradation mechanism, identifying predominant charge carriers and reactive species involved, while also assessing the durability of photodegradation processes. The impact of pH on the photocatalytic performance of B-TiO2 in degrading antibiotics explored, spanning pH levels from 2.5 to 10.5. An exploration on band alignment formation in B-TiO2 explains the effectiveness of it over Y-TiO2. Lastly, efficacy of B-TiO2 in degrading antibiotics in real RO brine with high level of salinity (60,200 ppm TDS) is demonstrated, which resulted with photodegradation efficiency of 31.25 % for OFX and 67.8 % for TC, proving applicability of integrated system as a sustainable purification approach. Moreover, the blockage of chloride ions quenching demonstrated improvements in photodegradation emphasizing the influence of chloride ions in high saline conditions.

Elucidating the photocatalytic mechanism of biomass-derived carbon dots nanocomposite for efficient degradation of MB and CR dyes: Insights into protein binding applications

This study introduces an environmentally sustainable method for synthesizing a nanocomposite using carbon quantum dots derived from green tea waste and zinc oxide. The single-step hydrothermal process not only addresses waste management but also yields a versatile nanocomposite with diverse applications. Rigorous characterization reveals its morphology, crystallinity, phase identification, structural behavior, optical properties, and chemical composition. Incorporating carbon quantum dots into the zinc oxide matrix reduces the band gap to 1.87 eV, enhancing charge separation and light-harvesting. This modification significantly boosts photocatalytic activity, achieving degradation efficiencies of 95.16 % for methylene blue (MB) and 93.21 % for congo red (CR) under visible light. The effects of pH, contact time, and photocatalyst concentration on dye degradation were explored. The nanocomposite, exhibiting both adsorption and photocatalytic performance, is poised for broad applications. Fluorescence quenching studies with lysozyme protein provide insights into potential applications across diverse fields, highlighting its environmentally friendly and multifunctional attributes.

Preparation and photocatalytic mechanism of magnetic Ag2S/CoFe1.95Dy0.05O4 Z‐scheme heterojunction

AbstractThe synthesis of high‐efficiency magnetic composite photocatalyst by doping magnetic cobalt ferrite and compounding single semiconductor photocatalyst is a promising strategy to improve the oxidation ability of photocatalytic systems. In this paper, CoFe1.95Dy0.05O4 (CFDO) was prepared by doping Dy element into magnetic CoFe2O4, and Ag2S (AS)/CFDO with high‐efficiency magnetic photocatalyst was synthesized by compounding AS with CFDO as the substrate. The photocatalytic samples were characterized by different advanced characterization methods, and their photocatalytic degradation of methylene blue (MB) was studied. The results show that AS/CFDO exhibits higher visible light response, excellent photogenerated charge separation ability and migration efficiency, and excellent catalytic performance in the catalytic degradation system. The photocatalytic activity of AS/CFDO was the highest, and its photocatalytic degradation kinetic constant K was 2.48 and 1.54 times that of AS and CFDO, respectively. In addition, the catalyst contained in the catalytically contaminated solution can be effectively separated by an external magnetic field to achieve multiple cycles of degradation and recycling. The cyclic degradation experiments showed that AS/CFDO exhibited high degradation stability during the photodegradation process. After the fifth reuse, the degradation efficiency was still more than 88.0%. Finally, the possible photocatalytic mechanism of the samples was discussed. Therefore, this work provides an effective solution for the construction of photocatalysts with high efficiency, magnetic recovery, and cyclic degradation stability and avoids the secondary pollution of catalysts to organic wastewater. It is of great significance to create an environmentally friendly catalytic method for efficient cyclic degradation of organic wastewater.

Photocatalytic mechanism of BaTi5O11 nanocrystals for methylene blue degradation

The electron-band structure of BaTi5O11 nanocrystals was calculated to explore their photocatalytic mechanism. The BaTi5O11 nanocrystals synthesized by a hydrothermal method had a direct band-gap of 3.51 eV, and 82 % methylene blue (MB) was photodegraded after 30 min UV-light irradiation. They showed good photocatalytic performance due to distorted TiO6 octahedra in the crystal structure and nano-size grains of BaTi5O11. The photogenerated carriers were formed by excitation of Ti-O bond which broke under UV-light irradiation, then migrated to the surface of BaTi5O11 nanocrystal. The adsorbed hydroxy groups on the surface were oxidized by photogenerated holes to form •OH radicals, and the photogenerated electrons could be captured by the adsorbed O2 to form •O2− radicals. Both •OH and •O2− radicals played the important role for MB photodegradation.

Direct Z-scheme GeC/GaSe heterojunction by first-principles study for photocatalytic water splitting

In this study, we constructed the direct Z-scheme heterojunction by vertically stacking monolayers of GeC and GaSe. And systematically explored its stability, electronic structure, optical absorption characteristics and photocatalytic mechanism with first principles calculations. Our results show that the GeC/GaSe heterojunction possesses an indirect-gap of 1.88 eV and exhibits a staggered energy-band structure. In comparison to the individual monolayers of GeC and GaSe, the GeC/GaSe heterojunction has more excellent absorption of far-ultraviolet and visible light. And the electrons and holes in the GeC/GaSe heterojunction have a transmission path resembling the letter Z. There is also an internal electric field from GeC to GaSe in the heterojunction, which accelerates the photoelectrons and holes along the Z direction when the heterojunction receives light. Furthermore, further studies suggest that the GeC/GaSe heterojunction can be utilized as a photocatalytic material for water splitting under pH = 0–14. Besides, the bandwidth and optical absorption properties of the GeC/GaSe heterojunction can be adjusted by biaxial strains. Moreover, Gibbs free energy calculations during water splitting demonstrate that the GeC/GaSe heterojunction exhibits a highly driven force for both OER and HER. Thus, direct Z-scheme GeC/GaSe heterojunction has the capability to be a promising photocatalyst for water splitting.

0D/2D Ti3+-TiO2/P-doped g-C3N4 S-scheme heterojunctions for efficient photocatalytic H2 evolution

The integration of heterogeneous photocatalysts has emerged as a promising approach to boost the effectiveness of photocatalytic reactions for hydrogen evolution. In this study, we explore the synergistic effects of Ti3+-TiO2/P-doped g-C3N4 heterojunctions on the enhancement of visible light-induced hydrogen generation efficiency. The photocatalytic hydrogen evolution performance of the as-prepared TPCN100 (280.38 μmol g−1 h−1) surpasses that of pristine P-doped g-C3N4 (34.89 μmol g−1 h−1) and Ti3+-TiO2 (39.71 μmol g−1 h−1) by factors of 8.0 and 7.1 respectively. Through a comprehensive investigation of the structural, electronic, and photocatalytic properties, the underlying mechanisms accountable for the observed enhancement in efficiency within the heterojunction system were elucidated. Based on the in-situ X-ray photoelectron spectrometer (XPS) examination, measurement of band edge, and electron paramagnetic resonance (EPR) analysis, the S-scheme photocatalytic mechanism was proposed. The integration of Ti3+-TiO2 and P-doped g-C3N4 offers new insights into the design of advanced photocatalytic materials for sustainable energy applications.