Degradation Of Gaseous Toluene Research Articles

Hydroxylated SiO2-modified {0 0 1}-TiO2 nanosheets as a surface multifunctional photocatalyst for enhanced degradation of gaseous toluene

The relatively weak activity and serious deactivation of anatase TiO2 nanosheet catalysts with highly exposed {001} facets ({001}-TiO2) limits its wide application in photocatalytic degradation of gaseous pollutants. Herein, we propose a hybrid photocatalyst composed of {001}-TiO2 and SiO2 with numerous hydroxyl groups (denoted as {001}-TiO2/HO-SiO2). The catalyst showed excellent performance for gaseous toluene degradation under UV illumination, with 99.2 % removal efficiency and 204.7 μmol L−1 CO2 yield (about 85.9 % mineralization efficiency) within 120 min. It also demonstrated superior durability over five consecutive cycles of toluene photodegradation. The modification of HO–SiO2 on {001}-TiO2 facilitate the selective adsorption of toluene on the catalyst surface by H-bonding interaction, and make the major poisoning species, benzoic acid, easily desorb from the surface, reducing the catalyst inactivation. Most importantly, we found that the formed TiOSi bond promotes the separation of photogenerated electron–hole pairs, and provides abundant available electrons for the formation of reactive oxygen radicals and the left holes for the conversion of toluene to benzyl radicals or oxidation of H2O to hydroxyl radicals, which results in the improved activity. This study highlights the importance of the introduction of secondary components with special functions on TiO2, which is helpful for the design of photocatalysts with high performance and anti-deactivation ability for treatment of volatile organic compounds.

Microwave-assisted synthesis of Ag/ZnO/diatomite composites for photocatalytic degradation of gaseous toluene

In this work, a novel Ag/ZnO/diatomite composites was synthesized by microwave-assisted hydrothermal technique and used for the photocatalytic degradation of gaseous toluene. Various approaches were used to characterize the structural, morphological, optical and photoelectric properties of the composites. Photocatalytic degradation of gaseous toluene by Ag/ZnO/diatomite composites under visible-light irradiation was investigated. The experimental results demonstrate that the degradation efficiency of Ag/ZnO/diatomite composites reaches 90.4 %, which is better than that of ZnO/diatomite composites and ZnO. Ag/ZnO/diatomite composites have a pseudo-first-order rate constant of 0.01543 min−1, which is 6.57 times more than that of ZnO. Through active species capture experiments, ·O2− and ·OH are the primary active species. Furthermore, the possible degradation mechanisms and pathways are proposed, the high performance of Ag/ZnO/diatomite composites can be attributed to the synergistic effect of ZnO, diatomite and Ag nanoparticles.

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.

Fabricating BiOBr/Bi2WO6 S-scheme heterojunction with interface modification strategy for efficient photocatalytic degradation of gaseous toluene

Fabricating BiOBr/Bi2WO6 S-scheme heterojunction with interface modification strategy for efficient photocatalytic degradation of gaseous toluene

Unraveling the generation mechanism of singlet oxygen in Bi2WxMo1-xO6 solid solution and roles in photocatalytic degradation of gaseous toluene under visible-light irradiation

Photocatalytic degradation volatile organic compounds (VOCs) represent an appealing strategy since the inexhaustible solar energy and facile reaction condition. In this work, a flower-like microsphere Bi2WxMo1-xO6 solid solution photocatalysts with abundant oxygen vacancies (OVs) were prepared via HTAB-assisted hydrothermal method. The mole ratio of W and Mo atoms were regulated by adjusting the stoichiometric ratio of their precursor. The optimized Bi2W0.25Mo0.75O6 presented outstanding photocatalytic performance with 96.8% of toluene degradation rate after 180 min of irradiation under visible light (>420 nm), which was 13.76 times higher than that of pure Bi2MoO6 and 10.32 times higher than that of pure Bi2WO6, respectively. The enhanced photocatalytic activity of Bi2W0.25Mo0.75O6 was attributed to the optimized band structure and efficient separation efficiency of carriers as well as the participation of singlet oxygen (1O2) radicals. Free radical trap experiments and electron spin resonance investigations revealed that 1O2, hydroxyl radical, and holes were the predominated reactive oxygen species (ROSs) in toluene degradation. Meanwhile, the generation of 1O2 was related to abundant OVs of Bi2W0.25Mo0.75O6 solid solution. This work suggested that solid solution with abundant OVs was an effective photocatalyst to improve the VOCs degradation activity under visible-light irradiation.

Efficient toluene degradation using Bacillus subtilis biofilm-supported Mn–Ce/zeolite catalysts

This study investigated a new approach for synthesizing Bacillus subtilis biofilm-supported Mn–Ce/zeolite catalysts for the degradation of gaseous toluene. Four different metal oxide nano-catalysts (ZMn, ZMnCe-10%, ZMnCe-20%, and ZMnCe-30%) were synthesized with varying ratios of manganese (Mn) and cerium (Ce) on zeolite nanoparticles. TEM, SEM, XRD, BET, XPS, and EDX mapping were used to examine these four samples, as well as simple zeolite. Based on these analyses, the catalytic activity of the prepared samples ZMn, ZMnCe-10%, ZMnCe-20%, and ZMnCe-30% for the complete oxidation of toluene and toluene intermediate products were tested with Non-thermal plasma (NTP) technology in a dielectric barrier discharge (DBD) reactor. Among all, ZMnCe-20% showed the highest toluene degradation efficiency (89%) at low concentrations (200 ​ppm) and humidity (>50%). Later, highly efficient and hydrophobic nano-biocatalysts were prepared by combining B. subtilis biofilm wild-type (WT) and engineered B. subtilis biofilm EPS with ZMnCe-20% catalyst. EPS is the main component found in biofilm matrix and plays a key role in influencing properties such as biofilm stability, electron transfer, surface roughness and hydrophobicity. Compared to WT B. subtilis biofilm, EPS overexpressed B. subtilis biofilm showed stronger growth and development on ZMnCe-20% nanocatalyst. Moreover, the NTP system packed with ZMnCe-20%/biofilm (EPS+) nano-biocatalyst exhibited the highest toluene degradation activity (99%) with (83%) CO2 selectivity, (up to 50%) reduction in NOx concentration and complete ozone decomposition at (250 ​ppm) toluene concentrations and increased humidity (>90%). High-energy electrons generated in the NTP system break the C–H and C–C bond between the rings of the toluene molecule, forming several byproducts which are later reacted with active radical species such as O, OH, and O3 and further converted into final degradation products (CO2 and H2O). The results demonstrated successful biofilm development and growth on the ZMnCe-20% catalyst with advanced features such as superhydrophobicity, H2O resistance, improved surface roughness, and electron generation. In short, the study's approach combines bioengineering and material science to develop sustainable nano-biocatalysts for removing VOCs in industrial and environmental settings.

Construction of CdS@g–C3N4 heterojunction photocatalyst for highly efficient degradation of gaseous toluene

Exploring efficient photocatalysts for the degradation of VOCs under visible light is a challenge. CdS@g–C3N4 heterojunction photocatalytic materials were developed in this study using a microwave-assisted sol-gel process. CdS@g–C3N4(0.2) photocatalyzed the maximum degradation of gaseous toluene under visible light irradiation, and the time required to achieve the same degradation rate was reduced by 270 min when compared to pure CdS. The morphological characterization, photoelectric property analysis, and DFT calculations all verified that the CdS nanoparticles were uniformly disseminated on the surface of g–C3N4, and that the interfaces were closely contacted to form a heterojunction interface with a built-in field. This enhances charge transfer from CdS to g–C3N4 while successfully decreasing electron-hole pair recombination caused by light. Furthermore, the energy band structure was altered to absorb longer wavelengths of light and extend the absorption spectral range, improving the photocatalytic material's efficacy for broad-spectrum light such as sunshine. This paper proposes methods for predicting and optimizing the surface structure of catalysts, as well as developing high-performance multi-heterojunction photocatalysts for the degradation of indoor VOCs.

Hydrophobic fluorine-doped carbon-wrapped TiO2 particles as efficient and stable photocatalysts for gaseous toluene degradation

Moisture-resistant TiO2-based catalysts with high activity and stability are urgently needed to satisfy requirements for the treatment of volatile organic compounds (VOCs). In this work, a novel hydrophobic F-doped carbon-wrapped TiO2 catalyst (TiO2 @HFC) was synthesized by a facile method and used for the photocatalytic degradation of toluene. TiO2 @HFC displays significantly higher activity under UV/Vis irradiation than commercial P25 TiO2, and remains stable after six cycles. The removal efficiency of toluene was 81.7% after 210 min of reaction, corresponding to a mineralization efficiency of 74.5%. Benefiting from the hydrophobic F-doped carbon layer modification, the incorporation of F into TiO2 crystals, and increased Ti3+ content, TiO2 @HFC is characterized by efficient separation and utilization of photoexcited charge carriers, enhanced adsorption of toluene, and robust resistance towards water vapor. This work demonstrates the potential application of the TiO2-based photocatalyst to efficiently remove VOCs in a humid environment.

The resin-supported iron-copper bimetallic composite as highly active heterogeneous Fenton-like catalysts for degradation of gaseous toluene.

In this study, a resin-supported iron-copper bimetallic heterogeneous Fenton catalyst with excellent removal performance, superior economy and outstanding recoverability was synthesized by an impregnation method and used to remove gaseous toluene. Experiments disclosed that 3-FeCu@LXQ-10 possessed extremely high catalytic capacity. At a temperature of 30 °C, an initial toluene concentration of 200 mg/m3 and H2O2 atomization amount of 3 mmol/h, the toluene removal efficiency of 3-FeCu@LXQ-10 was 97.50%. Experimental tests had revealed that the bimetallic supported catalysts exhibited higher catalytic activity than single metal-supported catalysts, owing to an interaction effect between iron and copper metal ions. Furthermore, electron paramagnetic resonance (EPR) and radical quenching tests were carried out, and the results indicated •OH radicals performed a key role in the Fenton-like process. In addition, the iron-copper bimetallic catalysts exhibited good reusability and stability characteristics during six degradation cycles. This study shows promising potential in using FeCu@LXQ-10 as a heterogeneous catalyst for removing toluene.

Decorating {0 0 1} TiO2 nanosheets on hydrophobic NaY zeolite: An efficient deactivation-resistant photocatalyst for gaseous toluene removal

Photocatalysis is regarded as a promising in situ air purification technology for the removal of volatile organic compounds. However, the deactivation of photocatalysts remains a serious issue that needs to be addressed. Herein, we report a novel dual-functional photocatalyst (TiO2@HYZ) with spatially separated catalytic sites and adsorption sites, which has been obtained by combining hydrophilic {001} TiO2 nanosheets with hydrophobic NaY zeolite. TiO2@HYZ showed excellent photocatalytic activity for the degradation of gaseous toluene under UV irradiation in humid air. The optimized TiO2@HYZ-2 (containing 45.7 wt% TiO2) achieved 96.6% toluene removal and 87.4% mineralization within 120 min. The specific reaction rate constant of TiO2@HYZ-2, pristine TiO2 and P25 normalized by the unit amount of TiO2 during the photocatalytic degradation process were calculated to be 0.481, 0.230 and 0.250 min−1 g−1, respectively. Moreover, TiO2@HYZ-2 showed superior durability, maintaining stable performance over repeated toluene degradation processes, even at high toluene concentration, whereas pristine TiO2 incurred severe deactivation with increasing number of photocatalysis cycles. The significantly enhanced activity and anti-deactivation property was attributed to a synergistic effect between HYZ and TiO2 in the catalyst structure, which strengthened the adsorption of toluene on HYZ and facilitated effective separation of photoexcited charge carriers on TiO2, thus avoiding the deposition of degradation intermediates on the active sites and simultaneously improving mineralization. This work provided a new perspective for the design of efficient and deactivation-resistant photocatalysts for air pollution remediation.

Enhancing the photocatalytic performance of the g-C3N4/BiOCl heterojunction in gaseous toluene degradation via K+ decoration in g-C3N4

Doping or constructing heterojunctions by coupling with other semiconductors are effective methods to improve the photocatalytic performance of graphitic carbon nitride (g-C3N4) in toluene degradation. Herein, thermally condensed synthesized K-doped g-C3N4 (KCN) is coupled with BiOCl via a hydrothermal method, and KCN/BOC heterostructures are obtained. The optimal KCN1/BOC heterojunction exhibits approximately 85% removal of toluene after 150 min irradiation under simulated solar light, which is 12.4 and 9.6 times higher than those of g-C3N4 and BiOCl, respectively. The superior performance of KOH-modified g-C3N4 is attributed to the electron transfer channels formed by the insertion of K+ into the g-C3N4 layers, which facilitate efficient charge separation and rapid electron transfer. Furthermore, the KCN/BOC heterostructure with the Z-scheme further improves the surface charge separation efficiency, which plays a critical role in the photocatalytic process. This work provides a facile and promising strategy for dual-strategy modification of g-C3N4 to enhance photocatalytic degradation activity.

Fabrication of Bi2O3 QDs decorated TiO2/BiOBr dual Z-scheme photocatalysts for efficient degradation of gaseous toluene under visible-light

Weak visible-light capture ability, ultrahigh charge recombination rate, and poor redox ability are crucial constraints to improve the photocatalytic performance for toluene degradation under visible-light. Hence, a dual Z-scheme of Bi2O3 quantum dots decorated TiO2/BiOBr photocatalysts (Bi2O3 QDs@TiO2/BiOBr) were prepared by a two-step hydrothermal method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were performed to identify the existence of Bi2O3 QDs and TiO2 that loaded on the surface of BiOBr. The introducing of oxygen vacancies in TiO2 broadened its light absorption region to the visible-light. The constitutes of Bi2O3 QDs and BiOBr were regulated and the optimized photocatalyst BT1-B10 exhibited 94.1 % of removal rate for gaseous toluene degradation after 150 min irradiation of visible-light (>420 nm) as well as good recoverability and durability. This result was obviously superior to other comparison samples. In-situ DRIFTs spectra and Gas Chromatography-Mass Spectrometry (GC-MS) were carried out to provide a possible pathway for the toluene degradation. Additionally, a dual-channel electron transfer model based on the Z-scheme was proposed, which presented desirable visible-light response region, efficient charge separation efficiency, and enhanced redox ability. Notably, hydroxyl radicals (•OH) served as the dominant active species was confirmed by electron spin resonance (ESR) and gas-phase capture tests, that was beneficial to the ring-opening of toluene degradation. This dual Z-scheme heterojunction of Bi2O3 QDs@TiO2/BiOBr photocatalyst showed great potential for the degradation of toluene under visible-light irradiation.

Experiments and DFT investigation of microwave-assisted sol–gel method prepared S-doped g-C3N4 for enhanced photocatalytic degradation of gaseous toluene

Doping S with defects to create heterojunction-like junctions is an effective method for increasing g-C3N4 photodegradation efficiency of gaseous toluene.

OPTIMIZING THE STRUCTURAL CHARACTERISTICS OF DRAFT TUBE IN A SPOUTED BED REACTOR FOR BEST PHOTOCATALYTIC DEGRADATION OF TOLUENE AND CO2 SELECTIVITY USING RESPONSE SURFACE METHODOLOGY

In this study, toluene degradation efficiency and carbon dioxide (CO2) selectivity in a spouted bed reactor with a porous draft tube were optimized using the response surface methodology. For this purpose, titanium dioxide (TiO2) was used as a catalyst for photocatalytic degradation of gaseous toluene in a dynamic mode under ultraviolet (UV) irradiation. The influence of draft tube parameters' (including height, diameter, gap, and porosity) on toluene degradation efficiency and CO2 selectivity (as the response variables) was investigated by central composite design. Analysis of variance (ANOVA) was applied to evaluate the significance of the variables' effects and the interaction between them. Results showed that maximum toluene degradation efficiency of 78.1 % and maximum CO2 selectivity of 88.7 % were obtained at 1.99 cm draft tube height, 1.3 cm draft tube diameter, 1.3 cm gap, and 60 % draft tube porosity. The highest F-values indicated that the gap is the most important variable affecting the toluene degradation efficiency and CO2 selectivity, while the draft tube diameter is the second important variable. The results of experiments at optimal levels of parameters with three replications showed a maximum toluene degradation efficiency of 78.8% (SD= 0.62) and maximum CO2 selectivity of 89.1 % (SD= 0.46). The study revealed that the spouted bed reactor with a porous draft tube has a good stability for volatile organic compounds (VOCs) degradation and mineralization.

Semi-solid electrolyte with layered heterometallic low-valent electron-mediator enabling indirect destruction of gaseous toluene

The electrochemical degradation of air pollutants, particularly volatile organic compounds (VOCs), at their gaseous state is a promising method. However, it remains at an infant stage due to sluggish solid–gas electron transfers at room temperature. We established a triphase reaction condition using a semi-solid electrolyte layer between the electrode and membrane to enhance the electron transfer at room temperature. A polyvinyl alcohol (PVA) gel layer was inserted between a bimetallic layered CuNi(CN)4 complex coated Cu foam electrode (TCNi-Cu) and Nafion 324 membrane for the degradation of gaseous toluene. The cyclic voltammetry of TCNi-Cu using a sodium hydroxide-coated copper mesh electrode at a triphase showed Cu1+ and Ni1+ stabilization at −0.7 and −0.9 V, respectively, which was similar to the liquid phase electron transfer behavior. The degradation capacity of gaseous toluene without using electrogenerated TCNi-Cu + PVA gel was 0.54 mg cm2 min−1, whereas that of TCNi-Cu + PVA gel layers was 1.17 mg cm−2min−1, which revealed the mediation effect at a triphase condition. Toluene was converted into oxygen-containing products, such as butanol, propanol, and acetone (without reduction products), which revealed that indirect oxidation occurred at the cathode using an in-situ generated oxidant, such as OH˙ radical. As an electron-mediator, Cu1+ was used to form oxidants for the degradation of toluene at −0.7 V. The toluene removal rate reached 1.4 μmol h−1, with an energy efficiency of 0.15 Wh L−1. This study is the first attempt to describe a liquid-electrolyte-free cathodic half-cell in electrochemical application to VOCs degradation, highlighting the electron transfer at room temperature.

Photocatalytic Degradation of Toluene by a TiO2 p-n Homojunction Nanostructure

The development of catalysts for the treatment of volatile organic compounds (VOCs) by photocatalytic oxidation is very important for treating industrial flue gases. Although defect engineering has been developed into an effective method to improve the photocatalytic activity of TiO2 semiconductor materials, few holistic studies have been performed on the structure and properties of TiO2. Herein, a one-step hydrothermal method was used to synthesize three types of nanoscale TiO2 (p-TiO2 with only Ti vacancies, n-TiO2 with only O vacancies, and pn-TiO2 with dual Ti/O vacancies) for the photocatalytic removal of gaseous toluene to determine the relationship between the redox capacity of the electron–hole pairs and the type of conductive semiconductors. It was found that pn-TiO2 exhibited a higher gaseous toluene conversion (99.6%) within 2 h, with 2.8-fold faster photocatalytic kinetics than p-TiO2 and 1.26-fold faster than n-TiO2. Based on the results of an experimental study and theoretical calculations, it was verified that the dual vacancies in pn-TiO2 enabled the valence and conduction bands to be fully exploited to generate ·OH and ·O2–, respectively, for the synergistic degradation of gaseous toluene. Because of the characteristics of the p-n homojunction, charge transfer and separation were efficiently increased in pn-TiO2, resulting in the effective treatment of gaseous toluene. In addition, after five cycles of photocatalytic degradation of toluene, the degradation rate by pn-TiO2 remained over 80%, indicating potential applications for pn-TiO2. In this study, a rational pathway is demonstrated for photocatalysts containing dual vacancies to degrade toluene based on the synergistic effect of free radicals, providing an inspiration for designing materials with vacancies or homojunctions and providing means of eliminating VOCs in practical applications.

Type-II heterojunction of Bi5O7I/WO3 anchored on Ni foam towards efficient photocatalytic degradation of VOCs

A photocatalytic membrane of Bi 5 O 7 I/WO 3 /Ni foam was first prepared by electrophoretic deposition of WO 3 and Bi 5 O 7 I on Ni foam. The Bi 5 O 7 I and WO 3 with mass ratio of 6:7 loaded on Ni foam (BWN-6/7) represented excellent photocatalytic performances. Approximately 95.2% of gaseous toluene (2000 mg m -3 ) was degraded over BWN-6/7 after the adsorption for 30 min and the light irradiation for 180 min. The BWN-6/7 could still degrade 81.6% of gaseous toluene after it was used for 4 rounds. Type-Ⅱ transfer pathway of charge between Bi 5 O 7 I and WO 3 promotes carrier separation efficiency of Bi 5 O 7 I/WO 3 , which is further boosted by Ni foam due to its excellent electricity conductivity. The photo-induced species such as h + and ∙OH play curial roles in the degradation of gaseous toluene. • An efficient photocatalytic film of Bi 5 O 7 I/WO 3 /Ni foam for toluene degradation is fabricated. • Type-Ⅱ transfer pathway of carriers between Bi 5 O 7 I and WO 3 is determined by self-designed experimental device. • DFT calculations predict the electrons flow direction between Bi 5 O 7 I/WO 3 and Ni foam. • Photocatalytic degradation mechanism of toluene over Bi 5 O 7 I/WO 3 /Ni foam is proposed.

A compact Z-scheme heterojunction of BiOCl/Bi2WO6 for efficiently photocatalytic degradation of gaseous toluene

Construction of Z-scheme heterojunction photocatalysts with efficient electron-hole pairs separation and robust oxidation abilities is a promising strategy to decompose volatile organic compounds (VOCs). Herein, UV-light-driven BiOCl and visible-light-driven Bi2WO6 were successfully combined via a one-pot hydrothermal method and compact Z-scheme heterojunction photocatalyst BiOCl/Bi2WO6 was obtained. Owing to the similar precursors and synthesis conditions, the integrated BiOCl/Bi2WO6 heterojunction was intimate and homogenous, which resulted in the efficient separation of photogenerated carriers, and generated abundant holes (h+), hydroxyl radicals (·OH) and superoxide radicals (·O2–). The optimal BiOCl/Bi2WO6 photocatalyst (BWOCl-2), achieved by tailoring the amount of hydrochloric acid, exhibited almost 100 % of toluene degradation and excellent durability. Electron spin resonance (ESR) results revealed that h+, ·O2– and ·OH were dominant active species in the BiOCl/Bi2WO6 photocatalytic system. The degradation intermediate products were monitored by in situ Diffuse Reflection Infrared Fourier Transform spectroscopy (DRIFTS) and the possible photocatalytic mechanism was also revealed according to the band structure of BiOCl/Bi2WO6 heterojunction. This work provided a novel avenue to design an efficient homogenous heterojunction photocatalyst for the efficient degradation of VOCs under sunlight.

Construction of Z-scheme Ag/AgCl/Bi2WO6 photocatalysts with enhanced visible-light photocatalytic performance for gaseous toluene degradation

As a typical aromatic volatile organic compounds (VOCs), toluene is difficult to be decomposed by photocatalysts under visible-light driven. Herein, the Ag/AgCl/Bi2WO6 heterojunction photocatalysts were synthesized by multi-step process involving chemical deposition of AgCl on the surface of Bi2WO6 and subsequently photoreduction of Ag0 nanoparticles by UV light. The as-synthesized photocatalysts were characterized by XRD, SEM, TEM, XPS, UV–vis, PL and ESR to investigate the microstructures and electronic structures. The corresponding degradation efficiencies of gaseous toluene were evaluated and the optimal Ag/AgCl/Bi2WO6 exhibited almost 99.9% removal rate after 60 min illumination with visible light (>420 nm). The optical absorption properties and radical trapping experiments revealed the possible energy band structure of Ag/AgCl/Bi2WO6 heterojunction. Finally, the possible enhancement mechanism was also proposed that the cooperation of surface plasmon resonance (SPR) effect, efficient separation of electron-hole pairs, extension of the carrier lifetime as well as the high redox potentials of Z-scheme heterojunction were the primary reasons. Therefore, construction of Z-scheme heterojunction of Ag/AgCl/Bi2WO6 with higher redox ability is an effective way to degradation gaseous toluene under visible-light irradiation.

Highly efficient visible-light-driven photocatalytic degradation of gaseous toluene by rutile-anatase TiO2@MIL-101 composite with two heterojunctions

The construction of heterophase junctions by rutile-anatase TiO2 is considered an effective strategy for toluene degradation, but the photogenerated electron utilization is still insufficient. In this study, the formation of type-II heterojunction by the encapsulation of Materials of Institut Lavoisier (MIL-101) by anatase is performed, and then the heterophase junction is further constructed to improve the catalytic performance of the photocatalyst. The enhancement of photocatalytic performance depends on the encapsulation of MIL-101 by anatase, the light absorption capacity of anatase, and the contact area of two heterojunctions. Photogenerated electrons are transferred to oxygen vacancies of anatase and promoting the generation of oxygen-containing radicals. The material certifies the synergistic effect of the heterophase junction and heterojunction design and provides a theoretical basis for application in the degradation of volatile organic compounds.