Toluene Conversion Research Articles

Modification of Fe on hydrophobic ZSM-5 zeolite: Optimization of adsorption and catalytic performance for decomposition of VOCs at low-temperature

The conjugation of high adsorption and excellent catalytic characteristics is desirable for the removal of volatile-organic-compounds (VOCs) at low-temperatures. In this study, ZSM-5 zeolites with varying Si/Al ratios (15, 30, 100, and 200) were synthesized using the hydrothermal-method to assess their adsorption capability for VOCs. Among them, the ZSM-5(30) sample exhibited a well-defined zeolite structure, exceptional hydrophobicity, a high surface area (SBET), and micropores, resulting in a higher toluene adsorption capacity of 135 mg/g compared to other adsorbents. Additionally, the ZSM-5(30) sample demonstrated excellent regenerative stability in both dry and humid environments. Consequently, ZSM-5(30), identified as the most effective adsorbent, was subjected to loading with various amounts of Fe metal for the catalytic-oxidation of toluene at low-temperatures. Due to its abundant oxygen-vacancies, adequate acid-sites, and various active oxygen-species, the Fe0.2/ZSM-5(30) catalyst (Fe/(Si + Al) = 0.2) not only exhibited a high adsorption capacity for toluene with good stability over five successive cycles but also demonstrated excellent performance in the catalytic oxidation of toluene. The complete conversion of toluene was attained at temperatures approximately 200 °C, with a gas hourly space velocity (GHSV) of 20,000 mL/(g∙h), and maintained stability for 40 h. Furthermore, in-situ diffuse-reflectance infrared-Fourier-transform-spectroscopy (DRIFTS) and gas chromatography-mass spectrometry (GC–MS) results, along with the Mars-Van-Krevelen model, were utilized to elucidate the adsorption and oxidation mechanism of toluene. The unique adsorption and oxidation capabilities of Fe0.2/ZSM-5(30) for toluene indicate its promising potential for the removal of VOCs in real industrial-environments. This study provides valuable insights for the design of high-performance bifunctional materials for the adsorption and catalytic-oxidation of VOCs.

Rational Atom Substitution to Obtain Efficient, Lead‐Free Photocatalytic Perovskites Assisted by Machine Learning and DFT Calculations

AbstractInorganic lead‐free halide perovskites, devoid of toxic or rare elements, have garnered considerable attention as photocatalysts for pollution control, CO2 reduction and hydrogen production. In the extensive perovskite design space, factors like substitution or doping level profoundly impact their performance. To address this complexity, a synergistic combination of machine learning models and theoretical calculations were used to efficiently screen substitution elements that enhanced the photoactivity of substituted Cs2AgBiBr6 perovskites. Machine learning models determined the importance of d10 orbitals, highlighting how substituent electron configuration affects electronic structure of Cs2AgBiBr6. Conspicuously, d10‐configured Zn2+ boosted the photoactivity of Cs2AgBiBr6. Experimental verification validated these model results, revealing a 13‐fold increase in photocatalytic toluene conversion compared to the unsubstituted counterpart. This enhancement resulted from the small charge carrier effective mass, as well as the creation of shallow trap states, shifting the conduction band minimum, introducing electron‐deficient Br, and altering the distance between the B‐site cations d band centre and the halide anions p band centre, a parameter tuneable through d10 configuration substituents. This study exemplifies the application of computational modelling in photocatalyst design and elucidating structure–property relationships. It underscores the potential of synergistic integration of calculations, modelling, and experimental analysis across various applications.

Rational Atom Substitution to Obtain Efficient, Lead-Free Photocatalytic Perovskites Assisted by Machine Learning and DFT Calculations.

Inorganic lead-free halide perovskites, devoid of toxic or rare elements, have garnered considerable attention as photocatalysts for pollution control, CO2 reduction and hydrogen production. In the extensive perovskite design space, factors like substitution or doping level profoundly impact their performance. To address this complexity, a synergistic combination of machine learning models and theoretical calculations were used to efficiently screen substitution elements that enhanced the photoactivity of substituted Cs2 AgBiBr6 perovskites. Machine learning models determined the importance of d10 orbitals, highlighting how substituent electron configuration affects electronic structure of Cs2 AgBiBr6 . Conspicuously, d10 -configured Zn2+ boosted the photoactivity of Cs2 AgBiBr6 . Experimental verification validated these model results, revealing a 13-fold increase in photocatalytic toluene conversion compared to the unsubstituted counterpart. This enhancement resulted from the small charge carrier effective mass, as well as the creation of shallow trap states, shifting the conduction band minimum, introducing electron-deficient Br, and altering the distance between the B-site cations d band centre and the halide anions p band centre, a parameter tuneable through d10 configuration substituents. This study exemplifies the application of computational modelling in photocatalyst design and elucidating structure-property relationships. It underscores the potential of synergistic integration of calculations, modelling, and experimental analysis across various applications.

Experimental and kinetic modeling study of tar partial oxidative reforming by dielectric barrier discharge plasma using toluene as a model compound

In this study, partial oxidation of toluene as a biomass tar surrogate was carried out in a dielectric barrier discharge (DBD) plasma reactor. In order to understand the reaction characteristics and thus potential of the approach, the effect of reaction temperature, O2/toluene molar ratio (OTR) and discharge power on performances was investigated by experiments and kinetic modeling. The results showed that the three factors could change the E/n and hence the G-values of species, as well as alter O2 concentration in background gas and input energy, leading to the variation in active species production and thus, the performance. Appropriate high temperatures, as well as higher OTRs and discharge power obtained better performances by promoting toluene destruction and gas product production. Excited N2 species play a crucial role in the process, by means of participating in reactions directly and strongly influencing on the production of secondary active species. At 300 °C, the highest toluene conversion of 100.0 % with an energy efficiency of 25.7 g/kWh was achieved without catalysts usage, a comparable performance as compared to the steam reforming by plasma catalysis, demonstrating the potential of this method for the purification of gasification gases. Furthermore, based on the rate of production (ROP) and sensitivity analyses of the model developed, as well as experimental results, the reaction mechanism was proposed.

Highly efficient steam reforming of biomass tar model compound using a high-entropy alloy-based structured catalyst

The development of efficient Ni-based catalysts for steam reforming of biomass tar is crucial for the widespread application of biomass gasification. Multimetal high-entropy alloys (HEAs) have emerged as promising catalysts that can potentially replace conventional metallic materials in various applications. In this study, we investigate NiFeCoMnCu-HEA catalysts supported on the surface of wood carbon (WC) for highly efficient steam reforming of toluene, a model compound for biomass tar. The synergistic effect between Ni and the other four metals in the HEA composition inhibits coke formation during the reaction process, while the appropriate mole ratio of Ni: (Fe + Co + Mn + Cu) reduces the particle size of HEA nanoparticles. Furthermore, the unique structure of wood carbon, with its long, interconnected, yet distorted microchannels, enhances the dispersion of active sites and improves mass transfer efficiency. As a result, the NiFeCoMnCu-HEAs/WC catalyst exhibits outstanding catalytic activity, achieving over 95% toluene conversion for 48 h at 650 °C. This performance surpasses that of the compared catalysts prepared in this work, namely NiFeCoMn/WC (39%), NiFeCoCu/WC (31%), and NiFeCo/WC (20%), underscoring the significance of the HEA structure. The findings also offer valuable insights into enhancing the performance of other nanostructures in the steam reforming of biomass tar.

Engineering the Crystal Facet of Monoclinic NiO for Efficient Catalytic Ozonation of Toluene.

Modulating oxygen vacancies of catalysts through crystal facet engineering is an innovative strategy for boosting the activity for ozonation of catalytic volatile organic compounds (VOCs). In this work, three kinds of facet-engineered monoclinic NiO catalysts were successfully prepared and utilized for catalytic toluene ozonation (CTO). Density functional theory calculations revealed that Ni vacancies were more likely to form preferentially than O vacancies on the (110), (100), and (111) facets of monoclinic NiO due to the stronger Ni-vacancy formation ability, further affecting O-vacancy formation. Extensive characterizations demonstrated that Ni vacancies significantly promoted the formation of O vacancies and thus reactive oxygen species in the (111) facet of monoclinic NiO, among the three facets. The performance evaluation showed that the monoclinic NiO catalyst with a dominant (111) facet exhibits excellent performance for CTO, achieving a toluene conversion of ∼100% at 30 °C after reaction for 120 min under 30 ppm toluene, 210 ppm ozone, 45% relative humidity, and a space velocity of 120 000 h-1. This outperformed the previously reported noble/non-noble metal oxide catalysts used for CTO at room temperature. This study provided novel insight into the development of highly efficient facet-engineered catalysts for the elimination of catalytic VOCs.

Catalytic oxidation of toluene over Co3O4-CeO2 bimetal oxides derived from Ce-based MOF

A series of Co–Ce oxide catalysts with different molar ratios were prepared by impregnation and pyrolysis using a Co-loaded Ce-based metal–organic framework as a precursor. Physicochemical properties of the catalysts were characterized by N2 adsorption–desorption measurements, X-ray diffraction, H2 temperature-programmed reduction, Raman analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, thermal desorption-gas chromatography-mass spectrometry and scanning electron microscopy. Toluene was selected as a reference to evaluate catalytic performance. Results show that the catalyst prepared at a Co/(Ce+Co) molar ratio of 0.3 exhibits excellent catalytic activity in the catalytic oxidation of toluene. The temperature at 90 % conversion of toluene (T90) is 262 °C which is significantly lower than the catalyst prepared by the traditional preparation method. The specific surface area is not the main factor affecting the reaction. The high activity is due to the better low temperature reducibility, abundant lattice defects, more active oxygen species, higher surface Ce3+ species (oxygen vacancies). What's more, 30Co-Ce has superior stability at different conversion rates and tolerance in the presence of water vapor. The results stated above indicate that the surface properties of the Co-Ce catalysts significantly affected the toluene combustion reaction.

Constructing Active Cu2+-O-Fe3+ Sites at the CuO-Fe3O4 Interface to Promote Activation of Surface Lattice Oxygen.

Activating surface lattice oxygen (Olatt) through the modulation of metal-oxygen bond strength has proven to be an effective route for facilitating the catalytic degradation of volatile organic compounds (VOCs). Although this strategy has been implemented via the construction of the TM1-O-TM2 (TM represents a transition metal) structure in various reactions, the underlying principle requires exploration when using different TMs. Herein, the Cu2+-O-Fe3+ structure was created by developing CuO-Fe3O4 composites with enhanced interfacial effect, which exhibited superior catalytic activity to their counterparts, with T90 (the temperature of toluene conversion reaching 90%) decreasing by approximately 50 °C. Structural analyses and theoretical calculations demonstrated that the active Cu2+-O-Fe3+ sites at the CuO-Fe3O4 interface improved low-temperature reducibility and oxygen species activity. Particularly, X-ray absorption fine structure spectroscopy revealed the contraction and expansion of Cu-O and Fe-O bonds, respectively, which were responsible for the activation of the surface Olatt. A mechanistic study revealed that toluene can be oxidized by rapid dehydrogenation of methyl assisted by the highly active surface Olatt and subsequently undergo ring-opening and deep mineralization into CO2 following the Mars-van Krevelen mechanism. This study provided a novel strategy to explore interface-enhanced TM catalysts for efficient surface Olatt activation and VOCs abatement.

Ti3+/Ti4+ and Co2+/Co3+ redox couples in Ce-doped Co-Ce/TiO2 for enhancing photothermocatalytic toluene oxidation

Cerium and cobalt loaded Co-Ce/TiO2 catalyst prepared by impregnation method was investigated for photothermal catalytic toluene oxidation. Based on catalyst characterizations (XPS, EPR and H2-TPR), redox cycle between Co and TiO2 (Co2+ + Ti4+ ↔ Co3+ + Ti3+) results in the formation of Co3+, Ti3+ and oxygen vacancies, which play important roles in toluene catalytic oxidation reaction. The introduction of Ce brings in the dual redox cycles (Co2+ + Ti4+ ↔ Co3+ + Ti3+, Co2+ + Ce4+ ↔ Co3+ + Ce3+), further promoting the elevation of reaction sites amount. Under full spectrum irradiation with light intensity of 580 mW/cm2, Co-Ce/TiO2 catalyst achieved 96% of toluene conversion and 73% of CO2 yield, obviously higher than Co/P25 and Co/TiO2. Co-Ce/TiO2 efficiently maintains 10-hour stability test under water vapor conditions and exhibits better photothermal catalytic performance than counterparts under different wavelengths illumination. Photothermal catalytic reaction displays improved activities compared with thermal catalysis, which is attributed to the promotional effect of light including photocatalysis and light activation of reactive oxygen species.

Steam reforming of toluene over Ni–Co/modified-activated carbon catalyst for hydrogen production: Thermodynamic and experimental analysis

An integrated thermodynamic and experimental analysis of steam reforming of toluene (SRT) over Ni–Co/modified-palm kernel shell activated carbon (AC) catalysts for H2 production has been investigated. The catalyst samples, synthesized with different AC support modifications methods (i.e., HNO3 reflux and H2O2 aging) and impregnation, are characterized by BET, TGA, FESEM-EDX, TEM, XRD, H2-chemisorption and TPO spectroscopies. Aspen Plus® simulation software is employed to perform the thermodynamic analysis to investigate the effect of wide range of operating parameters such as temperature (373–1473 K), pressure (1–30 atm) and steam-to-carbon (S/C) molar ratio (1–9) on product distribution using Gibbs free energy minimization. Optimum conditions of SRT with 86.4% H2 yield and complete toluene conversion are attained at 973 K, S/C ratio of 5 and atmospheric pressure. Next, the catalytic performance of Ni–Co/modified-AC for enhancing SRT to H2 is conducted in a fixed-bed reactor at selected conditions. It is revealed that Ni–Co/ACP catalyst confers 82.0% and 91.7% of H2 yield and toluene conversion, respectively. The results of thermodynamic simulation and experimental testing strongly corroborate the role of Ni–Co/ACP as a high-performance catalyst to enhance catalytic conversion of SRT.

Pt Nanoparticles on Beta zeolites for Catalytic Toluene Oxidation: Effect of the Hydroxyl Groups of Beta Zeolite**

AbstractStabilisation of metal species using hydroxyl‐rich dealuminated zeolites is a promising method for catalysis. However, insights into the interactions between the hydroxyl groups in zeolite and noble metals and their effects on catalysis are not yet fully understood. Herein, comparative studies were conducted using Pt catalysts supported on hydroxyl‐rich dealuminated Beta (deAl‐Beta) and the pristine proton‐form Beta (H‐Beta) for catalytic oxidation of toluene. The findings suggest that during impregnation the Pt precursor (i. e., Pt(NH3)4(NO3)2) interacted with different sites on deAl‐Beta and H‐Beta, leading to the formation of supported Pt nanoparticles with different physicochemical properties. In detail, for H‐Beta, the Pt precursor interacted with Al‐OH and isolated external Si‐OH sites, yielding Pt NPs with a higher Pt0 proportion of ~71 % compared to ~57 % Pt0 on deAl‐Beta. Comparatively, abundant hydroxyl groups on deAl‐Beta such as silanol nest and isolated internal Si‐OH stabilised highly active Pt‐O species. The resulting Pt/deAl‐Beta exhibited improved activity and anti‐coking ability than Pt/H‐Beta in catalytic toluene oxidation. For example, the temperature for 50 % toluene conversion was 193 °C for Pt/deAl‐Beta vs. 232 °C for Pt/H‐Beta, and the coke deposition was 1.7 % vs. 6.7 % (after the 24‐h longevity test), respectively. According to the toluene‐temperature programmed desorption (toluene‐TPD), 1H nuclear magnetic resonance (1H NMR) relaxation and in situ diffuse reflection Fourier transform spectroscopy (in situ DRIFTS) characterisation, the enhanced performance of Pt/deAl‐Beta could be ascribed to (i) the active Pt‐O sites stabilised by hydroxyl groups, which interact with toluene easily for conversion, and (ii) the acid‐free feature of the deAl‐Beta support, which avoids the formation of coke precursors (such as benzoate species) on the catalyst surface. Findings of the work can serve as the design guidelines for making effective supported metal catalysts using zeolitic carriers.

Treatment of Mixture Pollutants with Combined Plasma Photocatalysis in Continuous Tubular Reactors with Atmospheric-Pressure Environment: Understanding Synergetic Effect Sources.

This study investigates the pilot-scale combination of nonthermal plasma and photocatalysis for removing Toluene and dimethyl sulfur (DMDS), examining the influence of plasma energy and initial pollutant concentration on the performance and by-product formation in both pure compounds and mixtures. The results indicate a consistent 15% synergy effect, improving Toluene conversion rates compared to single systems. Ozone reduction and enhanced CO2 selectivity were observed when combining plasma and photocatalysis. This process effectively treats pollutant mixtures, even those containing sulfur compounds. Furthermore, tests confirm nonthermal plasma's in-situ regeneration of the photocatalytic surface, providing a constant synergy effect.

Metal organic framework template method for the preparation of bimetallic oxide CunCoOx catalysts for the catalytic oxidation of volatile organic compounds

A series of CunCoOx bimetallic oxides were synthesized by calcination of xCu/ZIF-67 precursors pre-impregnated with Cu2+. The Cu7CoOx catalyst demonstrated remarkable reactivity, reaching about 90 % conversion of toluene and ethylene at 194 °C and 162 °C. Additionally, Cu7CoOx was deemed suitable for applications at high space velocities, and also displaying superior stability. The physicochemical properties of CunCoOx were investigated by SEM, TEM, XRD, FTIR, BET, Raman, TG, O2-TPD, H2-TPR and XPS characterizations. The excellent catalytic performance of Cu7CoOx is attributed to the strong interaction of the two metal oxides, excellent redox ability, abundant lattice defects, more reactive oxygen species and higher concentrations of Co2+ and OLatt species. Density functional theory (DFT) calculation revealed CuO/Co3O4 (220) (Eads,O2 = −0.92 eV, Eads,toluene = −1.52 eV) displayed lower adsorption energy for toluene and oxygen molecules than Co3O4 (220) (Eads,O2 = −0.30 eV, Eads,toluene = −0.90 eV), which was favorable for the catalyst to catalyze the oxidation of VOCs. The possible degradation mechanism of toluene on Cu7CoOx was revealed using in situ DRIFTS. Thus, this work provides a non-noble metal catalyst with great application potential in VOCs treatment.

A study on the oxidation of toluene to benzaldehyde by air catalyzed by polyoxometalate loaded on activated carbon

At present, benzaldehyde is mainly produced in the way of liquid-phase chlorination of toluene followed by hydrolysis. Such method not only pollutes the environment with the discharge of large amount of waste water, but also limits its application into the field of food and medicine due to the existence of chlorides. In this paper, toluene is oxidized to benzaldehyde by air in acetic acid using polyoxometalate supported on activated carbon as a catalyst. The composition and preparation conditions of the catalyst have been explored. The optimum polyoxometalate composition is determined as Na5.1La0.7CoMn0.3Mo11.7O40·22.05H2O@AC by ICP-OES, FT-IR, XRD and TG. The optimum catalyst preparation conditions are pH1=6.3, pH2=3.8, T1=95°C, T2=85°C, activation temperature 220°C and activation time 4 h. The best experimental results are toluene conversion 13.18 %, benzaldehyde selectivity 40.43 % and benzaldehyde yield 5.33 %.

Ni0+ particle size-dependent pyrolytic reforming of toluene over Ni/Al2O3 for the co-production of hydrogen and CNTs

Pyrolytic reforming of toluene over Ni-based catalysts loaded on nano-sized and micro-sized γ-Al2O3 is investigated in a fixed bed reactor under the temperature from 500 °C to 800 °C. The physicochemical properties of γ-Al2O3 and Ni/Al2O3 catalysts were characterized by HRTEM, XPS, XRD and H2-pulse chemisorption. The metal Ni loaded on micro-sized γ-Al2O3 gave the steady toluene conversion of more than 80% and graphite yield of 87.3% after 1 h of reforming reaction. The rapid decrease of H2 yield from 5.2 mmol/g-toluene to 0.4 mmol/g-toluene over Ni/nano-Al2O3 was obtained during the 1 h of reforming reaction at 500 °C. The particle size of metal Ni over nano-sized and micro-sized γ-Al2O3 were centered at 7.8 nm and 28.8 nm, respectively. The metastable NiCx crystallites were observed over the spent Ni/nano-Al2O3 catalyst, while only metal Ni were obtained over the spent Ni/micro-Al2O3 catalyst. Ni0+ particle size-dependent crystalline phase was evidenced by MD simulations, where incorporation of more carbon atoms was achieved on small Ni particles. The energy barrier for –CH2 dehydrogenation over Ni32C, Ni4C and Ni3C were estimated to be 90.2, 105.1 and 116.0 kJ/mol through the DFT simulation, respectively. It can be concluded that the crystalline Ni phase was maintained over Ni/micro-Al2O3 with large Ni particle size, prolonging the catalytic endurance and promoting the CNTs (Carbon Nanotubes) growth without the deposition of unexpected amorphous carbon.

Triggering photocatalytic performance of La2CoxMn2-xO6 via heat activation.

The La-based perovskite (LaBO3) exhibits excellent optical properties. However, its valence band (VB) potential is not sufficiently positive to reach the oxidation potential required for the cleavage of chemical bonds (such as benzylic C-H), limiting its application in photocatalysis. Herein, we report the unconventional effects of heat activation on the reduction of the dissociation energy of benzylic C-H and aqueous H-O, thereby triggering the photocatalytic activity of La2CoxMn2-xO6 perovskites. Additionally, we demonstrate that photocatalysis is the main contributor to substrate conversion in the selective oxidation of toluene and reduction of CO2. Particularly, La2Co1.5Mn0.5O6 shows excellent performance with a product yield of 550.00 mmol gcat-1 and a toluene conversion of 22,866.67 μmol gcat-1 h-1. To the best of our knowledge, this is the highest reported product yield for the selective oxidation of benzylic C-H bond of toluene. Our findings provide insight into the specific role of heat activation in photocatalysis, which is crucial for breaking and overcoming the VB barrier to realize challenging reactions.

In situ construction of Mn-Fe multi oxides derived from K2FeO4 and MnSO4 for high-efficient degradation of toluene

In this work, a series of manganese-based multi oxide (Mn3O4-Fe2O3) was in-situ synthesized using K2FeO4 and MnSO4 as the precursor via one-step hydrothermal method. Catalytic evaluation shows that Mn3O4-Fe2O3-Ni performs the best activity among the prepared catalysts. T90% and T50% of toluene conversion on Mn3O4-Fe2O3-Ni are 257 and 223 °C, respectively, which are 59 and 28 °C lower than those of Mn3O4-Fe2O3-140. XRD analysis proves that the prepared catalysts are composed of Mn3O4 and Fe2O3; N2-BET indicates that Mn3O4-Fe2O3-Ni has a higher specific surface area; HRTEM analysis implies that the (103) and (112) of Mn3O4 (PDF #18–0803) crystal planes are exposed on Mn3O4-Fe2O3-140 and Mn3O4-Fe2O3-Ni, respectively, implying that the introduction of Ni can result in the change of exposed plane. Raman, XPS and O2-TPD analysis implies that there are abundant lattice defects and abundant surface adsorbed oxygen. DFT calculations suggests that the oxygen vacancies are more likely to be formed on the (112) plane in Mn3O4-Fe2O3-Ni than that of (103) plane in Mn3O4-Fe2O3-140, which is consistent with the analysis result of Raman spectra and O2-TPD. At last, the possible degradation route of toluene oxidation on Mn3O4-Fe2O3-Ni is induced.

Photothermal catalytic oxidation of toluene by perovskite oxide/biochar nanocomposite: Effect of biomass incorporation

The utilization of waste biomass for the development of full-spectrum response photothermal catalysts shows significant potential in catalytic oxidation of volatile organic compounds (VOCs). Herein, perovskite oxide LaCoO3/biomass-derived biochar nanocomposite was synthesized by the sol–gel method using wasted pomegranate peel as complex agent. The introduction of biomass resulted in improved dispersion of LaCoO3 particles and enhanced the adsorption of toluene attributed to the large specific surface area and rich functional groups of biochar. Furthermore, the biochar exhibited strong broadband absorption and efficient photo-thermal conversion under light illumination, which not only activated the lattice oxygen on the surface to react with toluene, but also increased the transmission rate of photogenerated charge carriers. The defects of LaCoO3 caused by carbon doping facilitated the circulation of oxygen species, leading to the generation of more reactive oxygen species. When the mass ratio of LaCoO3 to biomass was 1:0.6, the LaCoO3/biochar composite exhibited excellent photothermal catalytic performance with a T90 value of 270 °C (temperature at 90 % degradation) and displaying high stability. Moreover, In-situ DRIFTS analysis revealed that both adsorbed oxygen and lattice oxygen participated in the reaction with toluene, promoting the ring-opening reaction of toluene and subsequent conversion of intermediates.

Energy band matching Bi2WO6/black-TiO2 Z-scheme heterostructure for the enhanced visible-light photocatalytic degradation of toluene

By exploiting the distinct band alignment characteristics of various semiconductors, the Z-scheme heterostructure represents a significant method to improve the effectiveness of energy conversion processes. In this work, Bi2WO6/Black-TiO2 (BTB) compounds are developed using the hydrothermal method combined with sol-gel method. It is shown that the separation efficiency of photoinduced carriers on BTB is visibly raised via establishing a Z-scheme system with matched energy band structures. The surface carrier separation efficiency is closely related to photocatalytic activity. Under visible light, the degrading performance of toluene over BTB heterostructure is found to be markedly enhanced. BTB-3 exhibits the optimal photocatalytic activity of the group, achieving a toluene conversion of 90% after 120 min reaction, which is twice and 5.5 times larger than that of B-TiO2 and Bi2WO6, respectively. Furthermore, developing of BTB Z-scheme heterostructure can preserve the catalyst's initial redox capacity, thereby producing more significant active species, e.g., ·OH and ·O2−radicals, to efficiently decompose toluene. According to in-situ DRIFTS data, acids, aldehydes and alcohols are among the intermediates that are collected during various stages of toluene's photocatalytic breakdown. This work supplies a fresh, workable route for future photocatalytic volatile organic compounds degradation.

Multi-dimensional lead-free hybrid double perovskite toward efficient and stable photocatalytic selective oxidation of toluene

With unique photoelectronic properties, perovskites have drawn attention in photocatalysis. However, their activity and stability especially in moist environments is not appealing, despite it was demonstrated that the construction of three-dimensional (3D) and low-dimensional counterparts could result in boosting of activity and stability, respectively. Here, a lead-free hybrid double perovskite ((DETA)BiBr6/Cs2AgBiBr6, DCABB) was fabricated by uniformly dispersing 0D DETABiBr6 (DETA3+ = NH3+(CH2)2NH2+(CH2)2NH3+) in the matrix of 3D Cs2AgBiBr6. Benefited from the passivation of Br defects and resistance of water by DETA3+, the stability of DCABB improved in comparison to pristine 3D Cs2AgBiBr6. Moreover, the formation of DCABB increased the adsorption of O2 and the accumulation of photogenerated electrons on the surface of catalyst, consequently boosting the generation of active O2− and OH species. The DCABB displayed higher photocatalytic performance than its components in toluene selective oxidation under visible light illumination, achieving a toluene conversion of up to 100 %.