Degradation Of Volatile Organic Compounds Research Articles

Optimization of photothermal conversion and catalytic sites for photo-assisted-catalytic degradation of volatile organic compounds

Solar energy conversion is a promising strategy to enhance the elimination of volatile organic compounds (VOCs) and minimize power consumption. Herein, non-noble metal WC@WO3 as cocatalyst was composited with CeO2 to optimize photochemical and photothermal conversion for the catalytic ozonation of toluene and acetone. The photothermal conversion efficiencies of visible and infrared lights on 20%WC@WO3–CeO2 were 2.2 and 10.4 times higher than those on CeO2, respectively, which indicates that the equilibrium temperature of the catalyst remarkably increased under full-spectrum light irradiation. Moreover, WC@WO3 transferred electrons to CeO2 in 20%WC@WO3–CeO2 and thus remarkably improved the activity of catalytic sites. The synergy factor of light and O3 on 20%WC@WO3–CeO2 was 5.8, and the reaction rate of toluene and acetone reached 9274.5 and 35779.0 mg/(m3∙min), respectively. This work provides a low-cost and high-efficient catalyst for the utilization of solar energy for VOC control.

Hierarchically nanostructured Ag/ZnO/nBC for VOC photocatalytic degradation: Dynamic adsorption and enhanced charge transfer

The adsorption-photodegradation strategy can achieve continuous enrichment and efficient oxidation of volatile organic compounds (VOCs), but it requires a trade-off among adsorption, mass transfer, and charge transfer in this dynamic process. Therefore, the construction of an effective and stable catalytic system remains an immense challenge. Here, we report a strategy for constructing a hierarchically structured photocatalyst for efficiently degrading VOCs by assembling nanobiochar (nBC, ∼ 6.25 µm), the active center of ZnO (∼ 460 nm), and plasmonic-Ag nanoparticles (Ag NPs, ∼ 10 nm). Benefiting from its abundant surface functional groups (–OH, –CO, and –CO) and hierarchical structure-induced mesopores and macropores, VOCs can be quickly captured and dynamically diffused. Furthermore, Ag NPs build a charge transfer bridge and accumulate electrons to nBC from both the photogenerated electrons that are induced by ZnO and hot electrons from the local surface plasmon resonance (LSPR) effect of Ag NPs. Afterward, a desirable spatial separation of charge carriers and visible-light response can be achieved. Therefore, Ag/ZnO/nBC maximizes the reactive oxygen species (e.g., ·OH and ·O2−) and shows a 7.8 times higher degradation rate of formaldehyde than ZnO, and it also displays universality and stability with high photocatalytic efficiency. The photocatalytic performance was comprehensively determined based on the relative humidity, initial concentration, catalyst dose, and mass ratio of Ag NPs. This facile and universal strategy for architecting hierarchically structured photocatalysts provides an approach for enhancing photocatalytic performance for VOC degradation and environmental pollution treatment.

Experimental analysis of gas- and particle-phase organic byproducts formed by plasma-induced toluene destruction processes

• Organic byproducts were evaluated by NTP degradation of toluene at ambient temperature and atmospheric pressure. • PTR-TOFMS measurement showed that toluene degradation resulted in dozens of organic by-products. • Size distribution and number concentration of particles formed during toluene degradation were measured by SMPS. • NTP-induced polymerization and oxidation contribute to particle formation with diameters in the range of 10 and 100 nm. Non-thermal plasma (NTP) technology has great potential to treat volatile organic compounds (VOCs) at low concentrations and large volumes. In this work, toluene, one of the most stable VOCs, was employed as a model pollutant to study its degradation by double dielectric barrier discharge (DDBD) at ambient temperature and atmospheric pressure. The performance of the DDBD reactor was evaluated in terms of discharge power, removal efficiency, CO x selectivity, and byproduct formation. Online and continuous measurements by PTR-TOFMS showed that toluene degradation resulted in the formation of 12 major volatile organic byproducts as well as 7 minor ones with concentrations ranging from ppbv to ppmv. Moreover, the particle size distribution and number concentration of particles formed during toluene degradation were measured using a scanning mobility particle sizer, and the effects of discharge power, initial toluene concentration, gas flow rate and O 2 content on particle formation were systematically investigated. The results show that both NTP-induced polymerization and oxidation contribute to aerosol formation, and the total concentration of organic byproducts in the aerosol phase is about 10 7 cm −3 with diameters in the range of 10 and 100 nm. This pioneered investigation on gas- and particle-phase organic byproducts from toluene degradation by NTP would deepen the understanding of plasma degradation of VOCs and accelerate the practical application of NTP for VOCs treatment.

An efficient process for aromatic VOCs degradation: Combination of VUV photolysis and photocatalytic oxidation in a wet scrubber

The elimination of volatile organic compounds (VOCs) via vacuum ultraviolet (VUV) photolysis is greatly limited by low removal efficiency and gaseous byproducts generation, while photocatalytic oxidation of VOCs suffers from catalytic deactivation. Herein, a coupled process of gaseous VUV photolysis with aqueous photocatalytic oxidation with P25 as the catalyst was firstly proposed for efficient aromatic VOCs removal (VUV/P25). The removal efficiency of toluene reached 86.2% in VUV/P25 process, but was only 33.6% and 58.1% in alone gaseous VUV photolysis and aqueous ultraviolet photocatalytic oxidation (UV/P25) process, respectively. Correspondingly, the outlet CO2 concentration in VUV/P25 process reached 132 ppmv. Toluene was firstly destructed by high-energy photons generated from gaseous VUV photolysis, resulting in its incomplete oxidation to form soluble intermediates including acids, aldehydes, esters. These soluble intermediates would be further degraded and mineralized into CO2 in subsequent aqueous UV/P25 process. Notably, the concentrations of intermediates in VUV/P25 were much lower than those in VUV photolysis, indicating the synergy effect of VUV photolysis and UV/P25 process. The stability tests proved that VUV/P25 process maintained an excellent toluene degradation performance and P25 did not suffer from catalytic deactivation. In addition to toluene, the VUV/P25 system also achieved the efficient and sustainable degradation of styrene and chlorobenzene, suggesting its good application prospect in industrial VOCs treatment. This study proposes an efficient and promising strategy for deep oxidation of multiple aromatic VOCs in industries.

Infrared-to-visible upconversion enhanced photothermal catalytic degradation of toluene over Yb3+, Er3+: CeO2/attapulgite nanocomposite: Effect of rare earth doping

Developing low cost and efficient strategy to eliminate volatile organic compounds (VOCs) are quite urgent and challenging. Herein, CeO2 nanoparticles co-doped with Yb3+ and Er3+ were immobilized on attapulgite clay (ATP) for photothermal catalytic oxidation of toluene. The CeO2:Yb3+, Er3+/ATP exhibited outstanding catalytic activity with low T90 of 295 °C (temperature at 90% degradation), satisfactory stability and highly water resistance. The enhanced photothermal catalytic performance can be attributed to the optimal introduction of Yb3+ and Er3+, which promoted the up-conversion of near-infrared light (NIR) to visible light increasing the light utilization. The defects caused by Yb3+/Er3+ doping facilitated the adsorption of O2, while the active oxygen species generated from the defects and the photoinduced reactive species not only favored the oxidation of toluene in photothermal catalytic process, but also accelerated the reoxidation of reduced catalyst. Notably ATP support provided large specific surface area and abundant adsorption sites for toluene molecules to promote the deep oxidation and hindered the deactivation of catalysts caused by the accumulation of intermediates. In-situ DRIFTS test revealed that the alkoxide and benzoate appeared as the main intermediates, which can be deeply oxidized under light irradiation. Current work provides a new alternative for photothermal catalytic degradation of VOCs.

Catalytic degradation of benzene over non-thermal plasma coupled Co-Ni binary metal oxide nanosheet catalysts

Non-thermal plasma (NTP) has been demonstrated as one of the promising technologies that can degrade volatile organic compounds (VOCs) under ambient condition. However, one of the key challenges of VOCs degradation in NTP is its relatively low mineralization rate, which needs to be addressed by introducing catalysts. Therefore, the design and optimization of catalysts have become the focus of NTP coupling catalysis research. In this work, a series of two-dimensional nanosheet Co-Ni metal oxides were synthesized by microwave method and investigated for the catalytic oxidation of benzene in an NTP-catalysis coupling system. Among them, Co2Ni1Ox achieves 60% carbon dioxide (CO2) selectivity (SCO2) when the benzene removal efficiency (REbenzene) reaches more than 99%, which is a significant enhancement compared with the CO2 selectivity obtained without any catalysts (38%) under the same input power. More intriguingly, this SCO2 is also significantly higher than that of single metal oxides, NiO or Co3O4, which is only around 40%. Such improved performance of this binary metal oxide catalyst is uniquely attributed to the synergistic effects of Co and Ni in Co2Ni1Ox catalyst. The introduction of Co2Ni1Ox was found to promote the generation of acrolein significantly, one of the key intermediates found in NTP alone system reported previously, suggest the benzene ring open reaction is promoted. Compared with monometallic oxides NiO and Co3O4, Co2Ni1Ox also shows higher active oxygen proportion, better oxygen mobility, and stronger low-temperature redox capability. The above factors result in the improved catalytic performance of Co2Ni1Ox in the NTP coupling removal of benzene.

Harnessing Waste Heat from Indoor lamps for Sustainable Thermocatalytic Mineralization of Acetaldehyde using Platinized TiO2

This study demonstrates the first reported thermocatalytic oxidation of an indoor volatile organic compound (VOC), acetaldehyde, by harnessing the waste-heat energy from indoor light sources (e.g., halogen lamps) without additional energy inputs. With an optimal Pt–TiO2 catalyst, the designed catalyst-coated lampshade was successfully activated under waste-heat energy (∼120 °C) and achieved the complete mineralization of CH3CHO into CO2 (k = 0.02 min−1). The catalytic activity of Pt–TiO2 was extremely dependent on its preparation method which greatly influenced the characteristics (e.g., oxidation state and size) of Pt. The thermocatalytic oxidation mechanism of CH3CHO over Pt–TiO2 was investigated, which revealed that O2 and H2O sources play vital roles. Although Pt is an expensive noble metal, the thermocatalytic process on the Pt–TiO2-coated lampshade without additional energy, along with its outstanding activity, can offset the high material cost. The proposed strategy offers a sustainable and feasible method for the degradation of indoor VOCs.

Elucidating the role of confinement and shielding effect over zeolite enveloped Ru catalysts for propane low temperature degradation.

Volatile organic compounds (VOCs) are the main precursor for ozone formation and hazardous to human health. Light alkane as one of the typical VOCs is difficult to degrade to CO2 and H2O by catalytic degradation method due to its strong C-H bond. Herein, a series of ultrafine Ru nanoclusters (<0.95nm) enveloped in silicalite-1 (S-1) zeolite catalysts were designed and prepared by a simple one-pot method and applied for catalytic degradation of propane. The results demonstrate that the enveloped Ru1@S-1 catalyst has excellent propane degradation performance. Its T95 is as low as 294°C with moisture, and the turnover frequency (TOF) value is up to 5.07 × 10-3 s-1, evidently higher than that of the comparison supported catalyst (Ru1/S-1). Importantly, Ru1@S-1 exhibits superior thermal stability, water resistance and recyclability, which should be attributed to the confinement and shielding effect of the S-1 shell. The in-situ DRIFTS result reveals that the propane degradation over Ru1@S-1 follows the Mars-van-Krevelen (MvK) mechanism, where the hydroxy from the framework of zeolite can provide the active oxygen species. Our work provides a new candidate and guideline for an efficient and stable catalyst for the low-temperature degradation of the light alkane VOCs.

Modified Mn/ZSM-5 for Non-Thermal Plasma Mineralization of VOCs and DFT Simulation Using a Novel Y-Type ZSM-5 Model

Using a catalyst to mineralize volatile organic compounds (VOCs) in a Non-thermal Plasma (NTP) reactor is an effective method. In many kinds of catalysts for VOCs degradation, oxygen defect is a crucial factor affecting the catalytic activity. Three different methods (steaming, doping, plasma) were used to introduce possible oxygen defects into the Mn/ZSM-5 to prepare modified catalysts, which were evaluated in VOCs degradation activity using a Double Dielectric Barrier Discharge (DDBD) plasma device. Additionally, a novel Y-type ZSM-5 model was employed in the DFT simulation. The new Y-type ZSM-5 model used in this paper is a more realistic aperiodic model. It showed that introducing possible oxygen defects can substantially enhance degradation efficiency. Taking the catalyst with oxygen defects introduced by plasma as an example, the conversion (CO2 selectivity) of the methanol, acetone, and toluene could reach 100% (100%), 97.7% (99.1%), 91.2% (93.9%), respectively, at an initial concentration of 2000 ppm and specific input energy of 9 kJ/L. The results demonstrated that modification could significantly enhance the activity of the catalyst in decomposing VOCs at room temperature using non-thermal plasma catalysis. Theoretical simulation of density functional theory (DFT) revealed that the adsorption of adsorbate on the catalyst becomes easier after possible oxygen defects are introduced.

Treatment of wood by sulfate and hydroxyl radical oxidation produced from thermally-activated persulfate: VOC emission and wood property evaluation

ABSTRACT Wood emits volatile organic compounds (VOCs) that can affect people’s health and air quality. Based on advanced oxidation processes (AOPs), sulfate radicals produced via thermally-activated persulfate (Na2S2O8, KHSO5) can minimize VOCs. This research aims to apply this technique to minimize the VOC content in Pinus radiata. The results showed that terpenes and alcohols were the main VOCs emitted from Pinus radiata, which were greatly minimized using four treatments; however, acetic acid and 3-furaldehyde emissions increased. Furthermore, the temperature and oxidizing agent contributed to VOC degradation. Characterization results, including FTIR, XRD, color tests, and compressive strength indicated that the AOP treatment caused only a slight decline in the wood properties, while effectively reducing VOC emissions by as much as 32.75–61.05%.

Graphene-based porous nanohybrid architectures for adsorptive and photocatalytic abatement of volatile organic compounds

Volatile organic compounds (VOCs) represent a considerable threat to humans and ecosystems. Strategic remediation techniques for the abatement of VOCs are immensely important and immediately needed. Given a unique set of optical, mechanical, electrical, and thermal characteristics, inimitable surface functionalities, porous structure, and substantial specific surface area, graphene and derived nanohybrid composites have emerged as exciting candidates for abating environmental pollutants through photocatalytic degradation and adsorptive removal. Graphene oxide (GO) and reduced graphene oxide (rGO) containing oxygenated function entities, i.e., carbonyl, hydroxyl, and carboxylic groups, provide anchor and dispersibility of their surface photocatalytic nanoscale particles and adsorptive sites for VOCs. Therefore, it is meaningful to recapitulate current state-of-the-art research advancements in graphene-derived nanostructures as prospective platforms for VOCs degradation. Considering this necessity, this work provides a comprehensive and valuable insight into research progress on applying graphene-based nanohybrid composites for adsorptive and photocatalytic abatement of VOCs in the aqueous media. First, we present a portrayal of graphene-based nanohybrid based on their structural attributes (i.e., pore size, specific surface area, and other surface features to adsorb VOCs) and structure-assisted performance for VOCs abatement by graphene-based nanocomposites. The adsorptive and photocatalytic potentialities of graphene-based nanohybrids for VOCs are discussed with suitable examples. In addition to regeneration, reusability, and environmental toxicity aspects, the challenges and possible future directions of graphene-based nanostructures are also outlined towards the end of the review to promote large-scale applications of this fascinating technology.

Facile fabrication of the Ag nanoparticles decorated graphitic carbon nitride photocatalyst film for indoor air purification under visible light

Visible light photocatalysis represents a promising procedure for indoor air purification. Here we developed the Ag nanoparticles decorated graphitic carbon nitride photocatalyst film supported on glass substrate. This photocatalyst film can effectively use visible light to degrade various volatile organic compounds which contain formaldehyde, acetaldehyde, ethylene, benzene, toluene, and p-xylene and deactivate Escherichia coli, Staphylococcus aureus, and Candida albicans. The decoration of Ag nanoparticles enhanced the visible-light-driven activity of graphitic carbon nitride because Ag nanoparticles strongly absorb visible light through the localized surface plasmon resonance effect and facilitate the efficient separation of charge carriers by forming Schottky barrier with the semiconductor. Photo-generated holes and superoxide radical anions, rather than hydroxyl radicals, are the major active species in the photocatalytic degradation of volatile organic compounds and deactivation of microorganisms. The application potential of the developed photocatalyst film for indoor air purification was demonstrated by the efficient removal of HCHO and TVOC under a simulated indoor environment and the favorable recyclability of the photocatalyst.

Substrate-restricted methanogenesis and limited volatile organic compound degradation in highly diverse and heterogeneous municipal landfill microbial communities

Microbial communities in landfills transform waste and generate methane in an environment unique from other built and natural environments. Landfill microbial diversity has predominantly been observed at the phylum level, without examining the extent of shared organismal diversity across space or time. We used 16S rRNA gene amplicon and shotgun metagenomic sequencing to examine the taxonomic and functional diversity of the microbial communities inhabiting a Southern Ontario landfill. The microbial capacity for volatile organic compound degradation in leachate and groundwater samples was correlated with geochemical conditions. Across the landfill, 25 bacterial and archaeal phyla were present at >1% relative abundance within at least one landfill sample, with Patescibacteria, Bacteroidota, Firmicutes, and Proteobacteria dominating. Methanogens were neither numerous nor particularly abundant, and were predominantly constrained to either acetoclastic or methylotrophic methanogenesis. The landfill microbial community was highly heterogeneous, with 90.7% of organisms present at only one or two sites within this interconnected system. Based on diversity measures, the landfill is a microbial system undergoing a constant state of disturbance and change, driving the extreme heterogeneity observed. Significant differences in geochemistry occurred across the leachate and groundwater wells sampled, with calcium, iron, magnesium, boron, meta and para xylenes, ortho xylenes, and ethylbenzene concentrations contributing most strongly to observed site differences. Predicted microbial degradation capacities indicated a heterogeneous community response to contaminants, including identification of novel proteins implicated in anaerobic degradation of key volatile organic compounds.

Particulate matter capturing over manganese dioxides with different crystal structures

Particulate matter (PM) is the main contributor to air pollution, and filtration has been reported to be promising for PM capturing. Considering the complexity of polluted air (volatile organic compounds (VOCs) and ozone are likely concomitant with PM particles) and in view of the versatility of MnO2 for the degradation of VOCs and ozone, the feasibility of MnO2 materials as PM filtering media was investigated in this study, and the effect of crystal structure on PM filtration was clarified. Compared with the layered δ-MnO2, the MnO2 with tunnel structure (including 1 × 2-, 2 × 2- and 3 × 3-MnO2) exhibited greatly enhanced PM removal efficiencies, and particularly, the 3 × 3-MnO2 possessed not only significant activity for adsorbing PM particles but also high utilization efficiency of the active surface. Physicochemical properties of the adsorbents were studied by XRD, ATR, isothermal N2 adsorption, SEM and (HR)TEM. The correlation between pore characteristics and particle elimination activity demonstrates that the most developed mesoporous structure of the 3 × 3-MnO2 sample played an important role in strengthening the PM adsorption capability. Further comparison of the surface properties of the fresh and spent samples reveals that with respective to the occasion of δ-MnO2, the structure of 3 × 3-MnO2 was robust enough to resist collapse after PM capturing and the great accommodation of the inorganic and organic PM substances in the voluminous pores induced strong affinity between PM particles and 3 × 3-MnO2. Thereby, a higher particle filtration ability was retained.

Acid Etching-Induced In Situ Growth of λ-MnO2 over CoMn Spinel for Low-Temperature Volatile Organic Compound Oxidation.

Surface lattice oxygen is crucial to the degradation of volatile organic compounds (VOCs) over transition metal oxides according to the Mars-van Krevelen mechanism. Herein, λ-MnO2 in situ grown on the surface of CoMn spinel was prepared by acid etching of corresponding spinel catalysts (CoMn-Hx-Ty) for VOC oxidation. Experimental and relevant theoretical exploration revealed that acid etching on the CoMn spinel surface could decrease the electron cloud density around the O atom and weaken the adjacent Mn-O bond due to the fracture of the surface Co-O bond, facilitating electron transfer and subsequently the activation of surface lattice oxygen. The obtained CoMn-H1-T1 exhibited an excellent catalytic performance with a 90% acetone conversion at 149 °C, which is 42 °C lower than that of CoMn spinel. Furthermore, the partially maintained spinel structure led to better stability than pure λ-MnO2. In situ diffuse reflectance infrared Fourier transform spectroscopy confirmed a possible degradation pathway where adsorptive acetone converted into formate and acetate species and into CO2, in which the consumption of acetate was identified as the rate-limiting step. This strategy can improve the catalytic performance of metal oxides by activating surface lattice oxygen, to broaden their application in VOC oxidation.

Improving quantification of hydrogen peroxide by synchrotron vacuum ultraviolet photoionization mass spectrometry

Hydrogen peroxide (H2O2) plays a key role in the autoxidation of fuels related to ignition in compression engines, and in the degradation of volatile organic compounds (VOC) in the atmospheric autoxidation. Advanced synchrotron vacuum ultraviolet radiation photoionization mass spectrometry (SVUV-PIMS) is widely used for in-situ analysis of H2O2 in the gas phase autoxidation process. However, considerable uncertainty has been observed in the quantification of H2O2 by SVUV-PIMS. This work improves the quantification of H2O2 by re-evaluating its photoionization cross section (PICS). Spray vaporization, combined with a low pressure flow reactor, was used to minimize decomposition and wall loss of H2O2 in the PICS measurement. It was found that the PICS of H2O2 obtained here was lower than that reported in the literature by a factor of two. Adopting this newly obtained PICS significantly improved quantification of H2O2, and will prove valuable in evaluating the reaction kinetics of H2O2 and the development of combustion and atmospheric autoxidation models.

Development and Durability Analysis of the Functionalized Fabric

Nowadays, building insulation must be more and more effective to avoid energy loss. This can result in the lack of ventilation which can cause an increase in the concentration of pollutants in the indoor air, such as Volatile Organic Compounds (VOCs) which are harmful to human health. Different approaches have been proposed to reduce this problem such as ventilation, filtration, depolluting plants, etc. The aim of this study consists of developing functionalized textile substrate allowing the VOCs degradation, ideally into H2O and CO2, by the photocatalytic effect under visible light. It is necessary to have photocatalytic activity under visible light for indoor applications as the UV light is filtered by window glasses. To achieve this objective, firstly the samples of woven cotton fabrics are functionalized with the dispersion of silver doped/non-doped TiO2 in Carboxymethyl Cellulose (CMC) and water by padding process. After that, the treatment sustainability of the functionalized fabric is determined.

The interplay between selective etching induced cation defects and active oxygen species for volatile organic compounds degradation

Surface electronic structure of transition metal oxides plays a vital role in determining the catalytic performance. Herein, we present a selective etching strategy to tune the surface cation defect of the CuWO4 (CW) catalyst for improving the catalytic activity of volatile organic compounds (VOCs). HRTEM, SEM-EDS, EPR, and XPS show that the chelation of metal ions in acetic acid and ammonium hydroxide can help to remove a small number of surface cations in CW to form suitable W defects. Cu L-edge and O K-edge XAS, Raman, and O 1s XPS spectrum illustrate that cation defects can improve the hybrid orbits of metal-oxygen bonds, which increases the activity of surface lattice oxygen and metal sites. In-situ DRIFTS spectra reveal that CW with cation defects can easily adsorb toluene, cleave and oxidize benzene ring, and desorb CO2 because of more surface dangling bonds and active oxygen species. Therefore, the toluene conversion rates of CW-Aci and CW-Alk are much higher than CW in VOCs degradation and the catalytic performance improved 33 times and 22 times at 200 °C, respectively. This study offers a new pathway in engineering surface electronic structure and highlights the interplay between cation defects and active oxygen species.

Research Progress of a Composite Metal Oxide Catalyst for VOC Degradation

Volatile organic compounds (VOCs) are atmospheric pollutants that have been of concern for researchers in recent years because they are toxic, difficult to remove, and widely sourced and easily cause damage to the environment and human body. Most scholars use low-temperature plasma biological treatment, catalytic oxidation, adsorption, condensation, and recovery techniques to treat then effectively. Among them, catalytic oxidation technology has the advantages of a high catalytic efficiency, low energy consumption, high safety factor, high treatment efficiency, and less secondary pollution; it is currently widely used for VOC degradation technology. In this paper, the catalytic oxidation technology for the degradation of multiple types of VOCs as well as the development of a single metal oxide catalyst have been briefly introduced. We also focus on the research progress of composite metal oxide catalysts for the removal of VOCs by comparing and analyzing the metal component ratio, preparation method, and types of precursors and the catalysts' influence on the catalytic performance. In addition, the reason for catalyst deactivation and a correlation between the chemical state of the catalyst and the electron distribution are discussed. Development of a composite metal oxide catalyst for the catalytic oxidation of VOCs has been proposed.

Er single atoms decorated TiO2 and Er3+ ions modified TiO2 for photocatalytic oxidation of mixed VOCs

Photocatalytic degradation of single volatile organic compounds (VOCs) has been widely discussed while that of VOCs mixture has been rarely mentioned. Herein, Erbium (Er) single atoms decorated TiO2 (Er1-TiO2) and Er3+ ions modified TiO2 (Er3+-TiO2) with more adsorption sites and stronger capacity for producing reactive oxygen species were chosen for the photocatalytic degradation of single VOC (ethylene, acetaldehyde and o-xylene) and VOCs mixture (o-xylene-acetaldehyde mixture and o-xylene-ethylene mixture). The adsorption capacity for o-xylene was influenced by the introduction of acetaldehyde or ethylene. As for Er3+-TiO2, the calculated adsorption capacity for o-xylene was 4.44 μmol/g while that for o-xylene in o-xylene-acetaldehyde mixture and o-xylene-ethylene mixture were 1.03 μmol/g and 2.35 μmol/g, respectively. The degradation efficiency for o-xylene was also affected by the introduction of acetaldehyde or ethylene because of the competitive adsorption and the competitive availability of reactive oxygen species. As for Er3+-TiO2, the degradation efficiency for o-xylene was 90% while that for o-xylene in o-xylene-acetaldehyde mixture and o-xylene-ethylene mixture were 85% and 80%, respectively. Furthermore, the degradation route of o-xylene was influenced by the introduction of acetaldehyde or ethylene. This study is beneficial to comprehend the interaction mechanism between different VOCs in the photocatalytic degradation process.