Photocatalytic Degradation Of Acetaldehyde Research Articles

A novel ZnO-TiO2-Bi2WO6/Carboxymethyl chitosan composite with high antimicrobial activity and visible-light catalytic degradation of ethylene towards banana preservation in hot and humid environments

In order to solve the problem of significantly shortened storage time of bananas in hot and humid environment (e.g., 30 °C and 90 % relative humidity), this paper reports the preparation of ZnO-TiO2-Bi2WO6 (ZTB) ternary heterojunction antimicrobial photocatalysts composite carboxymethyl chitosan film (ZTB/CMCS). ZTB were prepared by hydrothermal method and composited with CMCS by surface deposition method to construct ZTB/CMCS edible nano-preservation film. It is noteworthy that the ZTB/CMCS composite film exhibited excellent antibacterial efficiency (>99.99 %) against E. coli and S. aureus suspensions (106 CFU/mL) after 24 h of incubation at 37 °C. Time-resolved photoluminescence (TRPL) spectroscopy showed that the incorporation of Zinc oxide nanoparticles (ZnO NPs) into the ZTB structure led to a decrease in fluorescence lifetime. Moreover, the interfacial interaction between ZnO and TiO2/Bi2WO6 inhibited the recombination of photogenerated electron-hole pairs, promoting carrier separation and improving photocatalytic activity. The combination of high antibacterial activity, photocatalytic degradation of ethylene and inhibition of gas exchange provided multiple protections for fruit preservation. Therefore, this work provides a novel, effective and safe method for prolonging the preservation of bananas in hot and humid environments.

Prolonging banana shelf life through visible light-induced ethylene scavenging using manganese-decorated TiO2 via KMnO4 reduction

Apart from being a good source of nutrition, bananas are also an essential worldwide commodity. However, bananas exhibit fast ripening and low shelf life, especially after artificial ripening. TiO2 can act as an ethylene scavenger through photocatalytic degradation of ethylene. In this work, Mn-decorated TiO2 was synthesized through MnO4- reduction on the surface of P25 TiO2. The aim is to prolong the shelf life of artificially ripened bananas. Based on characterization results, we found that Mn decoration increased absorption of visible light, with the interaction between TiO2 and Mn predicted to be a type I heterojunction. The photocatalytic activity was tested by ethylene photodegradation. It was found that TiO2/Mn was able to partially oxidize ethylene to formic acid under visible light. Furthermore, bananas stored in a fruit storage chamber with TiO2/Mn showed a 2-day delay in color change. This confirms that TiO2/Mn can be used as an ethylene scavenger.

Cellulose nanocrystals reinforced chitosan/titanium dioxide bionanocomposite with enhanced interfacial compatibility: Fabrication, characterization, and application in fresh-cut apple slices

This research aimed to investigate the feasibility of using a bionanocomposite made of chitosan, CNC, and TiO2 nanoparticles to package freshly sliced apples. At the outset, the effect of varying concentrations of CNC (1, 5, and 10 %) and TiO2 (1, 3, and 5 %) on the mechanical, thermal, and water sensitivity characteristics of the chitosan bionanocomposite was studied. Among different combinations, the bionanocomposite containing 10 % CNC and 3 % TiO2 displayed significant enhancements compared to neat chitosan film. Notably, it exhibited a substantial increase in tensile strength (78.2 %), glass transition temperature (26.7 %), and melting temperature (30.0 %) compared to neat chitosan film. Additionally, it demonstrated reduced WVP (27.8 %), FWS (44.4 %), and SR (50.7 %). These improvements were attributed to the synergistic interactions among chitosan, CNC, and TiO2 nanoparticles through hydrogen and oxygen bonding, corroborated by spectral changes in the material. The photocatalytic degradation of ethylene and microbes by UV-A (intermittent) activated TiO2 contained in the developed bionanocomposite was confirmed by the retention of acceptable quality and radical scavenging activity (70 % retention) of fresh-cut apple slices up to 11 days. The developed bionanocomposite can thus preserve the quality of ethylene-producing horticultural produce.

Photocatalytic degradation of ethylene in tubular microreactor coated with thin-film of TiO2: Mathematical modeling with experimental validation and geometry analysis using computational fluid dynamics simulations

The study aimed to establish a comprehensive understanding of the photocatalytic process and optimize the reactor design for efficient ethylene regulation to improve the shelf-life of fruits and vegetables. For this, it was performed 2D computational fluid dynamics modeling at two different reactor geometry (conventional cylindric reactor and annular cylindric reactor) using the conservation equations combined with Langmuir-Hinshelwood mechanism. A continuous single-phase multicomponent fluid flow with the reactor surface supported with a thin-film catalyst under UV-A light irradiation was simulated for initial ethylene concentration at 0.479–4.234 × 10−3 molC2H4 m−3 and inlet axial velocity at 0.0085–0.1019 m s−1. In the 2D CFD results, it was observed that the difference in ethylene concentration between the microreactor bulk and surface is only significant for high initial concentrations and axial velocities. Furthermore, it was found that the parabolic conversion profile remains unchanged for lengths greater than 10% of the reactor length across all geometries studied. The variation in reactor diameters resulted in a substantial reduction in ethylene conversion; however, the incorporation of an annular cylinder coated with a catalyst led to an enhancement in conversion rates, with improvements of approximately 28%, 17%, and 6% observed for diameters of 5 mm, 10 mm, and 20 mm, respectively. This reduction in improvement as diameter increase can be attributed to the laminar flow dynamics that impede the diffusion of ethylene molecules from the bulk to the catalytic surface. Consequently, the simulated data highlight the potential of employing a catalyst-doped annular cylinder as a promising strategy to increase ethylene conversion and extend the shelf life of fruits. However, it should be noted that the addition of an annular cylinder, while enhancing conversion, also introduces operational complexities and cost implications due to the significant increase in pressure drop associated with lower diameters.

Photocatalytic degradation of ethylene by mesoporous nano silica loaded chlorin e6

Green foods are usually harvested and stored before ripening, but excessive ethylene generated during storage can lead to the loss of vegetables and fruits. Photocatalytic oxidation provides a promising method to remove ethylene and extend the shelf life of green foods. In this study, a mesoporous nanosilica-loaded Ce6 composite nanomaterial (Ce6@SiO2) was designed and synthesized to adsorb ethylene into its pores and then degrade it under visible light illumination. The photosensitizer Ce6 in the mesopore produced large amounts of reactive oxygen species that degraded ethylene. The specific surface area was greatly increased by coating the material on the surface of a sodium alginate (SA) hydrogel membrane. This improved its degradation efficiency and facilitated the adsorption and degradation of ethylene during fruit storage. The ethylene removal capacity was studied by measuring the ethylene concentration and increases in the humidity in Tedlar gas bags. Practical applications were tested by observing color changes and surface decay of tomatoes stored with and without SA/Ce6@SiO2. The results showed the system may be used in practical commercial preservation systems.

Inactivation of SARS-CoV-2 and photocatalytic degradation by TiO2 photocatalyst coatings

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causative agent of the COVID-19, which is a global pandemic, has infected more than 552 million people, and killed more than 6.3 million people. SARS-CoV-2 can be transmitted through airborne route in addition to direct contact and droplet modes, the development of disinfectants that can be applied in working spaces without evacuating people is urgently needed. TiO2 is well known with some features of the purification, antibacterial/sterilization, making it could be developed disinfectants that can be applied in working spaces without evacuating people. Facing the severe epidemic, we expect to fully expand the application of our proposed effective approach of mechanical coating technique (MCT), which can be prepared on a large-scale fabrication of an easy-to-use TiO2/Ti photocatalyst coating, with hope to curb the epidemic. The photocatalytic inactivation of SARS-CoV-2 and influenza virus, and the photocatalytic degradation of acetaldehyde (C2H4O) and formaldehyde (CH2O) has been investigated. XRD and SEM results show that anatase TiO2 successfully coats on the surface of Ti coatings, while the crystal structure of anatase TiO2 can be increased during the following oxidation in air. The catalytic activity towards methylene blue of TiO2/Ti coating balls has been significantly enhanced by the followed oxidation in air, showing a very satisfying photocatalytic degradation of C2H4O and CH2O. Notably, the TiO2/Ti photocatalyst coating balls demonstrate a significant antiviral activity, with a decrease rate of virus reached 99.96% for influenza virus and 99.99% for SARS-CoV-2.

Evaluation of reactive oxygen species and photocatalytic degradation of ethylene using β-Ag2MoO4/g-C3N4 composites

The photocatalytic degradation of ethylene is an efficient technology applied to the fruit ripening control. When photocatalytic reactions remove ethylene from the storage and transportation environment of fruits and vegetables, the respiration rate decreases, and the quality of food is preserved for a long time. It is well known that photocatalysis involves the photogeneration of electron-hole pairs (e−/h+) under light irradiation, separation, and migration of charges on the material surface, oxidation and reduction reactions involving electrons and holes pairs, and charge recombination on the catalyst surface. In this study, we report the syntheses, characterization, and evaluation of photocatalytic activity of the β-Ag2MoO4/g-C3N4 photocatalysts to degrade ethylene in the gas phase under UV-A irradiation. The effect of the β-Ag2MoO4:g-C3N4 ratio on reactive oxygen species (ROS) generation and increasing the electron/hole charge separation is evaluated in detail. Under UV-A illumination and the absence of water, superoxide radicals are most efficiently produced in hybrid samples containing a higher g-C3N4 percentage, but lower O2·− amount is formed in pure g-C3N4. The hybrid samples containing higher amounts of g-C3N4 are more efficient to degrade ethylene because of better e− and h+ charge separation and superoxide radicals’ formation, which participate in ethylene degradation.

Theoretical Modeling of Photocatalytic Degradation Mechanism of Ethylene Over TiO2.

The photocatalytic degradation of ethylene over TiO2 has been widely studied, however, there are discrepancies between the degradation mechanisms proposed in experimental works. Some of them propose a degradation and mineralization mechanism trough ethoxide, acetaldehyde, acetic acid and finally carbon dioxide, whereas others did not find acetaldehyde or acetic acid, but formaldehyde and formic acid as intermediaries in the same process through the presence of the formyl radical HCOO · on the catalyst surface. Through ab initio calculations it is possible to analyze the published experimental mechanisms in order to theoretically assess their feasibility and establish the possible reaction intermediaries and generated products. In this work, we used the Density Functional Theory based method DFT-RPBE/6-31G** in order to determine energy values to then estimate the enthalpy changes associated with each of the stages proposed for the ethylene degradation and mineralization processes, with which we elucidated the thermodynamically most probable mechanism, which explains differences between experimental work reports. We found that the most favorable route is through the formation of acetic acid, however, only one of the carbon atoms is converted to CO2, the other one is also converted to CO2 but from the formaldehyde degradation. These results agree with and explain those reported from experimental works. The method we used was validated by obtaining deviations shorter than 5% when comparing bond lengths, bond angles, dihedral angles, and vibrational frequencies calculated in this work versus experimental published values for most of the molecules involved.

Photocatalytic degradation of ethylene in cold storage using the nanocomposite photocatalyst MIL101(Fe)-TiO2-rGO

To maintain the quality of harvested fruits and vegetables in a closed refrigerated environment, a novel nanocomposite photocatalyst MIL101(Fe)-TiO2-rGO (MTR) for ethylene degradation was synthesized. The characterization of MTR was analyzed by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and High-resolution transmission electron microscope (HRTEM). Moreover, with the good conductivity of rGO, MTR had the smallest band gaps according to ultraviolet–visible solid diffuse reflection (UV–Vis DRS) analysis; this small band gap size improved the utilization of light. According to the results of the photoluminescence spectra and electrochemical impedance spectra, the charge transfer resistance and transient photocurrent of MTR were improved. The redox process of Ti4+/Ti3+ from TiO2 and Fe3+/Fe2+ from MIL101(Fe) efficiently prevented the recombination of e--h+ pairs. In this cycle, oxidative active substances (•O2−) were provided, which played a key role in the ethylene degradation of MTR. Additionally, MTR has excellent gas adsorption capacity, and the photocatalytic degradation rate of C2H4 by MTR was 2.07 × 10-4 min−1, which is better than that of other photocatalysts. Furthermore, the photocatalytic activity of MTR was still stable after 4 times of recycling, indicating the potential to maintain the quality of horticultural products after harvesting.

Improved Capture and Removal Efficiency of Gaseous Acetaldehyde by a Self-Powered Photocatalytic System with an External Electric Field.

Using clean and sustainable stochastic energy from the environment to eliminate pollution caused by gaseous aldehydes would be an effective strategy to achieve the sustainable development of energy and preserve the environment. Here, a piston-based triboelectric nanogenerator (P-TENG) was used to enhance gaseous acetaldehyde absorption and photocatalytic degradation. An external electric field could be generated on a conductive substrate by the P-TENG, converting wind energy into electricity. This made it possible to efficiently degrade gaseous acetaldehyde in the photocatalytic system. Driven by a light breeze (3.0 m/s), the acetaldehyde removal rate of the system reached 63% within 30 min. The presence of an external electric field could generate more hydroxyl radicals (•OH), superoxide radicals (•O2-), and holes (h+), which has a positive effect on the photocatalytic degradation of acetaldehyde. The design and concept of this study not only realized the efficient conversion of renewable and sustainable random energy but also could be applied to the efficient removal of gaseous aldehydes, providing an effective way to create a cleaner environment.

Photocatalytic degradation of ethylene by TiO2 nanotubes/ reduced graphene oxide prepared by gamma irradiation

A nanocomposite photocatalyst of TiO2 nanotubes/reduced graphene oxide (rGO-TNTAs) were prepared by γ-ray radiolysis. The rGO-TNTAs were studied for photocatalytic decomposition of ethylene (C2H4) in a refrigerated environment. Degradation efficiency of ethylene by these materials was described by the apparent first-order rate constant (K). The composite was characterized by Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), Atomic force microscopy (AFM) and Field emission electron microscopy (FESEM). The preparing parameters for materials affecting the degradation efficiency in terms of the rate constant were studied, including the GO addition and the irradiation dose. The results showed that (1) gamma irradiation can induce GO to partial rGO, the rGO surface of rGO-TNTAs was smooth and loosely lamellar structure. (2) The K of the rGO-TNTAs is highly dependent on the GO addition and the irradiation dose. With a GO addition of 0.1 g and an irradiation dose of 20 kGy, the maximum K value of rGO-TNTAs could be obtained under the experimental conditions. (3) From analysis of the Raman spectroscopy spectrum, optimum changes had occurred in the intensity ratio of D-band to G-band of the GO that had been γ-ray-irradiated with a dose of 20 kGy, resulting in the K of rGO-TNTAs increased by 40.9% compared with that of TNTAs.

Degradation of acetaldehyde by Ag/TiO2 photocatalyst coated on polyester air filter

Acetaldehyde is a toxic mainstream in cigarette smoke. This study aims to apply Ag/TiO2 coated on a polyester air filter (PET) to degrade acetaldehyde. Ag/TiO2 was prepared by doping 10 mol% of silver (Ag) on TiO2 via impregnation method. The crystallinity and wavelength absorption of Ag/TiO2 particles were characterized by X-ray Diffraction (XRD) and UV-vis NIR spectrophotometer, respectively. Then, the Ag/TiO2 particles were mixed with two different binders such as Polyethylene glycols (PEG, Mw = 6,000 g/mol) and Polyacrylic acid (PAA) before coating on PET filter by dip-coating technique. The percentages of binder were varied from 0.3, 1, 3 and 5wt% by weight of photocatalyst particles. The photocatalytic activities of PET filters coated by Ag/TiO2 with different binders were examined by decolorization of 10−5 M methylene blue (MB) solution and degradation of acetaldehyde under visible light irradiation. The XRD results indicated that Ag/TiO2 had the combination of anatase phase, silver oxide (AgO) and metallic silver (Ago). After doping, the band gap energy of TiO2 was reduced from 3.28 eV to 3.22 eV (red-shift effect). The PET filters coated with 5% PEG-Ag/TiO2 and 3% PAA-Ag/TiO2 showed the MB decolorization efficiency of 88 % and 87%, respectively. The photocatalytic degradation of acetaldehyde was carried out by 3%PAA-Ag/TiO2. The degradation efficiency of acetaldehyde by 3%PAA-Ag/TiO2 filter was 96% within 96 h. The concentration of CO2 which was a product of photocatalysis increased simultaneously during the reaction. This was an evidence that acetaldehyde was degraded by the photocatalytic air filter.

Synthesis of TiO2/WO3 on Nickel Foam for the Photocatalytic Degradation of Ethylene

Synthesis of TiO₂/WO₃ on Nickel Foam for the Photocatalytic Degradation of Ethylene

Photocatalytic degradation of ethylene by TiO2 nanotubes/ reduced graphene oxide prepared by gamma irradiation

A nanocomposite photocatalyst of TiO2 nanotubes/reduced graphene oxide (rGO-TNTAs) were prepared by γ-ray radiolysis. The rGO-TNTAs were studied for photocatalytic decomposition of ethylene (C2H4) in a refrigerated environment. Degradation efficiency of ethylene by these materials was described by the apparent first-order rate constant (K). The composite was characterized by Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), Atomic force microscopy (AFM) and Field emission electron microscopy (FESEM). The preparing parameters for materials affecting the degradation efficiency in terms of the rate constant were studied, including the GO addition and the irradiation dose. The results showed that (1) gamma irradiation can induce GO to partial rGO, the rGO surface of rGO-TNTAs was smooth and loosely lamellar structure. (2) The K of the rGO-TNTAs is highly dependent on the GO addition and the irradiation dose. With a GO addition of 0.1 g and an irradiation dose of 20 kGy, the maximum K value of rGO-TNTAs could be obtained under the experimental conditions. (3) From analysis of the Raman spectroscopy spectrum, optimum changes had occurred in the intensity ratio of D-band to G-band of the GO that had been γ-ray-irradiated with a dose of 20 kGy, resulting in the K of rGO-TNTAs increased by 40.9% compared with that of TNTAs.

Effect of operational conditions on photocatalytic ethylene degradation applied to control tomato ripening

Ethylene is a phytohormone that promotes the ripening of climacteric fruits. When present in the transport and storage environments of fruits and vegetables, ethylene can cause the acceleration of maturation and senescence, leading to the need to dispose of the products. Thus, the elimination of this gas in storage chambers has been studied as an efficient way to improve the shelf-life of climacteric fruits and vegetables. The main objective of this study was to investigate the effect of the operating conditions on the photocatalytic degradation of ethylene in a continuous flow reactor using TiO2 under UV-A light in the absence or presence of tomato fruits. The results for the catalyst deposition showed a linear increase in the photocatalytic degradation of ethylene with increasing thickness of the catalyst deposited on the inner wall of the reactor, up to a constant degradation value. The dependence of the reaction rate was linear with high values for the flow rate, which is associated with the surface reaction. However, at a low flow rate, mass transfer limitations can affect the ethylene reaction rate. Under a kinetic regime, the Langmuir-Hinshelwood model was able to describe the effect of the ethylene gas concentration on its degradation rate. Increasing incident irradiance led to a linear increase in the ethylene conversion over the range studied. A continuous rate of ethylene gas production during tomato ripening of 0.3182 μmol kg−1 h−1 was observed. In a real application, the reactor with a TiO2 film thickness of 0.419 μm under an incident irradiance of 5.18 W m−2 was able to maintain the ethylene concentration in the gas phase close to zero and a lower value for the carbon dioxide in the gas phase was achieved. This is related to a decrease in the respiration rate, indicating that this is an efficient technology for improving the shelf life of cherry tomatoes.

Solvothermal synthesis of P25/Bi2WO6 nanocomposite photocatalyst and photocatalytic degradation of ethylene under visible light

P25/Bi2WO6 nanocomposite photocatalysts were synthesized by solvothermal method, and their photocatalytic activities were evaluated for the degradation of ethylene under visible light irradiation. The results show that P25/Bi2WO6 nanocomposites have higher photocatalytic activity than P25 and pure Bi2WO6. When the loading amount of P25 is 35%, the photocatalytic degradation of ethylene under visible light is the highest, which is 4.5 and 2.2 times higher than that of P25 and Bi2WO6, respectively. The improvement of the photocatalytic activity of the nanocomposite is mainly due to the formation of the staggered heterojunctions in the contact interface of P25 and Bi2WO6. This can refine the grain and produce lattice defects in the interface of the composite, which could provide more active sites. Therefore, the separation efficiency of the photogenerated electron-hole pair is improved, and the spectral response range is extended to the visible light region, thereby the absorption and utilization of light energy is improved.

Photocatalytic degradation of ethylene by Ga2O3 polymorphs.

In this work, we fabricated four different Ga2O3 polymorphs, namely, α-, β-, γ-, δ-Ga2O3, and investigated their photocatalytic activities by the degradation of ethylene under ultraviolet (UV) light irradiation. Owing to the more positive valence band, all these Ga2O3 polymorphs are more photocatalytic reactive than P25 during the degradation of ethylene. The normalized photocatalytic ethylene degradation rate constants of the as-prepared Ga2O3 polymorphs follow the order: α-Ga2O3 > β-Ga2O3 > γ-Ga2O3 > δ-Ga2O3, which is mainly determined by the position of VBM and the crystallinity of the samples. Among these Ga2O3 polymorphs, γ-Ga2O3, with the highest surface area, exhibits the highest activity during photocatalytic ethylene degradation, and the degradation rate constant is almost 10 times as that of P25. Furthermore, with the most positive CBM, γ-Ga2O3 produces the least CO. These attributes are beneficial for ethylene degradation during post-harvest storage of fruits and vegetables, which makes γ-Ga2O3 a potential candidate for practical photocatalytic ethylene degradations.

Fabrication of In2O3-Ag-Ag3PO4 composites with Z-scheme configuration for photocatalytic ethylene degradation under visible light irradiation

Photocatalytic degradation of ethylene under visible light remains a challenge at the frontiers of chemistry. In this study, In2O3-Ag-Ag3PO4 composite semiconductors with Z-scheme configuration were fabricated for the first time by in-situ synthesis of Ag3PO4 on In2O3 and subsequent photoreduction of Ag3PO4 to generate nano silver. Their performances on photocatalytic degradation of ethylene under visible light illumination were investigated. Results demonstrated that both the activity of ethylene photocatalytic degradation and Ag3PO4 photostabilization are considerably improved by making such a Z-scheme composite. According to the material design perspective and the application in the field of environmental pollutant remediation, the present research will provide potential value for further study on the removal of HC (Hydrocarbons) from the atmosphere and the stability concern of Ag3PO4 and other materials with photocorrosion.

Influence of humidity on the photo-catalytic degradation of acetaldehyde over TiO2 surface under UV light irradiation

We have studied the influence of water vapors on the activity of the photo-catalytic oxidation of acetaldehyde on the surface of TiO2 film under UV light (365nm) irradiation. Photo-catalysis experiments were performed at atmospheric conditions under various humidity levels (0, 16.8, and 33.6 relative humidity%) using a high vacuum chamber equipped with online gas-chromatography as a batch-type reactor. Acetaldehyde and H2O molecules competitively adsorbed on the surface of TiO2 film and the increase in the humidity decreased both the acetaldehyde removal and CO2 evolution rates. The rate of CO2 evolution was even more influenced by the humidity level of the gas mixture compared to the acetaldehyde removal rate, particularly over the certain level of relative humidity. We evidenced that the total oxidation of acetaldehyde was majorly mediated by oxygen molecules rather than H2O vapor under our experimental conditions. It is suggested that photo-catalytic total oxidation of acetaldehyde was promoted by the presence of large active sites ensemble near the adsorbed acetaldehyde, which were available to oxygen. Increase of humidity level disturbed this large ensemble, resulting in the reduction of photo-catalytic degradation rate of acetaldehyde under UV light irradiation.

TiO2 Nanotubes with Open Channels as Deactivation-Resistant Photocatalyst for the Degradation of Volatile Organic Compounds.

We synthesized ordered TiO2 nanotubes (TNT) and compared their photocatalytic activity with that of TiO2 nanoparticles (TNP) film during the repeated cycles of photocatalytic degradation of gaseous toluene and acetaldehyde to test the durability of TNT as an air-purifying photocatalyst. The photocatalytic activity of TNT showed only moderate reduction after the five cycles of toluene degradation, whereas TNP underwent rapid deactivation as the photocatalysis cycles were repeated. Dynamic SIMS analysis showed that carbonaceous deposits were formed on the surface of TNP during the photocatalytic degradation of toluene, which implies that the photocatalyst deactivation should be ascribed to the accumulation of recalcitrant degradation intermediates (carbonaceous residues). In more oxidizing atmosphere (100% O2 under which less carbonaceous residues should form), the photocatalytic activity of TNP still decreased with repeating cycles of toluene degradation, whereas TNT showed no sign of deactivation. Because TNT has a highly ordered open channel structure, O2 molecules can be more easily supplied to the active sites with less mass transfer limitation, which subsequently hinders the accumulation of carbonaceous residues on TNT surface. Contrary to the case of toluene degradation, both TNT and TNP did not exhibit any significant deactivation during the photocatalytic degradation of acetaldehyde, because the generation of recalcitrant intermediates from acetaldehyde degradation is insignificant. The structural characteristics of TNT is highly advantageous in preventing the catalyst deactivation during the photocatalytic degradation of aromatic compounds.