Catalytic Decomposition Of Ozone Research Articles

Interface reconfiguration of MnCO3/Mn3O4 heterostructure enhances the ozone decomposition in the entire humidity range

The catalytic efficiency of manganese-based catalysts in practical ozone decomposition applications is limited by challenging desorption of intermediate oxygen species and competitive adsorption of H2O molecules in humid environments. In this work, MnCO3/Mn3O4 composites with heterogeneous structures were synthesized through a facile one-step strategy. The obtained MnCO3/Mn3O4-1/2 catalyst exhibited high content of oxygen vacancies, fast electron mobility rate and obvious advantages in catalytic ozone decomposition performance at a space velocity of 600 L g−1 h−1 and 95% RH. In-situ DRIFT spectra indicated that the rate-determining steps for ozone decomposition of MnCO3 and Mn3O4 are the reaction of atomic oxygen with ozone to form O22- and desorption of O22-, respectively. MnCO3/Mn3O4 heterogeneous catalyst undergoes reconfiguration under ozone atmosphere, inducing discontinuous MnOx coatings on the MnCO3 surface, which form a potential difference with Mn3O4. MnCO3/Mn3O4 heterogeneous structure modulates the electronic state of active site, and the synergistic effect of MnCO3 and Mn3O4 improves catalytic performance.

Crystal facet engineering of K-OMS-2 for active site identification in catalytic ozone decomposition

Manganese oxide catalysts (MnOx) are expected to be utilized to catalytic ozone (O3) decomposition to curb indoor O3 pollution. However, the accumulation of oxygen-containing species (*OO) on the active site (oxygen vacancy, Ov) of MnOx limits the practical application. Herein, α-MnO2 with exposed {100} (Mn-100), {110} (Mn-110), or {310} (Mn-310) facet was synthesized, respectively. Mn-110 has preferred performance and stability, maintaining 99.9 % O3 conversion after 8 h under 35 % RH. Experimental and theoretical results indicated that the Mn-100 facet owns lower Ov content and *OO adsorption energy, exhibiting the highest specific area normalized activity. Mn-310 has a higher vacancy content and enhanced *OO adsorption energy, which resulted in a rapid accumulation of *OO species. Mn-110 has a moderate Ov content and *OO adsorption and thus exhibits optimal activity. This study hopes to point out a new optimization strategy for MnOx catalysts.

Effect of Interlayer Anions on NiFe Layered Double Hydroxides for Catalytic Ozone Decomposition.

NiFe layered double hydroxides (NiFe-LDH) exhibited an outstanding performance and promising application potential for removing ozone. However, the effect of interlayer anions on ozone removal remains ambiguous. Here, a series of NiFe-LDH with different interlayer anions (F-, Cl-, Br-, NO3-, CO32-, and SO42-) were prepared to investigate the effect of the interlayer anion on ozone removal for the first time. It was found that the interlayer anions are a key factor affecting the water resistance of the NiFe-LDH catalyst under moist conditions. NiFe-LDH-CO32- exhibited the best water resistance, which was much better than that of NiFe-LDH containing other interlayer anions. The in situ DIRFTS demonstrates that the carbonates in the interlayer of NiFe-LDH-CO32- will undergo coordination changes through the interaction with water molecules under moist conditions, exposing new metal sites. As a result, the newly exposed metal sites could activate water molecules into hydroxyl groups that act as active sites for catalyzing ozone decomposition. This work provides a new insight into the interlayer anions of LDH, which is important for the design and development of LDH catalysts with excellent ozone removal properties.

Preparation of CeO2 Supported on Graphite Catalyst and Its Catalytic Performance for Diethyl Phthalate Degradation during Ozonation

Catalysts for the efficient catalytic decomposition of ozone to generate reactive free radicals to oxidize pollutants are needed. The graphite-supported CeO2 catalyst was optimally prepared, and its activity in ozonation was evaluated using the degradation of diethyl phthalate (DEP) as an index. The stability of CeO2/graphite catalyst and the influence of operating conditions on its catalytic activity were investigated, and the mechanism of CeO2/graphite catalytic ozonation was analyzed. CeO2/graphite had the highest catalytic activity at a Ce load of 3.5% and a pyrolysis temperature of 400 °C with the DEP degradation efficiency of 75.0% and the total organic carbon (TOC) removal efficiency of 48.3%. No dissolution of active components was found during the repeated use of CeO2/graphite catalyst. The ozone dosage, catalyst dosage, initial pH, and reaction temperature have positive effects on the DEP degradation by CeO2/graphite catalytic ozonation. The presence of tert-butanol significantly inhibits the degradation of DEP at an initial pH of 3.0, 5.8, or 9.0, and the experimental results of the •OH probe compound pCBA indicate that the CeO2/graphite catalyst can efficiently convert ozone into •OH in solution. The DEP degradation in the CeO2/graphite catalytic ozonation mainly depends on the •OH in the bulk solution formed by ozone decomposition.

Space-confined manganese oxides nanosheets for efficient catalytic decomposition of ozone

Ground-level ozone has long posed a substantial menace to human well-being and the ecological milieu. The widely reported manganese-based catalysts for ozone decomposition still facing the persisting issues encompass inefficiency and instability. To surmount these challenges, we developed a mesoporous silica thin films with perpendicular nanochannels (SBA(⊥)) confined Mn3O4 catalyst (Mn3O4@SBA(⊥)). Under a weight hourly space velocity (WHSV) of 500,000 mL g−1 h−1, the Mn3O4@SBA(⊥) catalyst exhibited 100% ozone decomposition efficiency in 5 h and stability across a wide humidity range, which exceed the performance of bulk Mn3O4 and Mn3O4 confine in commonly reported SBA-15. Rapidly decompose 20 ppm O3 to a safety level below 100 μg m−3 in the presence of dust in smog chamber (60 × 60 × 60 cm) was also realized. This prominent catalytic performance can be attributed to the unique confined structure engenders the highly exposed active sites, facilitate the reactant-active sites contact and impeded the water accumulation on the active sites. This work offers new insights into the design of confined structure catalysts for air purification.

Ambient atmospheric application and influencing factors of ozone catalytic decomposition materials in a channel test

Surface ozone pollution is a significant environmental problem. In addition to the control of ozone precursors, direct catalytic decomposition of ozone is an effective control method with broad prospects. At present, the evaluation of the ozone decomposition performance of catalysts is typically performed in the laboratory, and the lack of scientific evaluation means to apply them to complex ambient atmosphere limits the practical application of ozone removal catalysts. Here, we devised a new evaluation method for ozone catalytic decomposition materials in the ambient atmosphere that can comprehensively evaluate the influence of various factors in the ambient atmosphere on performance. The results showed that ozone catalytic decomposition materials can maintain a decomposition efficiency of more than 20% in ambient atmosphere. The decomposition efficiency is mainly affected by distance, the closer the distance; the higher the decomposition efficiency. In addition, the concentration of ozone in the environment also affects the decomposition efficiency and shows a positive correlation. As the ozone concentration increased, the decomposition efficiency increased. An increase in relative humidity can cause a decline in decomposition efficiency, but this effect is eliminated with a decrease in humidity. In addition, the ozone catalytic decomposition materials can reduce the ozone concentration in the environment from 160 μg/m3to less than 100 μg/m3, which can play a great role in environmental ozone pollution control.

Enhanced water resistance mechanism in Ag-Hollandite for catalytic ozone decomposition

Catalytic ozone (O3) decomposition at ambient temperature is an efficient method to mitigate O3 pollution. However, practical application is hindered by the poor water resistance of catalysts. Herein, Ag-Hollandite (Ag-HMO) with varying Ag+ content was synthesized. Catalysts with more Ag+ exhibited improved efficiency and water-resistance, with the optimal one maintaining 98% O3 conversion at 70% relative humidity (RH) within 8 h. Physicochemical characterizations revealed that Ag+ had entered the tunnel of OMS-2, facilitating oxygen species removal. Notably, enhanced H2O desorption and the complete inhibition of chemisorbed water formation on Ag-HMO were the primary reasons for its high-efficiency O3 conversion across a wide humidity range. The underlying mechanism arises from the charge redistribution induced by the Ag-O interaction within the tunnel, which reduces acidity and modulates hydrophilicity. This study aims to contribute insights for designing catalysts with higher water-resistance.

Synthetic effect of supports in Cu-Mn-doped oxide catalysts for promoting ozone decomposition under humid environment.

The escalating levels of surface ozone concentration pose detrimental effects on public health and the environment. Catalytic decomposition presents an optimal solution for surface ozone removal. Nevertheless, catalyst still encounters challenges such as poisoning and deactivation in the high humidity environment. The influence of support on catalytic ozone decomposition was examined at a gas hourly space velocity of 300 L·g-1·h-1 and 85% relative humidity under ambient temperature using Cu-Mn-doped oxide catalysts synthesized via a straightforward coprecipitation method. Notably, the Cu-Mn/SiO2 catalyst exhibited remarkable performance on ozone decomposition, achieving 98% ozone conversion and stability for 10 h. Further characterization analysis indicated that the catalyst's enhanced water resistance and activity could be attributed to factors such as an increased number of active sites, a large surface area, abundant active oxygen species, and a lower Mn oxidation state. The catalytic environment created by mixed oxides can offer a clearer understanding of their synergistic effects on catalytic ozone decomposition, providing significant insights into the development of water-resistant catalysts with superior performance.

Rapid Ozone Decomposition over Water-activated Monolithic MoO3 /Graphdiyne Nanowalls under High Humidity.

Catalytic ozone (O3 ) decomposition at high relative humidity (RH) remains a great challenge due to the catalysts poison and deactivation under high humidity. Here, we firstly elaborate the role of water activation and the corresponding mechanism of the promoted O3 decomposition over the three-dimensional monolithic molybdenum oxide/graphdiyne (MoO3 /GDY) catalyst. The O3 decomposition over MoO3 /GDY reaches up to 100 % under high humid condition (75 % RH) at room temperature, which is 4.0 times as high as that of dry conditions, significantly surpasses other carbon-based MoO3 materials(≤7.1 %). The sp-hybridized carbon in GDY donates electrons to MoO3 along the C-O-Mo bond, facilitating water activation to form hydroxyl species. As a result, hydroxyl species dissociated from water act as new active sites, promoting the adsorption of O3 and the generation of new intermediate species (hydroxyl ⋅OH and superoxo ⋅O2 - ), which significantly lowers the energy barriers of O3 decomposition (0.57 eV lower than dry conditions).

Ethanol-thermal synthesis of colloidal-CeFeMn mixed-oxide as efficient catalytic material for atmospheric ozone decomposition

Catalytic decomposition of ozone (O3) shows great potential in eliminating harmful pollutant. However, developing efficient catalysts for atmospheric O3 remediation remains challenging. To address this problem, we have designed an active dispersion liquid (colloidal-CeFeMn mixed-oxide) for atmospheric O3 decomposition. The results show that the amorphous CeFeMn mixed-oxide activated at 150 °C has a larger specific surface area and more surface active sites (oxygen vacancies) than those samples activated at 160 °C and 170 °C. It also exhibits superior O3 decomposition activity at room temperature. Furthermore, ethanol-thermal activation of a CeFeMn-citric acid complex yielded CeFeMn mixed-oxide with small size and high element disorder, resulting in abundant redox pairs and catalytic active sites for O3 decomposition. With the coverage of the aformentioned colloidal-CeFeMn mixed-oxide, the inert surface of ordinary objects could be easily converted into active surfaces, reducing surrounding O3 concentration by 20–30 μg·m−3. This study provides valuable insight into catalyst design and would help to promote the practical application of catalytic decomposition for eliminating atmospheric O3.

The role of noble metals in TiO2 nanotubes for the abatement of parabens by photocatalysis, catalytic and photocatalytic ozonation

The role of modified TiO2 nanotubes (TNTs) with noble metals was studied for photocatalysis, catalytic and photocatalytic ozonation of a paraben’s mixture. The TNTs were obtained by anodization and were modified by photodeposition with 0.25 mol% of Au, Pt or Pd.Results showed that solar photocatalysis led to higher degradation than UVA radiation, and under UVA radiation, the use of 3 Pt-TNTs (3 TNTs plates modified with Pt) and 3 Pd-TNTs present the same effect as the use of 5 and 7 pristine-TNTs plates, respectively. The best parabens removal was achieved for Pd-TNTs under UVA radiation and pristine TNTs under solar radiation, with 43% and 81% removal in 120 min, respectively.All the catalytic and photocatalytic ozonation experiments led to less ozone consumption than single ozonation (transferred ozone dose (TOD) = 5.27 mgO3/L) with total parabens abatement. Catalytic ozonation experiments suggest that the presence of metals can promote the formation of oxidative radicals, with the Au-TNTs presenting best performance (TOD ≈ 3.59 mgO3/L) while pristine TNTs led to TOD = 4.98 mgO3/L. For photocatalytic ozonation, the pristine TNTs led to the lowest ozone consumption (TOD = 3.74 mgO3/L).Moreover, the use of hydroxyl radical scavenger showed that hydroxyl radical is formed during single and photocatalytic ozonation mechanism, which should be related to the natural and surface catalytic ozone decomposition.

Mass transfer model based on the spatial superposition assumption for simulating the catalytic ozone decomposition in downer reactor

A mass transfer model based on the spatial superposition assumption is proposed in this work to better reflect the effect of heterogeneous structure on the mass transfer behavior of the downer. Attributing to the special assumption of this model, fewer concentration parameters are required compared with the classic multi-scale method, which largely saves the calculation consumption. The simulation results of this model also could be in good agreement with the experimental data. Additionally, the calculated mass transfer coefficients are in the range from 10−3 to 10−1, which are approximately three orders of magnitude lower than that of the homogeneous structure. It is proved that the existence of clusters would seriously affect the gas-solid mass transfer effectiveness, thereby deteriorating the reaction rate. By simulating the distribution of ozone concentration in the catalytic ozone decomposition, it can be found that the mass transfer near the inlet region plays the dominant role while along the flow direction, the influence of reaction process becomes stronger than that of the mass transfer process and gradually turns to control the whole decomposition process. These results indicate that the present model is useful and could be applied for the simulation of mass transfer process in other gas-solid fluidized systems with heterogeneous structures.

Catalysts for highly water-resistant catalytic decomposition of ozone: Hausmannite Mn3O4 on exposed (101) crystal surface

Recently, ozone pollution has gradually replaced PM2.5 as the main pollutant affecting air pollution. In this study, we synthesized a series of Mn3O4 catalysts by hydrothermal method changing the precursors and tested their activities at different relative humidity, gas volume space velocity of 150,000 h−1 and 5 ppm ozone. Remarkably, Mn3O4-SO4 prepared with MnSO4 as precursor showed excellent catalytic ozone decomposition activity, almost completely converting 5 ppm of ozone at different relative humidity ranges. Finally, the most active Mn3O4-SO4 catalyst was tested for its usability limit at RH= 90%, after 28 h of testing under high humidity conditions, it had retained successfully the complete decomposition of low concentrations of ozone. The catalysts were characterized by XRD, Raman, HRTEM, XPS, BET, H2O-TPD and in situ IR NH3 adsorption. The characterization analysis revealed that the Mn3O4-SO4 surface could exposed a highly active (101) crystalline surface with high specific surface area, excellent hydrophobicity as well as ozone adsorption capacity, which were highly favorable for ozone decomposition under high humidity conditions. In this work, Mn3O4 exhibits good catalytic activity, which provides an additional option for future studies of manganese oxides.

Magnetic mining waste based-geopolymers applied to catalytic reactions with ozone

The demand for sustainable and low-cost materials for wastewater treatment is increasing considerably. In this scenario, geopolymers have gained great interest, due to their good mechanical properties, their ability to be produced from industrial waste and their adsorbent or catalytic properties. In this study, novel magnetic mining waste based-geopolymers were produced by incorporating a residue from phosphate waste rocks, which were extensively characterized (XRD, TGA/DTA, SEM, BET, XRF, FTIR, Mössbauer, ss-NMR and XPS). The materials produced showed formation of a dense framework, even with 75% incorporation of the residue. The iron oxides and their magnetic properties remained unchanged, and their application in advanced oxidation reactions were evaluated, in particular, as catalysts in ozonation reactions. All of the geopolymers presented catalytic activity in the ozonation reaction, with catalytic ozone decomposition values of up to 2.98 min−1, which is 99 times greater than non-catalyzed reactions. Moreover, the reuse (performed in three cycles) and hot filtration-like experiments demonstrated, respectively, the regenerability and heterogeneous catalytic properties of the produced materials, showcasing the potential of these waste materials for catalytic geopolymer production. demonstrating the potential of this waste to produce catalytic geopolymers.

Creating water-resistant oxygen vacancies in δ-MnO2 by chlorine introduction for catalytic ozone decomposition at ambient temperature

To alleviate the negative impact of water vapor on ozone decomposition, we proposed a chlorine-doping strategy to create water-resistant oxygen vacancies in δ-MnO2. Comprehensive characterizations illustrated that abundant oxygen vacancies were generated by chlorine-doping, while fewer water and intermediates accumulated during ozone decomposition. Accordingly, chlorine-doped δ-MnO2 exhibited excellent activity for ozone decomposition, keeping 97.7% removal of 2000 ppm ozone after running for 40 h under the relative humidity of 65%. DFT calculations confirmed that chlorine introduction reduced the formation energy of oxygen vacancies and enhanced the strength of Mn-O bond. The compressed Mn-O bonds liberate oxygen vacancies from being occupied by water vapor and reaction intermediates. This work demonstrates the effectiveness of chlorine introduction in creating oxygen vacancies and enhancing its resistance to water vapor, which affords a new avenue to design high-performance catalysts for ozone elimination.

Simultaneous ozonation of ethylbenzene and fluorene in water, soil, and air

Most of the studies regarding aromatic hydrocarbon degradation by ozone focus on individual treatment. Hence, two aromatic hydrocarbons, ethylbenzene (ETB) presented in water and fluorene (FL) distributed in soil, were selected to be eliminated simultaneously in water, soil, and air using ozone. In this study, the effect of the physicochemical properties of ETB and FL, the distribution of FL on sandy and agricultural soils, and the influence of the presence of moisture in both soils were analyzed. The chemical composition of the agricultural soil (mainly metal oxides) enhanced the FL degradation by the possible catalytic ozone decomposition into reactive species, such as •OH, O2•−, H2O2, O3•−, and O•, which reduced its treatment time 4.5-fold in this solid matrix compared to the sandy soil. Moreover, the moisture liberated from water by the gas flow and adsorbed on the soil bed (up to 0.33% at 180 min) reduced the ozonation time 2-fold in the agricultural and sandy soils, due to the •OH formation. Contrary to FL, the rapid elimination of ETB (< 20 min) in both soils did not allow to observe the possible effect of reactive species generation on ETB decomposition due to the low amount of moisture accumulated during this time (<0.06%). The proposed simultaneous ozonation scheme permitted to achieve up to 96% and 100% of the ETB and FL decomposition. Some identified by-products, such as maleic, malonic, oxalic, and formic acids, suggest that ozone and possible reactive species formed on the soil surfaces reacted with both compounds, leading to non-toxic simple by-products with their partial mineralization (≈80%), which was proven by a toxicity evaluation (phytotoxicity and eco-toxicity). The rapid and efficient simultaneous ozonation of aromatic hydrocarbons in water, soil, and air (only ETB) proves the feasibility of ozone to treat different organic pollutants in more than one phase.

Ultra-low-energy catalytic degradation of ozone by off-stoichiometric delafossite Cu–Cr–O for highly selective low-temperature solid-state O3 sensors

Off-stoichiometric copper-chromium delafossite featuring giant catalytic degradation of ozone is demonstrated for the very first time. This leads to the reversible low-temperature detection of ozone onto resistive thin-film devices to values as low as 50 ppb. The selectivity when compared with molecular oxygen is also evidenced. Near-Atmospheric Pressure X-Ray Photoelectron Spectroscopy led to the understanding of the ozone - Cu0·66Cr1·33O2 surface reaction. The partial oxidation of copper into Cu2+ dependence on the ozone concentration is for the first time revealed. The apparition of a new peak associated with chemisorbed oxygen proves that the specific sub-stochiometric copper sites of the delafossite phase are driving the efficient and selective catalytic decomposition of ozone into monoatomic oxygen at the neat surface of thin films. The sensing response in ambient air is not limited by ozone decomposition but by the number of available adsorption sites. This work discloses pioneering results for the sensing networks integration of competitive ozone sensors based on Cu0·66Cr1·33O2.

Eco-friendly in-situ synthesis of monolithic NiFe layered double hydroxide for catalytic decomposition of ozone

Eco-friendly in-situ synthesis of monolithic NiFe layered double hydroxide for catalytic decomposition of ozone

Efficient degradation of 2,3,5-trimethylpyrazine by catalytic ozonation over MnOx supported on biochar derived from waste tea leaves

In this study, a series of biochars derived from waste tea leaves and loaded with MnOx (Mn-nWT) was fabricated for use in heterogeneous catalytic ozonation (HCO). Excellent degradation of 2,3,5-trimethylpyrazine (TMP) was achieved. Characterization data indicated that Lewis acid sites, including multivalent Mn sites, oxygen vacancies and surface hydroxyl groups, were the main active sites responsible for the HCO activity of Mn-nWT. The Mn-nWT catalysts exhibited superior HCO activity compared with bulk biochar and MnOx under various experimental conditions. In particular, 0.05 g L−1 Mn-5WT gave 95.3% degradation of 5 μM TMP in 30 min at pH 7.0. Reactive oxygen species (mainly •OH) generated from catalytic decomposition of ozone by Mn-nWT contributed to the enhanced HCO performance. The second-order degradation rate constants of TMP with O3 and •OH are 2.3 ± 0.13 and (7.3 ± 1.31) × 109 M−1 s−1. The reusability and stability of Mn-5WT was demonstrated by outstanding TMP degradation efficiency (88.8%), negligible metal dissolution and minor differences in physical characterization after four cycles. Additionally, the impacts of water matrices (catalyst dose, ozone dose, pH, temperature, carbonate and natural organic matter) on the Mn-5WT HCO process were investigated thoroughly. This study found that loading of metal oxides onto biochar synergistically promoted the HCO process by enhancing the physical and chemical properties.

Amorphous nanophosphates of dual-metal (Co and Ni) for the decomposition of ozone under humid conditions

Ozone has gradually become a kind of air pollutant that can not be ignored. A highly efficient and stable catalyst for ozone decomposition in humid environments is still a challenge. This paper used a series of novel phosphate catalysts in the ozone field. With the increase of Ni Content in Co(3−x)Ni(x)(PO4)2, crystal formation in Co(3−x)Ni(x)(PO4)2, but excessive Ni destroyed the lattice structure of Co(3−x)Ni(x)(PO4)2 which becomes amorphous. As a result, the specific surface area of materials has an obvious enlargement along with an increase of the surface oxygen content from crystal to amorphous, which is beneficial for improving its active sites on the catalyst. At a condition of relative humidity (RH)= 65 %, Co(3−x)Ni(x)(PO4)2 exhibited outstanding catalytic activity and stability at room temperature. Most importantly, Co1.8Ni1.2PO4 could degrade O3 against the influence of water vapor at RH of 90 %. The research shows the development prospect of phosphate in the field of efficient catalytic decomposition of ozone.