Catalytic Activity For Toluene Oxidation Research Articles

Design and optimization of CuCo-LDO catalysts via ZIF-67 sacrificial templates for enhanced toluene oxidation: A comprehensive study on morphology, structure, and catalytic activity

The investigation into the development of an active transition-metal oxide catalyst with controllable morphology for the degradation of volatile organic compounds (VOCs) is a subject of considerable importance and warrants further exploration. In this study, ZIF-67 was prepared and employed as a sacrificial template, with varying quantities of Cu ions incorporated to synthesize layered copper-cobalt double oxide (CuCo-LDO) featuring a modifiable surface state. A comprehensive characterization of the CuCo-LDO catalysts was conducted, encompassing structural properties, morphology, surface chemical state, and redox properties, utilizing a range of analytical techniques. Subsequent evaluations included testing the catalytic activity for toluene oxidation and assessing stability performance. The results revealed that differing Cu contents played a pivotal role in inducing changes in the morphology and structure of CuCo-LDO, thereby significantly influencing its oxidation activity towards toluene. Notably, the flower-like structure of 3CuCo-LDO (Cu% = 20.14 wt.%) exhibited outstanding toluene oxidation activity attributable to its unique structure and composition. This research contributes novel insights to the design of highs-performance catalysts targeting volatile organic compounds.

Mesoporous Si-WO3-supported Pt catalysts with high catalytic performance and excellent water resistance for toluene oxidation

Reducing emissions of volatile organic compounds (VOCs) is an integral part of improving the quality of the atmospheric environment. Catalytic oxidation has become an effective means of treating low and medium concentration VOCs exhausts due to its advantages in terms of removal efficiency, energy saving and environmental protection. Due to the unique inherent properties of supported precious metal catalysts, they show good catalytic efficiency in VOCs emission reduction. In this study, the mesoporous Si-WO3 support was first synthesized by the P123-assisted sol-gel method, and the xPt/Si-WO3 catalysts with the actual loadings (x = 0.19, 0.48, and 0.81 wt%) of Pt nanoparticles (NPs) were then obtained, physicochemical properties of these materials were characterized using a variety of techniques, and their catalytic activities and water resistance for the oxidation of toluene were evaluated. The results showed that Pt NPs with an average particle size of 2.3−3.3 nm were highly dispersed on the mesoporous Si-WO3 support, and the 0.81Pt/Si-WO3 sample exhibited the highest catalytic activity for toluene oxidation at a space velocity of 20,000 mL/(g h) (T50% = 167 °C and T90% = 180 °C; specific reaction rate at 160 °C = 8.54 µmol/(gPt s), turnover frequency (TOFPt) at 160 °C = 1.67 × 10−3 s−1, and apparent activation energy = 45 kJ/mol). The good catalytic performance of 0.81Pt/Si-WO3 was associated with its large surface area, well dispersed Pt NPs, high adsorbed oxygen species concentration, large toluene adsorption capacity, and strong interaction between Pt NPs and mesoporous Si-WO3. The 0.81Pt/Si-WO3 sample possessed excellent water resistance, and the introduction of 5 vol% or 10 vol% water vapor to the reaction system enhanced toluene oxidation since part of water vapor participated in the oxidation of toluene. In addition, the toluene oxidation pathway might obey the sequence of (adsorbed toluene + adsorbed oxygen species) → benzyl alcohol → (benzoic acid and benzaldehyde) → maleic anhydride → (carbon dioxide and water).

Mn-MIL-100 non-thermally derived MnOx catalysts for toluene oxidation

Herein, a novel preparation method via non-thermal derivation by using Mn-MIL-100 as the precursor to synthesize MnOx catalysts was proposed. The synthesized catalysts were applied to toluene oxidation. Characterizations and experiments results showed that the more surface Mn3+, Oads species, large surface area, better low-temperature reducibility and higher lattice oxygen mobility of Mn-Na2CO3 prepared via Na2CO3 treatment induced its great catalytic activity for toluene oxidation.

Highly active and stable plate-like ZSM‑5 supported MnOx catalysts for toluene Oxidation: Effect of preparation methods

Catalysts consisting of MnOx supported on plate-like ZSM-5 with the Si/Al ratio of 70 (MnOx/PZ5) were synthesized using four different methods: in-situ growth (MnOx/PZ5-IG), ammonia precipitation (MnOx/PZ5-AP), citric acid complexation (MnOx/PZ5-CA), and traditional impregnation (MnOx/PZ5-TI). The catalytic activity of these catalysts for toluene oxidation was evaluated, and their physicochemical properties were characterized by several technologies. The results showed the catalytic activity for toluene oxidation was significantly influenced by the preparation methods. Notably, MnOx/PZ5-IG demonstrated the highest catalytic activity for oxidation of toluene with the specific activity per unit mass of Mn with 2.12 × 10-6 at 250 °C, 3.8 times higher than that of MnOx/PZ5-CA, offering new ideas for the design of low-cost materials for VOCs elimination in the future. The excellent performance of MnOx/PZ5-IG could be attributed to the higher Mn4+ ratio with more reducible, active surface adsorbed oxygen and dispersion of MnOx, which also showed high stability. Finally, the reaction mechanism analyzed by in-situ DRIFTS found that MnOx/PZ5-IG promoted the activity of surface lattice oxygen, conducive to increasing the reaction rate and facilitating the ring opening of benzene, thus, deepening the oxidation of toluene to CO2 and H2O.

Synthesis of xCe-MnO2 with three-dimensional ultra-thin nanosheet structure and its excellent low-temperature reducibility for toluene catalysis.

A series of xCe-MnO2 (x = 0-1) catalysts were synthesized using ammonium oxalate as a precipitator via the redox precipitation method and hydrothermal synthesis method. The results indicate that 0.25Ce-MnO2 exhibited the highest catalytic activity for toluene oxidation, with the T99 of 240°C. Characterization results from XRD, Raman, SEM, TEM, EDS-mapping, BET, and other techniques reveal that the 0.25Ce-MnO2 catalyst exhibited a three-dimensional multistage ultrathin nanosheet structure by adjusting the introduction amount of Ce, with abundant active sites, and effectively formed Ce-Mn homogeneous dispersion. The larger pore size and volume of 0.25Ce-MnO2 catalyst lead to it excellent toluene transfer ability. Furthermore, compared with MnO2, the crystal pattern of 0.25Ce-MnO2 shifted to the tetragonal cryptomelane type α-MnO2 phase and exposed more crystal planes which are beneficial to catalyze toluene. H2-TPR, O2-TPD, and XPS characterization further confirmed the strong interaction between Ce and Mn oxides, which exhibited better low-temperature reducibility and oxygen migration, along with abundant Ce3+ and Mn3+ species, where lattice oxygen played a major role. Moreover, in situ DRIFTS revealed that the 0.25Ce-MnO2 catalyst showed higher adsorption and desorption capacity for toluene than the MnO2 catalyst, and benzoate species were the key intermediates for catalytic oxidation. Additionally, benzoate and surface phenolic species were the key intermediates for catalytic oxidation of MnO2. Because 0.25Ce-MnO2 possesses better ability of converting toluene to benzoate species, it exhibits better activity.

Regulating catalytic stability of PtSnM/CeO2 (M = Mn, W, Nb) catalysts via the closely coupled multi-active sites to promote multicomponent VOCs oxidation

Pt-based commercial catalysts tend to be poisoned by chlorine species in the oxidation of chlorinated volatile organic compounds (CVOCs), which greatly limits their wide applications. It is vital to develop the active catalysts with good chlorine resistance. In the present work, the novel supported ternary metallic catalysts (PtSnM/CeO2; M = Mn, W, Nb) with the closely coupled multi-active sites show good catalytic performance and excellent chlorine resistance for the oxidation of toluene and chlorobenzene (CB), and can effectively inhibit formation of the toxic chlorine-containing by-products. The catalytic activity for toluene oxidation in the mixed VOCs system follows the sequence: PtSnMn/CeO2 > PtSnW/CeO2 ≈ PtSnNb/CeO2 > PtSn/CeO2 > Pt/CeO2. The change of the electron structure around Pt results in the difference in adsorption capacity of toluene and CB. The C−Cl bond is first dissociated at the Brønsted acid sites, and the non-chlorinated organic compounds are oxidized at the Pt sites that contact with the acid sites in the proximity. Additional water provides sufficient protons to react with Cl species, enhancing the desorption amount of HCl; furthermore, the water also reacts with the adsorbed oxygen to generate new oxygen species, which participates in the oxidation of VOCs, so as to accelerate the removal of Cl species on the catalyst surface and reduce the more toxic polychlorine by-products. This work is helpful for developing the supported noble metal catalysts with good chlorine-resistant performance in the oxidation of multicomponent VOCs under the actual industrial conditions.

Weak Metal-Support Interaction over CuO/TiO2 Catalyst Governed Low-Temperature Toluene Oxidation.

Regulating the metal-support interaction is essential for obtaining highly efficient catalysts for the catalytic oxidation of volatile organic compounds (VOCs). In this work, CuO-TiO2(coll) and CuO/TiO2(imp) with different metal-support interactions were prepared via colloidal and impregnation methods, respectively. The results demonstrated that CuO/TiO2(imp) has higher low-temperature catalytic activity, with a 50% removal of toluene at 170 °C compared to CuO-TiO2(coll). Additionally, the normalized reaction rate (6.4 × 10-6 mol·g-1·s-1) at 160 °C over CuO/TiO2(imp) was almost four-fold higher than that over CuO-TiO2(coll) (1.5 × 10-6 mol·g-1·s-1), and the apparent activation energy value (27.9 ± 2.9 kJ·mol-1) was lower. Systematic structure and surface analysis results disclosed that abundant Cu2+ active species and numerous small CuO particles were presented over CuO/TiO2(imp). Owing to the weak interaction of CuO and TiO2 in this optimized catalyst, the concentration of reducible oxygen species associated with the superior redox property could be enhanced, thus significantly contributing to its low-temperature catalytic activity for toluene oxidation. This work is helpful in exploring the influence of metal-support interaction on the catalytic oxidation of VOCs and developing low-temperature catalysts for VOCs catalytic oxidation.

Insight into the catalytic oxidation of toluene over M/ZSM-5 (M=Cu, Mn, Fe, Ce, Ti) catalysts

A series of metal oxide catalysts were prepared by impregnating Cu, Mn, Fe, Ce and Ti on ZSM-5 molecular sieve. The physicochemical properties of the catalysts were characterized by SEM, XRD, N2 adsorption/desorption, XPS, H2-TPR, and the catalytic oxidation of toluene was investigated. The results showed that Cu/ZSM-5 had rough surface, uniform distribution of metal, good pore structure, superior low-temperature reducibility and abundant adsorbed oxygen species. Cu/ZSM-5 with 5% loading exhibited excellent catalytic activity for toluene oxidation and the best sulfur resistance performance, with t90 (GHSV=24000 h−1) being 224 °C in SO2 environment. In-situ DRIFTS experiments revealed that the degradation path of toluene was as follows: toluene was first adsorbed on the surface of the catalyst to form adsorbed toluene, then it was converted into benzaldehyde and benzoic acid successively on the catalyst. And small molecule organics such as maleic acid and carboxylic acid were formed through ring opening reaction, and finally was oxidized to CO2 and H2O.

Facile synthesis of β-MnO2 via ozone oxidation for enhanced performance of toluene oxidation

In this work, a series of β-MnO2 catalysts is directly synthesized via ozone oxidation using the hydrothermal method. And the effect of hydrothermal temperature on catalytic activities of toluene oxidation is investigated. The catalytic evaluation shows that O3(HT)-160 prepared at 160 °C of hydrothermal temperature exhibits the best catalytic activity of toluene oxidation compared with other catalysts. By comparison of physicochemical properties, O3(HT)-160 possesses a bigger specific surface area and larger pore volume, which are beneficial to the adsorption and diffusion of toluene molecules. Meanwhile, O3(HT)-160 performs lower reductive temperature, higher ratio of Mn4+/(Mn3++ Mn2+) and Olatt/Oads and much more oxygen vacancies, which contributes to the cycle of redox ability, the complete oxidation of intermediates and the activation of oxygen. Moreover, combined with the results of in-situ DRIFTS and TD/GC–MS, the main intermediates are benzyl alcohol, benzaldehyde, benzoic acid and propylene glycol during toluene oxidation on O3(HT)-160. Furthermore, the catalytic mechanism is proposed for toluene oxidation on O3(HT)-160. This work provides a more convenient and simpler method to prepare β-MnO2 using ozone as the oxidizer compared with potassium permanganate and potassium persulfate.

Quenching-Induced Defect-Rich Platinum/Metal Oxide Catalysts Promote Catalytic Oxidation.

Enhancing oxygen activation through defect engineering is an effective strategy for boosting catalytic oxidation performance. Herein, we demonstrate that quenching is an effective strategy for preparing defect-rich Pt/metal oxide catalysts with superior catalytic oxidation activity. As a proof of concept, quenching of α-Fe2O3 in aqueous Pt(NO3)2 solution yielded a catalyst containing Pt single atoms and clusters over defect-rich α-Fe2O3 (Pt/Fe2O3-Q), which possessed state-of-the-art activity for toluene oxidation. Structural and spectroscopic analyses established that the quenching process created abundant lattice defects and lattice dislocations in the α-Fe2O3 support, and stronger electronic interactions between Pt species and Fe2O3 promote the generation of higher oxidation Pt species to modulate the adsorption/desorption behavior of reactants. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) characterization studies and density functional theory (DFT) calculations determined that molecular oxygen and Fe2O3 lattice oxygen were both activated on the Pt/Fe2O3-Q catalyst. Pt/CoMn2O4, Pt/MnO2, and Pt/LaFeO3 catalysts synthesized by the quenching method also offered superior catalytic activity for toluene oxidation. Results encourage the wider use of quenching for the preparation of highly active oxidation catalysts.

High-efficiency palladium/halloysite nanotubes catalyst for toluene catalytic oxidation: Characterization, performance and reaction mechanism

In this study, the halloysite treated with nitric acid was designed as a functionalized support material for favoring surface availability and dispersion of nanometric palladium (Pd) nanoparticles. The prepared supported catalysts were characterized by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), and O2 temperature-programmed desorption (O2-TPD). The catalytic performance and reaction mechanism of toluene oxidation were evaluated and proposed. Scanning and transmission electron microscopy images showed that 4–5 nm diameter Pd nanoparticles were uniformly dispersed on the external and edge surfaces of the A-Hal nanotubes and no obvious aggregations observed. The Pd nanoparticles were mainly present in the zero-valent state. The ratio of metallic Pd to Pd oxide species and adsorbed (Oads) to lattice (Olatt) presented a maximum value of 2.54 and 23.0, respectively, when the Pd loading was 0.5%. The prepared support catalysts exhibited a satisfactory catalytic performance and cycling stability for toluene conversion. Among the analyzed samples, the 0.5% Pd/A-Hal catalyst exhibited the highest catalytic activity for toluene oxidation, stability, and water resistance. Toluene conversions of 50% and 90% were obtained at 167 and 185 °C, respectively. In situ diffuse reflection Fourier transform spectroscopy measurements confirmed the intermediates generated during toluene oxidation and revealed that toluene oxidation occurred via the benzyl alcohol → benzaldehyde → benzoic acid → maleic anhydride reaction pathway over the obtained catalysts. These results were attributed to the high content of metal Pd species, abundant Oads species, and low-temperature reducibility. These results indicate that Hal support catalysts are promising materials for application in environmental protection.

Unraveling the role of OH groups over CeO2 derived from methanol modification for enhancing toluene oxidation: Experimental and theoretical studies

Developing efficient catalysts for catalytic oxidation of toluene at low temperatures is challenging. Herein, the OH groups and oxygen vacancies are introduced into CeO2 by methanol modification and applied in catalytic oxidation of toluene. CeO2-T-M, one of the modified CeO2, displays the greatest catalytic activity for toluene oxidation with T90 of 235 oC. In situ characterizations and theoretical calculations show that abundant OH groups and oxygen vacancies on the CeO2-T-M are well correlated with the catalytic activity. The OH groups facilitate the adsorption and activation of gaseous oxygen into adsorbed active oxygen species (O22-) and lattice oxygen (O2-) over oxygen vacancies. And the toluene and key intermediates (benzyl alcohol, benzaldehyde, benzoate, and maleic anhydride) are more easily adsorbed and oxidized on CeO2-T-M. Meanwhile, the consumed OH groups will be regenerated with activated lattice oxygen by dehydrogenation, thus the catalytic activity and stability for toluene oxidation are enhanced over modified CeO2.

Ca substitution improves the catalytic activity of perovskite LaCoO3 toward toluene: comprehension of electronic structure alteration.

For perovskite La1-xCaxCoO3 (Ca-x, x = 0-0.3), Ca-0.2 with the closest O p band center to the Fermi level, displays the best catalytic activity for toluene oxidation. The O p band center determines the reducibility and active oxygen content. This finding is beneficial for the design of highly active perovskite catalysts.

Enhanced catalytic activity of toluene oxidation over in-situ prepared Mn3O4-Fe2O3 with acid-etching treatment

Mn3O4-Fe2O3 composite catalysts are in-situ synthesized via advanced oxidation followed by modifying with hydrochloric acid to improve the catalytic toluene oxidation performance. Mn3O4-Fe2O3 modified with 1.0 M HCl (A-1.0) exhibited best activity of toluene oxidation. The temperature of 50% toluene conversion is 245 °C and the temperature of 90% conversion is 279 °C. There are much more abundant surface lattice oxygen species and higher amount of high valence manganese and iron ions on A-1.0 catalyst, which are beneficial for improving catalytic activity. In-situ DRIFTs indicated that benzaldehyde and benzoic acid are main intermediate products on A-1.0 catalyst during toluene oxidation.

PdPty/V2O5-TiO2: Highly Active Catalysts with Good Moisture- and Sulfur Dioxide-Resistant Performance in Toluene Oxidation

Catalytic performance and moisture and sulfur dioxide resistance are important for a catalyst used for the oxidation of volatile organic compounds (VOCs). Supported noble metals are active for VOC oxidation, but they are easily deactivated by water and sulfur dioxide. Hence, it is highly desired to develop a catalyst with high performance and good moisture and sulfur dioxide resistance in the oxidation of VOCs. In this work, we first adopted the hydrothermal method to synthesize a V2O5-TiO2 composite support, and then employed the polyvinyl alcohol (PVA)-protecting NaBH4 reduction strategy to fabricate xPdPty/V2O5-TiO2 catalysts (x and y are the PdPty loading (0.41, 0.46, and 0.49 wt%) and Pt/Pd molar ratio (2.10, 0.85, and 0.44), respectively; the corresponding catalysts are denoted as 0.46PdPt2.10/V2O5-TiO2, 0.41PdPt0.85/V2O5-TiO2, and 0.49PdPt0.44/V2O5-TiO2). Among all the samples, 0.46PdPt2.10/V2O5-TiO2 exhibited the best catalytic activity for toluene oxidation (T50% = 220 °C and T90% = 245 °C at a space velocity of 40,000 mL/(g h), apparent activation energy (Ea) = 45 kJ/mol), specific reaction rate at 230 °C = 98.6 μmol/(gPt s), and turnover frequency (TOFNoble metal) at 230 °C = 142.2 × 10−3 s−1. The good catalytic performance of 0.46PdPt2.10/V2O5-TiO2 was associated with its well-dispersed PdPt2.10 nanoparticles, high adsorbed oxygen species concentration, good redox ability, large toluene adsorption capacity, and strong interaction between PdPty and V2O5-TiO2. No significant changes in toluene conversion were detected when 5.0 vol% H2O or 50 ppm SO2 was introduced to the reaction system. According to the characterization results, we can realize that vanadium is the main site for SO2 adsorption while PdO is the secondary site for SO2 adsorption, which protects the active Pt site from being poisoned by SO2, thus making the 0.46PdPt2.10/V2O5TiO2 catalyst show good sulfur dioxide resistance.

Enhanced low temperature catalytic activity for toluene oxidation over core-shell LaMnO3@α-MnO2 catalyst with oxygen vacancies

Engineering oxygen vacancies is an effective strategy to enhance the catalytic activity of MnO2 based composite oxides in heterogenous reactions, such as volatile organic compounds (VOCs) oxidation reaction. Core-shell structure LaMnO3@α-MnO2 catalysts were prepared by hydrothermal method via varying the concentrations of LaMnO3 and used in toluene oxidation reaction. Irregular core-shell structure L@M-10 catalyst exhibits excellent low temperature catalytic activity and stability, achieving 100% toluene removal efficiency at 200 °C. The light-off temperature (T50) and complete conversion temperature (T90) are 235 and 271 °C even after five repetitive cycles, respectively. The interfacial effect of L@M-10 sample promotes the generation of oxygen vacancies, facilitating the formation of active oxygen species. A possible oxidation reaction mechanism of toluene over L@M-10 catalyst was proposed in combination with the in-situ DRIFTS results. Fast ring-opening reaction and quick transformation of carboxylate or anhydride species into final products CO2 and H2O explains the superior catalytic property and stability of L@M-10 sample. This work highlights the effect of interface on the catalytic activity and stability of LaMnO3@α-MnO2 catalyst towards toluene oxidation and can offer a new insight into the utilization of interfacial effect in thermocatalytic reactions.

Metal organic frameworks derived metal oxides prepared by oxygen vacancy engineering with the enhanced catalytic activity for toluene oxidation

Herein, MnOx catalysts were prepared by in situ pyrolysis of Mn metal organic frameworks (Mn-MOF). The Mn-5TA with proper doping of tartaric acid (Mn-MOF/ tartaric acid mass ratio of 5), exhibited superior catalytic activity and stability towards catalytic removal of toluene under simulated real-exhaust conditions. Mn3+ and oxygen vacancies were beneficial for toluene degradation, whereas Mn3+ can generate oxygen vacancies to maintain charge conservation and then responsible for toluene adsorption and generation of intermediates. In addition, the oxygen vacancies were explored by EPR, Raman and O2-TPD. Compared with other catalysts, Mn-5TA has higher oxygen vacancy contents. Meanwhile, in-situ DRIFTS also indicated that oxygen vacancies could play a key role in the adsorption-oxidation process of toluene. Therefore, the present study provides a simple method to introduce and control the content of oxygen vacancies, and the obtained results provide a new strategy for the rational design of efficient catalytic materials for the elimination of volatile organic compounds.

Waste eggshell membrane-templated three-dimensional CoOx catalyst for efficient low-temperature toluene oxidation with strong thermal stability

Eggshell membrane was used as the template to synthesize three-dimensional network CoOx catalysts. Besides, hydrogen reduction at 650 °C was adopted to simultaneously remove poisoned sulfur species and produce metal Co, which was self-oxidized on the catalyst surface at room-temperature, accompanied with better reducibility. Compared to counterpart CoOx (direct calcination of C4H6CoO4∙4 H2O), CoOx synthesized by using eggshell membrane possesses more Co3+ and lattice oxygen because its three-dimensional network structure is beneficial to the mass transfer of the reaction. The structure of applied catalyst will be reformed during the oxidation process. Although the active Co species are Co3+, the spillover of hydrogen from Co0 to surface leads to a better reducibility of ESM-CoOx, which significantly improves the low-temperature toluene oxidation activity of the catalyst. As a result, ESM-CoOx exhibits a best low-temperature catalytic activity of toluene oxidation (reaching 99% conversion at 250 °C, toluene reaction rate at 225 °C is 2.98 μmol gcat−1 s−1). Importantly, the above cobalt catalyst shows excellent thermal stability and 5 vol% water resistance at 250 °C. This work thus provides a novel process to tail highly active CoOx catalyst for low-temperature volatile organic chemicals oxidation in real application.

Effects of thermal aging on the electronic and structural properties of Pt-Pd and toluene oxidation activity

Catalytic oxidation is a feasible method for remediating volatile organic compounds (VOCs), due to its lower energy consumption and mineralization of VOCs into H2O and CO2. Noble metal-based catalysts are preferred for the catalytic oxidation of VOCs because of their superior activity, but they are usually deactivated by thermal aging which sinters the metal particles. Here, we report that Pt-Pd/Al2O3 thermally aged at 700–900 °C in air showed enhanced catalytic activity for toluene oxidation in humid conditions. There were electronic and structural changes in the thermally aged Pt-Pd/Al2O3, as confirmed by numerous analyses. Both Pt and Pd existed in a metallic rather than oxidized state without additional reduction steps. The noble metal particles were assembled to form Pt-Pd alloy, in the form of isolated Pd atoms surrounded by Pt atoms. This specific alloy structure was found to be crucial to the observed enhancement in catalytic toluene oxidation at low temperature.

Non-equilibrium plasma enhanced oxygen vacancies of CuO/CeO2 nanorod catalysts for toluene oxidation

The development of non-noble metal catalyst is essential for VOCs controlling. Cu-Ce based catalyst is a promising catalyst, and the oxygen vacancies dominants the catalytic oxidation process but the traditional calcination is not conducive to its generation. Herein a series of CuO/CeO2 nanorod catalysts for toluene oxidation were prepared with non-equilibrium plasma comparing with traditional calcination. It is found that the treatment of non-equilibrium plasma after calcination can significantly enhance the synergism between CuO active phase and CeO2 support leading to high dispersion of CuO. And the non-equilibrium plasma is favorable to increase Cu+/Cu2+ and Ce3+/Ce4+ ratios generating more oxygen vacancies in the catalyst. In the process of toluene oxidation, the rich oxygen vacancy can accelerate adsorption and activation of gaseous oxygen which consequently improve the catalytic activity for toluene oxidation.