Oxidation Of Organic Compounds Research Articles

Synthesis of cordierite using municipal solid waste incineration fly ash as one additive for enhanced catalytic oxidation of volatile organic compounds

Municipal solid waste incineration (MSWI) fly ash is a hazardous waste, which needs various recycling in order to reach “net-zero waste”. This work aimed to synthesize cordierite using MSWI fly ash as one additive and investigate influence of the additive on properties of the cordierite. As a result, the cordierite was successfully synthesized when the additive weight ratio was <15 % and the synthesis strategy was universally feasible for 14 kinds of different MSWI fly ashes. As a heat accumulator, the cordierite attained compressive strength of 42.1 MPa, water absorption of 26 %, bulk density of 1.87 g·cm−3, and open porosity of 47 %. After five cycles of thermal impact at 1200 °C, the strength was only decreased by 15 %. These properties were comparable to a commercial cordierite. As a catalyst carrier, after loading Mn and Cu species, the cordierite removed 100 % of toluene at 250 °C. In comparison, a commercial cordierite only got a removal of 34.4 %. The enhanced activity was attributed to co-existing spinel and bytownite as well as imbedded Zn and Cu in the MSWI fly ash-added cordierite. Therefore, this work devotes to hazardous recycling, green development, and cycled economy.

Substantially positive contributions of new particle formation to cloud condensation nuclei under low supersaturation in China based on numerical model improvements

Abstract. New particle formation (NPF) and subsequent particle growth are important sources of condensation nuclei (CN) and cloud condensation nuclei (CCN). While many observations have shown positive contributions of NPF to CCN at low supersaturation, negative NPF contributions were often simulated in polluted environments. Using the observations in a coastal city of Qingdao, Beijing, and Gucheng in north China, we thoroughly evaluate the simulated number concentrations of CN and CCN using an NPF-explicit parameterization embedded in the WRF-Chem model. For CN, the initial simulation shows large biases of particle number concentrations at 10–40 and 40–100 nm. By adjusting the process of gas–particle partitioning, including the mass accommodation coefficient (MAC) of sulfuric acid, the phase changes in primary organic aerosol emissions, and the condensational amount of nitric acid, the improvement of the particle growth process yields substantially reduced overestimation of CN. Regarding CCN, secondary organic aerosol (SOA) formed from the oxidation of semi-volatile and intermediate-volatility organic compounds (S/IVOCs) is called SI-SOA, the yield of which is an important contributor. At default settings, the SI-SOA yield is too high without considering the differences in precursor oxidation rates. Lowering the SI-SOA yield under linear H2SO4 nucleation scheme results in much-improved CCN simulations compared to observations. On the basis of the bias-corrected model, we find substantially positive contributions of NPF to CCN at low supersaturation (∼ 0.2 %) over broad areas of China, primarily due to competing effects of increasing particle hygroscopicity, a result of reductions in SI-SOA amount, surpassing that of particle size decreases. The bias-corrected model is robustly applicable to other schemes, such as the quadratic H2SO4 nucleation scheme, in terms of CN and CCN, though the dependence of CCN on SI-SOA yield is diminished likely due to changes in particle composition. This study highlights potentially much larger NPF contributions to CCN on a regional and even global basis.

Study of atmospheric glyoxal using multiple axis differential optical spectroscopy (MAX-DOAS) in India

Glyoxal (CHOCHO) is an important atmospheric trace gas formed by the oxidation of volatile organic compounds (VOCs). We present a study of atmospheric CHOCHO from three locations (Pune, Mahabaleshwar and Delhi) in India using Multi-Axis Differential Optical Spectroscopy (MAX-DOAS) observations. Pune and Delhi represent urban environments, whereas Mahabaleshwar represents a forested rural region. Differential slant column densities (dSCDs), vertical column densities (VCDs), surface volume mixing ratios (vmr) and vertical profiles of CHOCHO were measured and compared to satellite observations. Delhi showed the highest average CHOCHO VCD (1.57 ± 0.98 × 1015 molec. cm−2) and vmr (average of 0.43 ± 0.27 ppb), whereas Mahabaleshwar showed the lowest average VCD (0.66 ± 0.40 × 1015 molec. cm−2) and average vmr (0.08 ± 0.03 ppb) among the three sites. Average CHOCHO VCD (1.52 ± 0.66 × 1015 molec. cm−2) and vmr (0.33 ± 0.18 ppb) over Pune were close to but lower than Delhi. A large seasonal variation was observed in Pune, with the highest (1.82 ± 0.62 × 1015 molec. cm−2) and lowest (0.79 ± 0.45 × 1015 molec. cm−2) monthly average VCDs observed in January and May, respectively. This inter-annual pattern was observed in both ground-based and satellite observations. Satellite observations systematically underestimated the CHOCHO VCDs compared to ground-based observations. Comparison with previous studies shows that Pune and Delhi have similar levels of CHOCHO with respect to other urban regions, while Mahabaleshwar is comparable to other remote environments worldwide.

Electron donation promotes the dual activation of lattice oxygen and molecular oxygen: The Pt-Pd/CeO2 catalyst efficiently catalyzes toluene

Dual activation of molecular and lattice oxygen is an important step in the catalytic oxidation of volatile organic compounds. Herein, CeO2 was derived from MOF as an electron donor support to develop a co-catalyst with Pt-Pd alloy nanoparticles (Pt-Pd/CeO2). The Prepared Pt-Pd/CeO2 exhibits excellent catalytic activity towards toluene oxidation, showing a turnover frequency (TOF 0.26 s−1) higher than those of Pt/CeO2 (0.05 s−1) and Pd/CeO2 (0.02 s−1). Several in situ experimental techniques and density functional theory calculations have revealed that the introduction of Pd valence electrons can intensify the electronic metal-support interactions (EMSIs) effects of Pt-Pd/CeO2 catalysts, which can weaken the Ce-O bond, thereby promoting the production and circulation of lattice oxygen and oxygen vacancies, and modulating the d-band centre to enhance the adsorption and activation of reactants. This study presents a comprehensive investigation of toluene oxidation on alloy-supported catalysts, providing practical guidance for designing reliable catalysts suitable for industrial applications.

Carbonyl products of ozone oxidation of volatile organic compounds can modulate olfactory choice behavior in insects

Insects are a diverse group of organisms that provide important ecosystem services like pollination, pest control, and decomposition and rely on olfaction to perform these services. In the Anthropocene, increasing concentrations of oxidant pollutants such as ozone have been shown to corrupt odor-driven behavior in insects by chemically degrading e.g. flower signals or insect pheromones. The degradation, however, does not only result in a loss of signals, but also in a potential enrichment of oxidation products, predominantly small carbonyls. Whether and how these oxidation products affect insect olfactory perception remains unclear. We examined the effects of ozone-generated small carbonyls on the olfactory behavior of the vinegar fly Drosophila melanogaster. We compiled a broad collection of neurophysiologically relevant odorants for the fly from databases and literature and predicted the formation of the types of stable small carbonyl products resulting from the odorant's oxidation by ozone. Based on these predictions, we evaluated the olfactory detection and behavioral impact of the ten most frequently predicted carbonyl products in the fly using single sensillum recordings (SSRs) and behavioral tests. Our results demonstrate that the fly's olfactory system can detect the oxidation products, which then elicit either attractive or neutral behavioral responses, rather than repulsion. However, certain products alter behavioral choices to an attractive odor source of balsamic vinegar. Our findings suggest that the enrichment of small carbonyl oxidation products due to increased ozone levels can affect olfactory guided insect behavior. Our study underscores the implications for odor-guided foraging in insects and the essential ecosystem services they offer under carbonyl enriched environments.

Electrochemical investigations of the multicopper oxidase from Aquifex aeolicus under direct electron transfer with carbon electrodes

The study of redox proteins confined over an electrode surface is a powerful approach enabling precise modulation of the driving force for interfacial electron transfer through the control of the electrode potential. In this work, we present the investigation of a protein variant of the multicopper oxidase from Aquifex aeolicus obtained by directed evolution. Motivated by the enhanced performance of the protein variant for the oxidation of organic compounds in solution, the enzyme is studied under direct electron transfer with the electrode. A marked dependence of the redox potential with the pH of the electrolyte solution is observed, which is further confirmed by studies under non-turnover conditions. Further investigations show the need for an initial reductive activation to attain maximum bioelectrocatalytic activity for O2 reduction, in agreement with similar observations made for other multicopper oxidases (MCOs). Moreover, the influence of chloride ions on the bioelectrocatalytic reaction is described. The O2-reduction activity is barely affected at KCl concentrations as high as 100 mM. However, a shift in the O2-reduction potential towards more negative values is observed at low pH, explaining the apparent loss in activity for the oxidation of organic substrates in the presence of KCl. The obtained results contribute to a more detailed understanding of the electrochemical properties of metallo-oxidases and other MCOs.

Inferring the diurnal variability of OH radical concentrations over the Amazon from BVOC measurements

The atmospheric oxidation of biogenic volatile organic compounds (BVOC) by OH radicals over tropical rainforests impacts local particle production and the lifetime of globally distributed chemically and radiatively active gases. For the pristine Amazon rainforest during the dry season, we empirically determined the diurnal OH radical variability at the forest-atmosphere interface region between 80 and 325 m from 07:00 to 15:00 LT using BVOC measurements. A dynamic time warping approach was applied showing that median averaged mixing times between 80 to 325 m decrease from 105 to 15 min over this time period. The inferred OH concentrations show evidence for an early morning OH peak (07:00–08:00 LT) and an OH maximum (14:00 LT) reaching 2.2 (0.2, 3.8) × 106 molecules cm−3 controlled by the coupling between BVOC emission fluxes, nocturnal NOx accumulation, convective turbulence, air chemistry and photolysis rates. The results were evaluated with a turbulence resolving transport (DALES), a regional scale (WRF-Chem) and a global (EMAC) atmospheric chemistry model.

Enhanced selective catalytic oxidation of triethylamine by VOx-modified CuO@TiO2 catalyst through increased amount of Lewis acid sites and adsorbed oxygen species on catalyst surface

The selective catalytic oxidation (SCO) of nitrogenous volatile organic compounds (NVOCs) has recently garnered significant attention. However, the SCO processes for tertiary amines (such as triethylamine) have not been reported. The impact of vanadium doping in CuO@TiO2 and Cu loading on SCO of TEA to N2 was investigated in this study. The surface acidity of the catalyst is primarily influenced by the VOx doping, as indicated by the results of NH3-TPD and pyridine-IR. Additionally, XPS and H2-TPR results reveal that the highly dispersed CuO species is the key oxidative component in the catalyst. SEM and TEM results show that VOx is beneficial to enhance the dispersion of CuO in the catalyst. The adsorbed oxygen content of CuO@TiO2 catalyst is increased by VOx-modification, as indicated by EPR result. An appropriate amount of adsorbed oxygen in the catalyst can improve the oxidation activity of the catalyst and assure high selectivity of N2. Finally, through the in-situ DRIFTs the reaction intermediate NHx is captured, and a reliable SCO reaction pathway of TEA is proposed. This study provides a solution for the disposal of tertiary amines from NVOCs.

Catalytic Oxidation of Volatile Organic Compounds Alone or in Mixture over Mg4Al2−xCex Mixed Oxides

This study investigates Ce-containing MgAl layered double hydroxides (LDH), focusing on its structural and catalytic properties. Mg4Al2−xCex (x = 0; 0.4; 0.8; 2) hydrotalcite-like compounds were prepared using the co-precipitation method. The effects of cerium content and calcination temperature on the structural and catalytic properties of Ce-containing MgAl LDH were investigated. The samples were characterized by XRD, BET, Raman, XPS, and DTA/TGA techniques. The catalytic activity of the resulting compound in n-butanol oxidation was studied. Increasing the calcination temperature (from 280 to 500 °C) caused changes in the structural, textural, and reducibility properties. The Mg4Al2−xCex LDH structure series (calcined at 280 °C) exhibited the highest catalytic activity, especially for x = 2. The material’s properties improved with increased Ce content, allowing complete butanol conversion below 280 °C. The formation of active sites occupied by cerium within the LDH structure, along with its reducibility properties, contributed to the material’s performance. The Ce3+/Ce4+ redox couple in the external layers enhanced O2− diffusion and their activation into nucleophilic species, facilitating butanol transformation. Adding water vapor to the reaction mixture slightly decreased the butanol oxidation, while the presence of ethyl acetate and butanol together exhibited a mutual inhibitory effect, with butanol demonstrating a more prominent influence.

Possibility of a Point Explosion due to the Presence of UV Radiation and Mercury Vapor in the Reaction Medium for Oxidation of Organic Compounds on the Example of Propane

Possibility of a Point Explosion due to the Presence of UV Radiation and Mercury Vapor in the Reaction Medium for Oxidation of Organic Compounds on the Example of Propane

Biocatalytic Attributes of Laccase and its Applications in Bioremediation

Abstract: Laccases are proteins with multiple copper atoms that utilize molecular oxygen to catalyze the oxidation of organic compounds by a radical-catalyzed mechanism. They are the main focus of researchers due to their varied applications, for example, waste detoxification, textile transformation, and biosensor applications. Laccases help in the degradation of xenobiotics, such as polycyclic aromatic hydrocarbons, pesticides, and chlorinated phenolics. They are used to bleach textiles and decolorize dyes. They also play a bioremediatory role in the pulp and paper industry for the detoxification of effluent. : Moreover, laccases help in the removal of detrimental micropollutants, such as nonylphenol and bisphenol A. They also degrade wastewater contaminants, such as 2-hydroxybiphenyl, naproxen, and diethyl phthalate. The remarkable biocatalytic attributes of laccases, coupled with their wide range of applications, make them a promising solution for the treatment of pollutants and contaminants.

Insights into non-crystalline structure of solid solution Ce-Mn co-oxide nanofibers for efficient low-temperature toluene oxidation.

The controllable preparation of efficient non-crystalline solid solution catalysts is a great challenge in the catalytic oxidation of volatile organic compounds. In this work, series non-crystalline solid solution structured Ce-Mn co-oxide nanofibers were creatively prepared by adjusting Ce/Mn molar ratios using electrospinning. 0.20CeMnOx (the ratio of Ce to Mn was 0.2) displayed an outstanding low-temperature toluene oxidation activity (T90 = 233 °C). The formation of the amorphous solid solution and the unique nanofiber structure both contributed to a large specific surface area (S = 173 m2 g-1) and high adsorbed oxygen content (Oads/O = 41.3%), which enhanced the number of active oxygen vacancies. The synergies between non-crystalline structure and active oxygen species markedly improved oxygen migration rate as well as redox ability of the catalysts. Additionally, in situ diffuse reflectance infrared Fourier transform spectra showed that the absorbed toluene could be completely oxidized to CO2 and H2O with benzyl alcohol, benzaldehyde, benzoic acid, and maleic anhydride as intermediates. In summary, this study provided an alternative route for the synthesis of non-crystalline metal co-oxide nanofibers.

Highly Efficient RGO-Supported Pd Catalyst for Low Temperature Hydrocarbon Oxidation

The work presents Pd-containing catalysts for practical application with enhanced low-temperature activity in the complete oxidation of volatile organic compounds (VOCs) using innovative combinations of reduced graphene oxide (RGO) and alumina. The catalysts were characterized by XRD, SEM, TEM, XPS, low-temperature N2-adsorption, and CO chemisorption. The tests on complete catalytic oxidation of different VOC (propane, butane, hexane, dimethyl ether, toluene, propylene) and CO were carried out. The reaction kinetics and the mechanism of the reaction of complete oxidation of toluene are being investigated in detail. The results show that the new catalyst design makes it able to completely oxidize the studied VOCs and CO at low temperatures (100–350 °C) with long-term stability. Using a variety of instrumental methods, it was established that for high activity and long-term stability, the optimal ratio Pd/PdO should be close to 1:1. The most probable mechanism of complete toluene oxidation is the mechanism of Langmuir–Hinshelwood. The high activity and the weak effect of water on the catalyst performance leads to further perspectives for the application of the currently developed approach for the preparation of large-scale monolithic catalytic systems for air pollution control.

Effect of the surface composition of MnOX-CeOX 3D-printed monolithic catalysts toward total oxidation of toluene.

Successful fabrication of Mn-based 3D-printed monoliths by stereolithography (SLA) is reported for the first-time in this work. The catalytic performances, as function of the surface composition, of the developed monoliths were evaluated by the total oxidation of toluene. The monolith with a surface composition of Mn0.7Ce0.3 showed the highest catalytic efficiency (98%) with a T90 value of 322 °C and acceptable catalytic stability after a second reaction cycle. By changing space velocity values, the T90 value can decrease to 311 °C. Microstructural and surface characterizations confirm the formation of Mn2O3 and Ce species on Mn sites and the homogeneous dispersion of Mn and Ce species on the surface of the 3D-printed monoliths. For comparison purposes, a single MnOX and CeOX monoliths were also synthesized and tested by toluene total oxidation, which confirms the cooperative effect between the oxygen storage capacity of Ce and the redox ability of Mn species observed in Mn0.7Ce0.3 monolith catalyst, giving rise to the highest catalytic activity. These results pointed out the promising catalytic properties of the developed Mn-based 3D-printed monolith catalysts for the total oxidation of volatile organic compounds at a low cost, which is an interesting alternative to mitigating atmospheric emissions.

Characterization, Sources, and Chemical Processes of Submicron Aerosols at a Mountain Site in Central China

AbstractA field campaign (29 May to 14 June 2018) was conducted at a mountain site in central China. The chemical composition of non‐refractory submicron particulate matter (NR‐PM1) and the particle number size distribution (PNSD) were measured, respectively. The mean NR‐PM1 mass concentration was 20.94 ± 10.14 μg m−3, among which organics (47%) was the most abundant component, followed by sulfate (37%), ammonium (11%), nitrate (4%), and chloride (1%). Notably, sulfate accounted for more than 70% of the secondary inorganic aerosols. Positive matrix factorization (PMF) analysis of the composition data resulted in three organic aerosol (OA) factors: hydrocarbon‐like OA (HOA), oxygenated OA I (OOA‐I), and oxygenated OA II (OOA‐II). The secondary organic aerosol (SOA) composed of the latter two factors (SOA: OOA‐I + OOA‐II) was dominant in OA (80.7%). The PMF analysis of the PNSD data yielded three factors: new particle formation related mode, growth mode, and accumulation mode, among which the last factor dominated both number and volume ratios. The sulfate formation was characterized by the sulfur oxidation ratio (SOR), heterogeneous sulfate production rate (Phet), and gaseous sulfuric acid concentration, representing secondary sulfate transformation, heterogeneous reactions, and gas phase reactions, respectively. The results showed that Phet was well correlated with both sulfate concentrations and SOR, especially during the polluted periods. Our study demonstrates that photochemically‐driven heterogeneous reactions contribute dominantly to the sulfate formation and SOA is formed predominantly by photochemical oxidation of volatile organic compounds under high temperatures and ultraviolet (UV) intensities, and NOX concentrations on Mt. Wudang during the campaign period.

Preparation of rare earth metal ions promoted MnOx@halloysite catalyst for highly efficient catalytic oxidation of toluene

Halloysite with nanotube structure is a potential functional support to prepare high-performance catalysts for the oxidation of volatile organic compounds (VOCs) at low temperatures. In this work, rare earth metal ions promoted MnOx@halloysite system were synthesized and demonstrated improved toluene oxidation. The obtained catalyst exhibits excellent catalytic performance, including toluene conversion efficiency (T90 = 232 °C), CO2 selectivity (100%), super long-term stability and water resistance under the condition of toluene concentration with 1000 ppm. It has been demonstrated that the La-promoted halloysite-supported MnOx catalyst increased the ratio of Mn3+ and the number of surface oxygen vacancies, facilitating the formation of active oxygen species and enhancing low-temperature catalytic activity. Moreover, in situ diffuse reflectance infrared Fourier transform spectroscopy confirmed the intermediates generated during toluene oxidation. Toluene oxidation occurred via the benzyl alcohol → benzoate → anhydride reaction pathway over the obtained catalysts. This work provides a considerable experimental basis for understanding the catalytic performance and reaction mechanism of rare earth metal ions promoting the manganese oxides supported by clay minerals for toluene oxidation and paves the way for the development of high-performance catalysts toward toluene oxidation.

A Comparative Study of Ground-Gridded and Satellite-Derived Formaldehyde during Ozone Episodes in the Chinese Greater Bay Area

Formaldehyde (HCHO) plays an important role in atmospheric photochemical reactions. Comparative studies between ground-based and satellite observations are necessary to assess and promote the potential use of column HCHO as a proxy for surface HCHO and volatile organic compound (VOC) oxidation. Previous studies have only validated temporal and vertical profile variations at one point, with limited studies comparing horizontal spatial variations due to sparse monitoring sites. The photochemistry-active Chinese Greater Bay Area (GBA) is a typical megacity cluster as well as a large hotspot of HCHO globally, which recorded a high incidence of ozone (O3) pollution. Here, we conducted the first comparative study of ground-gridded (HCHOgg) and satellite-derived (HCHOsd) HCHO during typical O3 episodes in the GBA. Our results revealed a good correlation between HCHOgg and HCHOsd, with a correlation coefficient higher than 0.5. Cloud coverage and ground pixel sizes were found to be the dominant factors affecting the quality of HCHOsd and contributing to the varying satellite pixel density. Daily averages of HCHOsd effectively improved the HCHOsd accuracy, except in areas with low satellite pixel density. Furthermore, a new quality control procedure was established to improve HCHOsd from Level 2 to Level 3, which demonstrated good application performance in O3 sensitivity analysis. Our findings indicate that the correlation between satellite observations and surface air quality can be optimized by spatiotemporal averaging of hourly HCHOsd, given the advent of geostationary satellites. Considering the representative range of sampling sites in this comparative study, we recommend establishing VOC monitoring stations within a 50 km radius in the GBA to further analyze and control photochemical pollution.

Recovery of Tellurium from Waste Anode Slime Containing High Copper and High Tellurium of Copper Refineries

Tellurium is used in cadmium tellurium-based solar cells. Mercury cadmium telluride is used as a sensing material for thermal imaging devices. High-purity tellurium is used in alloys for electronic applications. It is one of the important raw materials for solar energy applications. It is used as an alloying element in the production of low-carbon steel and copper alloys. Tellurium catalysts are used chiefly for the oxidation of organic compounds and as vulcanizing/accelerating agents in the processing of rubber compounds. Even though several researchers tried to recover tellurium from different raw materials, there is no attempt to develop a process flow sheet to recover tellurium from waste anode slime having a high tellurium concentration. In this study, optimum conditions were developed to recover Te and Cu from anode slime with the composition Cu: 31.8%, Te: 24.7%, and As: 0.96%. The unit operations involved are leaching, purification, and electro winning. The optimum conditions for producing Te at a recovery of 90% are found to be roasting of anode slime at 450 °C without the addition of soda ash followed by leaching in 1 M NaOH at 10% pulp density for 2 h. The purity of Te metal achieved was up to 99.99%, which could provide a sustainable energy future. The major impurities of the tellurium are observed to be in the order: Se &gt; Sb &gt; As &gt; Cu.

Deep oxidation of propane over PtIr/TiO2 bimetallic catalysts: Mechanistic investigation of promoting roles of Ir species

The catalytic deep oxidation of light alkanes is challenging due to the inert nature of the light alkanes. In this work, bimetallic PtIr/TiO2 catalysts with different Pt/Ir ratios were prepared and tested for the deep oxidation of propane. The reaction rate was much improved by the addition of Ir in the catalyst, and the highest turnover frequency (0.031 s−1 at 200 °C) was obtained on a catalyst with a Pt/Ir molar ratio of 3 (3Pt1Ir/TiO2) catalyst, which was 2-fold higher than that on the pristine Pt/TiO2 (0.014 s−1). The addition of Ir in the Pt/TiO2 resulted in stabilized metallic Pt0 under the reaction condition, as well as improved oxygen adsorption capacity, which promoted the adsorption/activation of propane and oxygen molecules. Moreover, detailed kinetics revealed that the reaction pathway switched from competitive adsorption of propane and oxygen on the Pt atoms to non-competitive adsorption of propane on Pt and oxygen on Ir, which thus provided new insights on the design of highly effective catalysts for deep oxidation of volatile organic compounds.

3D snowflake graphene modified α-MnO2 Catalyst: Enhancing the Low-Temperature catalytic activity for VOCs degradation

Manganese oxide is a promising catalyst for volatile organic compounds oxidation with merits of low cost, abundant valence states, diverse crystal forms and morphology, however, its catalytic activity at low temperature (<200 °C) is limited due to the poor dispersion and inferior electron transfer. To solve these problems, a novel 3D snowflake graphene is doped into α-MnO2 to fabricate rGO@α-MnO2 catalyst to enhance the catalytic activity at low temperature. Compared with α-MnO2, the rGO@α-MnO2 catalysts present larger specific surface area and pore volume, which facilitates the adequate contact reaction between active component and VOCs. The unique graphene electronic bridge promotes the electron transfer on rGO@α-MnO2, which results in higher concentration of surface defects and more surface adsorbed oxygen to the catalyst. The performance tests show that the catalyst doped with 4% 3D snowflake graphene has the best activity, which can achieve 90% toluene conversion at 155 °C, and even 100% toluene conversion with 80% CO2 selectivity at 200 °C. In particular, 4%rGO@α-MnO2 demonstrates excellent catalytic stability and moisture resistance, presenting similar catalytic performance after 5 cycles for both the dry and high relative humidity (RH = 85%) conditions. The excellent activity of 4%rGO@α-MnO2 can be attributed to the enhancement of toluene adsorption energy after graphene doping and the defect induced by the interface effect between graphene and (211) facet. In general, 3D snowflake graphene doping provides a convenient and cost-effective method to enhance the low-temperature activity of the α-MnO2 catalyst, presenting great application potential.