Modified Deposition Precipitation Method Research Articles

Au Nanoparticles Supported on Hydrotalcite-Based MMgAlOx (M=Cu, Ni, and Co) Composite: Influence of Dopants on the Catalytic Activity for Semi-Hydrogenation of C2H2

Semi-hydrogenation of acetylene to ethylene over metal oxide-supported Au nanoparticles is an interesting topic. Here, a hydrotalcite-based MMgAlOx (M=Cu, Ni, and Co) composite oxide was exploited by introducing different Cu, Ni, and Co dopants with unique properties, and then used as support to obtain Au/MMgAlOx catalysts via a modified deposition–precipitation method. XRD, BET, ICP-OES, TEM, Raman, XPS, and TPD were employed to investigate their physic-chemical properties and catalytic performances for the semi-hydrogenation of acetylene to ethylene. Generally, the catalytic activity of the Cu-modified Au/CuMgAlOx catalyst was higher than that of the other modified catalysts. The TOR for Au/CuMgAlOx was 0.0598 h−1, which was 30 times higher than that of Au/MgAl2O4. The SEM and XRD results showed no significant difference in structure or morphology after introducing the dopants. These dopants had an unfavorable effect on the Au particle size, as confirmed by the TEM studies. Accordingly, the effects on catalytic performance of the M dopant of the obtained Au/MMgAlOx catalyst were improved. Results of Raman, NH3-TPD, and CO2-TPD confirmed that the Au/CuMgAlOx catalyst had more basic sites, which is beneficial for less coking on the catalyst surface after the reaction. XPS analysis showed that gold nanoparticles exhibited a partially oxidized state at the edges and surfaces of CuMgAlOx. Besides an increased proportion of basic sites on Au/CuMgAlOx catalysts, the charge transfer from nanogold to the Cu-doped matrix support probably played a positive role in the selective hydrogenation of acetylene. The stability and deactivation of Au/CuMgAlOx catalysts were also discussed and a possible reaction mechanism was proposed.

Catalytic ethanolysis of Hanglaiwan long flame coal to organic small-molecular compounds under mild conditions over SAPO-34-supported nickel nanoparticle catalyst

SAPO-34-supported nickel nanoparticle catalyst Ni/SAPO-34 was prepared by a modified deposition-precipitation method and nickel nanoparticles were uniformly dispersed onto the SAPO-34 crystal surface. Hanglaiwan long flame coal (HLFC) was subjected to the catalytic ethanolysis (CE) over Ni10%/SAPO-34 at 300 °C under 1 MPa of initial nitrogen pressure for 4 h to obtain more soluble organic small-molecule compounds (SOSMCs). Ni10%/SAPO-34 can effectively activate ethanol to release H+, +CH2CH3, and H-, and then precisely cleave >CH-O- and >Car-O- bridged bonds in HLFC. As a result, the total yield of soluble portion (SP) increases from 43.2 to 60.5 wt%. Arenes and oxygen-containing organic compounds are the main SOSMCs detected in SPCE from the CE and SPNCE from the ethanolysis, and the yields of arenes, hydroarenes, and phenols in SPCE are higher than those in SPNCE. In addition, compared to SPNCE, the condensation degree of aromatic rings in SPCE is higher. This investigation provides a promising alternative to the clean and value-added utilization of low-rank coals.

Solvent-mediated selective hydroconversion of benzyloxybenzene over a Ni/β40 catalyst

During biomass conversion, solvent types often play an important role in determining product selectivity and reaction mechanisms. Nevertheless, solvent function remains poorly understood. Herein, Ni/β40 was prepared by a slightly modified deposition-precipitation method and used for the catalytic hydroconversion (CHC) of benzyloxybenzene (BOB) to dicyclohexylmethane (DCHM) or toluene and phenol mediated by solvent types. The results show that solvent types, atmospheres, and Ni20/β40 synergistically control product regulation. In n-hexane (H), DCHM was first produced with the selectivity of 94.5% under the optimum conditions (180 °C, 2 MPa H2, and 4 h). In isopropanol (IP), toluene and phenol were unique products under the optimal conditions (180 °C, 0.5 MPa H2, and 4 h). The characterizations of Ni20/β40 and variation of product distributions from the CHC of BOB demonstrates that BOB conversion to DCHM in H via the >CH-O- bond cleavage induced by H+ addition, benzylium addition to ortho and para positions of phenol, H…H transfer to the resulting 2-benzylphenol and 4-benzylphenol, dehydroxylation of 2-benzylcyclohexanol and 4-benzylcyclohexanol produced, together with benzene rings hydrogenation. By contrast, conversion of BOB to toluene and phenol in IP only depends on the cleavage of >CH-O- bond induced by H+ addition. Furthermore, Ni20/β40 exhibites splendid reusability.

Synergistic effect of acidity and active phases for nickel nanoparticles supported HZSM-5 catalysts on lignin-related model compounds hydrodeoxygenation performance under mild conditions

The cleavage >C-O- bridge bonds and saturate aromatic rings of oxygen compounds from lignin is increasingly important in catalytic hydrodeoxygenation (HDO) for lignin upgrading and value-added utilization. Therefore, the catalytic behavior of a series of HZSM-5 (HZ-5) with different Si/Al ratios (n = 25, 50, 170, and 200) and acidity levels supported Ni nanoparticles (NPs) were prepared by modified deposition-precipitation method for catalytic HDO of lignin-related model compounds (LRMCs). The effects Ni loading, HZ-5 texture, and acid properties on catalytic activity, products distribution, and mechanism were systematically investigated. Furthermore, as-prepared catalysts were characterized by X-ray diffraction, N2 adsorption, scanning electron microscope, energy dispersive spectrometer, pyridine infrared, NH3-temperature programmed desorption, X-ray photoelectron spectrometer, and used for catalytic HDO of LRMCs with different >C-O- bridge bonds and aromatic rings, including oxydibenzene, oxybis(methylene)dibenzene, benzyloxybenzen, and oxydinaphthalene. These results indicate that Ni/HZ-5(n) can activate H2 to biatomic hydrogen (H‧‧‧H) and heterogeneously split H‧‧‧H to relatively mobile H+ and immobile H- with synergistic effect of Ni NPs, further leads to cleave the >Cal-O- and >Car-O- bridge bonds with different conversion through active hydrogen transfer. Additionally, effective modulate of catalytic HDO of LRMCs would be helpful to further maximize the target product yield on the basis of this mechanism at 160 °C for 5 MPa initial hydrogen pressure (mild conditions).

Colloidal and nanosized catalysts in organic synthesis: XXV. Reductive alkylation of nitroarenes with alcohols in the presence of a supported copper nanocatalyst

Using a modified deposition-precipitation method followed by sodium borohydride reduction of the precursor deposited on γ-Al2O3, copper-containing catalysts were obtained, which allow the continuous process of reductive alkylation of nitroarenes with alkanols at 200-220°C and atmospheric pressure of hydrogen with mono- N -alkylated products selectivity up to 100% and complete conversion of nitroarenes.

Selective catalytic ethanolysis of C-O bonds in lignite-related model compounds and Xilinguole lignite over difunctional Ni/HZSM-5 in H2-free system

Catalytic cracking of C-O bond is one of the important strategies for conversion of lignite into soluble organic matter. Ni/HZSM-5 was prepared by a modified deposition precipitation method with the Ni mass ratio ranging from 5% to 20% and evaluated by catalytic cracking benzyloxy benzene (BOB) and benzyl ether (BE). BOB was completely converted in ethanol over Ni15%/HZSM-5 under 1 MPa N2 at 240 °C for 2 h, while BE was completely converted at 180 °C. Ethanol could be activated to CH3CH2O· and H· over Ni nanoparticles supported on HZSM-5, which cleaved the C-O bond in BOB and BE. Additionally, the Ni15%/HZSM-5 was also successfully applied in catalytic ethanolysis of resides from ethanolysis Xilinguole lignite (XL) without H2 at 300 °C. The soluble portion yields from ethanolysis of XL and catalytic ethanolysis of residue are 47.8% and 15.1%, respectively. Soluble portion 1 (SP1) and catalytically soluble portion 1 (SP1C) were identified by gas chromatography/mass spectrometry. Different from SP1 mainly containing esters and phenols, SP1C is mainly composed of alkanes, arenes, and esters. In conclusion, catalytic ethanolysis of lignite in H2-free system is a potential way to cleave C-O bonds and prepare lignite-derived organic chemicals.

Enhancement of the catalytic activity of Suzuki coupling reactions by reduction of modified carriers and promotion of Pd/H2-PrxOysurface electron transfer

Pd/H2-PrxOynanotubes were prepared by electrostatic spinning, high-temperature calcination and modified deposition–precipitation method, and exhibited high catalytic performance for Suzuki coupling reaction under mild conditions.

Tailored synthesis of Ag/AgBr nanostructures coupled activated carbon with intimate interface interaction for enhanced photodegradation of tetracycline

Tailored synthesis of Ag/AgBr nanostructures (AABR) with intimate interface interaction for enhanced photocatalytic performance is a challenge for its extensive applications. Herein, tailored Ag/AgBr nanostructures promoted with char-microwave activated carbon (ACK) was synthesized through a modified deposition-precipitation method. The influence of four reaction parameters comprising of a mass of surfactant, temperature, ACK mass and ammonium hydroxide volume for the AABR-ACK composites were optimized using response surface methodology (RSM). Their simultaneous interactions on removal efficiency of tetracycline (TC) antibiotics under visible light were investigated under visible light. The high photocatalytic degradation of TC over AABR-ACK composites was governed by ammonium hydroxide volume and temperature. The SEM, XRD, FTIR, TEM, optical and electrochemical properties of the composites from these influential parameters, evidenced the formation of tailored AABR-ACK nanostructures with intimate interface interaction. The tailored near spheres nanostructures of AABR promoted with ACK boosted the visible light absorption, intimate interface contact, which promotes photo-induced charge pairs separation for the enhanced visible-light photocatalytic activity of AABR-ACK 7 composite TC (87 %). In addition, AABR-ACK 7 composite possessed significant recycle efficiency up to four consecutive cycles. The mineralization efficiency of AABR-ACK 7 on TC achieved 78.5 % and possible degradation pathways of TC were proposed. This work offers good insight into the tailored design of visible-light responsive heterojunction photocatalysts for sustainable environmental remediation.

CO oxidation and CO-PROX reactions over Au catalysts supported on different metal oxides: a comparative study

Comparative research about the total CO oxidation and CO-PROX reaction over Au-based materials supported on different oxides was carried out. CeO2, MnO2, TiO2 and SiO2 with nominal content of 1 wt.% of Au were prepared by a modified deposition–precipitation method. The samples were characterized by XRF, XRD, BET, H2-TPR and HR-TEM techniques. Catalytic results of the CO oxidation in the absence and presence of hydrogen showed that the supports and Au/SiO2 were inactive. For the Au/MnO2 and Au/TiO2 samples, CO conversion was lower in the presence of H2, while for Au/CeO2 the conversion of CO in the CO-PROX was higher compared to that in the total CO oxidation. These results show that the impact of H2 on CO oxidation over Au catalysts is dependent on the charactersitics of the materials that, in turn, are influenced by the nature of the support.

Spectroscopic Evidences for the Size Dependent Generation of Pd Species Responsible for the Low Temperature CO Oxidation Activity on Pd-SBA-15 Nanocatalyst

A comprehensive size dependent CO oxidation activity has been demonstrated for Pd-SBA-15 catalysts with Pd NPs of varying sizes such as 1-2, 4-6 and 7-10 nm. Pd-SBA-15 catalyst with smallest sized NPs (Pd-S-N) has been synthesized by modified deposition precipitation method recently developed in our lab. Pd-S-N catalyst (reduced at 400 °C) demonstrated CO oxidation activity with lower light off temperature (50 °C), clearly one of the best reported for a Pd-silica system. A detailed XPS and in-situ DRIFTS analyses further supported by XAS and DFT calculations reveal the presence of easily decomposable highvalent Pd-oxide on co-ordinatively unsaturated Pd sites (Pdcus). Weak binding of CO on Pdcus sites in small Pd NPs leaving sites for oxygen activation is attributed to the low temperature activity of Pd-S-N for CO oxidation.

Catalytic hydroconversion of soluble portion in the extraction from Hecaogou subbituminous coal to clean liquid fuel over a Y/ZSM-5 composite zeolite-supported nickel catalyst

A novel and highly active Y/ZSM-5 composite zeolite (YZCZ)-supported nickel bifunctional catalyst (Ni/YZCZ) was prepared using a modified deposition–precipitation method to uniformly disperse Ni nanoparticles (NNPs) onto YZCZ. Hecaogou subbituminous coal was exhaustively extracted with isometric carbon disulfide and acetone mixed solvent under ultrasonic irradiation to afford the extractable portion (EP) in the yield of 18.4%. EP was subjected to catalytic hydroconversion (CHC) in n-hexane over Ni/YZCZ under 5 MPa of initial hydrogen pressure at 160 °C for 24 h to afford catalytically hydroconverted EP (CHCEP). Both EP and CHCEP were analyzed with a gas chromatograph/mass spectrometer (GC/MS) and quadrupole exactive orbitrap mass spectrometer (QPEOTMS). As a result, cyclanes, alkenes, and hydroarenes were only detected in CHCEP and the relative content (RC) of alkanes in CHCEP is much higher than that in EP, while the RCs of both arenes, especially condensed arenes, and oxygen-containing organic compounds in EP are predominantly higher than those in CHCEP and nitrogen-containing organic compounds were only detected in EP. According to the CHC of coal-related model compound oxydibenzene (ODB), Ni/YZCZ can effectively activate H2 to biatomic active hydrogen (H⋯H), which is then split to an immobile H− attached on Ni/YZCZ and a relatively mobile H+. The H⋯H transfer leads to the hydrogenation of aromatic rings (ARs) in EP and ODB followed by heteroatom removal from the hydrogenated EP and ODB. In addition, due to the appropriate acidity, uniformly dispersed NNPs, and mesoporous structure of YZCZ, Ni/YZCZ proved to be still active for the CHC after 3 cycles and recoverable.

Systems and methods for cracking hydrocarbon streams such as crude oils utilizing catalysts which include zeolite mixtures

A novel and highly active Y/ZSM-5 composite zeolite (YZCZ)-supported nickel bifunctional catalyst (Ni/YZCZ) was prepared using a modified deposition–precipitation method to uniformly disperse Ni nanoparticles (NNPs) onto YZCZ. Hecaogou subbituminous coal was exhaustively extracted with isometric carbon disulfide and acetone mixed solvent under ultrasonic irradiation to afford the extractable portion (EP) in the yield of 18.4%. EP was subjected to catalytic hydroconversion (CHC) in n-hexane over Ni/YZCZ under 5 MPa of initial hydrogen pressure at 160 °C for 24 h to afford catalytically hydroconverted EP (CHCEP). Both EP and CHCEP were analyzed with a gas chromatograph/mass spectrometer (GC/MS) and quadrupole exactive orbitrap mass spectrometer (QPEOTMS). As a result, cyclanes, alkenes, and hydroarenes were only detected in CHCEP and the relative content (RC) of alkanes in CHCEP is much higher than that in EP, while the RCs of both arenes, especially condensed arenes, and oxygen-containing organic compounds in EP are predominantly higher than those in CHCEP and nitrogen-containing organic compounds were only detected in EP. According to the CHC of coal-related model compound oxydibenzene (ODB), Ni/YZCZ can effectively activate H2 to biatomic active hydrogen (H⋯H), which is then split to an immobile H− attached on Ni/YZCZ and a relatively mobile H+. The H⋯H transfer leads to the hydrogenation of aromatic rings (ARs) in EP and ODB followed by heteroatom removal from the hydrogenated EP and ODB. In addition, due to the appropriate acidity, uniformly dispersed NNPs, and mesoporous structure of YZCZ, Ni/YZCZ proved to be still active for the CHC after 3 cycles and recoverable.

Ag2CO3 anchored on BiOI/CoFe2O4 composites with p-n-p heterojunctions: Highly enhanced activity for photocatalytic oxidation of Hg0 under fluorescent light irradiation

Ag2CO3 anchored on BiOI/CoFe2O4 composites with p-n-p heterojunctions were synthesized by means of a facile modified deposition-precipitation method and were utilized to explore their activities for toxic elemental mercury (Hg0) removal under fluorescent light (FSL) irradiation. The obtained samples were characterized via N2 adsorption-desorption, XRD, VSM, SEM, TEM, XPS, EDS, UV–vis DRS, ESR, Transient photocurrent techniques. The Ag2CO3/BiOI/CoFe2O4 composites (AgCBi-CFO-4) with 4 wt. % of Ag2CO3 to BiOI/CoFe2O4 showed remarkably enhanced activity for Hg0 removal, which was ascribed to the combination effect of AgCBi-CFO-4 photocatalyst and FSL irradiation. Photocatalytic activity of AgCBi-CFO-4 increased by 40% and 30% in comparison with BiOI and BiOI/CoFe2O4 samples, respectively. The performance of AgCBi-CFO-4 was greatly influenced by some experimental factors such as FSL irradiation, strongly alkaline solution, CO32− ions and SO2. Due to the formation of intimate p-n-p heterojunction among p-type BiOI, n-type Ag2CO3 and p-type CoFe2O4, the ternary composites exhibited the enhanced visible-light absorbance performance and efficient separation of the charge carriers, thereby exerting a significantly positive effect on photocatalytic activity. The investigation clearly displayed that the superoxide radicals (O2−) generated by AgCBi-CFO-4 photocatalyst were the main contributor to an efficient Hg0 removal.

Enhancement of SCR performance of monolithic Mn–Ce/Al2O3/cordierite catalysts by using modified deposition precipitation method

AbstractMn–Ce catalysts have been widely studied for low‐temperature selective catalytic reduction (SCR) of NOx with NH3; however, most of them are powdery or granular. Monolithic catalysts which are more suitable for practical industrial applications still need detailed exploration. In this research, a series of monolithic Mn–Ce/Al2O3/cordierite catalysts were prepared by impregnation (IMP), deposition precipitation (DP), and modified deposition precipitation (MDP) methods. The catalyst MDP3 which depositing alumina and MnOx–CeOx simultaneously for three times by MDP method showed the best activity, and it performed much better at low temperature than the catalysts prepared by IMP and DP methods. MDP3 also showed the best resistance to H2O and SO2. It was thought that Mn–Al and Mn–Al–Ce clusters formed in the preparation of MDP3 and enhanced the interaction between the mixed oxides, as indicated by the characterization results. MDP3 prepared by MDP method showed the largest BET surface area, good redox capabilities, and the highest atomic ratios of Ce3+ and Ob. Hence, MDP was proved to be an effective method to enhance the interaction between the washcoat and the active phase, which resulted in preparing a good performance monolithic SCR catalyst.

Efficient removal of Hg0 from simulated flue gas by novel magnetic Ag2WO4/BiOI/CoFe2O4 photocatalysts

A series of novel ternary Ag2WO4/BiOI/CoFe2O4 hybrids synthesized by a facile modified deposition-precipitation method were utilized to explore their activities for toxic elemental mercury (Hg0) removal under fluorescent light (FSL) irradiation. The as-prepared materials were characterized by various methods and the experimental parameters such as Ag2WO4 content, fluorescent light irradiation, and inorganic anions were investigated in detail. The characterizations revealed that Ag2WO4 and CoFe2O4 were successfully dispersed on the surface of BiOI and heterogeneous hybrid was generated. The separation of electrons and holes (h+) could be efficiently promoted due to the combination of Ag2WO4, BiOI and CoFe2O4 with suitable match of band gaps under FSL irradiation. The experimental results manifested that Ag2WO4 content, fluorescent light irradiation, inorganic carbonate ions and SO2 gas all possessed conspicuous effects on Hg0 removal. Among the heterogeneous photocatalysts, Ag2WO4(0.1)BiOI/CoFe2O4 demonstrated the optimal activity for Hg0 removal and superior stable performance, which also could be easily recovered from the reaction solution by an extra magnet. Superoxide radicals (O2−) and holes (h+) were confirmed to be the main reactive substances for higher Hg0 removal.

High pressure CO2photoreduction using Au/TiO2: unravelling the effect of co-catalysts and of titania polymorphs

A series of Au/TiO2based catalysts with low gold loading (0.1–0.5 wt%) were prepared by a modified deposition–precipitation method and their activity was tested for CO2photoreduction in the liquid phase at high pressure (7 bar).

Surface Probing by Spectroscopy on Titania-Supported Gold Nanoparticles for a Photoreductive Application

The continuous increase in scientific reports concerning photocatalysis and in particular CO2 photoreduction in recent years reveals the high degree of interest around the topic. However, the adsorption and activation mechanisms of CO2 on TiO2, the most used photocatalyst, are poorly understood and investigated. Gold nanoparticles were prepared by a modified deposition-precipitation method using urea and a chemical reductant. Bare P25 was used as reference. Combined spectroscopic investigations of fresh and spent samples with photoactivity studies reported in this article provide new insights to the role of CO2 adsorption and carbonate formation on Au/TiO2 during CO2 photocatalytic reduction. The key intermediates’ and products’ adsorption (CO, methanol, ethanol) was studied, coupled with X-ray photoelectron microscopy (XPS) and UV-Visible spectroscopy. The adsorption of CO2 on fresh and spent catalysts changes radically considering the carbonate formation and the gold surface presence. Methanol and ethanol revealed new adsorbed species on Au with respect to bare titania. The characterisation of the spent catalysts revealed the good stability of these samples.

Photocatalytic performance and antibacterial activity of visible light driven silver iodide anchored on Graphitic-C3N4 binary composite

This study mainly focuses on the photocatalytic and antimicrobial properties of silver iodide supported graphitic carbon nitride (AgI@g-C3N4) composite. AgI@g-C3N4 composite was obtained through modified deposition-precipitation method and the photocatalytic performance efficiency of the synthesized AgI@g-C3N4 composite was evaluated for degradation of methyl orange (MO) dye solution under visible light irradiation. A central composite design (CCD) with response surface methodology (RSM) optimization tool was used to investigate the interactive effects of the three main independent rate determining operational process variables such as pH, AgI@g-C3N4 dosage and initial MO concentration on the colour removal efficiency. The maximum decolorization efficiency of 94.75% was obtained at pH 8.42, 2.34 g/L of AgI@g-C3N4 dosage and 17.7 mg/L of initial MO concentration. All the experimental values of decolorization efficiency were found to be in good agreement with predicted values obtained from CCD analysis (R2 = 0.9978). Furthermore, the antimicrobial activity for AgI@g-C3N4 composite in the elimination of Escherichia coli (E. coli) bacteria was studied using disc diffusion method.

A direct Z-scheme plasmonic AgCl@g-C3N4 heterojunction photocatalyst with superior visible light CO2 reduction in aqueous medium

A direct Z-scheme AgCl@g-C3N4 composite with different ratios of AgCl loaded on g-C3N4 was constructed through modified deposition-precipitation method and as prepared composite was well characterized. The photocatalytic performance efficiency of AgCl@g-C3N4 composite was evaluated for the reduction of CO2 in an aqueous medium under visible light irradiation. The gas chromatographic analysis confirms the formation of methane, acetic acid and formic acid as products. The experimental results indicated that the AgCl@g-C3N4 composite displays better photocatalytic activity than pure AgCl and g-C3N4. Effects of metal loading concentration (0.5–1.5 wt%), catalyst dosage (1–4 g L−1), reaction medium (triethanolamine (TEA)), water and sodium hydroxide (NaOH)), irradiation time and catalyst stability on the CO2 reduction reaction were investigated. The maximum yield and selectivity of methane, acetic acid and formic acid from CO2 in TEA medium over was about 53.03 μmol g−1, 6.01 μmol g−1, 2.51 μmol g−1 and 88.87%, 10.08% and 1.05% respectively for 8 h, 3 g L−1 of 1%AgCl@g-C3N4. However, no formation of acetic acid and formic acid were observed in the water mediated system. The enhanced photocatalytic activity towards CO2 reduction reaction was attributed to the combination effect of Z-scheme g-C3N4 and AgCl heterojunction, an absence of electron mediator, which efficiently inhibits the recombination rate and improved photocatalytic activity of g‐C3N4. This study will provide a new insight for fabrication of Z-scheme g-C3N4 based photocatalytic system for environmental remediation.

Complete Oxidation of Methane on Co3O4/CeO2 Nanocomposite: A Synergic Effect

Development of nonprecious metal-based catalysts highly active for complete oxidation of CH4 at a temperature ≤600 °C is significant for removing unburned CH4 at exhaust of engines of vehicles using natural gas or liquefied petroleum gas. CeO2 is active for complete oxidation of CH4. Co3O4 has been identified as a promising catalyst for this reaction. A Co3O4/CeO2 nanocomposite catalyst consisting of ceria nanorods supported on Co3O4 nanoparticles was prepared through a modified deposition precipitation method. The Co3O4/CeO2 nanocomposite exhibits high activity for complete oxidation of methane with an apparent activation energy of 43.9 kJ/mol, which is obviously lower than 95.1 kJ/mol of pure CeO2 and 89.7 kJ/mol of pure Co3O4, suggesting a synergetic effect between Co3O4 and CeO2. Surface of the Co3O4/CeO2 nanocomposite during complete oxidation of CH4 in the temperature range of 200–500 °C and potential stable intermediate of this catalysis were identified with ambient pressure X-ray photoelectron spectroscopy (AP-XPS).