49 results on '"Peng, Feng"'
Search Results
2. Enhancing the catalytic activity of carbon nanotubes by nitrogen doping in the selective liquid phase oxidation of benzyl alcohol.
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Luo, Jin, Peng, Feng, Wang, Hongjuan, and Yu, Hao
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BENZYL alcohol , *OXIDATION , *CARBON nanotubes , *NITROGEN , *LIQUID phase epitaxy , *CHEMICAL vapor deposition - Abstract
Abstract: Nitrogen-doped carbon nanotubes (N-CNTs) were prepared by chemical vapor deposition method and employed as carbon-based catalysts for selective oxidation of benzyl alcohol to benzaldehyde with molecular oxygen as the terminal oxidant under the mild reaction conditions. The results showed that the N-CNTs exhibited much higher activity than the undoped CNTs, and the improved catalytic activity was probably attributed to the introduction of electron-rich nitrogen atoms in the graphitic domains enhanced electron transfer. Moreover, N-CNTs displayed excellent stability without an obvious loss in activity and selectivity for benzyl alcohol oxidation after eight cycling reactions. The results presented herein pave the way for the development of novel carbon catalyst for the liquid-phase oxidation of benzyl alcohol. [Copyright &y& Elsevier]
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- 2013
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3. Aerobic Liquid-Phase Oxidation of Ethylbenzene to Acetophenone Catalyzed by Carbon Nanotubes.
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Luo, Jin, PENg, FENg, Yu, Hao, Wang, Hongjuan, and ZhENg, WENxu
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CARBON nanotubes , *METAL catalysts , *OXIDATION , *ETHYLBENZENE , *ACETOPHENONE , *OXYGEN , *PEROXIDES , *CATALYSIS - Abstract
It was reported for the first time that carbon nanotubes (CNTs) as metal-free catalyst exhibited an excellent activity in the selective oxidation of ethylbenzene (EB) to acetophenone (AcPO) in the liquid-phase with oxygen as the oxidant. The reasonable mechanism responsible for the liquid-phase oxidation of EB on CNTs was proposed. The results demonstrated that the CNTs played an important role in the decomposition of 1-phenylethyl hydroperoxide (PEHP) and contributed to the production of AcPO, owing to π-π interactions between the radical species and peroxides and the graphene sheets of the CNTs. Surface carboxylic groups of the CNTs were unfavorable to EB oxidation. Adsorption energies of the radical species and peroxides on pristine and modified CNTs with carboxylic groups were calculated by DFT. These theoretical calculations were well consistent with the experimental results, and also supported the presented mechanistic pathway of EB oxidation on CNTs. This study not only presents a facile and effective alternative to cobalt-based catalysts for the selective oxidation of EB to AcPO but also gives new insight into the effect of surface structures on carbon-catalyzed reactions, and further pushes forward the research on carbon catalysis. [ABSTRACT FROM AUTHOR]
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- 2013
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4. Selective liquid phase oxidation of benzyl alcohol catalyzed by carbon nanotubes
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Luo, Jin, Peng, Feng, Yu, Hao, and Wang, Hongjuan
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BENZYL alcohol , *CARBON nanotubes , *CATALYTIC oxidation , *CHEMICAL reactions , *TEMPERATURE effect , *SURFACE chemistry , *SCANNING electron microscopy - Abstract
Abstract: A HNO3-promoted benzyl alcohol catalytic oxidation system was developed in the presence of carbon nanotubes (CNTs), using molecular oxygen as the terminal oxidant under the mild reaction conditions. The effects of solvent, reaction temperature, amount of HNO3, catalyst loading and surface structure of CNTs on the catalytic performances have been investigated. The CNTs showed excellent catalytic activity exhibiting benzyl alcohol conversion of 96.2% and benzaldehyde selectivity of 88.3% under optimal conditions. In particular, it had remarkable reusability without a significant loss in its activity and selectivity after six consecutive usages. The carbon catalysts were characterized by N2 adsorption–desorption, FT-IR (Fourier transform infrared spectroscopy), Raman, SEM (scanning electron microscopy) and TEM (transmission electron microscopy) techniques. A possible reaction pathway has been proposed, it is clarified that HNO2 attacks benzyl alcohol to generate benzyl nitrite, which is decomposed to benzaldehyde over the HNO3-promoted CNTs-catalyzed system, and electron transfer in graphene sheets plays an important role in the decomposition of benzyl nitrite. These results not only provide an attractive metal-free alternative to noble-metal-catalyzed systems but also come up with a better understanding of the mechanism of CNTs as a metal-free catalyst for the liquid-phase oxidation of benzyl alcohol. [Copyright &y& Elsevier]
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- 2012
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5. Novel phosphorus-doped multiwalled nanotubes with high electrocatalytic activity for O2 reduction in alkaline medium
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Liu, Ziwu, Peng, Feng, Wang, Hongjuan, Yu, Hao, Tan, Jun, and Zhu, Lili
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ELECTROCATALYSIS , *PHOSPHORUS , *CARBON nanotubes , *CHEMICAL reduction , *MICROCHEMISTRY , *SOLUTION (Chemistry) , *PHOSPHINE - Abstract
Abstract: Phosphorus-doped multiwalled carbon nanotubes (MCNTs) were synthesized by the thermolysis and characterized by electron microscopy and microanalysis technique and evaluated with electrochemical methods. The results revealed that carbon nanotube length became shorter, the tube diameters increased and the yield of MCNTs reduced gradually with the increase of the concentration of triphenylphosphine in toluene solution, and the tube diameters increased with the increase of the synthesis temperature. Moreover, the phosphorus doping significantly improved the electrocatalytic activity of carbon nanotubes for the oxygen-reduction reaction in alkaline media, and the carbon nanotubes doped with small amounts of phosphorus exhibited higher electrocatalytic activity and stability than Pt/C catalyst. [Copyright &y& Elsevier]
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- 2011
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6. Development of stable PtRu catalyst coated with manganese dioxide for electrocatalytic oxidation of methanol
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Zhou, Chunmei, Peng, Feng, Wang, Hongjuan, Yu, Hao, Peng, Cheng, and Yang, Jian
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ELECTROCATALYSIS , *MANGANESE oxides , *METHANOL , *TRANSITION metal catalysts , *SURFACE coatings , *CARBON nanotubes , *OXIDATION-reduction reaction - Abstract
Abstract: Manganese dioxide was coated on multiwall carbon nanotubes-supported PtRu particles to prepare the MnO2/PtRu/CNT catalyst by a facile oxidation–reduction method. The prepared catalyst showed a high stability for electrocatalytic oxidation of methanol. After 2000 potential cycles, 55% activity still remained for MnO2/PtRu/CNT catalyst, while only 30% activity remained for PtRu/CNT, which indicated that the electrochemical stability of MnO2/PtRu/CNTs was improved significantly. MnO2 in MnO2/PtRu/CNTs prevented the dissolution of PtRu particles as well as the corrosion of the CNT supports, resulting in the improvement of the stability and activity. [ABSTRACT FROM AUTHOR]
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- 2010
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7. Hydrostatic-pressure induced phase transition of phonons in single-walled nanotubes
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Peng, Feng and Qingchao, Meng
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HYDROSTATIC pressure , *PHASE transitions , *ELECTRON-phonon interactions , *CARBON nanotubes , *MAGNETIC fields , *PARAMAGNETISM , *STATISTICAL physics - Abstract
Abstract: We study the effect of the hydrostatic pressure on the phonons in single-walled carbon nanotubes (SWNTs) in a magnetic field. We calculate the magnetic moments of the phonons using a functional integral technique, and find that the phonons in SWNTs undergo a pressure-induced phase transition from the paramagnetic phase to the diamagnetic phase under hydrostatic pressure 2GPa. We explain the mechanism of generating this phase transition. [Copyright &y& Elsevier]
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- 2009
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8. The role of RuO2 in the electrocatalytic oxidation of methanol for direct methanol fuel cell
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Peng, Feng, Zhou, Chunmei, Wang, Hongjuan, Yu, Hao, Liang, Jiahua, and Yang, Jian
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RUTHENIUM compounds , *OXIDATION , *FUEL cells , *CATALYSTS , *METHANOL , *CARBON nanotubes , *NANOPARTICLES - Abstract
Abstract: Pt/CNTs, PtRu/CNTs, Pt/RuO2/CNTs and RuO2/Pt/CNTs were prepared to understand the role of RuO2 in anodic catalyst of direct methanol fuel cell (DMFC). The results show that the presence of Ru, no matter in alloy or in oxide, can improve the CO electrooxidation ability. RuO2 in Pt–Ru binary catalyst, which situates between CNTs and Pt particles, can exert its CO electrooxidation ability best. Another role of RuO2 in Pt–Ru binary catalyst is to promote Pt nanoparticles to disperse uniformly on CNTs to obtain larger EAS, resulting in higher activity of methanol electrocatalytic oxidation. [Copyright &y& Elsevier]
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- 2009
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9. Carbon nitride polymer sensitized TiO2nanotube arrays with enhanced visible light photoelectrochemical and photocatalytic performanceElectronic supplementary information (ESI) available: Experimental methods, photocatalytic activity test, XPS analysis, additional figures, and additional references. See DOI: 10.1039/c1cc13862f.
- Author
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Zhou, Xiaosong, Peng, Feng, Wang, Hongjuan, Yu, Hao, and Fang, Yueping
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CARBON nanotubes , *TITANIUM dioxide , *PHOTOELECTROCHEMISTRY , *PHOTOCATALYSIS , *ELECTROFORMING , *X-ray photoelectron spectroscopy , *INORGANIC synthesis - Abstract
Novel carbon nitride polymer sensitized TiO2nanotube arrays with high photocatalytic activity and photoelectrochemical response under visible light irradiation are prepared by electrodeposition. [ABSTRACT FROM AUTHOR]
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- 2011
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10. Enhanced activity of Pt/CNTs anode catalyst for direct methanol fuel cells using Ni2P as co-catalyst.
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Li, Xiang, Luo, Lanping, Peng, Feng, Wang, Hongjuan, and Yu, Hao
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PLATINUM alloys , *CARBON nanotubes , *CARBON electrodes , *METHANOL as fuel , *FUEL cell electrodes , *NICKEL phosphide - Abstract
The direct methanol fuel cell is a promising energy conversion device because of the utilization of the state-of-the-art platinum (Pt) anode catalyst. In this work, novel Pt/Ni 2 P/CNTs catalysts were prepared by the H 2 reduction method. It was found that the activity and stability of Pt for methanol oxidation reaction (MOR) could be significantly enhanced while using nickel phosphide (Ni 2 P) nanoparticles as co-catalyst. X-ray photoelectron spectroscopy revealed that the existence of Ni 2 P affected the particle size and electronic distribution of Pt obviously. Pt/CNTs catalyst, Pt/Ni 2 P/CNTs catalysts with different Ni 2 P amount were synthesized, among which Pt/6%Ni 2 P/CNTs catalyst exhibited the best MOR activity of 1400 mAmg −1 Pt, which was almost 2.5 times of the commercial Pt/C-JM catalyst. Moreover, compared to other Pt-based catalysts, this novel Pt/Ni 2 P/CNTs catalyst also exhibited higher onset current density and better steady current density. The result of this work may provide positive guidance to the research on high efficiency and stability of Pt-based catalyst for direct methanol fuel cells. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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11. Pt nanoparticles interacting with graphitic nitrogen of N-doped carbon nanotubes: Effect of electronic properties on activity for aerobic oxidation of glycerol and electro-oxidation of CO.
- Author
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Ning, Xiaomei, Yu, Hao, Peng, Feng, and Wang, Hongjuan
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NANOPARTICLES manufacturing , *CARBON nanotubes , *GLYCERIN , *CHEMICAL reactions , *NANOSTRUCTURED materials - Abstract
Effects of specific nitrogen functionality and oxidative functionalization of the surfaces of nitrogen-doped carbon nanotubes (NCNTs) on the interaction between Pt nanoparticles (NPs) and NCNTs have been systematically investigated. Their catalytic consequences were studied using aerobic oxidation of glycerol and electro-oxidation of CO as probing reactions. By transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray diffraction (XRD), it was revealed that nitrogen dopant obviously enhanced the dispersion of Pt NPs. Strong interaction between Pt and NCNTs was observed. Graphitic nitrogen preferentially interacted with Pt NPs, evidenced by strong electron transfer from graphitic nitrogen as electron donor to metallic Pt NPs. The oxygen-containing groups introduced by H 2 O 2 oxidation of NCNTs may reduce the donor–acceptor interaction due to the electronegativity of oxygen. By changing the nitrogen amount of NCNTs and introducing oxygen groups, the electron enrichment of Pt NPs can be tuned. Superior catalytic activity was achieved over Pt/NCNTs in the oxidation of glycerol and electro-oxidation of CO, compared with conventional carbon nanotubes as support. Moreover, for both aerobic oxidation of glycerol and electro-oxidation of CO, it was observed that the intrinsic activity depended strongly on the electron enrichment of Pt NPs, ascribed to Pt4 f 7/2 (0) binding energy from XPS, suggesting a promising approach to improving catalytic activity by maximizing the interaction between Pt NPs and graphitic nitrogen sites. [ABSTRACT FROM AUTHOR]
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- 2015
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12. Confined Cobalt on Carbon Nanotubes in Solvent‐free Aerobic Oxidation of Ethylbenzene: Enhanced Interfacial Charge Transfer.
- Author
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Su, Yongzhao, Chen, Zhicheng, Huang, Jiangnan, Wang, Hongjuan, Yu, Hao, Zhang, Qiao, Cao, Yonghai, and Peng, Feng
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CATALYSTS , *CARBON nanotubes , *CHARGE transfer , *CHEMICAL processes , *ETHYLBENZENE , *OXIDATION , *DENSITY functional theory - Abstract
Aerobic oxidation of hydrocarbons yielding corresponding oxygenated products is one of the most important chemical processes. In current work, carbon nanotubes supported encapsulated cobalt nanoparticles with carbon layers (Co@C/CNTs) were synthesized and utilized as catalysts in the oxidation of ethylbenzene (EB) in the liquid phase, exhibiting high catalytic performance. The synergistic effect between Co@C and CNTs played the vital role on facilitating the decomposition of peroxides to enhance the overall activity. The inadequate covered Co@C on CNTs surface were considered as catalytic sites. Density functional theory revealed that the exist of Co nanoparticles could improve the interaction between the catalyst and intermediate free radicals, which were significant for EB oxidation. Last but not least, the electron transfer on carbon surface was enhanced by the incorporation of Co@C nanoparticles, which greatly improved the catalytic performance on EB oxidation. This study provides a new insight into the Co‐based catalysts in the aerobic oxidation of hydrocarbons. [ABSTRACT FROM AUTHOR]
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- 2022
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13. Inhibitory effect of Zn2+ on the chain‐initiation process of cumene oxidation.
- Author
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Chen, Zhicheng, Li, Yuhang, Cao, Yonghai, Zhang, Qiao, Yu, Hao, and Peng, Feng
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FREE radical reactions , *CUMENE , *ACTIVATION energy , *DENSITY functional theory , *CARBON nanotubes , *FREE radicals - Abstract
Carbon nanotubes (CNTs) have excellent catalytic activity in liquid phase reaction, especially in aerobic oxidation of cumene. In previous work, the conversion of cumene was 41.8% and the selectivity of cumene hydroperoxide was 71.5%, which was catalyzed by CNTs. But a small amount of impurity Zn2+ totally blocked up the aerobic oxidation of cumene that catalyzed by CNTs, which is an unexpected discovery. By analyzing the catalytic mechanism of CNTs, the inhibition effect of Zn2+ is locked on the abstraction of H atom from cumene. The inhibition of Zn2+ is confirmed in two effects by density functional theory calculations. First, due to the strongly coordination of active oxygen species (ROS) by Zn2+, the energy barrier of initial reaction increases to 1.90 eV, which is nearly 4 times higher than that of the only ROS promoted‐process. Second, the interaction of Zn2+ and RO· or ROO· to inhibits the chain propagation reaction of free radicals. This work precisely demonstrates that the inhibition effect of Zn2+ on initial reaction of cumene. The most significant thing is that the effect of metallic heteroatoms is not negligible in organic oxidation reaction. [ABSTRACT FROM AUTHOR]
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- 2021
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14. Pt/IrO2/CNT anode catalyst with high performance for direct methanol fuel cells
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Wang, Hongjuan, Zheng, Jiadao, Peng, Feng, and Yu, Hao
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PLATINUM nanoparticles , *CATALYSTS , *METHANOL as fuel , *FUEL cells , *CARBON nanotubes , *IRIDIUM compounds , *HYDROGEN peroxide - Abstract
Abstract: Carbon nanotube immobilized IrO2 (IrO2/CNT) was prepared by a simple oxidation method with hydrogen peroxide as an oxidant and used as an improved catalyst support to load active Pt to prepare Pt/IrO2/CNT anode catalyst for direct methanol fuel cell. Electrochemical measurement revealed that Pt/IrO2/CNT exhibits much higher activity for methanol oxidation and better CO tolerance than Pt/CNT. The anodic peak current of methanol oxidation on Pt/IrO2/CNT (873.1A gPt −1) is 2.6 times that of Pt/CNT catalyst (335.7A gPt −1). The enhanced performance of Pt/IrO2/CNT is attributed to the fact that IrO2 improves the dispersion of Pt nanoparticles, and lowers the charge transfer resistance in methanol electrooxidation. [Copyright &y& Elsevier]
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- 2013
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15. Pt supported on phosphorus-doped carbon nanotube as an anode catalyst for direct methanol fuel cells
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Liu, Ziwu, Shi, Qianqian, Peng, Feng, Wang, Hongjuan, Zhang, Rufan, and Yu, Hao
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PLATINUM catalysts , *PHOSPHORUS , *NANOSTRUCTURED materials synthesis , *NANOTUBES , *CARBON nanotubes , *CATALYST supports , *FUEL cells , *METHANOL as fuel , *ANODES , *ELECTROCATALYSIS - Abstract
Abstract: Phosphorus-doped multiwalled carbon nanotubes (P-MCNTs) were synthesized by thermolysis and employed as supports to prepare Pt/P-MCNTs catalyst for direct methanol fuel cells (DMFCs). Pt/P-MCNTs exhibited much higher electrocatalytic activity and longer-term stability for methanol oxidation than Pt/MCNTs in acidic medium, due to the higher dispersion and utilization rate and the improvement of intrinsic activity for methanol oxidation of Pt nanoparticles, indicating a highly potential application of Pt/P-MCNTs in DMFCs. [Copyright &y& Elsevier]
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- 2012
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16. Facile synthesis of MnO2/CNT nanocomposite and its electrochemical performance for supercapacitors
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Wang, Hongjuan, Peng, Cheng, Peng, Feng, Yu, Hao, and Yang, Jian
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ORGANIC synthesis , *NANOCOMPOSITE materials , *MANGANESE oxides , *CARBON nanotubes , *ELECTROCHEMISTRY , *SUPERCAPACITORS , *IMPEDANCE spectroscopy , *ELECTRIC discharges , *VOLTAMMETRY , *X-ray diffraction , *OXIDATION-reduction reaction , *POTASSIUM permanganate - Abstract
Abstract: A nanocomposite of manganese dioxide coated on the carbon nanotubes (MnO2/CNTs) was synthesized by a facile direct redox reaction between potassium permanganate and carbon nanotubes without any other oxidant or reductant addition. The morphology, microstructure and crystalline form of this MnO2/CNT nanocomposite were characterized by scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties are characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD). The results show that the facile prepared MnO2/CNTs nanocomposite shows specific capacitance of 162.2Fg−1 at the current density of 0.2Ag−1 and excellent charge/discharge property with 90% of its specific capacitance kept after 2000 cycles at the current density of 5Ag−1. [Copyright &y& Elsevier]
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- 2011
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17. Mechanism study on adsorption of acidified multiwalled carbon nanotubes to Pb(II)
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Wang, Hongjuan, Zhou, Ailin, Peng, Feng, Yu, Hao, and Yang, Jian
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LEAD , *HEAVY metals , *ADSORPTION (Chemistry) , *CARBON nanotubes - Abstract
Abstract: Adsorption of acidified multiwalled carbon nanotubes (MWCNTs) to heavy metal using Pb(II) as a model was investigated and characterized by many techniques. The main adsorption mechanism of acidified MWCNTs to Pb(II) is proposed on the basis of adequate analysis. The results show that the oxygenous functional groups can be formed on MWCNTs after MWCNTs were treated by concentrated nitric acid. The oxygenous functional groups play an important role in Pb(II) adsorption to form chemical complex adsorption, which accounts for 75.3% of all the Pb(II) adsorption capacity. The Pb(II) in the form of PbO, Pb(OH)2, and PbCO3 adsorbed on the surface of the acidified MWCNTs is only 3.4% of the total Pb(II) adsorption capacity. The Pb(II) species adsorbed on acidified MWCNTs mainly aggregate on the ends and at the defects sites on the acidified MWCNTs. [Copyright &y& Elsevier]
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- 2007
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18. Facile preparation of RuO2/CNT catalyst by a homogenous oxidation precipitation method and its catalytic performance
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Fu, Xiaobo, Yu, Hao, Peng, Feng, Wang, Hongjuan, and Qian, Yu
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NANOPARTICLES , *NANOTUBES , *FULLERENES , *OXIDATION - Abstract
Abstract: Ruthenium(IV) oxide (RuO2) nanoparticles supported by herringbone carbon nanotubes (CNTs) were synthesized by a homogenous-oxidation-precipitation (HOP) method with H2O2. The morphology and composition of the resulting composite were characterized by TEM, XPS, XRD, TG and TPR. CNTs exhibited the better ability to induce the formation of highly dispersed nanoparticles, compared with common used supports, such as γ-Al2O3 and activated carbon. Amorphous hydrous RuO2 nanoparticles uniformly dispersed on the surface of CNTs. The average size of RuO2 was significantly reduced to 1.35nm. This result leads to the high activity and excellent selectivity, which has been demonstrated in the aerobic oxidation of alcohols to aldehydes or ketones. The new preparation technique of CNT-supported oxide nanoparticles reported in this paper has great potential for various catalytic applications. [Copyright &y& Elsevier]
- Published
- 2007
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19. New Understanding of Selective Aerobic Oxidation of Ethylbenzene Catalyzed by Nitrogen‐doped Carbon Nanotubes.
- Author
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Su, Yongzhao, Li, Yuhang, Chen, Zhicheng, Huang, Jiangnan, Wang, Hongjuan, Yu, Hao, Cao, Yonghai, and Peng, Feng
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CARBON nanotubes , *ETHYLBENZENE , *ALKYL radicals , *CHEMICAL yield , *FREE radicals , *OXIDATION , *ADENOSYLMETHIONINE , *HYDROCRACKING - Abstract
Selective aerobic oxidation of hydrocarbons undergoes a free‐radical chain reaction to yield corresponding value‐added products is the significant process in the chemical industry. Nanocarbons with heteroatoms doping as free‐metal catalysts have been proved to be excellent alternatives in various fields of reactions. In this work, nitrogen doped carbon nanotubes (NCNTs) were applied for the aerobic oxidation of ethylbenzene (EB) in the liquid‐phase. The catalytic performance was unexpectedly suppressed, even lower than the control experiment, which is totally different from earlier publications. Mechanistic studies demonstrated that N doping would inhibit the abstraction of α‐H from EB molecule and end the radical propagation, thus suppressing the overall activity. Addition of TBHP would be helpful for the α‐H abstraction and forming alkyl radicals, which start the Franck‐Rabinowitch cage reaction and promote radical propagation in the presence of carbon catalysts. Herein, a higher catalytic efficiency with 46 % EB conversion and 72 % AcPO selectivity were obtained over NCNTs with O2 and TBHP as dual‐oxidants. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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20. Facile synthesis of porous hollow iron oxide nanoparticles supported on carbon nanotubes
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Wu, Yingsi, Yu, Hao, Peng, Feng, and Wang, Hongjuan
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POROUS materials , *IRON oxides , *NANOPARTICLES , *CARBON nanotubes , *TEMPERATURE effect , *CHEMICAL synthesis - Abstract
Abstract: Porous hollow iron oxide nanoparticles (PHNPs) supported on carbon nanotubes (CNTs) were facilely synthesized by etching Fe@FexOy/CNT with dilute nitric acid aqueous solution at ambient temperature without the assistance of any surfactants and ligands. The mean diameter of hollow iron oxide nanoparticles was about 17nm, with a wall thickness of about 4nm. The formation mechanism of PHNPs is discussed based on the characterization results from TEM, XRD and H2-TPR. The combination of nanoscale Kirkendall effect and selective acid etching is proposed to be responsible for the formation of CNT supported PHNPs, through a transformation from core/void/shell structures to hollow nanoparticles. [Copyright &y& Elsevier]
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- 2012
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21. Highly efficient and acid-corrosion resistant nitrogen doped magnetic carbon nanotubes for the hexavalent chromium removal with subsequent reutilization.
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Huang, Jiangnan, Cao, Yonghai, Qin, Binhao, Zhong, Guoyu, Zhang, Ju, Yu, Hao, Wang, Hongjuan, and Peng, Feng
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THERMAL stability , *ELECTROLYTIC reduction , *CARBON nanotubes , *CORROSION & anti-corrosives , *NANOPARTICLES - Abstract
Graphical abstract NMCNTs was synthesized though a facile method, displaying a high removal efficiency and stability in the acid solution and then re-utilized as the catalyst in the electrochemical reduction of CO 2 with a good faradic efficiency (over 90% total efficiency and about 50% for the CO production at 0.6 V). Highlights • Nitrogen doped magnetic carbon nanotubes (NMCNTs) were synthesized. • NMCNTs displayed a high efficiency in the Cr(VI) removal. • NMCNTs showed a high stability in the acid solution. • Recycled NMCNTs was an excellent catalyst for electrochemical reduction of CO 2. Abstract Highly efficient and acid-corrosion resistant for carbon adsorbent in hexavalent chromium removal is a significant property in the practical application. In this study, nitrogen doped carbon nanotubes with encapsulated Fe and Fe 3 C were synthesized through a facile pyrolysis procedure using melamine and ferric chloride as precursors, displaying an excellent efficiency and stability for hexavalent chromium removal. High maximum removal capacities with 35.26 and 970.87 mg g−1 were obtained in neutral and acid solutions, respectively, due to the adsorption process, reduction reaction between Fe0 or Fe2+ nanoparticles and Cr(VI) ions. The unexpected high stability in acid solution (pH at 1) after five recycles was observed for the first time, ascribed to N doping and the tubular structure with encapsulated ferric carbide, which could be resistant to the acid corrosion. After a simple treatment, the used adsorbent could be re-utilized as catalysts for the electrochemical reduction of CO 2 with high faradic efficiency (over 90% total efficiency and about 50% for CO production at −0.6 V), demonstrating a promising potential for reutilizing the used carbon adsorbents. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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22. Catalytic wet air oxidation of phenol over carbon nanotubes: Synergistic effect of carboxyl groups and edge carbons.
- Author
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Cao, Yonghai, Li, Bo, Zhong, Guoyu, Li, Yuhang, Wang, Hongjuan, Yu, Hao, and Peng, Feng
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CARBON nanotubes , *CARBOXYL group , *CATALYTIC activity , *OXIDATION , *OXYGEN - Abstract
It has been widely documented that the oxygen-containing functionalities, especially carboxyl groups, on carbon surfaces play crucial roles in the catalytic wet air oxidation (CWAO) reactions. Herein, the CWAO of phenol with molecular O 2 as terminal oxidant using cylindrical and herringbone carbon nanotubes (CNTs) underwent different treatments as catalysts were conducted in batch mode. It was uncovered that the catalytic function of carboxyl groups strongly depended on the structure of CNTs. Parallel CNTs ( p -CNTs) with cylindrical graphitic walls displayed the highest catalytic activity after nitric acid oxidation, due to the carboxylated carbon debris (CDs) coating on surfaces. For herringbone CNTs ( h- CNTs), carboxyl groups are mostly linked to its sidewalls, where abundant edge carbons were exposed, providing an enhanced CWAO activity. The positively synergistic effect of carboxyl groups and adjacent edge carbons was responsible for the activation of O 2 , leading to the improved CWAO activity. This study provides a new insight into the structural effect of carbon materials on the CWAO of phenol. [ABSTRACT FROM AUTHOR]
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- 2018
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23. A kinetics study on cumene oxidation catalyzed by carbon nanotubes: Effect of N-doping.
- Author
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Mu, Chunlin, Cao, Yonghai, Wang, Hongjuan, Yu, Hao, and Peng, Feng
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OXIDATION of hydrocarbons , *CARBON nanotubes , *NITROGEN , *DOPING agents (Chemistry) , *CUMENE , *CHEMICAL kinetics - Abstract
Selective oxidation of hydrocarbons is of great industrial importance. Nanocarbons are recently found highly active for the aerobic oxidation of cumene. In this work, a detailed kinetics study of cumene oxidation catalyzed by carbon nanotubes (CNTs) and nitrogen doped CNTs (NCNTs) was carried out to disclose the crucial influence of N doping in the cumene oxidation. A kinetics model based on the radical reaction mechanism of cumene oxidation was developed, which contained 7 major elementary steps. The kinetics parameters of cumene oxidation upon CNTs and N-doped CNTs (NCNTs) were obtained by the non-linear aggression of the experimental concentration–time data. Mechanistic insights into the effect of N-doping on carbon catalysis were achieved by comparing the kinetics parameters of CNTs and NCNTs. The decomposition of ROOH was found to be the rate-determine step of the cumene oxidation. The nitrogen doping could reduce the activation energy of CHP decomposition, thereby could remarkably accelerate the overall reaction rate of cumene oxidation. The nitrogen doping could also strengthen the interactions between O 2 , RO , RO 2 and the carbon catalysts. Hence, the selectivities to acetophenone and 2-benzyl-2-propanol were improved. This study provides the insight towards the catalytic role of N dopants in the aerobic oxidation of cumene. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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24. Trace iron impurities deactivate palladium supported on nitrogen-doped carbon nanotubes for nitrobenzene hydrogenation.
- Author
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Dong, Baoqiang, Li, Yuhang, Ning, Xiaomei, Wang, Hongjuan, Yu, Hao, and Peng, Feng
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PRECIOUS metals , *NANOSTRUCTURED materials , *CARBON nanotubes , *HYDROGENATION , *NITROBENZENE , *CATALYSTS - Abstract
Nitrogen-doped carbons can effectively stabilize noble metal particles to achieve high catalytic performances. However, the metallic impurities in carbon nanomaterials, e.g. the residual growth catalysts of carbon nanotubes (CNTs), have some unforeseen effects on the catalysis involving nanocarbons. Herein, we demonstrate that the residual growth catalysts of N-doped CNTs (NCNTs) may significantly deactivate Pd catalysts for the hydrogenation of nitrobenzene. Through high-resolution transmission electron microscopy and CO-stripping, it was determined that the N dopants improved the dispersion of Pd nanoparticles. However, the iron, at ppm level, in residual catalysts encapsulated inside NCNTs can transfer onto the surface of Pd to block active sites so that the activity of Pd/NCNTs was much lower than that of Pd/CNTs. The similar effect was observed for most of the common metallic impurities in carbon materials, including Co, Ni, Mn, Cr, Cu, Zn, Mo, Al and Mg. To exploit the N-doped carbons, we deposited N-doped carbon layers on purified CNTs through pyridine pyrolysis and then supported Pd nanoparticles. By this means, the activity of Pd for nitrobenzene hydrogenation was improved by 3.85 folds compared to conventional CNTs, emphasizing the importance of controlling impurities in N-doped carbon materials for high performance catalysts. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
25. Quantification of electron transfer on carbon nanotubes: Effect of edge defects on electro-oxidation of glycerol catalyzed by platinum.
- Author
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Ming, Jingyan, Fu, Hongquan, Yang, Guangxing, Wang, Hongjuan, Huang, Jiangnan, Peng, Feng, Cao, Yonghai, and Yu, Hao
- Subjects
- *
CHARGE exchange , *CARBON nanotubes , *X-ray photoelectron spectroscopy , *BEER-Lambert law , *ELECTROLYTIC oxidation , *PLATINUM - Abstract
[Display omitted] • A facile method was established to evaluate the ET reaction rate. • Quantification of ET on d -CNTs is achieved. • Surface defects on d -CNTs are beneficial for the ET reaction rate. • ET ability of d -CNTs on MSI is revealed in the electrooxidation of glycerol. It is still an ongoing challenge to quantitatively determine the number of transferred electrons from carbon supports to metallic catalysts, which is highly related to their catalytic performance. In this work, a facile method combining electrochemical and spectroscopic technologies was proposed to evaluate the electron transfer (ET) reaction rate on carbon nanotubes (CNTs) with defects. Using 7,7,8,8-tetracyanoquinonedimethane (TCNQ) as an electron-accepting molecule, the transferred electrons from CNTs were quantitatively determined through the Beer-Lambert law and coulometric analysis. It was revealed that the edge defects on CNTs are beneficial for the ET reaction rate, due to the lower local work function. Hence, the defective CNTs supported Pt nanoparticles (Pt/ d -CNTs) performed the higher activity in the electrooxidation of glycerol, suggesting the influence of the ET ability of d -CNTs on the electronic metal-support interaction. This scenario is supported by density function theory calculation and X-ray photoelectron spectroscopy. Our results pave a new way to the facile evaluation of electronic metal–carbon interaction. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
26. Electron transfer dependent catalysis of Pt on N-doped carbon nanotubes: Effects of synthesis method on metal-support interaction.
- Author
-
Ning, Xiaomei, Li, Yuhang, Dong, Baoqiang, Wang, Hongjuan, Yu, Hao, Peng, Feng, and Yang, Yanhui
- Subjects
- *
ELECTRON-transfer catalysis , *PLATINUM catalysts , *CARBON nanotubes , *CATALYST supports , *NITROGEN , *DOPING agents (Chemistry) - Abstract
The influence of catalyst synthesis strategy, including ethylene glycol (EG) reduction, sodium borohydride reduction and impregnation-H 2 -reduction, on the metal-support-interaction of Pt on nitrogen-doped carbon nanotubes (Pt/NCNTs) was systematically investigated and summarized. The catalytic performances were explored in the electro-oxidation reactions of glycerol, formic acid and CO, and the hydrolysis of ammonia borane (AB). Through X-ray photoelectron spectroscopy (XPS), density functional theory calculations and CO stripping technique, it was revealed that the synthesis methods drastically affected the electronic property of Pt nanoparticles (NPs). Pt NPs preferentially interacted with graphitic nitrogen in EG reduction method due to the electron donating property of graphitic nitrogen, while preferentially interacted with pyridinic nitrogen and defects in the impregnation-H 2 -reduction method due to the vacancies containing N P favoring the charged metal ion adsorption. The catalytic activity strongly depended on the electronic property of Pt NPs, which can be ascribed by the binding energy of Pt4f 7/2 (0) from XPS. The higher catalytic activity was obtained over electron-enriched Pt NPs for the electro-oxidation reactions. On the other hand, electron-deficient Pt NPs had better intrinsic activity in AB hydrolysis. The results herein suggested that appropriate synthesis method should be rationally applied to maximize the activities of Pt for targeting reactions benefited from electron-enriched or electron-deficient metal NPs. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
27. Solvent effect on the allylic oxidation of cyclohexene catalyzed by nitrogen doped carbon nanotubes.
- Author
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Cao, Yonghai, Yu, Hao, Wang, Hongjuan, and Peng, Feng
- Subjects
- *
CARBON nanotubes , *CYCLOHEXENE , *DOPING agents (Chemistry) , *OXIDATION , *ORGANIC solvents , *CATALYTIC activity - Abstract
A wide spectrum of, up to 22, organic solvents, including aprotic/protic aliphatics/aromatics, was studied to achieve a comprehensive understanding to the solvent effect on the cyclohexene oxidation. It was found that the catalytic activity was significantly influenced by the viscosity, polarity and basicity of solvents in this reaction. Among these solvents, the polar aprotic aliphatic solvents displayed higher catalytic reactivities than other types of solvents. A volcano curve was found describing the dependence of activity on solvent basicity because of the suitable stability of intermediates. Among the solvents investigated, acetonitrile afforded the highest activity and selectivity of 2-cyclohexen-1-one, because of a good compromise between strong polarity and moderate basicity. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
28. Ni foams decorated with carbon nanotubes as catalytic stirrers for aerobic oxidation of cumene.
- Author
-
Mu, Chunlin, Huang, Kuntao, Cheng, Tianyuan, Wang, Hongjuan, Yu, Hao, and Peng, Feng
- Subjects
- *
CARBON nanotubes , *CATALYTIC oxidation , *NICKEL , *CUMENE , *HYDROCARBONS , *FILTERS & filtration - Abstract
Carbon nanotubes (CNTs) have received intensive scientific interests as a metal-free catalyst for the oxidation reactions of hydrocarbons in the liquid phase. However, its application in the liquid reaction is limited by the costly catalyst filtration process. Herein, a structured CNT catalyst was fabricated via growing CNTs on Ni foams with a porous Al 2 O 3 coating layer. The resultant structured CNTs were used both as catalysts and as stirrer in a rotating foam stirrer reactor. The catalytic performance was evaluated in the production of cumene hydroperoxide by the aerobic oxidation of cumene. Under optimized experimental conditions, the cumene conversion reached 25.1%, 14% higher than that of commercial CNTs in a slurry reactor. The excellent adhesion strength of CNTs on the foam and catalytic stability in 5 runs of recycling were demonstrated, opening a new way to employing CNTs as a metal-free catalyst in the liquid phase reactions. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
29. One-pot melamine derived nitrogen doped magnetic carbon nanoadsorbents with enhanced chromium removal.
- Author
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Cao, Yonghai, Huang, Jiangnan, Li, Yuhang, Qiu, Song, Liu, Jiurong, Khasanov, Airat, Khan, Mojammel A., Young, David P., Peng, Feng, Cao, Dapeng, Peng, Xiangfang, Hong, Kunlun, and Guo, Zhanhu
- Subjects
- *
NANOTUBES , *NANOSTRUCTURED materials synthesis , *CARBON nanotubes , *MELAMINE , *NITROGEN , *CHROMIUM removal (Sewage purification) , *CHEMICAL derivatives , *SOLUTION (Chemistry) , *DOPING agents (Chemistry) - Abstract
Novel nitrogen doped magnetic carbons (NMC), in-situ synthesized through facile pyrolysis-carbonization processes using Fe(NO 3 ) 3 and melamine as precursors, were demonstrated as excellent nanoadsorbents to remove Cr(VI) effectively. The achieved removal capacity in both neutral and acidic solution was 29.4 and 2001.4 mg g −1 respectively, much higher than the reported adsorbents so far. The unprecedented high adsorption performance can be attributed to the incorporation of the nitrogen dopant, which increased the negative charge density on the surface of adsorbent and thereby enhanced the interaction between the adsorbents and Cr(VI) ions. The density functional theory (DFT) calculation demonstrated that the nitrogen dopants can decrease the adsorption energy between the Cr(VI) ions and NMC (−3.456 kJ mol −1 ), lower than the undoped sample (−3.344 kJ mol −1 ), which boosted the adsorption behavior. Chemical rather than physical adsorption was followed for these magnetic nanoadsorbents as revealed from the pseudo-second-order kinetic study. Furthermore, the NMC showed high stability with recycling tests for the Cr(VI) removal. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
30. MnO2 nanoparticles supported on CNTs for cumene oxidation: Synergistic effect and kinetic modelling.
- Author
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Deng, Yuchan, Chen, Zhicheng, Huang, Jiangnan, Yang, Guangxing, Zhang, Qiao, Liu, Zili, Cao, Yonghai, and Peng, Feng
- Subjects
- *
CUMENE , *OXIDATION , *NANOPARTICLES , *METALLIC oxides , *CATALYTIC oxidation , *CARBON nanotubes - Abstract
[Display omitted] • MnO 2 /CNTs catalysts for cumene oxidation is prepared. • Synergistic effect between MnO 2 and CNTs facilitating CHP decomposition is observed. • Kinetic modelling of 7 elementary steps is established. • MnO 2 /CNTs mainly accelerates the initial and terminal steps. • Enhanced k 80 and reduced E a are obtained over MnO 2 /CNTs. Synergistic effects between the carbon materials and metal oxides usually are considered as the significant factor in the selective oxidation of hydrocarbons. In current study, MnO 2 /CNTs catalysts were prepared under mild condition and applied in the cumene oxidation. As high as 73.44% cumene conversion with 59.06% selectivity of 2-phenyl-2-propanol(PP) was obtained over 21.23-MnO 2 /CNTs, which is much higher than those of CNTs-catalysis and MnO 2 -catalysis systems. The decomposition of cumene hydroperoxide (CHP), a key step for cumene oxidation, was proved to be facilitated by the interaction between MnO 2 nanoparticles and CNTs, which also confirmed from the DFT calculations. These results demonstrated that the synergistic effect between MnO 2 nanoparticles and CNTs would greatly enhance the activity and tune the distribution of products selectivity. The kinetic modeling study in this work further revealed that the interactions between MnO 2 nanoparticles and CNTs would accelerate all the elementary steps, especially, the homolytic cleavage of CHP. The reaction rate constant (k 80 = 9 h−1) for 21.23-MnO 2 /CNTs is 450-folds of CNTs (k 80 = 0.02 h−1). Moreover, the concentration distributions of acetophenone (AP) and PP were well illustrated from the kinetic study. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
31. Promoting role of bismuth and antimony on Pt catalysts for the selective oxidation of glycerol to dihydroxyacetone.
- Author
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Ning, Xiaomei, Li, Yuhang, Yu, Hao, Peng, Feng, Wang, Hongjuan, and Yang, Yanhui
- Subjects
- *
BISMUTH , *ANTIMONY , *PLATINUM catalysts , *GLYCERIN , *DIHYDROXYACETONE , *CARBON nanotubes - Abstract
The group 15 metals, bismuth and antimony, play important roles in promoting noble-metal-catalyzed oxidation reactions toward high value-added chemicals. Herein, we report that the selective oxidation of glycerol to 1,3-dihydroxyacetone (DHA) catalyzed by Pt supported on N-doped carbon nanotubes (Pt/NCNT) can be significantly promoted in the presence of Bi or Sb in reaction solution. This catalyst system showed not only comparable even better performance to the Pt/NCNT with pre-loaded Bi, but also the greatly simplified catalyst preparation. It was found that the Bi-promoted Pt/NCNT underwent dynamic surface reconstruction through leaching and adsorption of Bi adatoms, due to the formation of glyceric acid. By characterizing the adsorption of Bi on Pt catalyst with high-resolution transmission electron microscopy, CO-stripping, horizontal attenuated total reflection infrared spectroscopy and X-ray photoelectron spectroscopy, it has been ascertained that Bi preferentially deposits on the step sites of Pt, and then blocks the terrace sites to promote the Pt catalyst mainly through a geometrical effect, which facilitates the activation and transformation of the secondary hydroxyl group of glycerol through the chelation between substrate and Pt–Bi sites. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
32. Chemically drilling carbon nanotubes for electrocatalytic oxygen reduction reaction.
- Author
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Zhong, Guoyu, Wang, Hongjuan, Yu, Hao, Wang, Haihui, and Peng, Feng
- Subjects
- *
CARBON nanotubes , *DRILLING & boring , *ELECTROCATALYSTS , *OXIDATION-reduction reaction , *OXYGEN reduction , *COBALT oxides - Abstract
Carbon nanotubes (CNTs) were chemically drilled by supporting cobalt oxide in a controllable way. A series of drilled CNTs with different Co loadings were prepared, characterized and used as the oxygen reduction reaction electrocatalysts. The results show that for the drilled CNTs with the cobalt loading less than 8 wt%, the defects or edge carbons as dominating factor increase the electrocatalytic oxygen reduction reaction (ORR) activity; for the drilled CNTs with the cobalt loading more than 12 wt%, the electron transfer resistance becoming the main determinant decreases the ORR activity. The properly drilled CNTs show dramatically enhanced ORR performance than the original CNTs. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
33. Enhanced activity and durability of platinum anode catalyst by the modification of cobalt phosphide for direct methanol fuel cells.
- Author
-
Li, Xiang, Wang, Hongjuan, Yu, Hao, Liu, Ziwu, Wang, Haihui, and Peng, Feng
- Subjects
- *
CATALYTIC activity , *ANODES , *DIRECT methanol fuel cells , *COBALT phosphide , *PLATINUM catalysts , *CARBON nanotubes - Abstract
In this study, carbon nanotubes (CNTs) supported Pt-cobalt phosphide (CoP) electrocatalyst (Pt/CoP/CNTs) is designed and prepared for methanol oxidation (MOR) for the first time. The modification of CoP decreases the Pt particle size significantly and increases the electrochemical surface areas due to the interaction between Pt and CoP, which is evidenced by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Among all these catalysts, Pt/4%CoP/CNTs catalyst exhibits the best MOR activity of 1600 mA mg −1 Pt , which is six times that of Pt/CNTs. Moreover, this catalyst also exhibits the higher onset current density and steady current density than the other Pt-based catalysts. The work provides a promising method to develop the highly active and stable Pt-based catalyst for direct methanol fuel cells. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
34. Si-doped carbon nanotubes as efficient metal-free electrocatalysts for O2 reduction in alkaline medium.
- Author
-
Fu, Xin, Wang, Quan-De, Liu, Ziwu, and Peng, Feng
- Subjects
- *
SILICON compounds , *DOPING agents (Chemistry) , *CARBON nanotubes , *ELECTROCATALYSTS , *OXYGEN reduction , *PLATINUM catalysts - Abstract
To decrease the high cost of cathodic electrocatalysts caused by platinum-based catalysts in fuel cells, a series of silicon-doped carbon nanotubes with different Si contents were synthesized by the thermolysis of trimethylphenylsilane and xylene and used as low-cost metal-free catalysts for the oxygen reduction reaction (ORR). Electrochemical tests showed that the electrocatalytic activities of the synthesized Si-doped carbon nanotubes towards the ORR all were higher than that of pure carbon nanotubes and their ORR activities did not enhance proportionally with the increase of silicon doping content in alkaline medium, indicating a promising potential for designing low-cost and efficient metal-free electrocatalysts in future alkaline fuel cell devices. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
35. Nitrogen doped carbon nanotubes with encapsulated ferric carbide as excellent electrocatalyst for oxygen reduction reaction in acid and alkaline media.
- Author
-
Zhong, Guoyu, Wang, Hongjuan, Yu, Hao, and Peng, Feng
- Subjects
- *
NITROGEN , *CARBON nanotubes , *MELAMINE , *FERRIC chloride , *CARBIDES - Abstract
Nitrogen doped carbon nanotubes (NCNTs) with encapsulated Fe 3 C nanoparticles (Fe 3 C@NCNTs) are synthesized by a simple direct pyrolysis of melamine and ferric chloride. The characterization results reveal that Fe 3 C is mainly encapsulated in the interior of NCNTs and N species is mainly distributed on the outside surface of NCNTs. Iron and iron carbide catalyze the growth of NCNTs and are wrapped by carbon to form Fe 3 C@NCNTs. The as-prepared Fe 3 C@NCNTs catalyst exhibits superior oxygen reduction reaction (ORR) activity, excellent methanol tolerance and long-term stability in both acid and alkaline media. It is proven that the doped N is the main active site for ORR and the inner Fe 3 C with outside carbon form the synergetic active site to enhance ORR activity. The ORR mechanism of direct four electron transfer pathway is proved in acid and alkaline media. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
36. Low Pt content catalyst supported on nitrogen and phosphorus-codoped carbon nanotubes for electrocatalytic O2 reaction in acidic medium.
- Author
-
Liu, Ziwu, Qu, Junfeng, Fu, Xin, Wang, Quande, Zhong, Guoyu, and Peng, Feng
- Subjects
- *
PLATINUM catalysts , *PHOSPHORUS , *DOPING agents (Chemistry) , *CARBON nanotubes , *ELECTROCATALYSTS , *CHEMICAL reactions , *FUEL cell electrodes - Abstract
To design low-cost and efficient cathode electrocatalysts and push forward the commercialization of fuel cells, low platinum content catalyst supported on nitrogen and phosphorus-codoped carbon nanotubes (Pt/NP-CNTs) for the oxygen reduction reaction (ORR) were prepared. Electrochemical tests demonstrated that the Pt/NP-CNTs catalyst exhibited much high ORR activity and remarkable stability in acidic media due to the strong interaction between NP-CNT support and Pt catalyst evidenced by the calculation of the density functional theory, showing a good potential application for a future low-cost proton exchange membrane fuel cell device. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
37. An opposite change rule in carbon nanotubes supported platinum catalyst for methanol oxidation and oxygen reduction reactions.
- Author
-
Li, Xiang, Wang, Hongjuan, Yu, Hao, Liu, Ziwu, and Peng, Feng
- Subjects
- *
CARBON nanotubes , *PLATINUM catalysts , *CATALYST supports , *MASS transfer , *OXIDATION of methanol , *OXIDATION-reduction reaction , *ELECTROCATALYSIS - Abstract
Abstract: The electrocatalytic performances of carbon nanotubes supported platinum (Pt/CNTs) with different Pt loadings for oxygen reduction reaction (ORR) and methanol oxidation (MOR) are studied contrastively. Pt/CNTs showed an opposite change rule along different Pt loadings for ORR and MOR, which is discussed based on the charge transportation and mass transfer. The results show that at low Pt loading, proton conduction is the key factor, which determines the MOR activity; at high Pt loading, mass transfer is crucial, which decides the ORR activity of Pt/CNT catalysts. The viewpoint proposed in this paper can guide the design and preparation of Pt based catalysts for the commercialization of direct methanol fuel cells. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
38. Enhancing the catalytic activity of carbon nanotubes by filled iron nanowires for selective oxidation of ethylbenzene.
- Author
-
Luo, Jin, Yu, Hao, Wang, Hongjuan, and Peng, Feng
- Subjects
- *
CATALYTIC activity , *CARBON nanotubes , *IRON compounds , *ETHYLBENZENE , *NANOWIRES , *CHARGE exchange - Abstract
Abstract: Iron nanowire filled carbon nanotubes (Fe@CNTs) were synthesized by chemical vapor deposition method and employed as heterogeneous catalysts for selective oxidation of ethylbenzene to acetophenone with molecular oxygen. The results showed that filled iron nanowires efficiently enhanced the catalytic activity of CNTs, arising from improving electron transfer. Moreover, Fe@CNTs could be easily separated from the reaction mixtures by external magnet and displayed excellent stability with no significant loss of catalytic activity after six cycling reactions. The result presented herein paves the way for the development of novel carbon catalysts for the liquid phase oxidation of ethylbenzene. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
39. Aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by carbon nanotubes without any promoter.
- Author
-
Luo, Jin, Yu, Hao, Wang, Hongjuan, Wang, Haihui, and Peng, Feng
- Subjects
- *
CATALYST supports , *AEROBIC bacteria , *BENZYL alcohol , *BENZALDEHYDE , *CARBON nanotubes , *GRAPHENE , *OXIDATION-reduction reaction - Abstract
Highlights: [•] Carbon nanotubes (CNTs) can catalyzes benzyl alcohol (BzOH) to benzaldehyde (BzH). [•] A reasonable mechanism for the liquid-phase oxidation of BzOH on CNTs is proposed. [•] Electron transfer in graphene skeletons plays an important role. [•] Nitrogen doping efficiently enhances the catalytic activity of CNTs for BzOH to BzH. [•] Carbon catalyst displays outstanding recyclability. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
40. The effect of edge carbon of carbon nanotubes on the electrocatalytic performance of oxygen reduction reaction.
- Author
-
Zhong, Guoyu, Wang, Hongjuan, Yu, Hao, and Peng, Feng
- Subjects
- *
CARBON nanotubes , *ELECTROCATALYSIS , *OXIDATION-reduction reaction , *CHEMICAL potential , *DENSITY functional theory , *QUANTITATIVE chemical analysis - Abstract
Abstract: The oxygen reduction reaction (ORR) has been investigated on fish-bone carbon nanotubes (F-CNTs) and parallel carbon nanotubes (P-CNTs). The results showed that the F-CNTs exhibited much higher activity than P-CNTs, which originated from the higher fraction of edge carbon atoms. The dependence of ORR peak potential on the fraction of edge carbon atoms was determined quantitatively for the first time. The density functional theory calculations clearly unveiled the mechanism of edge carbon atoms facilitating the ORR performance. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
41. Tuning the Selectivity in the Aerobic Oxidation of Cumene Catalyzed by Nitrogen-Doped Carbon Nanotubes.
- Author
-
Liao, Shixia, Chi, Yumei, Yu, Hao, Wang, Hongjuan, and Peng, Feng
- Subjects
- *
CARBON nanotubes , *NITROGEN , *CATALYSTS , *OXIDATION , *CUMENE , *AROMATIC compounds - Abstract
In this study it is demonstrated that carbon nanotubes (CNTs) with doped nitrogen atoms in graphitic domains (NCNTs) can act as a new class of metal-free catalysts exhibiting excellent activity in the aerobic oxidation of cumene. We proved that NCNTs can promote the decomposition of hydroperoxide cumene with exceptionally high activity, resulting in strongly increased cumene conversion and extraordinarily high selectivity to acetophenone and 2-benzyl-2-propanol. The incorporation of nitrogen altered the surface electron structure of the CNTs and tuned the reactivity and selectivity. DFT calculations revealed that the remarkable improvement of catalytic performance of NCNTs is caused by the strong interaction between hydroperoxide cumene and the NCNTs. NCNTs also exhibited desirable recyclability after four cycling tests. This study not only provides a novel method for the cumene oxidation to high-value-added products at moderate reaction temperatures and oxygen atmospheric pressure, but also gives new insights into the effect of surface nitrogen doping on carbon-catalyzed liquid-phase oxidation of aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
42. Design, synthesis and the electrochemical performance of MnO2/C@CNT as supercapacitor material.
- Author
-
Wang, Hongjuan, Peng, Cheng, Zheng, Jiadao, Peng, Feng, and Yu, Hao
- Subjects
- *
MANGANESE oxides , *CARBON nanotubes , *NANOTUBES , *NANOSTRUCTURED materials synthesis , *ELECTROCHEMISTRY , *PERFORMANCE evaluation , *SUPERCAPACITORS , *COMPOSITE materials - Abstract
Highlights: [•] Carbon-coated carbon nanotubes are designed and synthesized to prepare MnO2/C@CNT. [•] The sacrificial carbon in C@CNT endows it suitable for the higher loading of MnO2. [•] MnO2/C@CNT composite with high MnO2 loading presents superior specific capacitance. [•] MnO2/C@CNT composite shows excellent cyclic stability. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
43. Mechanistic Insight into the Catalytic Oxidation of Cyclohexane over Carbon Nanotubes: Kinetic and In Situ Spectroscopic Evidence.
- Author
-
Yang, Xixian, Wang, Hongjuan, Li, Jing, Zheng, Wenxu, Xiang, Rong, Tang, Zikang, Yu, Hao, and Peng, Feng
- Subjects
- *
CARBON nanotubes , *NANOSTRUCTURED materials , *CHEMICAL reactions , *PEROXIDES , *KETONES , *CYCLOHEXANE - Abstract
As some of the most interesting metal-free catalysts, carbon nanotubes (CNTs) and other carbon-based nanomaterials show great promise for some important chemical reactions, such as the selective oxidation of cyclohexane (C6H12). Due to the lack of fundamental understanding of carbon catalysis in liquid-phase reactions, we have sought to unravel the role of CNTs in the catalytic oxidation of C6H12 through a combination of kinetic analysis, in situ spectroscopy, and density functional theory. The catalytic effect of CNTs originates from a weak interaction between radicals and their graphene skeletons, which confines the radicals around their surfaces. This, in turn, enhances the electron-transfer catalysis of peroxides to yield the corresponding alcohol and ketone. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
44. Nitrogen-, phosphorous- and boron-doped carbon nanotubes as catalysts for the aerobic oxidation of cyclohexane
- Author
-
Cao, Yonghai, Yu, Hao, Tan, Jun, Peng, Feng, Wang, Hongjuan, Li, Jing, Zheng, Wenxu, and Wong, Ning-Bew
- Subjects
- *
CARBON nanotubes , *NANOTUBES , *NANOSTRUCTURED materials synthesis , *NITROGEN , *DOPING agents (Chemistry) , *OXIDATION of cyclohexane , *CHEMICAL vapor deposition , *CHEMICAL reactions , *SURFACE area - Abstract
Abstract: Nitrogen-, phosphorous- and boron-doped carbon nanotubes (N-CNTs, P-CNTs and B-CNTs) were prepared by a chemical vapor deposition method using xylene as carbon source and aniline-NH3, triphenyl phosphine and triethyl borate as nitrogen, phosphorous and boron precursors, respectively. By tailoring the composition of reactants and reaction atmosphere, N-CNTs with nitrogen contents from 0% to 4.36% and P-CNTs with phosphorous contents from 0.55% to 5.14% were synthesized. N- and P-CNTs are active for the oxidation of cyclohexane in the liquid phase with molecular oxygen as oxidant. The highest mass-normalized activity, 761mmolg−1 h−1, was achieved over N-CNTs synthesized from aniline in an NH3 atmosphere, while the highest surface-area-normalized activity, 28mmolm−2 h−1, was observed over P-CNTs. B-doping does not improve the activity of CNTs. The effect of the number of nitrogen functionalities and defects was investigated to reveal the structure–activity relationship of the doped CNTs. By using the work function as an indicator of the electron donation of carbon, an exponential dependence of specific activity on work function was discovered for N- and P-CNTs, suggesting that the electron transfer on the surfaces of CNTs plays a central role in the CNT-catalyzed oxidation of cyclohexane. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
- View/download PDF
45. A Novel Carbothermal Synthesis Route for Carbon Nanotube Supported FeP Nanoparticles.
- Author
-
Yao, Zhiwei, Hai, Hang, Lai, Zhuangchai, Zhang, Xiaohong, Peng, Feng, and Yan, Changfeng
- Subjects
- *
CARBON nanotubes , *NANOTUBES , *NANOSTRUCTURED materials synthesis , *IRON compounds , *PHOSPHIDES , *NANOPARTICLE synthesis , *TEMPERATURE-programmed reduction , *REDUCING agents , *STOICHIOMETRY - Abstract
A novel carbothermal route for the synthesis of supported FeP nanoparticles was developed. In contrast to the conventional H-temperature-programmed reduction (TPR) method, this route uses carbon nanotubes (CNTs) as support and reducing agent. Additionally, FeP nanoparticles can be obtained using FeO and ammonium hydrogen phosphate as precursors by this route. The Fe:P precursor ratio has a significant effect on the phase composition of iron phosphide product, and near pure FeP can be obtained on CNTs with a phosphorus content a little beyond the stoichiometric ratio. It was observed that the FeP product had a smaller particle size than that obtained from the commonly used iron phosphate precursor. It was found that the size of FeP nanoparticles obtained via this carbothermal route appeared to depend on the size of Fe-containing precursor, which indicated that it was possible to synthesize FeP nanoparticles with a wide size range by systematically adjusting the particle size of FeO precursor on CNTs. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
46. High efficient conversion of cellulose to polyols with Ru/CNTs as catalyst
- Author
-
Wang, Hongjuan, Zhu, Lili, Peng, Song, Peng, Feng, Yu, Hao, and Yang, Jian
- Subjects
- *
ENERGY conversion , *CELLULOSE , *POLYOLS , *HYDROLYSIS , *HYDROGENATION , *RUTHENIUM , *CARBON nanotubes , *CATALYSTS , *RENEWABLE energy sources , *CHEMICAL reactions - Abstract
Abstract: Cellulose, as an energy substance with tremendous resources, is reproducible and is a breakthrough point for the research of renewable energy. It is urgent and necessary to realize the conversion of cellulose with high efficiency under the mild condition. Ru immobilized on CNTs (Ru/CNTs) catalyst was prepared and used to the reaction of cellulose to polyols. The influence factors, such as the Ru loading amount, reaction time, reaction temperature and hydrogen pressure were investigated. The role that Ru/CNTs played in the reaction and the procedure of cellulose to polyols were discussed. The experimental results show that cellulose can be converted into C2-C6 polyols with the yield up to 38% catalyzed by Ru/CNTs with 4 wt% Ru loading and at the temperature of 225 °C and the hydrogen pressure of 6 MPa within the reaction time of 30 min. The conversion of cellulose to polyols catalyzed by Ru/CNTs is in fact a two-step reaction with cellulose first to reducing sugar and then to polyols. In the process of cellulose to polyols, CNTs promotes the cellulose to convert into reducing sugar by hydrolysis and Ru catalyzes the conversion of the reducing sugar to polyols by hydrogenation. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
47. Deactivation and regeneration of RuO2·xH2O/CNT catalyst for aerobic oxidation of benzyl alcohol
- Author
-
Yu, Hao, Zhang, Yan, Fu, Xiaobo, Peng, Feng, Wang, Hongjuan, and Yang, Jian
- Subjects
- *
CATALYST poisoning , *CARBON nanotubes , *METAL catalysts , *OXIDATION , *RUTHENIUM compounds , *ALCOHOL , *TOLUENE , *FOURIER transform infrared spectroscopy - Abstract
Abstract: The reusability of hydrous ruthenium(IV) dioxide nanoparticles supported by carbon nanotubes (RuO2·xH2O/CNT) was investigated in aerobic oxidation of benzyl alcohol in toluene. The used catalyst was characterized by multiple techniques, including FT-IR, HRTEM, XPS and TGA. RuO2·xH2O/CNT deactivated mainly due to the accumulation of excess water as coproduct in weakly polar organic solvent. It was found that the used catalyst can be easily regenerated within a hot water bath, which effectively eliminates the excess water from the catalyst. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
48. CoMn2O4 supported on carbon nanotubes for effective low-temperature HCHO removal.
- Author
-
Zeng, Yongjian, Jiang, Qiang, Yang, Xixian, Liu, Defei, Cao, Yonghai, Wang, Hongjuan, Peng, Feng, and Yu, Hao
- Subjects
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CARBON nanotubes , *TRANSITION metal oxides , *CATALYTIC oxidation , *CATALYTIC activity , *METALLIC oxides , *SOLID solutions - Abstract
Formaldehyde (HCHO) is harmful to environment and human health, even at extremely low concentrations. Catalytic oxidation on metal oxides is an effective method for HCHO removal. Transition metal oxides have attracted much attention due to its advantages of low cost and good redox properties, but it requires the high reaction temperature and energy consumption to reach the good catalytic activity for HCHO removal. In this work, Mn-Co mixed oxides supported on carbon nanotubes (CNTs) were prepared for enhancing the low-temperature catalytic activity of HCHO removal. The results of XRD, TEM and XPS characterization confirmed the formation of CoMn 2 O 4 solid solution on CNTs. The highest relative content of Co3+, Mn3+ and active lattice oxygen were achieved at the optimal composition of 3Mn-1Co. The HCHO oxidation test showed that CoMn 2 O 4 /CNTs (3Mn-1Co) had the best catalytic activity at 160 °C, obtaining 95% HCHO (100 ppm) removal efficiency and 95% CO 2 selectivity at GHSV = 30,000 mL g cat -1 h-1. Compared with the similar catalysts previously reported in literatures, CoMn 2 O 4 /CNTs was of the lower T 90 value for HCHO oxidation. Image 1 • Mn/Co molar ratio of 3:1 was prone to form CoMn 2 O 4 solid solution on CNTs. • The formation of active lattice oxygen on CoMn 2 O 4 was beneficial to HCHO oxidation. • The combination of CNTs and Co-Mn oxides solid solution is promising to prepare catalysts for HCHO removal. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
49. Surface oxidized nano-cobalt wrapped by nitrogen-doped carbon nanotubes for efficient purification of organic wastewater.
- Author
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Yang, Guanrong, Li, Yuhang, Yang, Siyuan, Liao, Jihai, Cai, Xin, Gao, Qiongzhi, Fang, Yueping, Peng, Feng, and Zhang, Shengsen
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CARBON nanotubes , *SEWAGE , *ADSORPTION capacity , *RHODAMINE B , *HYDROGEN bonding , *NATURAL dyes & dyeing , *ANTIBIOTIC residues - Abstract
• Surface oxidized nano-cobalt wrapped by N-doped carbon nanotubes (Co@CoO/NC) is prepared. • Co@CoO/NC has a strong adsorption capacity for both some dyes and antibiotics. • The magnetic nano-Co@CoO/NC exhibits excellent stability and reusability. • The main adsorption force is hydrogen bonding and π-π EDA interaction. Dyes and antibiotics in the wastewater discharged by factories have caused immeasurable harm to natural water bodies. It is of great significance to remove the organic pollutants from wastewater. Herein, a novel magnetic nanomaterial of surface oxidized nano-cobalt wrapped by nitrogen-doped carbon nanotubes (Co@CoO/NC) was prepared through a one-step annealing method and used as efficient adsorbing material for tetracycline (TC) and rhodamine B (RhB). The maximum adsorption capacity of the optimal Co@CoO/NC for RhB and TC was 679.56 mg·g−1 and 385.60 mg·g−1, respectively. As a kind of magnetic recyclable and reused adsorbent, Co@CoO/NC could respectively maintain 75% and 84% of absorption capacities for TC and RhB after four repetitions. The adsorption processes were well matched with the pseudo-second-order kinetic model and the Langmuir model. The Zeta potential, XPS, FT-IR and theoretical calculation results showed that the hydrogen bonding and π-π electron donor-acceptor interaction dominated the adsorption of TC and RhB. Due to the presence of CoO on the surface of Co nanoparticles, cation exchange and surface complexation also played an essential role in the adsorption of TC. This work provides a new opportunity for the rational design and construction of efficient, stable and easily recyclable adsorbents in environmental remediation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
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