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Complete Oxidation of Methane on NiO Nanoclusters Supported on CeO2 Nanorods through Synergistic Effect Xiaoyan Zhang, Stephen D. House, Yu Tang, Luan Nguyen, Yuting Li, Adedamola A. Opalade, Judith Yang, Zaicheng Sun, and Franklin (Feng) Tao ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b00234 • Publication Date (Web): 05 Mar 2018 Downloaded from http://pubs.acs.org on March 8, 2018
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ACS Sustainable Chemistry & Engineering
Complete Oxidation of Methane on NiO Nanoclusters Supported on CeO2 Nanorods through Synergistic effect Xiaoyan Zhang,abc Stephen House,e Yu Tang,c Luan Nguyen,c Yuting Li,c Adedamola A. Opalade,c Judith C. Yang,e Zaicheng Sun,d* Franklin (Feng) Taoc* a
State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Changchun, 130033 Jilin, P. R. China b University of Chinese Academy of Sciences, Beijing 100000, P. R. China c Department of Chemical and Petroleum Engineering and Department of Chemistry, University of Kansas, Lawrence, KS, 66045, USA d School of Chemistry, Beijing University of Technology, Beijing, 100080, P. R. China e Department of Chemical and Petroleum Engineering, University of Pittsburgh, PA, 15261, USA
Abstract Catalytic complete oxidation of CH4 at relative low temperatures is significant for removal of unburned CH4 in exhaust of combustion engines fueled with natural gas or liquefied petroleum gas. Here the nanocomposite catalyst (NiO/CeO2) consisting of CeO2 nanorods and supported NiO nanoclusters was prepared by a two-step wet-chemistry method. This nanocomposite catalyst exhibits high catalytic activity for complete oxidation of CH4 in the temperature range of 350-600 oC. CH3-like intermediate bound to Ni cations was observed at a relatively low temperature by ambient pressure Xray photoelectron spectroscopy under a catalytic condition. Parallel kinetic studies of NiO/SiO2, CeO2 and NiO/CeO2 catalysts show that the apparent barrier for complete oxidation of CH4 on NiO/CeO2 (69.4±4KJ/mol) is much lower than 95.1±5 kJ/mol of pure CeO2 and 98.4±5 kJ/mol of NiO/SiO2, supported by the turn-over frequency of NiO/CeO2 significantly higher than NiO and CeO2. These differences show a synergic effect between CeO2 nanorods and its supported NiO nanoclusters. This synergic effect results from the interface of NiO and CeO2 observed in TEM. The lattice oxygen atoms at the interface exhibits high activity based on the lower reduction temperature uncovered in the studies of temperature-programmed reduction of H2. *: To whom all correspondence should be addressed to. Email:
[email protected] (FT) and
[email protected] (SZ) KEYWORDS: NiO, CeO2, methane, complete oxidation, AP-XPS
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Introduction CH4 is one of the main gas components in exhaust of vehicles using natural gas or liquefied petroleum gas as fuels of their combustion engines. Different from gasoline-fueled engines, the engines of vehicles using natural gas or liquefied petroleum gas perform combustions of light hydrocarbons at relatively low temperatures, typically
