In situ studies of surface of NiFe₂O₄ catalyst during complete oxidation of methane

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• 作者：Shiran Zhang^a ; ^b ; ¹ ; Junjun Shan^a ; ^b ; ¹ ; Longhui Nie^c ; Luan Nguyen^a ; ^b ; Zili Wu^d ; Franklin (Feng) Tao^a ; ^b ; ^{franklin.feng.tao@ku.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：complete oxidation ; transition metal oxide ; methane ; In situ study
• 刊名：Surface Science
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：648
• 期：Complete
• 页码：156-162
• 全文大小：830 K

文摘

NiFe₂O₄ with an inverse spinel structure exhibits high activity for a complete oxidation of methane at 400 °C–425 °C and a higher temperature. The surface of the catalyst and its adsorbates were well characterized with ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and in situ infrared spectroscopy (IR). In situ studies of the surface of NiFe₂O₄ using AP-XPS suggest the formation of methoxy-like and formate-like intermediates at a temperature lower than 200 °C, supported by the observed vibrational signatures in in situ IR studies. Evolutions of C1s photoemission features and the nominal atomic ratios of C/(Ni + Fe) of the catalyst surface suggest that the formate-like intermediate is transformed to product molecules CO₂ and H₂O in the temperature range of 250–300 °C. In situ studies suggest the formation of a spectator, − O_latticeCH₂O_lattice −. It strongly bonds to surface through CO bonds and cannot be activated even at 400 °C.