Defect-Induced Efficient Partial Oxidation of Methane over Nonstoichiometric Ni/CeO2 Nanocrystals

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• 作者：Provas Pal ; Rajib Kumar Singha ; Arka Saha ; Rajaram Bal ; Asit Baran Panda
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：June 18, 2015
• 年：2015
• 卷：119
• 期：24
• 页码：13610-13618
• 全文大小：504K
• ISSN：1932-7455

文摘

We report the development of a highly crystalline Ni/CeO₂ catalyst with varying amounts of Ni content using ammonium carbonate complex solution of cerium(IV) at a low temperature. The catalyst was characterized by XRD, XPS, BET-surface area, TEM, and H₂-TPR analysis. We have observed that the maximum incorporation of Ni in CeO₂ crystal system as the substitution point defect took place up to impregnation of 2.5% Ni, and an almost maximum reduction of unit cell parameter was observed. Further increase in the amount of Ni, the additional Ni may create interstitial point defects with surface defects. The synthesized catalysts showed defect-dependent catalytic activity for low temperature (鈭?50 掳C) methane activation to form synthesis gas. The 7.5 wt % Ni/CeO₂ catalyst showed 98% conversion of methane with 73 and 71% selectivity of CO and H₂, respectively, at 800 掳C without any deactivation until 50 h on time on stream. We also believe that with enhancement of Ni loading, the interstitial point defects and the surface defects due to the formation of the Ce鈥揙鈥揘i鈥揙鈥?layer, with under-coordinated oxygen atom, on the surface may be the possible reason for the high activity of the catalyst with Ni loading between 5 and 7.5 wt %. With further increase of Ni loading, the Ni nanoparticles were formed with the expense of the Ce鈥揙鈥揘i鈥揙鈥?layer and in-turn decreased the catalytic activity.