Reduction of Nano-Cu2O: Crystallite Size Dependent and the Effect of Nano-Ceria Support

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• 作者：Junhua Song ; Philip P. Rodenbough ; Wenqian Xu ; Sanjaya D. Senanayake ; Siu-Wai Chan
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：August 6, 2015
• 年：2015
• 卷：119
• 期：31
• 页码：17667-17672
• 全文大小：402K
• ISSN：1932-7455

文摘

Copper(I) oxide (Cu₂O) is an effective catalyst in the CO oxidation reaction. While high surface to volume ratio in nanoparticles will increase their catalytic efficiency, it posts a stability problem. Here we study the stability of nano-cuprite against reduction as a function of its crystallite size and upon interaction with a nano-ceria support. A systematic analysis of isothermal reduction of a series size of monodispersed Cu₂O nanocrystals (卤7%) with time-resolved X-ray diffraction (TR-XRD) provides the time-resolved phase fraction of Cu₂O and the time when reduction product of Cu (fcc) first appears. The initial phase fraction of nano-Cu₂O is less than one with the balance attributed to an amorphous CuO shell. Since no peaks of crystalline CuO (monoclinic) were observed, a core鈥搒hell structure with an amorphous CuO shell is proposed. From the analysis, Cu²⁺ content in corresponding to shell increases from 0 to 33% as Cu₂O decreases to 8 nm from the bulk. Based on the reduction profiles, a time size reduction (TSR) diagram is constructed for the observed Cu₂O phase behavior during reduction. The incorporation onto a nano-CeO₂ support (7 nm) significantly stabilizes our nano-Cu₂O in a reducing atmosphere. The oxygen supply propensity in terms of oxygen nonstoichiometry of CeO_2鈥?i>y is shown to be lower when a larger crystallite size CeO₂ (20 nm) support is used. The larger oxygen capacity in smaller nano-CeO₂ support is analyzed and explained by the 鈥淢adelung model鈥?with size-dependent bulk modulus of nano-ceria.