Enhancing Catalytic CO Oxidation over Co3O4 Nanowires by Substituting Co2+ with Cu2+

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• 作者：Minjie Zhou ; Lili Cai ; Michal Bajdich ; Max Garc铆a-Melchor ; Hong Li ; Jiajun He ; Jennifer Wilcox ; Weidong Wu ; Aleksandra Vojvodic ; Xiaolin Zheng
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：August 7, 2015
• 年：2015
• 卷：5
• 期：8
• 页码：4485-4491
• 全文大小：530K
• ISSN：2155-5435

文摘

Co₃O₄ is an attractive earth-abundant catalyst for CO oxidation, and its high catalytic activity has been attributed to Co³⁺ cations surrounded by Co²⁺ ions. Hence, the majority of efforts for enhancing the activity of Co₃O₄ have been focused on exposing more Co³⁺ cations on the surface. Herein, we enhance the catalytic activity of Co₃O₄ by replacing the Co²⁺ ions in the lattice with Cu²⁺. Polycrystalline Co₃O₄ nanowires for which Co²⁺ is substituted with Cu²⁺ are synthesized using a modified hydrothermal method. The Cu-substituted Co₃O₄_Cux polycrystalline nanowires exhibit much higher catalytic activity for CO oxidation than pure Co₃O₄ polycrystalline nanowires and catalytic activity similar to those single crystalline Co₃O₄ nanobelts with predominantly exposed most active {110} planes. Our computational simulations reveal that Cu²⁺ substitution for Co²⁺ is preferred over Co³⁺ both in the Co₃O₄ bulk and at the surface. The presence of Cu dopants changes the CO adsorption on the Co³⁺ surface sites only slightly, but the oxygen vacancy is more favorably formed in the bonding of Co³⁺鈥揙鈥揅u²⁺ than in Co³⁺鈥揙鈥揅o²⁺. This study provides a general approach for rational optimization of nanostructured metal oxide catalysts by substituting inactive cations near the active sites and thereby increasing the overall activity of the exposed surfaces.