Significant Roles of Carbon Pore and Surface Structure in AuPd/C Catalyst for Achieving High Chemoselectivity in Direct Hydrogen Peroxide Synthesis

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• 作者：Sunwoo Yook ; Han Chang Kwon ; Young-Gu Kim ; Woosung Choi ; Minkee Choi
• 刊名：ACS Sustainable Chemistry & Engineering
• 出版年：2017
• 出版时间：January 3, 2017
• 年：2017
• 卷：5
• 期：1
• 页码：1208-1216
• 全文大小：621K
• ISSN：2168-0485

文摘

Direct synthesis of hydrogen peroxide (H₂O₂) from hydrogen (H₂) and oxygen (O₂) has been widely investigated as an attractive way for small-scale/on-site H₂O₂ production. Among various catalysts, carbon-supported AuPd catalysts have been reported to exhibit the most promising H₂O₂ productivity and selectivity. In this work, to better understand the catalytic role of the surface properties and porous structures of the carbon supports, we systematically investigated AuPd catalysts supported on various nanostructured carbons including activated carbon, carbon nanotube, carbon black, and ordered mesoporous carbons. The results showed that a high density of oxygen functional groups on the carbon surface was essential for synthesizing highly dispersed bimetallic catalysts with effective AuPd alloying, which is a prerequisite for achieving high H₂O₂ selectivity. Regarding porous structure, a solely mesoporous carbon support was superior to microporous ones. Microporous carbons such as activated carbon suffered from diffusion limitation, leading to significantly slower H₂ conversion than mesoporous catalysts. Furthermore, H₂O₂ produced from AuPd catalyst in the micropores was more prone to subsequent disproportionation/hydrogenation into H₂O due to retarded diffusion of the H₂O₂ out of the microporous structure, which led to decreased H₂O₂ selectivity. The present study showed that solely mesoporous carbons with high surface oxygen content are most desirable as a support for AuPd catalyst in order to achieve high H₂O₂ productivity and selectivity.