Titanium Dioxide/Reduced Graphene Oxide Hybrid Photocatalysts for Efficient and Selective Partial Oxidation of Cyclohexane

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• 作者：Yasuhiro ShiraishiShingo Shiota ; Hiroaki Hirakawa ; Shunsuke Tanaka ; Satoshi Ichikawa ; Takayuki Hirai
• 刊名：ACS Catalysis
• 出版年：2017
• 出版时间：January 6, 2017
• 年：2017
• 卷：7
• 期：1
• 页码：293-300
• 全文大小：537K
• ISSN：2155-5435

文摘

Partial oxidation of cyclohexane (CHA) to cyclohexanone (CHA-one) with molecular oxygen (O₂) is one of the most important reactions. Photocatalytic oxidation has been studied extensively with TiO₂-based catalysts. Their CHA-one selectivities are, however, insufficient because the formed CHA-one is subsequently decomposed by photocatalysis involving the reaction with superoxide anion (O₂^●–) produced by one-electron reduction of O₂ on TiO₂. Here we report that TiO₂, when hybridized with reduced graphene oxide (rGO), catalyzes photooxidation of CHA to CHA-one with enhanced activity and selectivity under UV light (λ > 300 nm). The TiO₂/rGO hybrids produce CHA-one with twice the amount formed on bare TiO₂ with much higher selectivity (>80%) than that on bare TiO₂ (ca. 60%). The conduction band electrons photoformed on TiO₂ are transferred to rGO, promoting efficient charge separation and enhanced photocatalytic cycles. The trapped electrons on rGO selectively promote two-electron reduction of O₂ and suppress one-electron reduction. This inhibits the formation of O₂^●–, which promotes photocatalytic decomposition of the CHA-one formed. These properties of rGO therefore facilitate efficient and selective formation of CHA-one on the hybrid catalyst.