Synergistic Effect of Co3O4 Nanoparticles and Graphene as Catalysts for Peroxymonosulfate-Based Orange II Degradation with High Oxidant Utilization Efficiency

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• 作者：Chengxiang Wang ; Penghui Shi ; Xiaodong Cai ; Qunjie Xu ; Xuejun Zhou ; Xiaolv Zhou ; Dong Yang ; Jinchen Fan ; Yulin Min ; Honghua Ge ; Weifeng Yao
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：January 14, 2016
• 年：2016
• 卷：120
• 期：1
• 页码：336-344
• 全文大小：562K
• ISSN：1932-7455

文摘

Cobalt oxide and graphene nanocomposites (Co₃O₄/graphene) are fabricated as heterogeneous catalysts to accelerate sulfate radical generation in Orange II degradation. The Co₃O₄/graphene catalyst is characterized through X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy. Results show that the Co₃O₄/graphene catalysts are prepared successfully. Co₃O₄ or graphene solely exhibits slight catalytic activity, but their hybrid (Co₃O₄/graphene) efficiently degrades and removes Orange II from an aqueous solution in the presence of peroxymonosulfate (PMS). Orange II is completely removed or degraded (100%) within 7 min by using the composite catalysts; by contrast, Orange II is partially removed when Co₃O₄ or graphene is used alone under the same conditions. These phenomena suggest a synergistic catalytic activity of Co₃O₄ and graphene in the hybrid. To investigate the causes of the synergistic interactions of the Co₃O₄/graphene composites, we summarize previous studies and propose an electron transfer pathway between Co₃O₄ and graphene. We then perform density functional theory calculations to describe the specific features of the composite structures. The hybrid structure is more conductive than the individual semiconductor cobalt oxide clusters because of the hybridization between Co-4d orbital and graphene-p orbital. Fukui indices of electrophilic attack indicate that Co²⁺, not Co³⁺, is the active site. Therefore, the PMS activation processes and Orange II degradation pathways are involved in an electrochemical process. Graphene functions as a wire because of its excellent electrical conductivity during oxidation.