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

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 ...