Encapsulate Co₃O₄ within ultrathin graphene sheets to enhance peroxymonosulfate activation by tuning surface...

Heterojunctions composed of cobalt-based materials and carbon materials have been recognized as the efficient catalysts for peroxymonosulfate (PMS) activation to generate reactive oxygen species for the removal of environmental contaminants. However, the role of carbon materials in promoting the heterojunction systems has not been fully understood. This study synthesized a heterojunction material of graphene sheets encapsulating Co₃O₄ (GCO-500) through the pyrolysis of cobalt MOF and applied it to activate PMS for the removal of lomefloxacin. The results showed a high removal rate of 93.59 % with a degradation rate of k₁ = 0.0156 min^-1. Co₃O₄ clusters was encapsulated within ultrathin graphene sheets (<2 nm). DFT calculations revealed that graphene layers improve the electron transfer ability of Co₃O₄ and increased the d-band center of Co₃O₄ (-1.61 eV) that promote the adsorption of PMS on GCO-500 (-1.32 eV). In the meanwhile, organic pollutant was enriched in graphene layers with high adsorption energy (-13.08 eV), which greatly enhanced the degradation efficiency of pharmaceuticals. This study provides an effective catalyst for PMS activation and sheds light on the fundamental electronic-level understanding of cobalt-based and carbon heterojunction catalysts in PMS activation.