Co3O4 nanosheets modified by Ni@C nanoparticles as effective flow-through electrode for electro-activation of PMS: Ni@C as electron shuttle for accelerated Co3+/Co2+ cycle in bulk Co3O4

Electro-assisted activation of peroxymonosulfate (EA-PMS) by transition metals oxides (TMOs) has been extensively studied for the removal of organic pollutants. Despite TMOs possess considerable activity and affinity to PMS, their poor bulk conductivity still limits the electron exchange during the TMδ/δ+1 redox cycle, especially the efficient reduction of TMδ+1 via cathodic process. In this study, carbon felt loaded with modified Co3O4 nanosheets (Co@FCF) was fabricated and applied as the flow-through electrode of EA-PMS process, where the Co3O4 nanosheets were embedded with numerous metallic Ni particles encapsulated within carbon layers (Ni@C). Driven by weak electric current, continuous electrons can be supplied to the bulk Co3O4 from the electron-rich Ni@C nanoparticles, resulting in accelerated Co3+/Co2+ cycle, enhanced production of SO4·− and improved energy utilization efficiency. Electrochemical tests along with density functional theory calculations indicate that the unique structure of Co@FCF played essential role in the enhanced performance.