N-doped carbon nanotubes encapsulating Co materials with strong magnetic properties generate ˙O2− through activation of hydrogen peroxide to effectively degrade rhodamine B†

The encapsulation of metal Co nanoparticles in N-doped carbon was achieved through a facile hydrothermal and pyrolysis technique to isolate the nanocrystalline Co metal, thus preventing their mobilization and aggregation. The materials prepared at 400 °C were confirmed to be Co₂C@NC; they were then converted into Co@NC and Co@NCNT at calcination temperatures of 500 °C and 600 °C, respectively. Co@NCNT presents stronger magnetic properties with 135.2 emu g⁻¹ saturation magnetization, 17.8 emu g⁻¹ remanence and 290.2 coercivity, as well as high catalytic activity for the advanced oxidation degradation of Rhodamine Blue with H₂O₂, providing a degradation rate of >99%. The contribution of the various lattice planes of the crystalline Co to saturation magnetization and the catalytic reactivity was explored. The active sites on the catalyst surface and the recovery and reusability of the catalyst were determined. Additionally, quenching experiments conducted by adding tert-butanol (TBA), 1,4-benzoquinone (p-BQ) and 2,2,6,6-tetramethylpiperidine (TEMP) to the reaction system were conducted, proving that the ˙O₂⁻ radicals produced by the catalyst activating H₂O₂ play a key role in the oxidation degradation.