Spatial confinement of cobalt crystals in carbon nanofibers with oxygen vacancies as a high-efficiency catalyst for organics degradation

Catalytic activation of peroxymonosulfate (PMS) to generate radicals has received considerable and increasing attention in the environmental catalysis for treatment of recalcitrant pollutants. In the current study, a series of highly porous, cobalt-loaded activated carbon nanofibers (Co/CNFs) were prepared by one-pot electrospinning followed by thermal treatment. Observations showed that the limited addition of Co (≤8%) had no obvious effect on the morphology of the resulted CNFs, but it did affect the surface area and porosity of the CNFs as well as the carbon graphitic process during the carbonization. The applicability of this confined nanoreactor used in sulfate-radical based advanced oxidation processes (SR-AOPs) was systematically investigated. The effect of pH on the radical generation and organics removal was examined. The oxygen species on the CNFs played an important role in the activation of PMS. The carbon layer encapsulated on the Co crystal surface inhibited the Co leaching during the reaction and increased the catalytic efficiency due to the enhanced interfacial charge transfer. Meanwhile, the carbon layer could synchronously function as the adsorptive active sites during the degradation of organics. Results showed that the Co/CNFs possessed the highest catalytic efficiency under neutral pH, corresponding to the sulfate radical generation. The Co leaching and XPS results showed that the Co served as the main active site in PMS activation.