Multivalent cobalt species supported on graphene aerogel for degradation of sulfamethoxazole via high-valent cobalt-oxo species

Abstract

Peroxymonosulfate(PMS)-based advanced oxidation technologies have rapidly evolved in the past few years with cobalt being one of the most powerful PMS activators, demonstrating considerable potential in environmental pollution control. Using water-soluble sulfonated cobalt(II) phthalocyanine as the precursor, a graphene-based catalyst with a three-dimensional macrostructure containing Co(II) and Co(III) was created through simple freeze-drying and high-temperature calcination herein. The multivalent cobalt effectively improved the reaction rate of material activation PMS to degrade SMX, and the presence of the sp2-hybridized carbon lattice accelerated the electron-transfer rate. Through quenching experiments and electron paramagnetic resonance, it was demonstrated that high-valent cobalt-oxo species [Co(IV) = O] were the primary active components of the reaction system, and that the cobalt–nitrogen active components and N vacancy structure in the material were conducive to the formation of high-valent Co(IV) = O species and 1O2. Furthermore, after reusing the manufactured materials 10 times, the reaction system was still able to remove SMX efficiently, allowing for the practical implementation of PMS advanced oxidation technology. Thus, the current study considerably contributes to the investigation of the PMS reaction mechanism of multivalent cobalt-doped graphene catalytic materials.