Controllable fabrication of Co-CoO architecture: Morphology, defects and metal components toward efficient degradation of organic pollutants

Cobalt and its oxides are the most recognized catalysts for advanced oxidation processes based on peroxymonosulfate (PMS). However, the easy optimization of morphology, defects and metal components of Co-based catalysts to generate more active centers remains challenging. In this study, a kind of multicomponent cobalt-based catalyst has been synthesized with a simple and effective strategy by introducing sodium carbonate in the precursor solution. The appropriate concentration of sodium carbonate favored the construction of multi-level pore structures, thus facilitating the exposure of more active centers and accelerating the mass transfer of the guest materials during the removal process. Besides, the sodium carbonate concentration is beneficial for modulating the degree of carbon defects and the efficiency of metal components of Co and CoO, resulting in higher conductivity and greater electron transfer media, which helps activate PMS for degradation of PNP. The honeycomb-like Co-CoO architecture (Co-CoO/NC-h) showed the best performance of PNP degradation with a removal rate of 99.3% in 25 min, and the activity was still up to 93.4% after 5 cycles. The magnetic Co-CoO/NC-h presented strong recovery stability due to the enhanced interaction between cobalt and cobalt oxide nanoparticles with nitrogen-doped carbon. Quenching tests and EPR demonstrated the specific contribution of free and non-free radicals in the degradation of PNP. The biological toxicity of the solution after degradation reaction was evaluated, and possible degradation pathways for PNP were proposed. Overall, this work provides a simple and effective strategy for tuning morphology, defects and metal components to activate PMS for the degradation of organic pollutants in wastewater.