Fe、Co、N CO-doped Hollow Carbon Capsules And Fenton Reaction Research

In recent decades,water pollution caused by refractory organics has become a challenging problem due to the continuous introduction of new chemicals.Antibiotics was a representative of these refractory organics.The Fenton-like reaction based on PMS was considered to have great potential for the removal of antibiotics from wastewater.However,for the commonly used transition metal catalysts,some problems including narrow p H application range and metal leaching,remarkably limited their application.Therefore,it is urgent to develop a catalyst to well address the above mentioned problems.The carbon-based composites have been widely used in the various application fields,due to their unique physical,chemical and structural properties.The carbon materials could effectively activate PMS in heterogeneous Fenton reaction,which usually involved two activation routines:free radical oxidation pathway and non-free radical pathway.By encapsulating the transition metal into the carbon layer could further regulate their electronic state,leading to an enhanced degradation performance.In this paper,Fe,Co,N co-doped hollow carbon capsules（Fe/Co-NCHCs）were prepared by a hard-template method.The tetracycline（TC）was used as the target to explore the degradation parameters,reveal possible mechanism of PMS activation,and evaluate its catalytic performance.The morphology and structure of Fe/Co-NCHCs were carefully characterized by SEM,TEM,XRD,FT-IR,Raman and XPS.Further analysis showed that the chemical structure and composition of N-doped hollow carbon capsules was changed after involvement of Fe and Co element.More defects appeared in Fe,Co,N co-doped hollow carbon capsules,leading to a better catalytic property.Moreover,XPS measurements indicated that the contents of active sites and species in Fe/Co-NCHCs,such as pyridine-N,graphite-N,sp²-C and C=O were the highest among reference samples including Fe-NCHCs and NCHCs.During the degradation process,the parameters were optimized for Fe/Co-NCHCs/PMS system.Thermodynamic studies indicated that TC degradation was an endothermic,entropy increase,and non-spontaneous process.To explore the catalytic mechanism,free radical quenching experiment,electron paramagnetic resonance test and electrochemical measurement were carried out.It was believed that the TC degradation mainly undergone the non-free radical pathway guided by singlet oxygen,and the electron transfer pathway also played an important role.Through the recycle experiment,Fe/Co-NCHCs had good stability,since 80.7%of degradation efficiency was remained within 40 min even after the 5^thcycle.of degradation efficiency were still well-preserved.The possible degradation intermediates of TC were deduced by high performance liquid chromatography/Time-of-flight mass spectrometer.