Yolk-shell Fe2O3@mesoporous hollow carbon sphere hybrid sub-micro reactors for effective degradation of organic contaminants

Carbon–metal oxide composites are important class of catalytic materials in persulfate (PS)/peroxymonosulfate (PMS) activation. But, their poor catalytic stability during oxidation limits its practical use. Herein, we demonstrate the yolk-shell architecture strategy for the fabrication of highly stable Fe2O3 mesoporous carbon hollow spheres (Fe2O3@MCHS) catalyst. The prepared material exhibits high PS activation ability for effective degradation of phenolics. The surface properties of hybrid Fe2O3@MCHS system were examined using FE-SEM, TEM, BET and VSM techniques. Physical characterization data confirmed that Fe2O3@MCHS sub-micro reactors possess a magnetic property, high specific surface area (SSA; >1200 m2 g−1), orderly arranged mesopores, and excellent degree of particle dispersion. Owing to the fact, the Fe2O3@MCHS catalyst exhibited highest reactivity for the degradation of 2,4-dichlorophenol and bisphenol-A by PS even with very low catalyst dosage (10 mg L−1). ESR and scavenging experiments exclude the role of reactive radicals and other reactive oxygen species (ROS) (1O2) during pollutant degradation. Open circuit potential (OCP) measurements further reveal that low pollutant degradation efficiencies in the presence of 1O2 scavengers (L-histidine and NaN3) were caused due to strong interaction between scavenging molecules and catalytic surfaces rather than ROS quenching. Electrochemical investigation also supports that degradation occurs through mediating electron transfer from pollutant to Fe2O3@MCHS. This study provides new understanding in PS activation and also in developing stable PS activating hybrid catalytic systems for pollutant degradation.