Rational synthesis of micronano dendritic ZVI@Fe3O4 modified with carbon quantum dots and oxygen vacancies for accelerating Fenton-like oxidation

The zero valence iron (ZVI) Fenton-like catalyst has two main defects: one defect is that the surface passivation impairs the reusability of catalysts, and the other defect is the deactivation under neutral working pH. To overcome these problems, we synthesized a dendrite-like ZVI@Fe3O4 composite modified with carbon quantum dots (CQDs) and oxygen vacancies (OVs) by electrodeposition and solvothermal treatments. The results showed that the CQDs (approximately 5 nm) with polar C-groups on the surface of the composites were derived from the carbonization of glucose during thermal treatment, and the OVs (atomic scale) at the junction of Fe3O4 and the CQDs were induced by the reduction of the CQDs. The synthesized composite possessed excellent catalytic activity and reusability. Under the condition of 6 mmol/L H2O2, the synthesized composite catalyst with the dose of 0.10 g/L completely removed 35 ppm phenol within 10 min at pH 4.0 and within 60 min at neutral pH. Furthermore, the catalytic mechanism was proposed. The reducing effect of CQDs accelerated the =Fe3+/=Fe2+ cycle, and the surface polar C-groups promoted the adsorption of phenol molecules; the OVs induced the formation of acidic micro regions and facilitated the dissociation of the O-O bonds in H2O2 into center dot OH, extending the application range of pH from similar to 4.0 to the neutral condition during the Fenton-like process. (C) 2019 Elsevier B.V. All rights reserved.