Owing to the electron donor-acceptor properties of GO, the active sites ( Fe2+) of Fe3O4 are not oxidised ( Fe3+) in the heterogeneous Fenton-like reaction. GO plays a sacrificial role via the oxidation of (C=C) carbon domains, and transferring electrons to Fe3O4. Therefore, GO-Fe3O4 confers superior catalytic efficiency, recyclability and longevity, otherwise not available in Fe3O4.
Zubir, N. A., Yacou, C., Motuzas, J., Zhang, X., Zhao, G. X. S., & Diniz da Costa, J. C. (2015). The sacrificial role of graphene oxide in stabilising a Fenton-like catalyst GO-Fe3O4. Chemical Communications, 51(45), 9291 - 9293. https://doi.org/10.1039/c5cc02292d