Graphene oxide–iron oxide (GO–Fe3O4) nanocomposites were synthesised by co-precipitating iron salts onto GO sheets in basic solution. The results showed that formation of two distinct structures was dependent upon the GO loading. The first structure corresponds to a low GO loading up to 10 wt%, associated with the beneficial intercalation of GO within Fe3O4 nanoparticles and resulting in higher surface area up to 409 m2 g−1. High GO loading beyond 10 wt% led to the aggregation of Fe3O4 nanoparticles and the undesirable stacking of GO sheets. The presence of strong interfacial interactions (Fe-O-C bonds) between both components at low GO loading lead to 20% higher degradation of Acid Orange 7 than the Fe3O4 nanoparticles in heterogeneous Fenton-like reaction. This behaviour was attributed to synergistic structural and functional effect of the combined GO and Fe3O4 nanoparticles.

Owing to the electron donor-acceptor properties of GO, the active sites ([triple bond, length as m-dash]Fe(2+)) of Fe3O4 are not oxidised ([triple bond, length as m-dash]Fe(3+)) in the heterogeneous Fenton-like reaction. GO plays a sacrificial role via the oxidation of (C[double bond, length as m-dash]C) carbon domains, and transferring electrons to Fe3O4. Therefore, GO-Fe3O4 confers superior catalytic efficiency, recyclability and longevity, otherwise not available in Fe3O4.