LAUSR

Abstract Steel rolling sludge containing high amounts of iron was recycled for the first time via a facile hydrothermal method and used as ferric ions source for CoFe2O4/graphene nanocomposite electrode. CoFe2O4 agglomeration is weakened by introducting graphene, which is crucial for improving efficient ions transport pathways in energy storage devices. The CoFe2O4/graphene complex exhibits a rough morphology and a porous nanostructure with a high specific surface area of 191.5 m2 g−1. The material also shows excellent Faradaic redox reactions with high specific capacity of 166.5C g−1 and 127.0C g−1 at 0.5 and 10 A g−1, respectively, which are higher than that of simple, dense CoFe2O4 particles (121.6C g−1 at 0.5 A g−1). Furthermore, the electrode demonstrates outstanding cycle stability with 79.3% capacitance retained after 5000 cycles. Hence, the proposed resource reuse strategy can be used to prepare CoFe2O4/graphene nanocomposites for supercapacitors.