Tailoring rGO-NiFe₂O₄ hybrids to tune transport of electrons and ions for supercapacitor electrodes

Spinel transition metal oxide is a promising pseudocapacitive materials but the instability gives it narrow practical application. It is shown herein, that an effective remedy for these problems can be achieved by introducing highly conductive two dimensional (2D) reduced graphene oxide (rGO) substrate on which NiFe₂O₄ nanoparticles are well distributed. The rGO-NiFe₂O₄ hybrids with different NiFe₂O₄ contents were tailored to explore the source of the improvement in capacitance performance. It is found that rGO nanosheets in the hybrid can be used as a conductive substrate to accelerate the electron transport. Moreover, NiFe₂O₄ nanoparticles with a certain volume can simultaneously prevent the restacking of rGO and increase the pseudocapacitance. The G-N3 (30 wt% NiFe₂O₄) hybrid holds enhanced specific capacitance up to 210.9 F g⁻¹ at 0.5 A g⁻¹ far above that of pristine NiFe₂O₄ (50 F g⁻¹), and exhibits superior cycle stability with no obvious capacity loss even after 5000 cycles. This research indicates that a tailoring method can promote the electrochemical performance of NiFe₂O₄, and hopefully accelerate the commercialization of spinel transition metal oxides as electrode materials for supercapacitor.