Spinel nickel ferrite nanoparticles strongly cross-linked with multiwalled carbon nanotubes as a bi-efficient electrocatalyst for oxygen reduction and oxygen evolution

It is of great concern to explore new electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, spinel NiFe₂O₄ nanoparticles cross-linked with the outer walls of multiwalled carbon nanotubes (MWCNTs) were successfully prepared by a simple, scalable hydrothermal method. The as-synthesized NiFe₂O₄/MWCNT nanohybrid shows not only a better ORR catalytic activity than pure NiFe₂O₄ and MWCNTs, but also a close four-electron reaction pathway. Meanwhile, the NiFe₂O₄/MWCNT nanohybrid exhibits a much higher OER catalytic activity when compared to NiFe₂O₄, MWCNTs and commercial Pt/C in terms of the onset potential and current density. Moreover, the NiFe₂O₄/MWCNT nanohybrid demonstrates the preeminent long-term durability measured by the current-time chronoamperometric test for both the ORR and OER, which evidently outperforms commercial Pt/C. The excellent bi-functional electrocatalytic activities of the NiFe₂O₄/MWCNT nanohybrid are attributed to the strong coupling between the NiFe₂O₄ nanoparticles and the MWCNTs as well as the network structure.