Spinel Nickel Ferrite Nanoparticles Supported on a 1T/2H Mixed-Phase MoS2 Heterostructured Composite as a Bifunctional Electrocatalyst for Oxygen Evolution and Oxygen Reduction Reactions

A composite electrocatalyst of NiFe2O4 supported on a 2H/1T multiphase MoS2 nanosheet is reported. The as-prepared NiFe2O4/MoS2 heterostructured composite exhibited an excellent bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity. The composite electrocatalyst exhibited an OER current density of 10 mA cm–2 with an overpotential of 330 mV in 1 M KOH comparable to that of IrO2. On the other hand, the composite electrocatalyst exhibited an ORR onset potential (Eonset) of 0.82 V vs RHE. The K–L plot and rotating ring-disk electrode analysis evidenced that the ORR on the NiFe2O4/MoS2 heterostructure follows closely the 4 e– transfer process similar to Pt/C and delivered notable electrochemical stability after 5000 potential cycles with retention of about 90% diffusion-limiting current density. The H2–O2 anion exchange membrane fuel cell (AEMFC) employing the cathode electrode fabricated with the NiFe2O4/MoS2 composite showed a peak power density of ∼20 mW cm–2. In contrast, a peak power density of ∼51 mW cm–2 was realized for the AEMFC employing the Pt/C cathode electrode under identical operating conditions. Considering the excellent bifunctional activity, good electrochemical performance and stability, and the low-cost facile synthetic approach, the NiFe2O4/MoS2 heterostructured composite developed in this study can be considered as a potential candidate for energy conversion and storage applications.