Spinel Nickel Ferrite Nanoparticles Supported on a 1T/2H Mixed-Phase MoS₂Heterostructured 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.