Morphology-controlled NiFe2O4 nanostructures: Influence of calcination temperature on structural, magnetic and catalytic properties towards OER

Abstract

Nickel ferrite nanoparticles, NiFe2O4, were prepared using the EDTA-Citrate complexation method. A systematic study was carried out on the microstructural, morphology, magnetic, vibrational and electrochemical properties of the samples. According to Rietveld refinements, all samples are single-phase with spinel cubic structure with sizes ranging from 15 to 93 nm. Electron microscopy analyzes revealed the formation of aggregates made of several nanocrystals. The aggregates have triangular shape that changes in size as a function of the calcination temperature. The magnetic hysteresis curves at 300 K are typical of ferrimagnetic materials and showed increasing values of magnetic parameters with the size of the crystallites. The results demonstrated a significant NiFe2O4 catalytic activity towards oxygen evolution reaction (OER) in an alkaline medium with overpotential of 326 mV vs. RHE at J = 10 mA cm−2 for the particles obtained at 400 °C (NFO400), and high electrochemical stability over 15 h under an electrolysis current of J = 10 mA cm−2. LSV, Tafel, SA, Jm, TOF and EIS analysis revealed that decreasing particle size favors kinetics through a more efficient process of mass and charge transfer.