Structural and electrochemical properties of Fe-doped NiAl₂O₄ oxides

Abstract

A new spinel solid solution system of Ni1_-xFe_xAl₂O₄ (0.0 ≤ x ≤ 0.5) was synthesized through sol-gel method. The effect of Fe doping on the nickel aluminate prepared was investigated. The synthesized powders were characterized by means of X-ray diffraction, thermogravimetric and differential thermal analysis, fourier transform infrared spectroscopy, scanning electron microscopy and electrochemical measurements. From the preceding analysis, it can be shown that compounds show a single spinel phase in the temperature range 650-1000°C and the solubility of iron in the NiAl₂O₄ structure was limited to samples with the iron content x < 0.6. The electrochemical measurements indicate that the catalytic activity is strongly influenced by iron doping. The highest electrode performance is achieved with Ni_0.7Fe_0.3Al₂O₄ (i=86.84 mA/cm²) which is ~ 27 times greater than that of NiAl₂O₄ ( i=3.22 mA/cm²) at E= +0.8V. After one hundred cycles, the stability of the doped electrode with 30% of iron is much better than the undoped electrode.