Influence Of Mno₂Additive On The Electrochemical Performance Of NiFe₂O₄Anode

Graphite anode in auminum industry has caused the high pollution, high consumption and high cost. NiFe2O4spinel materials have the high stability, low coefficient of thermal expansion and good corrosion resistance and are the best choice as inert anode materials In this paper, We investigated the impact of adding different amounts of MnO2on the electrochemical performance of NiFe2O4anode.NiFe2O4(molar ratio of NiO:Fe2O3=1:1) of adding MnO2in mass fraction0.5%,1.0%,1.5%,2.0%,2.5%MnO2was synthesied. The AC impedance and polarization curve of NiFe2O4in a3AlF6-Al2O3-NaCl (molar ratio0.85:0.05:0.1) molten salts and NaCl-CaCl2(molar ratio0.45:0.55) was studied. The results show that:the conductivity of NiFe2O4was increased with the addition of MnO2.With the increase in the amount of MnO2, the conductivity of NiFe2O4decreased firstly and then increased. The conductivity of NiFe2O4with2.0%MnO2is of the greatest. With the increase in temperature increases, the conductivity of NiFe2O4increases. Adding MnO2reduced the anodic overpotential of NiFe2O4in molten CaCl2-NaCl-CaO and increased the reaction current. Impedance spectra were fitted by the equivalent circuit of Rs(Q1/R1)(Q2/R2)(C/R3) and the equivalent circuit parameters were obtained.X-ray diffraction was used to analyze the composition the prepared NiFe2O4. There is no new phases in the samples after adding MnO2. NiFe2O4may form a solid solutin with MnO2The lattice constant of NiFeaO4after adding MnO2was increased and was activated. In different ionic radius and ionic valent, the replacement of Mn4+by Fe3+resulted in lattice distortions. To the maintain neutral, the replacement each three Fe3+ions, producing a positive ion vacancy and the lattice distortions.Scanning electron microscopy was used to analyze the morphology of NiFe2O4. Adding MnO2refined the grain of NiFe2O4. Particles of NiFe2O4with2.0%MnO2is the tightest and NiFe2O4was densified.