Ball-Milled (Cu-Ni-Fe + Fe2O3) Composite as Inert Anode for Aluminum Electrolysis

A (Cu-Ni-Fe+Fe2O3) composite was prepared by ball milling and evaluated as an oxygen-evolving anode for aluminum electrolysis. The material was prepared by first milling elemental Cu, Ni and Fe powders to form a Cu(Ni,Fe) solid solution. Then, the milling operation was resumed for different periods of time (from 30 min to 4 h) in presence of a fixed amount of nanosized Fe2O3 particles to achieve the desired stoichiometry (Cu65Ni20Fe15)(98.6)O-1.4. After 4 h of milling, Fe2O3 precipitates are found to be homogeneously dispersed in the Cu-Ni-Fe matrix. The powder was then heated at 1000 degrees C and pressed to form an electrode for evaluation in low-temperature (700 degrees C) KF-AlF3 electrolyte at an anode current density of 0.5 A cm(-2) for 20 h. The cell voltage was stable at ca. 4.5 V and the Cu, Fe and Ni contamination of the produced Al and electrolyte were quite low, resulting in an estimated anode erosion rate of 1.2 cm year(-1). This good corrosion resistance is attributed to the formation of a protective NiFe2O4-rich layer on the electrode during Al electrolysis, which is likely to be favored by the presence of the finely dispersed Fe2O3 precipitates acting as nucleation sites for the formation of NiFe2O4. (C) 2013 The Electrochemical Society. All rights reserved.