New Insights into the Electrochemical Behavior of Hematite (α-Fe₂O₃) Microparticles in Strong Aqueous Basic Electrolyte: Formation of Metallic Iron

A detailed electrochemical study of cubic α-Fe₂O₃ microparticles has been carried out in strong aqueous LiOH electrolyte. The α-Fe₂O₃ was synthesized hydrothermally and investigated in the form of an electrochemical cell using an alkaline solution, ‘α-Fe₂O₃|LiOH (saturated), ZnSO₄ (1 M)|Zn’. In this cell, the α-Fe₂O₃ cathode showed a reversible capacity of ca 220 mAh/g within cut-off voltages of 0 and 1.5 V under the constant current of 0.3 mA. The electrochemical performance was attributed to the reversible formation of both proton and lithium intercalation products (FeOOH and LiFeO₂) detected in the cathode material. Interestingly, at a lower discharge current of 0.1 mA, some of the hematite phase was reduced to metallic iron after yielding 336 mAh/g. The various possible electro-reduction reactions, which have direct electro-hydrometallurgical implications, are analyzed and discussed.