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.