Electrochemical Reduction of Metal Oxides

Electrochemical reductions of metal oxides were investigated in molten salt electrolyte consisting of Li 2 O and LiCl at 650 °C with a three-electrode electrochemical cell, namely, a fuel basket cathode loaded with metal oxides (TiO 2 , NO, etc.), a glassy carbon crucible anode, and a Ni/NiO reference electrode. Reductions were carried out in an interrupted mode at various cathodic potentials and total applied charges. Current-time profiles were recorded during reductions, where current increase and decrease indicated formation and reduction of lithium intermediates. Reduction pathways have been derived by analyzing reduced products with X-ray diffraction (XRD). It is shown that the reductions follow a stage-wise reaction process with intermediates such as LiTiO 2 in TiO 2 reduction, and different metal oxides reductions follow different reduction routes. Cyclic voltammetry (CV) of lithium salts were measured before and after reductions. The possibility of reutilizing salts after reductions is determined by comparing CV measurements before and after reductions, and the results are different for reduction of different metal oxides. It is found that a higher applied reduction potential (in magnitude), more charges and fresh lithium electrolyte are preferred in metal oxides reductions. Moreover, one of the keys to improve reduction efficiency is discussed to be the enhancement of oxygen diffusion outward the fuel basket.