Electrochemical Studies of Titanium in Molten Fluorides

The electrochemical reduction of Ti(IV) in molten LiF ‐ NaF ‐ KF [ 46.5 – 11.5 – 42.0 mole per cent ( m / o ) ] at 500°C was studied by means of linear sweep voltammetry, chronopotentiometry, and chronoamperometry. The reduction of Ti(IV) to Ti(III) was found to proceed reversibly at both platinum and pyrolytic graphite electrodes; further reduction of Ti(III) to the metal was shown to be a reversible process involving alloy formation with the platinum electrode. Standard electrode potentials for the processes, Ti ( IV ) + e = Ti ( III ) and Ti ( III ) + 3 e = Ti , are − 0.058 and − 1.798 V , respectively (both vs. a unit mole fraction Ni ( II ) / Ni electrode). The electrochemical oxidation of Ti(III) at unsheathed platinum and sheathed glassy carbon electrodes was studied in molten LiF ‐ BeF 2 ‐ ZrF 4 ( 65.6 – 29.4 – 5.0 m / o ) at 500 ° C . Evidence for a reversible electrode reaction was obtained from voltammetric and chronopotentiometric studies. A standard potential of +0.197V ( vs . a unit mole fraction Ni ( II ) / Ni electrode) was determined for the process Ti ( III ) = Ti ( IV ) + e . The more anodic value of the standard potential of the Ti ( IV ) / Ti ( III ) couple in LiF ‐ BeF 2 ‐ ZrF 4 in comparison to LIF ‐ NaF ‐ KF reflects the higher acidity (Lewis concept) of the LiF ‐ BeF 2 ‐ ZrF 4 melt.