The kinetics process of a Pb(ii)/Pb(0) couple and selective fabrication of Li–Pb alloys in LiCl–KCl melts

Abstract

The electrode reaction of Pb(II) and co-reduction of Li(I) and Pb(II) were investigated on a tungsten electrode in LiCl-KCl eutectic melts by a range of electrochemical techniques. From cyclic voltammetry and square wave voltammetry measurements, the reduction of Pb(II) was found to be a one-step diffusion-controlled reversible process with the exchange of 2 electrons. The diffusion coefficients of Pb(II) were computed, and they obey the Arrhenius law. Using the linear polarization technique, the kinetic parameters, such as exchange current intensity (j 0 ), standard rate constant (k 0 ) and charge transfer resistance (R ct ) for the Pb(II)/Pb(0) couple on a tungsten electrode were studied at different temperatures, and the activation energy is 27.32 kJ mol À1 , smaller than the one for diffusion of Pb(II), which further confirmed that the reduction of Pb(II) was controlled by diffusion. A depolarisation effect for Li(I) reduction was observed from the results of cyclic voltammetry, square wave voltammetry and chronopotentiometry due to the formation of Li-Pb alloys by co-reduction of Li(I) and Pb(II). Furthermore, five Li-Pb intermetallic compounds, LiPb, Li 8 Pb 3 , Li 3 Pb, Li 10 Pb 3 and Li 17 Pb 4 characterized by scanning electronic microscopy and X-ray diffraction, were selectively prepared by potentiostatic electrolysis on a tungsten electrode and galvanostatic electrolysis on a liquid Pb electrode, respectively.

Electrochemical Coreduction of Gd(III) with Pb(II) and Recovery of Gd from LiCl-KCl Eutectic Assisted by Pb Metal

“…2a (blue line), compared with Fig. 1, some redox signals of C/C′, I/I′, II′ and D can be observed.According to the previous result,51 C/C′ and D pertain to the reduction/dissolution of metallic Pb and the formation of Pb-Li alloy compound, respectively. However, the anodic peak D′ related to the reduction peak D does not appear, which may be that the anodic peak B' is very strong and the anodic peak D′ may be covered.…”

Electrochemical properties of yttrium on W and Pb electrodes in LiCl–KCl eutectic melts

“…The anodic/cathodic signals of V′/V detected at about −0.38/−0.40 V pertain to the dissolution and deposition of Pb metal. 50 It can be inferred from the shape of the redox signals (III/III′), that the system is soluble–soluble, and III/III′ are related with the formation/dissolution of (Li–Pb) solid solution. The deposition potential of Li on liquid Pb electrode can be seen at more positive value than that on W electrode due to the formation of (Li–Pb) solution, and process is expressed as following: Li( i ) in LiCl–KCl + e − + Pb = (Li–Pb) solution …”

Electrochemical Production of Bismuth in the KCl–PbCl2 Melt

“…The electrochemical reaction of lead ions reduction is reversible according to the two-valence scheme; the diffusion coefficient, calculated according to Sanda’s equation, is equal to D Pb(II) = 2.26 × l0 −5 cm 2 /s for 873 K. It is found that potentiostatic lithium reduction on the preliminary deposited lead results in the formation of a liquid Li–Pb alloy, whereas Mg–Li–Pb alloys form only after an MgCl 2 addition to the melt. Later, Han et al [ 10 ] studied the kinetics of cathode processes on the indifferent electrode at lead ions Pb 2+ reduction in the LiCl–KCl melt. Zhu [ 11 ] analyzed Pb (II) electrochemical behavior on the tungsten electrode in the molten NaCl–KCl eutectic at 700 °C using voltammetry and chronopotentiometry.…”