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

摘要

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(-1), 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, Li8Pb3, Li3Pb, Li10Pb3 and Li17Pb4 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.