Electrochemical Behavior of Pr(Ⅲ) in the LiCl-KCl Melt on a Ni Electrode†

doi:10.7503/cjcu20140405

Abstract

Abstract:

The electrochemical behavior of Pr(Ⅲ) on a Ni electrode in the LiCl-KCl melt and the alloying mechanism of Pr-Ni alloys were investigated by cyclic voltammetry, square wave voltammetry, chronopoten-tiometry and open-circuit chronopotentiometry. Cyclic voltammetry and square wave voltammetry experiments indicate that the reduction of Pr(Ⅲ) ions into Pr metal occur in a single step with three electrons exchanged. Compared with the cyclic voltammograms on an inert Mo electrode, four reduction peaks are observed, which indicates the under-potential deposition of Pr(Ⅲ) on the reactive Ni electrode due to the formation of Pr-Ni intermetallic compounds. The Pr-Ni alloys obtained by potentiostatic electrolysis were characterized by X-ray diffraction(XRD) and scanning electron micrograph-energy dispersive spectrometry(SEM-EDS). The results show that only one Pr-Ni intermetallic compound, i.e. PrNi₂, PrNi₃, Pr₂Ni₇ or PrNi₅, is obtained at each potential, respectively. This process can also be used for other electrochemical formation of lanthanide-Ni alloys.

Key words: Electrochemical behavior, Under-potential deposition, Potentiostatic electrolysis, Pr-Ni intermetallic compound

CLC Number:

O646

TrendMD:

LI Mei, LI Wei, HAN Wei, ZHANG Milin, YAN Yongde. Electrochemical Behavior of Pr(Ⅲ) in the LiCl-KCl Melt on a Ni Electrode^†[J]. Chem. J. Chinese Universities, 2014, 35(12): 2662.

Figures/Tables 8

Fig.1 Cyclic voltammograms of LiCl-KCl melts before(a, b) and after(c, d) the addition of PrCl3(1.25×10-4 mol/L) at 873 K S=0.322 cm2, scan rate: 0.1 V/s. a. LiCl-KCl, Mo electrode; b. LiCl-KCl, Ni electrode; c. LiCl-KCl-PrCl3, Mo electrode; d. LiCl-KCl-PrCl3, Ni electrode.

Fig.2 Variation of cathodic peak current as a function of the potential scan rate on a Mo electrode(S=0.322 cm2) in LiCl-KCl-PrCl3[c(PrCl3)=1.25×10-4 mol/L] melt at 873 K

Fig.3 Square wave voltammogram on a Ni electrode in LiCl-KCl-PrCl3[c(PrCl3)=1.25×10-4 mol/L] melt(S=0.322 cm2) at 873 K Pulse height: 25 mV; potential step: 1 mV; frequency: 30 Hz.

Fig.4 Chronopotentiograms at different current intensities on a Ni electrode(S=0.322 cm2) in LiCl-KCl-PrCl3[c(PrCl3)=1.25×10-4 mol/L] melt at 873 K

Fig.5 Open-circuit transient curve by potentiosta-tic electrolysis at -2.3 V(vs. Ag/AgCl) for 60 s on a Ni electrode(S=0.322 cm2) in LiCl-KCl-PrCl3[c(PrCl3)=1.25×10-4 mol/L] melt at 873 K

Fig.6 XRD patterns of Pr-Ni alloys by potentiostatic electrolysis on a Ni electrode(S=2.3 cm2) in LiCl-KCl-PrCl3[c(PrCl3)=1.25×10-4 mol/L] melt at 873 K a. -1.2 V for 10 h; b. -1.6 V for 8 h; c. -1.8 V for 6 h; d. -2.0 V for 2 h.

Fig.7 SEM images of Pr-Ni alloys by potentiostatic electrolysis on a Ni electrode(S=2.3 cm2) in LiCl-KCl-PrCl3[c(PrCl3)=1.25×10-4 mol/L] melt at 873 K (A) -1.2 V, 10 h; (B) -1.6 V, 8 h; (C) -1.8 V, 6 h; (D) -2.0 V, 2 h.

Fig.8 EDS analysis of Pr-Ni alloy by potentiostatic electrolysis on a Ni electrode(S=2.3 cm2) in the LiCl-KCl-PrCl3[c(PrCl3)=1.25×10-4 mol/L] melt at 873 K (A) -1.2 V, 10 h; (B) -1.6 V, 8 h; (C) -1.8 V, 6 h; (D) -2.0 V, 2 h.

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