Electrochemical and spectroscopic analyses for praseodymium complexes in potassium bis(trifluoromethylsulfonyl)amide melts

Abstract

In this study, the electrochemical behavior of praseodymium complex; Pr(III) in potassium bis(trifluoromethyl-sulfonyl) amide; K[NTf2] melts was under investigation. There is speculation that the first peak of reduction at + 2.27 V is probably Pr(IV) formation. The electrochemical analysis revealed that the electrodeposition reaction of Pr(III) to Pr(0) would cause the reduction peak of Pr(III) at + 0.87 V at 488 K. By semi-integral and semi-differential analysis, the diffusion coefficient and activation energy of Pr(III) in K[NTf2] melts were measured in the range of 473–493 K. Chronoamperometry was also used to evaluate the nucleation behavior of Pr(III). It was found that Pr nucleation mechanism changed from instantaneous to progressive nucleation when the overpotential became more negative than Pr(0) deposition potential. The early-stage electrodeposits were identified in the metallic state by XPS analysis. In addition, the coordination states of Pr(III) in K[NTf2] melts have been studied by Raman spectroscopy. The concentration dependence of the deconvoluted Raman spectra was investigated for Pr(III) in K[NTf2] in the range 0.23–0.45 mol kg− 1. The solvation number of Pr(III) in K[NTf2] melts was determined to be 5.14, according to the conventional analysis.