Investigation of electrodeposition behavior for Nd(III) in [P2225][TFSA] ionic liquid by EQCM methods with elevated temperatures. (20th December 2016)

• Record Type: Journal Article
• Authors: Ota, Hisashi; Matsumiya, Masahiko; Sasaya, Naoko; Nishihata, Keiichi; Tsunashima, Katsuhiko
• Is Part Of: Electrochimica acta. Volume 222(2016)
• Page Start: 20
• Page End: 26
• Publication Date: 2016-12-20
• Subjects: Electrodeposition -- EQCM methods -- Ionic liquid -- Neodymium metal; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2016.11.038
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: The electrodeposition behavior of Nd(III) in [P2225 ][TFSA] ionic liquid was investigated by EQCM. The electrodeposition of Nd(0) metal in [P2225 ][TFSA] ionic liquid was demonstrated from the CPE/EQCM. The EDX and XPS analyses of the electrodeposits were identified as a greater part of metallic neodymium. Abstract: The electrodeposition behavior of Nd(III) in an ionic liquid, triethyl-pentyl-phosphonium bis(trifluoromethyl-sulfonyl) amide ([P2225 ][TFSA]), was investigated on an electrochemical quartz crystal microbalance (EQCM) at elevated temperatures. Cyclic voltammetry with EQCM measurements of Nd(III) in [P2225 ][TFSA] at 363, 373 and 378 K were performed. A clear cathodic peak with increasing mass and decreasing ηρ (where η is the viscosity and ρ is the density) was observed at −2.79 V. Considering the results of our previous investigations, this peak indicated the reduction of Nd(III) to Nd(0) as [Nd (III) (TFSA)5 ] 2− + 3e − → Nd(0) + 5[TFSA] − . In addition, the apparent molar mass, M app, between −2.49 and −2.94 V calculated from the mass change was 140.4 g mol −1, which was close to the theoretical value for the electrodeposition reaction of Nd(III)/Nd(0), 144.2 g mol −1 . Moreover, controlled potential electrolysis with EQCM (CPE/EQCM) measurements at −3.20 V was performed for 0.05 and 0.10 M Nd(III) in [P2225 ][TFSA] at 373 K. The calculated M app values in 0.05 and 0.10 M Nd(III) in the initial stage of CPE/EQCM analysis were 147.3 and 148.8 g mol −1, respectively, which were close to the theoretical value for reduction of Nd(III) to Nd(0), 144.2 g mol −1 ; thus, electrodeposition of Nd(0) metal was also proved by the CPE/EQCM analysis. Furthermore, energy-dispersive X-ray and X-ray photoelectron spectroscopy analyses of the blackish electrodeposits obtained by the CPE/EQCM measurements were identified as primarily metallic neodymium because the Nd 3d5/2 spectrum was detected within 980.5–981.5 eV.