Electrochemical Behaviour and Chemical Species of Sm(II) in AlCl3‐NaCl with Different Lewis Acidity

• Published in: Chemistry : a European journal 2022-07, Vol.28 (42), p.e202200443-n/a
• Main Authors: Chen, Jiazhuang, Zhong, Yuke, Liu, Yalan, Zhang, Lei, Li, Mei, Han, Wei, Chai, Zhifang, Shi, Weiqun
• Format: Article
• Language: English
• Subjects: Absorption spectra; Acidity; Aluminum chloride; Chemical speciation; Chemistry; coordination modes; Diffusion; Diffusion coefficient; Electrochemical analysis; Electrochemistry; in situ electron absorption spectroscopy; lanthanides; Lewis acidity melt; Melting point; Melting points; Oxidation; Samarium; Sodium chloride
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202200443

AlCl3‐NaCl was utilized as an electrolyte in this work due to its low melting point and Lewis acidity, in which samarium exists in two oxidation states, Sm(III) and Sm(II), resulting in unique electrochemical behaviours. Sm metal dissolves in AlCl3‐NaCl melt to form SmCl2, which is verified by electrochemical and spectroscopic techniques. As the Lewis acidity of the melt increases, the diffusion coefficient of Sm(II) gradually increases, and the activation energy of diffusion decreases. Moreover, an additional co‐reduction peak of Sm3+ and AlCl4− is observed to be more positive than that of Al(0)/Al(III) in Lewis basic melt, which may be tightly correlated with the variation of Sm(II) coordination in AlCl3‐NaCl melt and ligand variation from Cl− to AlCl4− and Al2Cl7− as the Lewis acidity of the AlCl3‐NaCl melt increases, according to the in situ electronic absorption spectra of Sm in this melt. Sm(II) diffuses faster with the increase of Lewis acidity of AlCl3‐NaCl, which is due to the different coordination circumstance of Sm(II). With the Lewis acidity increase, the anions involved in Sm(II) complexation gradually range from Cl− to AlCl4− and Al2Cl7−. The difference of complex structure is also reflected in the in situ UV‐Vis absorption spectrum.