Exploring the mechanisms and interfacial processes of metal electrodeposition

Electrodeposition;Magnesium

Spatney, Russell Leonard ; Gewirth ; Andrew A.

关键词: Electrodeposition;    Magnesium;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/89053/SPATNEY-THESIS-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Electrodeposition of multivalent metal cations in nonaqueous solvents is ultimatelymore difficult compared to aqueous systems. This is due to lower conductivity and a smallerlibrary of soluble electrolytes. In many cases, synthesis procedures are required to obtainfunctional electrolytes. Comparison of these systems to aqueous counterparts is therefore verychallenging. In some cases, the solvent itself can be used as another platform for side reactionsto occur. Magnesium organohaloaluminate electrolytes in a THF solvent oxidize the solvent toγ-butryolactone (GBL). This conversion slowly degrades the active electrolyte and causes filmsof organic matter to build on the electrode surface as the magnesium metal is deposited andredissolved over several cycles. A decrease in the reported coulombic efficiency (i.e. theamount of charge removed from the surface to the amount deposited) is also observed for bothorganohaloaluminates studied. In conjunction, the mass removed to the mass deposited isalways above 90% efficient. This suggests that uncharged mass is consistently deposited alongwith magnesium in later cycles. Given this, the stability and lifetime of theorganohaloaluminates is lower than previously reported.When electrodepositing other multivalent cations such as copper or zinc, informationregarding the general mechanism of the nucleation and growth can be gleaned by observingchronoamperometric data at early times in a potential step experiment. When observed in anaqueous environment, copper metal in a CuSO4 electrolyte deposits according to aninstantaneous model at pH 3 and a progressive model at pH 1. In a nonaqueous environment, asimilar system of CuCl2 shows instantaneous nucleation behavior. A direct comparison is not available due to the insolubility of CuSO4 in acetonitrile and copper deposition in water using CuCl2 is too quick to be observed.