(471a) Electric Double Layer in the Electrodeposition of Aluminium from Ionic Liquids

Electric
Double Layer in the Electrodeposition of Aluminium from Ionic Liquids

Yong Zheng, Yongjun Zheng, Huichao Lv, Dayong Tian,
Yinyin Liu

(College of Chemical
and Environmental Engineering, Anyang Institute of Technology, Anyang 455000,
Henan, China)

Since the end of 19th
century, the production of aluminium has been mainly
conducted by the Hall-Heroult
electrolytic process. However, this method suffers from many problems,
including high operating temperature, high energy consumption and high CO₂
emission. Therefore,
it's necessary to develop new methods for the low-temperature and low-energy
electrolysis of aluminium. Ionic liquids (ILs) are
labeled as room-temperature molten salts, which have a bright prospect in this field[1, 2]. During the electrolysis, electric double layer
of electrode interface/IL plays an important role in the formation and morphology
of aluminium deposits.

From above background,
this work mainly focuses on the composition and structure of electric double
layer formed in some typical chloroaluminate ILs,
such as [Emim]Cl/AlCl₃
(1-ethyl-3-methylimidazolium chloroaluminate), [Bmim]Cl/AlCl₃ (1-butyl-3-methylimidazolium
chloroaluminate) and [Amim]Cl/AlCl₃ (1-allyl-3-methylimidazolium chloroaluminate). Firstly, systematic measurements of cyclic
voltammetry, chronoamperometry
and impedance spectroscopy were performed to get a deeper insight into the
electrochemical behavior of these ILs. On the basis of density functional
theory calculations, the effect of ILs' composition, structure and cation-anion interaction on the electric double layer was
analyzed. Experimental results show that the polarity and alkyl chain of imidazolium cation, as well as
interaction energy between ions is key to aluminium electrodeposition
process.

Figure 1 Electrochemical
impedance spectroscopy of Pt electrode in Lewis acidic [Emim]Cl/AlCl₃

References:

[1] Giridhar P., Zein El Abedin S., Endres F. Electrochim. Acta, 2012, 70: 210-214.

[2] Armand
M., Endres F., MacFarlane D R., et al. Nat. Mater.,
2009, 8: 621-629.

Acknowledgements: This
work was supported by the National Natural Science Foundation of China (No.21406002),
Government Decision-making Subject of Henan Province (No.2014351) and
Doctoral
Scientific Research Foundation of Anyang Institute of Technology.