The Role of Additives in the Electroreduction of Sodium Ions in Chloroaluminate-Based Ionic Liquids

Abstract

Ionic liquids are an ionically conductive medium that can provide a wide potential window for the study of electrochemical processes. We have observed that the degree of ionization of the ions depends on the charge density of the ions with significant ion pairing possible. Previously, it was shown that sodium ions can be reduced only to sodium metal if an acidic additive ͑e.g., SOCl 2) is added to the liquid. It is shown here that the additive increases the degree of dissociation of the Na ϩ from its counterion in the liquid, making it available for electrodeposition. The observed increase in ionic conductivity provided by the SOCl 2 supports this proposed mechanism. It is believed that the additive coordinates with chloride in the liquid, to provide greater freedom for the Na ϩ ion. In addition, conditions were found for the reduction of sodium ions to sodium metal without the use of an additive.

Microwave Irradiation for the Facile Synthesis of Transition‐Metal Nanoparticles (NPs) in Ionic Liquids (ILs) from Metal–Carbonyl Precursors and Ru‐, Rh‐, and Ir‐NP/IL Dispersions as Biphasic Liquid–Liquid Hydrogenation Nanocatalysts for Cyclohexene

“…[1] The controlled and reproducible synthesis of defined and stable M-NPs is very important for a range of applications. [2][3][4][5][6][7] M-NPs can be synthesized in ionic liquids (ILs) [8] through chemical reduction [9][10][11][12][13] or decomposition [14] of metal salts or metal complexes, and by means of photochemical [15,16] or electroreduction, [17][18][19] without the need of extra stabilizing molecules or organic solvents. [20][21][22] Recently, we communicated the preparation of transition-metal nanoparticles by thermal decomposition of metal carbonyls in ILs.…”

Synthesis of Co, Rh and Ir nanoparticles from metal carbonyls in ionic liquids and their use as biphasic liquid–liquid hydrogenation nanocatalysts for cyclohexene

“…The controlled and reproducible synthesis of defined and stable metal nanoparticles (MNPs) is of very high importance for different fields of applications [5][6][7][8][9][10]. Metal nanoparticle syntheses in ionic liquids (ILs) are carried out through the reduction [11][12][13][14] or decomposition [15] of metal salts or metal complexes, photochemical [16,17] or electro-reduction [18][19][20], and recently also by thermal and photochemical decomposition of metal carbonyls [21][22][23].…”

DOE STI Product/Final Report Number 3 Electrochemical Investigation of Novel Electrolytes for Ambient Temperature Sodium Batteries

“…Thionyl chloride (SOCl 2 ) has been shown to increase the conductivity by increasing the degree of dissociation of the Li + and Na + from their counter-ions allowing electrodeposition to occur. 34 The ~10% increase in the conductivity of the Na-only melt (and little change in the Li-only melt)…”

“…Salts I, II, VI, VIII, and IX ( Conductivity measurements were performed using a custom-built probe and ThermoOrion conductivity meter. 34 Two platinum plates were set a fixed distance apart and the corners were sealed in glass to prevent bending or movement of the plates.…”

“…23,24,42 It was proposed that Na + ions coordinate with AlCl 4 -in the ILs and the SOCl 2 serves to weaken this coordination, freeing Na + ions for reduction to the metal. 34 In this work, PCl 5 , a weaker Lewis acid than aluminum chloride, was added to a neutralized N = 0.55 BME IL. Initially, the liquid was stirred at room temperature for a day prior to performing CV tests and only the irreversible reduction of the cation was observed, similar to when no additive was present.…”