Formation of super-concentrated hydrochloric acid in the third phase in tertiary amine N235-PtCl_6^(2-)-HCl system and its influences on the Pt microemulsion extraction

In this paper,we have investigated the formation of the third-phase in tertiary amine(N235)-PtCl62--HCl system and the microscopic phase structural evolution of platinum-loaded organic phases before and after the occurrence of the third-phase.The third-phase is characterized by various spectroscopic techniques,and the small angle X-ray scattering(SAXS) experiments demonstrate the appearance of nano-aggregates,i.e.,water-in-oil reversed micelles,in the third phase.The experimental results indicate that(1) formation of the third phase is related to the aggregation behaviors of nano-reversed micelles in which a super-concentrated hydrochloric acid formed with the H+ to H2O molar ratio being much higher than that of the conventional 37 wt% saturated hydrochloric acid.(2) The occurrence of the super-concentrated HCl results in a great amount of H+ and Cl-ions enriched and confined within the nano-water pools of W/O reversed micelles in third phase.Therefore,the coordination behaviors of platinum complex ions in that super-concentrated hydrochloric acid are very different from their corresponding behaviors in bulk aqueous solutions.It is possible that H+ ions participate in the formation of such complexes as HmPtCl6z+ in the super-concentrated hydrochloric acid.(3) The relative contents of various HmPtCl6z+ complexes are different corresponding to the H+ ion concentrations in confined nanowater pools.The association ability of the acidified tertiary amine N235 molecules(R3NH+) with various HmPtCl6z+ complexes plays an important role in affecting the platinum extraction behaviors.

Effects of water on the structure and transport properties of room temperature ionic liquids and concentrated electrolyte solutions

Transport properties and the associated structural heterogeneity of room temperature aqueous ionic liquids and especially of super-concentrated electrolyte aqueous solutions have received increasing attention,due to their potential application in ionic battery.This paper briefly reviews the results reported mainly since 2010 about the liquid-liquid separation,aggregation of polar and apolar domains in neat RTILs,and solvent clusters and 3D networks chiefly constructed by anions in super-concentrated electrolyte solutions.At the same time,the dominating effect of desolvation process of metal ions at electrode/electrolyte interface upon the transport of metal ions is stressed.This paper also presents the current understanding of how water affects the anion-cation interaction,structural heterogeneities,the structure of primary coordination sheath of metal ions and consequently their transport properties in free water-poor electrolytes.

Uncovering the critical impact of the solid electrolyte interphase structure on the interfacial stability

Solid electrolyte interphase(SEI)plays a critical role in determining the interfacial stability,which in turn impacts the plating/stripping process of the lithium metal anode.Substantial research has been focused on the composition of SEI and its contribution to the interfacial stability.Herein,we illustrate the significance of SEI structure,in a comprehensive comparison of a diluted electrolyte(1 M LiTFSI-PC)and a super-concentrated electrolyte(8 M LiTFSI-PC).Illustrated by in situ optical and atomic force microscope observation,homogeneous plating on lithium anode is achieved in the concentrated electrolyte.However,x-ray photoelectron spectroscopy and molecular dynamics simulations reveal that,contrary to the general understanding,the components of SEI is nearly identical for lithium anode cycled in both two electrolytes.Detailed characterizations demonstrate the structure of SEI is quite different.In concentrated electrolyte,a compact structure of SEI layer can be obtained,mainly due to the reduced solubility and outstanding formation kinetics of the interfacial layer.This work provided a new understanding to the excellent performance of super-concentrated electrolyte in lithium metal battery.