One-dimensional Pt nanofibers formed by the redox reaction at the ionic liquid|water interface

Abstract

Pt nanofibers have been prepared with a redox reaction occurring spacio-selectively at the liquid-liquid interface between a highly hydrophobic ionic liquid (IL) and water (W), which has been utilized as two dimensional reaction field. The preparation is conducted based on the concept of the coupling between ion transfer (IT) and electron transfer (ET) across the IL|W interface, which previously enabled direct formation of dendritic Au nanofibers at the IL|W interface (Chem. Commun., 2015, 51, 13638). The successful preparation of Pt nanofibers has manifested the generality of the IL|W interface method for the formation of metal nanofibers. Electrochemical measurements at the IL|W interface have confirmed that IT of PtCl4 2from W to IL is actually coupled with ET between PtCl4 2initially dissolved in W and decamethylferrocene in IL, leading to the spontaneous formation of Pt nanofibers at the IL|W interface. Herein, IT of PtCl4 2ions from W to IL not merely neutralizes the excess charges generated in each liquid phase by ET, but also provides PtCl4 2into IL as reactants for the growth of Pt nanofibers that takes place at the IL side of the IL|W interface. The electrocatalytic activity of the Pt nanofibers in oxygen reduction reaction (ORR) has also been evaluated.

Template-Free and Spontaneous Formation of Vertically Aligned Pd Nanofiber Arrays at the Liquid–Liquid Interface between Redox-Active Ionic Liquid and Water

“…52 In our previous studies, the L|L interfacial method by using the electrochemically polarizable IL|W interface was proved to be a valid strategy for the preparation of noble metal nanofibers. [53][54][55] Due to their designability, ILs can play multiple roles rather than just as a solvent. When ILs contain redox-active groups in the cation or anion, the IL itself can be the reducing agent for the metal precursor ions and the hydrophobic liquid constituting the RAIL and redox species dissolved in W. 56,57 However, up till now, there is no precedent report on the use of RAIL to prepare metal nanostructures at the RAIL|W interface.…”

“…S14) display that the midpoint potential (Emid) of the IT of FcMDDA 2+ is 290 mV more positive than that of PdCl4 2− (see Supporting Information for the detailed discussion).With the reaction proceeding, half of the generated FcMDDA 2+ remains inside the RAIL (eqn 4). They should have been gradually diffused to the RAIL bulk, which would result in the color change of RAIL just as W. However, the RAIL bulk of the IL|W interface,[53][54][55] the nanofibers in the Pd NFAs is only 8 micrometers in the length. The Au and Pt nanofibers can grow to such long length due to a favored IT of metal precursors (AuCl4 − and PtCl4 2− ) from W to the IL bulk, but the relatively short length of nanofibers in the Pd NFAs implies that the transfer of PdCl4 2from W to the RAIL bulk is restricted.…”

“…The IT of PdC4 2− from W to the FcMDDA 2+ enriched intermediate layer is facilitated by the strong electrostaticinteraction between the two divalent ions. The PdCl4 2− remained in W and transferred into the intermediate layer will be the reactants for growing Pd metal on the W side as particles and on the RAIL side as nanofibers, respectively, the latter of which is like the case of Pt nanofibers 55. At the second stage, when all of…”

Potential Dependence of the Ionic Structure at the Ionic Liquid/water Interface Studied Using MD Simulation

“…Ionic liquids (ILs) that are composed of hydrophobic ions are immiscible with water and form an IL-water (W) two-phase system. The IL-W two-phase system has promising applications in solvent extraction of ions, [1][2][3][4][5][6][7][8][9] nanomaterials synthesis, [10][11][12][13][14][15][16][17][18] and also in electrochemical devices such as ion-selective electrode, 19 lithium-ion battery, 20 and fuel cell. 21 In these applications the IL|W interface is an electrochemical reaction site where the ion and electron transfer reactions occur, and therefore, it is important to clarify the structure at the IL|W interface and its dependence on the interfacial potential difference.…”

Simultaneous Synthesis of One-and Two-Dimensional Gold Nanostructures/Reduced Graphene Oxide Composites in the Redox-Active Ionic Liquid/Water Interfacial System

“…The metal nanostructures formed at the IL|W interface are prevented from agglomeration, which is possibly due to the rigid multilayering structures formed by IL ions at the interface [64]. Moreover, the IL|W interfacial system provides two disparate growth environments towards W and IL for metal nanostructures and makes it possible to connect the two portions with different morphologies together with the joint at the IL|W interface [61]. When an IL contains a redox-active group with cations or anions, such as RAIL, it can act as a reducing agent for metal precursor and liquid substrate simultaneously in the RAIL|W interfacial system.…”