Study of Electron Transfer across the Liquid/Ice-like Matrix Interface by Scanning Electrochemical Microscopy
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- 作者：Zhiquan Zhang ; Jinyou Ye ; Peng Sun ; Yi Yuan ; Yuehong Tong ; Jiming Hu ; and Yuanhua Shao
- 刊名：Analytical Chemistry
- 出版年：2002
- 出版时间：April 1, 2002
- 年：2002
- 卷：74
- 期：7
- 页码：1530 - 1536
- 全文大小：104K
- 年卷期：v.74,no.7(April 1, 2002)
- ISSN：1520-6882
文摘
In this work, we report the findings of a study on scanningelectrochemical microscopy (SECM) to investigate theinterfacial electron-transfer (ET) reaction between the7,7,8,8-tetracyanoquinodimethane radical anion (TCNQ
-)in 1,2-dichloroethane and ferricyanide in an ice-likematrix (a mixture of insulting ice and conductive liquid)under low temperatures. Experimental results indicatethat the formed liquid/ice-like matrix interface is superficially similar in electrochemical characteristics to aliquid/liquid interface at temperatures above -20 
C.Furthermore, imaging data show that the surface of theice-like matrix is microscopically flat and physically stableand can be applied as either a conductive or an insultingsubstrate for SECM studies. Perchlorate ion was selectedas the common ion in both phases, the concentrations ofwhich controlled the interfacial potential difference. Theeffect of perchlorate concentration in the DCE phase oninterfacial reactions has been studied in detail. Theapparent heterogeneous rate constants for TCNQ- oxidation by Fe(CN)63- in another phase under different temperatures have been calculated by a best-fit analysis,where the experimental approach curves are comparedwith the theoretically derived relationships. Reaction ratedata obey Butler-Volmer formulation before and after thefreezing point, which is similar to most other known casesof ET reactions at liquid/liquid interfaces. However, thereis a sharp change observed for heterogeneous rate constants around the freezing point of the aqueous phase,which reflects the phase transition. At temperatures below-20 C, surface-confined voltammograms for the reduction of ferricyanide were obtained, and the ice-like matrixbecame an insulating one, which indicates that the aqueous phase is really a frozen phase.
-)in 1,2-dichloroethane and ferricyanide in an ice-likematrix (a mixture of insulting ice and conductive liquid)under low temperatures. Experimental results indicatethat the formed liquid/ice-like matrix interface is superficially similar in electrochemical characteristics to aliquid/liquid interface at temperatures above -20 C.Furthermore, imaging data show that the surface of theice-like matrix is microscopically flat and physically stableand can be applied as either a conductive or an insultingsubstrate for SECM studies. Perchlorate ion was selectedas the common ion in both phases, the concentrations ofwhich controlled the interfacial potential difference. Theeffect of perchlorate concentration in the DCE phase oninterfacial reactions has been studied in detail. Theapparent heterogeneous rate constants for TCNQ- oxidation by Fe(CN)63- in another phase under different temperatures have been calculated by a best-fit analysis,where the experimental approach curves are comparedwith the theoretically derived relationships. Reaction ratedata obey Butler-Volmer formulation before and after thefreezing point, which is similar to most other known casesof ET reactions at liquid/liquid interfaces. However, thereis a sharp change observed for heterogeneous rate constants around the freezing point of the aqueous phase,which reflects the phase transition. At temperatures below-20 C, surface-confined voltammograms for the reduction of ferricyanide were obtained, and the ice-like matrixbecame an insulating one, which indicates that the aqueous phase is really a frozen phase.