Electrochemical processes at a flowing organic solventaqueous electrolyte phase boundary

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• 作者：Stuart M. MacDonald ; John D. Watkins ; Yunfeng Gu ; Kamran Yunus ; Adrian C. Fisher ; Galyna Shul ; Marcin Opallo ; Frank Marken
• 关键词：Phase transfer catalysis ; Electrochemistry ; Microfluidic ; Phase boundary ; Hydrodynamic ; n-Butylferrocene ; Ion extraction ; Electrosynthesis
• 刊名：Electrochemistry Communications
• 出版年：2007
• 期刊代码：29_13882481
• 类别：ch
• 出版时间：August 2007
• 卷：9
• 期：8
• 页码：2105-2110
• 文件大小：414 K

摘要

A microfluidic double channel device was employed to study reactions at a flowing liquidc="http://www.sciencedirect.com/scidirimg/entities/2223.gif" alt="mid" border=0>liquid interface in contact with a gold electrode. The rectangular flow cell was calibrated for both single phase liquid flow and biphasic liquidc="http://www.sciencedirect.com/scidirimg/entities/2223.gif" alt="mid" border=0>liquid flow for the case of the immiscible N-octyl-2-pyrrolidone (NOP)c="http://www.sciencedirect.com/scidirimg/entities/2223.gif" alt="mid" border=0>aqueous electrolyte system. The influence of flow direction and speed and liquid viscosity on the position of the phase boundary was examined.

The cience?_ob=MathURL&_method=retrieve&_udi=B6VP5-4NXRMP2-B&_mathId=mml6&_user=10&_cdi=6197&_rdoc=48&_acct=C000050221&_version=1&_userid=10&md5=f3adeb4f3463cb192411aa467b024417">c="http://www.sciencedirect.com/cache/MiamiImageURL/B6VP5-4NXRMP2-B-D/0?wchp=dGLzVlz-zSkWb" alt="Click to view the MathML source" align="absbottom" border="0" height=22 width=102> redox system was employed in aqueous solution to calibrate the flow cell in the absence and in the presence of the organic NOP phase. A significant ȁc;undercutting” of the organic phase into the aqueous phase was observed in particular for shorter gold band electrodes. The triple phase boundary reaction zone was visualized with a colour reaction based on the oxidation of N-benzylaniline. An approximate expression can be given to predict the mass transport controlled limiting currents even under two-phase flow conditions. Next, n-butylferrocene in NOP (without intentionally added electrolyte) was employed as the organic redox system with 0.1 M NaClO₄ as the adjacent aqueous electrolyte phase. Under these conditions the electrochemical reaction only proceeded at the organic liquidc="http://www.sciencedirect.com/scidirimg/entities/2223.gif" alt="mid" border=0>aqueous liquidc="http://www.sciencedirect.com/scidirimg/entities/2223.gif" alt="mid" border=0>solid electrode triple phase boundary reaction zone and significant currents were observed. In contrast to the processes at conventional liquidc="http://www.sciencedirect.com/scidirimg/entities/2223.gif" alt="mid" border=0>electrode interfaces, these currents decreased with an increasing flow rate. The level of conversion at the triple phase boundary reaction zone can be further enhanced (i) at sufficiently slow flow rates and (ii) at larger electrodes. Bulk electrosynthetic processes are feasible, but the reactor design has to be further improved.