...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Study of the electrochemical reduction of dioxygen in acetonitrile in the presence of weak acids
【24h】

Study of the electrochemical reduction of dioxygen in acetonitrile in the presence of weak acids

机译：在弱酸存在下电化学还原乙腈中双氧的研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The electrochemical reduction of dioxygen has been studied in acetonitrile at glassy-carbon electrodes. The initial step is the reversible one-electron reduction to form superoxide. In the presence of hydrogen-bond donors (water, methanol, 2-propanol), the superoxide forms a complex with the donor resulting in a positive shift in the potential that can be analyzed to obtain formation constants for these complexes. Stronger acids result in protonation of the superoxide followed by reduction to produce HO2-. In the absence of hydrogen-bond donors, the reduction of superoxide occurs at very negative potentials, and this second reduction peak is very much drawn-out along the potential axis, indicating a small value of the transfer coefficient, alpha. The addition of hydrogen-bond donors, HA, brings about a positive shift in this peak, without a noticeable change in shape. The reaction occurring at the second peak is a concerted proton and electron transfer (CPET) in which the electron is transferred to superoxide and a proton is transferred from HA to the superoxide, forming HO2- and A(-) in a concerted process. An estimation of the standard potential for this reaction shows that the second reduction always occurs at a high driving force, which explains the small value of alpha that is observed. Consistent with a CPET, a kinetic isotope effect, HA versus DA, was detected for the three hydrogen-bond donors. The increasing positive shift of the second peak with increasing water concentration has been interpreted as being a consequence of the change in the formal potential, as water is both a reactant in the process and a participant through the hydrogen-bond stabilization of the anions.
机译：已经研究了乙腈在玻碳电极上的电化学还原方法。第一步是可逆的单电子还原形成超氧化物。在存在氢键供体（水，甲醇，2-丙醇）的情况下，超氧化物与供体形成配合物，导致电势发生正向偏移，可以分析该电位以获得这些配合物的形成常数。强酸会导致超氧化物质子化，然后还原生成HO2-。在没有氢键供体的情况下，超氧化物的还原在非常负的电势下发生，并且该第二还原峰沿电势轴非常大，表明转移系数α的值很小。氢键供体HA的添加使该峰发生正向移动，而形状没有明显变化。在第二个峰发生的反应是协调的质子和电子转移（CPET），其中电子转移到超氧化物，质子从HA转移到超氧化物，在协调过程中形成HO2-和A（-）。对该反应的标准电势的估计表明，第二还原总是在高驱动力下发生，这解释了所观察到的α值较小。与CPET一致，检测到三个氢键供体的动力学同位素效应HA对DA。第二峰随着水浓度的增加而增加的正位移已被解释为形式电位变化的结果，因为水既是过程中的反应物，又是阴离子的氢键稳定化参与者。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号