非恒稳含时电极过程中涨落-耗散的电化学效应——恒电势滴汞电极体系的随机热力学模型

以滴汞电极体系为模型,对非恒稳恒电势动态不可逆电极过程中的耗散-涨落效应进行了系统的研究.基于滴汞电极体系的电化学特征,提出了一个简化的含时随机热力学模型,从而可能对这类重要的含时物理化学过程进行涨落和耗散的定量分析.借助该简化的模型,成功地建立了恒电势滴汞电极过程的基本随机热力学公式,由此推出耗散-涨落效应的理论极谱曲线.在滴汞电极生长缓慢及扩散步骤严重滞后情况下,含时的滴汞电极过程将趋于在有效扩散层厚度演化的慢流型上的准定态过程.在这种准定态近似下,具体分析了涨落对极谱曲线的影响.结果表明,在涨落影响可以忽略的近平衡区,从耗散-涨落导出的极谱方程与从平衡态Nernst公式导出的极谱方程完全吻合.还计算了一个涨落诱导的极谱曲线偏离的典型范例.

Electrochemical Effect Induced by Fluctuations-dissipation of Time-dependent Electrode Processes--The Stochastic Model of Potentiostatic DME Systems

A stochastic theory of non-equilibrium thermodynamics of time-dependent potentiostatic D.M.E. processes was established in this paper. Based on a simplified stochastic model of non-steady state irreversible electrode processes the quantitative analysis of both the fluctuations and dissipation in this kind of important physico-chemical systems becomes possible. By means of it, we introduce successfully the basic stochastic formula of non-equilibrium thermodynamics of the potentiostatic DME(dropping mercury electrode) processes as well as a stochastic algorithm useful for theoretical deduction of the polarogram curve. Furthermore, in a limit case of the slow growth of the drop for the DME process with very hesitative diffusion steps(ΨEC→0) the polarogram equation induced by the fluctuations is derived under the quasi-steady state approximation. The result corroborates the polarogram equation from Nernst formula in the near equilibrium region. As a typical illustration, an example is given to calculate the deviation of polarogram curve induced by the fluctuations. Under the condition that the asymptotic form of probability distribution is established on the basis of the central limit theorem, the deviation of the current becomes the largest with the potential close to the half-wave potential. This means the fluctuations have great influence on the half-wave potential with very hesitative diffusion steps.