Hamann Thomas W, Gstrein Florian, Brunschwig Bruce S, Lewis Nathan S
Division of Chemistry and Chemical Engineering, 210 Noyes Laboratory, 127-72, California Institute of Technology, Pasadena, California 91125, USA.
J Am Chem Soc. 2005 Oct 12;127(40):13949-54. doi: 10.1021/ja0515452.
The interfacial energetic and kinetics behavior of n-ZnO/H2O contacts have been determined for a series of compounds, cobalt trisbipyridine (Co(bpy)3(3+/2+)), ruthenium pentaamine pyridine (Ru(NH3)5 py(3+/2+)), cobalt bis-1,4,7-trithiacyclononane (Co(TTCN)2(3+/2+)), and osmium bis-dimethyl bipyridine bis-imidazole (Os(Me2bpy)2(Im)2(3+/2+)), which have similar formal reduction potentials yet which have reorganization energies that span approximately 1 eV. Differential capacitance vs potential and current density vs potential measurements were used to measure the interfacial electron-transfer rate constants for this series of one-electron outer-sphere redox couples. Each interface displayed a first-order dependence on the concentration of redox acceptor species and a first-order dependence on the concentration of electrons in the conduction band at the semiconductor surface, in accord with expectations for the ideal model of a semiconductor/liquid contact. Rate constants varied from 1 x 10(-19) to 6 x 10(-17) cm4 s(-1). The interfacial electron-transfer rate constant decreased as the reorganization energy, lambda, of the acceptor species increased, and a plot of the logarithm of the electron-transfer rate constant vs (lambda + deltaG(o)')(2)/4lambda k(B)T (where deltaG(o)' is the driving force for interfacial charge transfer) was linear with a slope of approximately -1. The rate constant at optimal exoergicity was found to be approximately 5 x 10(-17) cm4 s(-1) for this system. These results show that interfacial electron-transfer rate constants at semiconductor electrodes are in good agreement with the predictions of a Marcus-type model of interfacial electron-transfer reactions.
已针对一系列化合物测定了n-ZnO/H₂O接触的界面能量和动力学行为，这些化合物包括三（联吡啶）钴（Co(bpy)₃(3⁺/2⁺)）、五氨吡啶钌（Ru(NH₃)₅py(3⁺/2⁺)）、双（1,4,7-三硫杂环壬烷）钴（Co(TTCN)₂(3⁺/2⁺)）和双（二甲基联吡啶）双咪唑锇（Os(Me₂bpy)₂(Im)₂(3⁺/2⁺)），它们具有相似的形式还原电位，但重组能跨度约为1电子伏特。利用微分电容对电位和电流密度对电位的测量来测定这一系列单电子外层球型氧化还原对的界面电子转移速率常数。每个界面都表现出对氧化还原受体物种浓度的一级依赖性以及对半导体表面导带中电子浓度的一级依赖性，这与半导体/液体接触的理想模型预期相符。速率常数在1×10⁻¹⁹至6×10⁻¹⁷cm⁴ s⁻¹之间变化。随着受体物种的重组能λ增加，界面电子转移速率常数降低，并且电子转移速率常数的对数对(λ + ΔG⁰')²/4λk₈T（其中ΔG⁰'是界面电荷转移的驱动力）的作图呈线性，斜率约为 -1。对于该系统，发现最佳放能性下的速率常数约为5×10⁻¹⁷cm⁴ s⁻¹。这些结果表明，半导体电极处的界面电子转移速率常数与界面电子转移反应的Marcus型模型的预测高度吻合。
