北京大学电剖析电化学反应动力学.ppt

Ent ire excess charge density as-q in solution distributed on OHP (b) CAPACITOR OHP +⊕⊕⊕ Electritied Interface consists of Excess charg two layers of chorge- Double layer (a)a doub/e layer, a simple hypothetical type of electrified interface in which a layer of ions on the ohP constitutes the entire ex- cess charge gs in the solution The solvation sheaths of these ions and the first row of water molecules on the electrode are not shown in the diagram. (b The electrical equivalent of such a double layer is a par- allel-plate condense  Benzene Wat NaCl Nacl Solutionl olution i etol HHH Membrane Oriented dipole Some exampl electrified interface Double lavers are characteristic of all phase boundaries IV, Inm, the field strength(gradient of potential) is enormous-it is of the order 107 V/cm. The effect of this enormous field at the electrode electrolyte interface is, in a sense, the essence of electrochemistry!  电极 电极溶 溶剂分子 +○ ++++ 阴离子 阳高子 特性吸附离 HP 0 IHP OHP Helmholtz Gouy-Chapman Helmholtz Gouy-Chapman 图 Grahame双电层模型 a)无特性吸附时ψ为正值的示意图(b)有特性吸附时为负值的示意图  Helmholtz内层 (HP, inner Helmholtz plane 和 Helmholtz外 层(OHP, outer Helmholtz plane 0, 从此图可得到一个具体 的双电层大小的概念 双电层中的紧密屡厚度 大约是3A.分散层约 8A.个双电层约11A 或稍大于11A。 这虽是汞/溶液界面情况 汞/Nc(03molL)界面双电层电位分布图 其它电极的双电层尺寸 也大政如此。  Chapter Four Fundamentals of Kinetics and mechanism of Electrode reactions Introduction The mechanism of electron transfer at an electrode 2345 The theory of electrode reaction The relation between current and over potential Microscopic interpretation of electron transfer and Marcus theory  电化学反应动力学 问题 电极的电子结构对电化学反应有什么影响? 电化学反应速率和电极电位有什么关系? Ox + ne Rd (4.1) (异相氧化还原反应) 4.1,导言 在此仅介绍没有化学键形成或断开的电极反应,即简电子 转移反应( Outer- Sphere electron Transfer),并且仅涉及 步骤 电子反应  Homogenous Electran Transfer Outer-sphere Ca(NHs i+Cr(bpy3-CONHa+ Cr(bpy)3 nner -spherA Go(NH3i3 CP*+ Cr(H2O)6*-(NH3i Co CI Cr(H2O)9 Heterogeneous Electron Transfer nnar-sphere M M E