基本概念梳理
- $E_o$, the standard equilibrium potential (or standard electrode potential), is defined as the equilibrium potential of an electrode reaction when all components are in their standard states, measured against the standard hydrogen electrode (SHE).
标准电极电位是反应处在标准状态下(298K,所有离子的浓度都是1mol/L)，的平衡电位，其数值可在标准电位表中查出，也可以根据热力学上的数据自行运算。
eg：在腐蚀电化学原理(曹楚南)一书中，常见金属相对于H电极的标准平衡电位是：
| 反应 | SHE(V) |
|---|---|
| $Li$=$Li^+$+$e^-$ | -3.024 |
| Ca=Ca^2+^+2e^-^ | -2.87 |
| Mg=Mg^2+^+2e^-^ | -2.34 |
| Al=Al^3+^+3e^-^ | -1.67 |
| Zn=Zn^2+^+2e^-^ | -0.762 |
自己计算的方法如下，首先在德国爱德华久保热力学和物质动力学基金会找到对应离子的化学势；
网站的数据遵循标准：(1)在标准状态下 (T = 298 K, p = 101,3 kPa)，(2)在溶液标准浓度下 (1000 mol/m3)，(3)处于理想状态下，没有分子间相互作用的气体或溶解物质，(4)由元素的天然同位素组成的所有物质。
单位μ代表kJ/mol，1 eV/atom = 96.49 kJ/mol，网站中“,”代表小数点
| 元素 | 网站数据(μ) | ev/atom | 计算平衡电位 |
|---|---|---|---|
| Li^+^ | -293.80 | -3.0449 | -3.0449 |
| Ca^2+^ | -553.04 | -5.7316 | -2.8658 |
| Mg^2+^ | -456.01 | 4.726 | -2.363 |
| Al^3+^ | -485.34 | -5.03 | -1.6767 |
| Zn^2+^ | -147.03 | -1.5238 | -0.7619 |
- $E_e$,equilibrium potential of an electrode, 平衡电极电位。大多数时候，反应都无法在标准状态下进行。由于此时离子浓度较标准状态下发生变化，平衡随之移动，平衡电位也会相继发生改变。
- 反应的氧化态和还原态，注意能斯特方程的浓度方法，+氧化态在上面的浓度
Oxidised State + ne- ⇌ Reduced State
能斯特方程
The Nernst equation links the equilibrium potential of an electrode, Ee, to its standard potential(standard equilibium potential), E0, and the concentrations or pressures of the reacting components at a given temperature. It describes the value of Ee for a given reaction as a function of the concentrations (or pressures) of all participating chemical species.
In its most fundamental forms, the Nernst equation for an electrode is written as:
$E_e$=$E_0$+$\frac{RT}{zF}ln\frac{[Oxidised]}{[Reduced]}$
or
$E_e$=$E_0$+$\frac{2.303RT}{zF}log\frac{[Oxidised]}{[Reduced]}$
or
$E_e$=$E_0$+$\frac{2.303$k_b$T}{ze}log\frac{[Oxidised]}{[Reduced]}$
[Click here for a full derivation of Nernst equation – popup]
R is the universal gas constant (8.3145 J K-1 mol-1)
T is the absolute temperature
z is the number of moles of electrons involved in the reaction as written
F is the Faraday constant (96 485 C per mole of electrons)
The notation [reduced] represents the product of the concentrations (or pressures where gases are involved) of all the species that appear on the reduced side of the electrode reaction, raised to the power of their stoichiometric coefficients. The notation [oxidised] represents the same for the oxidised side of the electrode reaction.
Explanation of Activity