含义Meaning
电极反应的电流密度与过电势的关系：阳极、阴极两个方向的速率都随电势指数变化，净电流为二者之差。交换电流密度 j₀ 衡量电极反应本身的快慢（催化活性）。
Electrode current density versus overpotential: anodic and cathodic rates each vary exponentially with potential, and the net current is their difference. The exchange current density j₀ measures intrinsic electrode kinetics (catalytic activity).
符号说明Symbols
| 符号Symbol | 含义 Meaning | 单位 Unit |
|---|---|---|
| \(j_0\) | 交换电流密度exchange current density | A·m⁻² |
| \(\alpha_a, \alpha_c\) | 阳极、阴极传递系数（单电子步 α_a + α_c = 1，常约 0.5）anodic and cathodic transfer coefficients (sum 1 for a one-electron step, often ≈0.5) | 1 |
| \(\eta\) | 过电势overpotential | V |
推导Derivation
按过渡态理论，施加电势使电子转移活化能改变 \(\mp\alpha F\eta\)。
By transition-state theory, potential shifts the activation energy by ∓αFη.
阳极电流 \(j_a = j_0e^{\alpha_aF\eta/RT}\)，阴极 \(j_c = j_0e^{-\alpha_cF\eta/RT}\)；η = 0 时二者相等（= j₀），净电流为零。
Anodic and cathodic currents balance at η = 0.
净电流 \(j = j_a - j_c\)；小 η 时线性化，大 η 时一项可忽略得塔费尔式。
Net current; linear at small η, Tafel at large η.
适用条件与局限Assumptions & limitations
假设无传质限制（电极表面浓度 = 本体浓度）；电流大时出现极限扩散电流。
Assumes no mass-transport limitation; limiting currents appear at high rates.
多电子、多步反应需按决速步修正传递系数。
Multistep reactions need adjusted coefficients.