Cyclic Voltammetric Diagnostics for Inert, Uniform Density Films
Cyclic Voltammetric Diagnostics for Inert, Uniform Density Films
复制标题
惰性均匀密度薄膜的循环伏安诊断
DOI：
10.1149/2.025306jes
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发表时间：
2013
影响因子：
3.9
通讯作者：
Leddy, Johna
中科院分区：
文献类型：
--
作者：
Knoche, Krysti L.;Hettige, Chaminda;Moberg, Paul D.;Amarasinghe, Sudath;Leddy, Johna
电极上均匀密度、电化学惰性薄膜的定量表征是通过氧化还原探针的循环伏安法（CV）来实现的，该探针将电解质分配到薄膜中。电化学惰性薄膜在探针的伏安窗口中不产生法拉第电流。在仿真模型中，探针在薄膜中预平衡，在电极处电解，在薄膜和溶液中扩散，并跨薄膜溶液界面提取。膜厚为ℓ。扩散长度 δ 近似于伏安法扰乱探针浓度的电极的距离；扫描速率 ν 为 δ∝ ν− 1/2。在高 ν 时，δ< ℓ 和伏安形态是半无限线性扩散的典型特征。随着 ν 变慢，δ≳ ℓ 和 CV 形态会随着薄膜和溶液中相对探针通量的变化而变化。对于更高的溶液通量，伏安图呈现 S 形（S 形）特征；较高的膜通量会产生高斯（薄层 CV）特性。对于薄膜和溶液扩散系数 D f 和 D s 以及 κ（薄膜中探针浓度与溶液的平衡比），诊断结果为 κ√(D f/D s) 和 ℓ 2/D f。由于诊断适用于所有 ν，因此影片仅通过 CV 即可完全参数化。如果没有这些诊断，完整的表征需要第二次稳态伏安测量。使用 Nafion 和聚（苯乙烯磺酸盐）惰性聚合物薄膜中的 [Ru (bpy) 3] 2+（探针）对诊断进行审查。
Quantitative characterization of uniform density, electrochemically inert films on electrodes is achieved by cyclic voltammetry (CV) of a redox probe that partitions from electrolyte into the film. Electrochemically inert films generate no faradaic current in the voltammetric window of the probe. In simulation models, probes pre-equilibrate into films, electrolyze at electrodes, diffuse in film and solution, and extract across film solution interfaces. Film thickness is ℓ. Diffusion length δ approximates distance from the electrode where voltammetry perturbs probe concentration; δ∝ ν− 1/2 for scan rate ν. At high ν, δ< ℓ and voltammetric morphologies are typical of semi-infinite linear diffusion. As ν slows, δ≳ ℓ and CV morphologies can change with relative probe flux in the film and solution. For higher solution flux, voltammograms assume sigmoidal (S-shaped) characteristics; higher film flux generates gaussian (thin layer CV) characteristics. For film and solution diffusion coefficients D f and D s and κ the equilibrium ratio of probe concentration in film to solution, diagnostics yield κ√(D f/D s) and ℓ 2/D f. Because diagnostics apply for all ν, films are fully parameterized by CV alone. Without these diagnostics, full characterization requires a second, steady state voltammetric measurement. Diagnostics are vetted with [Ru (bpy) 3] 2+(probe) in inert polymer films of Nafion and of poly (styrenesulfonate).