Morphology and adsorbate dependence of ionic transport in dye sensitized mesoporous TiO2 films
Morphology and adsorbate dependence of ionic transport in dye sensitized mesoporous TiO2 films
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DOI：
10.1021/jp980819n
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发表时间：
1998-05-21
影响因子：
3.3
通讯作者：
Grätzel, M
中科院分区：
文献类型：
--
作者：
Papageorgiou, N;Barbé, C;Grätzel, M
通过模拟电化学不活跃的介孔胶体薄膜的薄层电池结构中的稳态传质，可以预测含碘电解液的极限电流作为薄膜孔隙率的函数。然后，在给定实验确定的极限电流的情况下，通过模型中孔隙率参数的最佳拟合来确定层的孔隙率。孔隙度与BET测量结果吻合较好。在光电化学电池的应用中，如用于太阳能转换装置的染料敏化纳米晶光电极，锐钛矿型二氧化钛等染料负载薄膜的孔隙率对其效率起着至关重要的作用。特别是，这项工作的结果表明，吸附敏化剂顺式-(SCN-)(2)双(2，2‘-联吡啶-4，4’-二羧酸)Ru(II)的存在似乎降低了原始裸膜孔隙率高达30%。这取决于初始裸膜孔隙率和染料直径，从而导致涂层膜内的有效传质极限相当低。三碘化合物在这些多孔电极中的有效扩散系数相对于自由流值并没有明显偏离，这表明介孔对所涉及的传输机制有影响。
By modeling the steady-state mass transport in a thin-layer cell configuration involving an electrochemically inactive mesoporous colloidal film, the limiting currents of an iodine containing electrolyte can be predicted, as a function of the film porosity. The porosity of the layer is then determined by best fit of the porosity parameter in the model, given the experimentally determined limiting currents. Satisfactory agreement is found with the porosity values obtained by BET measurements. In photoelectrochemical cell applications such as dye sensitized nanocrystalline photoelectrodes for solar energy conversion devices, the porosities of the dye loaded films of e.g. anatase TiO2 play an essential role with respect to their efficiency. In particular, the findings of this work demonstrate that the presence of adsorbed sensitizer cis-(SCN-)(2) bis(2,2'-bipyridyl- 4,4'-dicarboxylate)ruthenium(II) in TiO2 colloidal films appears to decrease the original naked film porosity by up to 30%. This depends on the initial bare film porosity and the dye diameter, thus resulting in a considerably lower effective mass-transport limit within the coated films. The effective diffusion coefficient of triiodide in these porous electrodes was found to not deviate significantly with respect to the free-stream values, suggesting an influence of mesoporosity on the transport mechanisms involved.