Unraveling the charge transfer/electron transport in mesoporous semiconductive TiO2 films by voltabsorptometry.
Unraveling the charge transfer/electron transport in mesoporous semiconductive TiO2 films by voltabsorptometry.
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通过伏吸光度法揭示介孔半导体 TiO2 薄膜中的电荷转移/电子传输。
DOI：
10.1039/c5cp00023h
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
B. Limoges
中科院分区：
文献类型：
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作者：
C. Renault;L. Nicole;C. Sanchez;C. Costentin;V. Balland;B. Limoges
在这项工作中，我们证明，计时光阻法，更具体地说，循环伏安法是特别适合的技术，用于获得一个全面的了解的动态电子转移/电荷传输在一个透明的介孔金属氧化物膜内装载有氧化还原活性染料。这是说明与两个不同的血红素为基础的氧化还原探针吸附在高度有序的介孔TiO 2薄膜（蒸发诱导自组装，EISA制备）的光谱电化学响应的定量分析。在有限线性扩散-反应模型的基础上，建立了极限情况下的解析表达式，定量地分析、预测和解释了吸附的氧化还原物种的异常伏安响应与施加在膜上的电势的函数关系（即，作为从绝缘状态到导电状态的转变的函数，反之亦然）。特别是，我们能够准确地确定吸附的氧化还原物种和多孔半导体之间的界面电荷转移速率。另一个重要的和意想不到的发现，推断从伏安图，是一个界面电子转移过程主要由扩展的导带态的EISA TiO 2膜，而不是由本地化的陷阱在带隙。这是一个显著的结果，与先前观察到的由随机烧结的TiO 2纳米颗粒形成的染料敏化太阳能电池的结果形成对比，这种行为归因于EISA TiO 2中局部表面态的密度特别低。本方法还提供了一个独特的和简单的访问激活驱动力的关系，根据马库斯理论，从而打开新的机会，不仅调查染料敏化太阳能电池中的电子复合动力学的驱动力的影响，但也研究电子转移/传输机制相结合的纳米结构的半导体电极和异质性氧化还原活性催化剂的异质性光电催化系统。
In this work, we demonstrate that chronoabsorptometry and more specifically cyclic voltabsorptometry are particularly well suited techniques for acquiring a comprehensive understanding of the dynamics of electron transfer/charge transport within a transparent mesoporous semiconductive metal oxide film loaded with a redox-active dye. This is illustrated with the quantitative analysis of the spectroelectrochemical responses of two distinct heme-based redox probes adsorbed in highly-ordered mesoporous TiO2 thin films (prepared from evaporation-induced self-assembly, EISA). On the basis of a finite linear diffusion-reaction model as well as the establishment of the analytical expressions governing the limiting cases, it was possible to quantitatively analyse, predict and interpret the unusual voltabsorptometric responses of the adsorbed redox species as a function of the potential applied to the semiconductive film (i.e., as a function of the transition from an insulating to a conductive state or vice versa). In particular, we were able to accurately determine the interfacial charge transfer rates between the adsorbed redox species and the porous semiconductor. Another important and unexpected finding, inferred from the voltabsorptograms, is an interfacial electron transfer process predominantly governed by the extended conduction band states of the EISA TiO2 film and not by the localized traps in the bandgap. This is a significant result that contrasts those previously observed for dye-sensitized solar cells formed of randomly sintered TiO2 nanoparticles, a behaviour that was ascribed to a particularly low density of localized surface states in EISA TiO2. The present methodology also provides a unique and straightforward access to an activation-driving force relationship according to the Marcus theory, thus opening new opportunities not only to investigate the driving-force effects on electron recombination dynamics in dye-sensitized solar cells but also to study the electron transfer/transport mechanisms in heterogeneous photoelectrocatalytic systems combining nanostructured semiconductor electrodes and heterogeneous redox-active catalysts.