Daviddi Enrico, Chen Zhiting, Beam Massani Brooke, Lee Jaemin, Bentley Cameron L, Unwin Patrick R, Ratcliff Erin L
Department of Chemistry , University of Warwick , Coventry CV4 7AL , United Kingdom.
Department of Materials Science and Engineering , University of Arizona , Tucson , Arizona 85721 , United States.
ACS Nano. 2019 Nov 26;13(11):13271-13284. doi: 10.1021/acsnano.9b06302. Epub 2019 Nov 7.
Conductive polymers are exceptionally promising for modular electrochemical applications including chemical sensors, bioelectronics, redox-flow batteries, and photoelectrochemical systems due to considerable synthetic tunability and ease of processing. Despite well-established structural heterogeneity in these systems, conventional macroscopic electroanalytical methods-specifically cyclic voltammetry-are typically used as the primary tool for structure-property elucidation. This work presents an alternative correlative multimicroscopy strategy. Data from laboratory and synchrotron-based microspectroscopies, including conducting-atomic force microscopy and synchrotron nanoscale infrared spectroscopy, are combined with potentiodynamic movies of electrochemical fluxes from scanning electrochemical cell microscopy (SECCM) to reveal the relationship between electrode structure and activity. A model conductive polymer electrode system of tailored heterogeneity is investigated, consisting of phase-segregated domains of poly(3-hexylthiophene) (P3HT) surrounded by contiguous regions of insulating poly(methyl methacrylate) (PMMA), representing an ultramicroelectrode array. Isolated domains of P3HT are shown to retain bulk-like chemical and electronic structure when blended with PMMA and possess approximately equivalent electron-transfer rate constants compared to pure P3HT electrodes. The nanoscale electrochemical data are used to model and predict multiscale electrochemical behavior, revealing that macroscopic cyclic voltammograms should be much more kinetically facile than observed experimentally. This indicates that parasitic resistances rather than redox kinetics play a dominant role in macroscopic measurements in these conductive polymer systems. SECCM further demonstrates that the ambient degradation of the P3HT electroactivity within P3HT/PMMA blends is spatially heterogeneous. This work serves as a roadmap for benchmarking the quality of conductive polymer films as electrodes, emphasizing the importance of nanoscale electrochemical measurements in understanding macroscopic properties.
由于具有相当大的合成可调性和易于加工的特点，导电聚合物在包括化学传感器、生物电子学、氧化还原液流电池和光电化学系统在内的模块化电化学应用中极具前景。尽管这些系统中已确立了结构异质性，但传统的宏观电分析方法——特别是循环伏安法——通常被用作阐明结构与性能关系的主要工具。这项工作提出了一种替代性的相关多显微镜策略。将来自实验室和基于同步加速器的显微光谱学的数据，包括导电原子力显微镜和同步加速器纳米级红外光谱学的数据，与扫描电化学池显微镜（SECCM）的电化学通量的动电位电影相结合，以揭示电极结构与活性之间的关系。研究了一个具有定制异质性的模型导电聚合物电极系统，该系统由聚（3-己基噻吩）（P3HT）的相分离域组成，周围是绝缘聚（甲基丙烯酸甲酯）（PMMA）的连续区域，代表一个超微电极阵列。研究表明，与纯P3HT电极相比，P3HT的孤立域在与PMMA混合时保留了块状的化学和电子结构，并具有近似相等的电子转移速率常数。纳米级电化学数据被用于模拟和预测多尺度电化学行为，结果表明宏观循环伏安图在动力学上应该比实验观察到的要容易得多。这表明在这些导电聚合物系统的宏观测量中，寄生电阻而非氧化还原动力学起主导作用。SECCM进一步证明，P3HT/PMMA共混物中P3HT电活性的环境降解在空间上是不均匀的。这项工作为评估导电聚合物薄膜作为电极的质量提供了路线图，强调了纳米级电化学测量在理解宏观性质方面的重要性。
