Department of Science and Technology, Linköping University, 60174 Norrköping, Sweden.
Department of Physics, Chemistry, and Biology, Linköping University, 58183 Linköping, Sweden.
Proc Natl Acad Sci U S A. 2018 Nov 20;115(47):11899-11904. doi: 10.1073/pnas.1806087115. Epub 2018 Nov 5.
Electrochemistry is an old but still flourishing field of research due to the importance of the efficiency and kinetics of electrochemical reactions in industrial processes and (bio-)electrochemical devices. The heterogeneous electron transfer from an electrode to a reactant in the solution has been well studied for metal, semiconductor, metal oxide, and carbon electrodes. For those electrode materials, there is little correlation between the electronic transport within the electrode material and the electron transfer occurring at the interface between the electrode and the solution. Here, we investigate the heterogeneous electron transfer between a conducting polymer electrode and a redox couple in an electrolyte. As a benchmark system, we use poly(3,4-ethylenedioxythiophene) (PEDOT) and the Ferro/ferricyanide redox couple in an aqueous electrolyte. We discovered a strong correlation between the electronic transport within the PEDOT electrode and the rate of electron transfer to the organometallic molecules in solution. We attribute this to a percolation-based charge transport within the polymer electrode directly involved in the electron transfer. We show the impact of this finding by optimizing an electrochemical thermogalvanic cell that transforms a heat flux into electrical power. The power generated by the cell increased by four orders of magnitude on changing the morphology and conductivity of the polymer electrode. As all conducting polymers are recognized to have percolation transport, we believe that this is a general phenomenon for this family of conductors.
电化学是一个古老但仍然蓬勃发展的研究领域，因为电化学反应的效率和动力学在工业过程和（生物）电化学装置中非常重要。在金属、半导体、金属氧化物和碳电极中，已经对异相电子从电极向溶液中的反应物转移进行了很好的研究。对于这些电极材料，电极材料内部的电子输运与电极和溶液之间界面处发生的电子转移之间几乎没有相关性。在这里，我们研究了导电聚合物电极和电解质中氧化还原对之间的异相电子转移。作为基准体系，我们使用聚（3,4-亚乙基二氧噻吩）（PEDOT）和水相电解质中的铁氰化/亚铁氧化还原对。我们发现，PEDOT 电极内部的电子输运与溶液中有机金属分子的电子转移速率之间存在很强的相关性。我们将其归因于聚合物电极中直接参与电子转移的基于渗流的电荷输运。我们通过优化电化学热伏打电池来展示这一发现的影响，该电池将热通量转化为电能。通过改变聚合物电极的形态和电导率，电池产生的功率增加了四个数量级。由于所有导电聚合物都被认为具有渗流输运，我们相信这是此类导体的普遍现象。
