Robayo-Molina Iván, Crespo Gastón A, Cuartero María
Deparment of Chemistry, School of Engineering Science in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Teknikringen 30, SE-100 44 Stockholm, Sweden.
UCAM-SENS, Universidad Católica San Antonio de Murcia, UCAM Hitech, Avda. Andres Hernandez Ros 1, 30107 Murcia, Spain.
ACS Omega. 2024 Feb 6;9(7):8162-8172. doi: 10.1021/acsomega.3c08656. eCollection 2024 Feb 20.
Despite the distribution of relaxation time (DRT) method providing clear insights about processes that go unnoticed by traditional electrochemical impedance spectroscopy (EIS) analysis, it has not yet been adopted to solve electroanalytical systems. As an illustration case, we apply the DRT method to deconvolve EIS data from solid-state voltammetric ion-selective electrodes (ISEs). The main aim is to shed light on the underlying working mechanism across the different materials and interfaces, specifically, the doping of a conducting polymer when covered with a very thin (ca. 230 nm) permselective membrane. Although frequency-dependent AC measurements in EIS allow the separation of processes that contribute to the electrical signal, interpretation of the data is challenging. DRT may overcome this inconvenience by revealing a series of peaks corresponding to the predominant electrochemical processes, without any preknowledge on those. To demonstrate our hypothesis, we examine the conducting polymer poly(3-octylthiophene) (POT) linked to a membrane with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB) as the cation exchanger, in which the lipophilic anionic part (TFPB) is responsible for the POT doping when it gets electrochemically oxidized (POT). The investigation of EIS data obtained under different conditions with the DRT method showed the occurrence of several processes. We have attributed two of these to two different conformational changes in the POT film in connection with p-type charge-transfer doping. Indeed, the kinetics is found to follow a Butler-Volmer behavior, with average charge transfers of 0.5 and 0.3 mol of electrons for each peak. Overall, we demonstrate the utility of the EIS-DRT tandem to separately study charge-transfer events that interconnect along the same (interfacial segmented) system, which cannot be reached by using classical electrochemical approaches. These kinds of insights are necessary for a more efficient design and high-level exploitation of voltammetric ISEs but also other electrochemical systems such as catalysts, batteries, and photovoltaic cells.
尽管弛豫时间分布（DRT）方法能清晰洞察传统电化学阻抗谱（EIS）分析中未被注意到的过程，但它尚未被用于解决电分析系统问题。作为一个示例，我们应用DRT方法对固态伏安离子选择性电极（ISE）的EIS数据进行去卷积处理。主要目的是阐明不同材料和界面的潜在工作机制，具体而言，是研究覆盖有非常薄（约230纳米）的选择性渗透膜时导电聚合物的掺杂情况。尽管EIS中频率相关的交流测量允许分离对电信号有贡献的过程，但数据解释具有挑战性。DRT可以通过揭示一系列对应于主要电化学过程的峰来克服这一不便，而无需对这些过程有任何先验知识。为了证明我们的假设，我们研究了与以四[3,5-双（三氟甲基）苯基]硼酸钠（NaTFPB）作为阳离子交换剂的膜相连的导电聚合物聚（3-辛基噻吩）（POT），其中亲脂性阴离子部分（TFPB）在电化学氧化（POT）时负责POT的掺杂。用DRT方法对在不同条件下获得的EIS数据进行研究表明，存在几个过程。我们将其中两个过程归因于POT薄膜中与p型电荷转移掺杂相关的两种不同构象变化。事实上，动力学遵循巴特勒-沃尔默行为，每个峰的平均电荷转移量分别为0.5和0.3摩尔电子。总体而言，我们证明了EIS-DRT串联用于分别研究沿同一（界面分段）系统相互关联的电荷转移事件的实用性，这是使用经典电化学方法无法实现的。这些见解对于更高效地设计和高水平开发伏安ISE以及其他电化学系统（如催化剂、电池和光伏电池）是必要的。
