Kwon Osung, Lee Jihoon, Son Hyungju, Park Jaehyoung
Faculty of Science, Tabula Rasa College, Keimyung University in Seongseo, Daegu 42601, Republic of Korea.
AET Co., Ltd., Daegu 41967, Republic of Korea.
Polymers (Basel). 2024 Feb 22;16(5):604. doi: 10.3390/polym16050604.
Proton exchange membranes are an essential component of proton-exchange membrane fuel cells (PEMFC). Their performance is directly related to the development of ionic channel networks through hydration. Current sensing atomic force microscopy (CSAFM) can map the local conductance and morphology of a sample surface with sub-nano resolution simultaneously by applying a bias voltage between the conducting tip and sample holder. In this study, the ionic channel network variation of Nafion by hydration has been quantitatively characterized based on the basic principles of electrodynamics and CSAFM. A nano-sized PEMFC has been created using a Pt-coated tip of CSAFM and one side Pt-coated Nafion, and studied under different relative humidity (RH) conditions. The results have been systematically analyzed. First, the morphology of PEMFC under each RH has been studied using line profile and surface roughness. Second, the CSAFM image has been analyzed statistically through the peak value and full-width half-maximum of the histograms. Third, the number of protons moving through the ionic channel network (NPMI) has been derived and used to understand ionic channel network variation by hydration. This study develops a quantitative method to comprehend variations in the ionic channel network by calculating the movement of protons into the ionic channel network based on CSAFM images. To verify the method, a comparison is made between the NPMI and the changes in proton conductivity under different RH conditions and it reveals a good agreement. This developed method can offer a quantitative approach for characterizing the morphological structure of PEM. Also, it can provide a quantitative tool for interpretating CSAFM images.
质子交换膜是质子交换膜燃料电池（PEMFC）的重要组成部分。它们的性能直接与通过水合作用形成的离子通道网络的发展相关。电流传感原子力显微镜（CSAFM）通过在导电探针和样品支架之间施加偏置电压，能够同时以亚纳米分辨率绘制样品表面的局部电导率和形貌。在本研究中，基于电动力学和CSAFM的基本原理，对水合作用下Nafion离子通道网络的变化进行了定量表征。使用CSAFM的铂涂层探针和一侧涂有铂的Nafion创建了一个纳米级PEMFC，并在不同相对湿度（RH）条件下进行了研究。对结果进行了系统分析。首先，使用线轮廓和表面粗糙度研究了每个RH条件下PEMFC的形貌。其次，通过直方图的峰值和半高宽对CSAFM图像进行了统计分析。第三，推导了通过离子通道网络移动的质子数（NPMI），并用于了解水合作用下离子通道网络的变化。本研究开发了一种定量方法，通过基于CSAFM图像计算质子进入离子通道网络的移动来理解离子通道网络的变化。为了验证该方法，比较了不同RH条件下的NPMI和质子电导率的变化，结果显示出良好的一致性。这种开发的方法可以为表征PEM的形态结构提供一种定量方法。此外，它还可以为解释CSAFM图像提供一种定量工具。
