Xu Zhiling, Yuan Shu, An Lu, Shen Shuiyun, Xu Qian, Yan Xiaohui, Zhang Junliang
Institute of Fuel Cells, School of Mechanical Engineering, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China.
MOE Key Laboratory of Power Machinery and Engineering, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China.
ACS Appl Mater Interfaces. 2023 Mar 1;15(8):10735-10743. doi: 10.1021/acsami.2c21977. Epub 2023 Feb 20.
A potential approach to enhance the suppressed proton conductivity of nanoscale ultrathin Nafion films is to adjust the ionomer structure via regulating the catalyst-ionomer interaction. To understand the interaction between substrate surface charges and Nafion molecules, self-assembled ultrathin films (∼20 nm) were prepared on the SiO model substrates, which were modified with silane coupling agents to carry either negative (COO) or positive (NH) charges. Specifically, the surface energy, phase separation, and proton conductivity were investigated by contact angle measurements, atomic force microscopy, and microelectrodes to illuminate the relationship between the substrate surface charge, thin-film nanostructure, and proton conduction. Compared to electrically neutral substrates, ultrathin films formed faster on the negatively charged substrate with an 83% increase in proton conductivity but formed more slowly on the positively charged substrate, with proton conductivity decreased by 35% at 50 °C. The surface charges interact with sulfonic acid groups of Nafion molecules to alter molecular orientation, resulting in different surface energies and phase separation, which are responsible for proton conductivity variation.
增强纳米级超薄全氟磺酸膜（Nafion膜）受抑制的质子传导率的一种潜在方法是通过调节催化剂-离聚物相互作用来调整离聚物结构。为了理解基底表面电荷与Nafion分子之间的相互作用，在经硅烷偶联剂修饰以带有负电荷（COO）或正电荷（NH）的SiO模型基底上制备了自组装超薄膜（约20纳米）。具体而言，通过接触角测量、原子力显微镜和微电极研究了表面能、相分离和质子传导率，以阐明基底表面电荷、薄膜纳米结构与质子传导之间的关系。与电中性基底相比，在带负电荷的基底上形成超薄膜的速度更快，质子传导率提高了83%，但在带正电荷的基底上形成速度更慢，在50°C时质子传导率降低了35%。表面电荷与Nafion分子的磺酸基团相互作用以改变分子取向，从而导致不同的表面能和相分离，这是质子传导率变化的原因。
