Effectively facilitating the proton conduction of proton exchange membrane by polydopamine modified hollow metal−organic framework

An effective proton conduction accelerator, polydopamine (PDA) modified hollow metal−organic framework (DHZIF-8), was designed and constructed. Composite proton exchange membrane (PEM) with excellent proton conductivities was obtained by incorporation of DHZIF-8 into Nafion matrix. The hydrophilic groups on surface and hollow structure of DHZIF-8 endowed the composite PEM with higher water retention capacity, which was especially conducive to fast transportation of protons. Moreover, the proton conducting hindrance throughout DHZIF-8 was sufficiently alleviated by the hollow structure. Besides, the constituted acid−base pairs between –SO3H of Nafion and –NH2/–NH– of DHZIF-8 could work as effective proton transfer pathways. These greatly facilitated the proton conduction of the composite PEM. Its proton conductivities boosted up to 0.255 S/cm under 80 °C, 95% RH, and 3.66 mS/cm under 120 °C, anhydrous condition, which were approximately 1.5 and 2.2 times greater than those of Nafion control-membrane (0.104 S/cm and 1.14 mS/cm), respectively. Additionally, the maximum power density of the composite PEM reached up to 270.8 mW/cm2, which was about 58% higher than that of Nafion control-membrane (171.5 mW/cm2). This study provides a referable strategy for designing and constructing functionalized MOFs with specific structures to effectively facilitate the proton conduction of PEMs.