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

Abstract

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 –SO 3 H of Nafion and –NH 2 /–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/cm 2 , which was about 58% higher than that of Nafion control-membrane (171.5 mW/cm 2 ). This study provides a referable strategy for designing and constructing functionalized MOFs with specific structures to effectively facilitate the proton conduction of PEMs. An effective proton conduction accelerator, polydopamine (PDA) modified hollow metal−organic framework (DHZIF-8), was incorporated into Nafion matrix to construct composite proton exchange membrane (PEM) with excellent proton conductivities. The proton conduction of composite PEM was greatly facilitated mainly by higher water retention capacity and formed acid-base pairs. • Polydopamine modified hollow MOF (DHZIF-8) was constructed as excellent proton conduction accelerator. • Proton conduction of PEM was effectively facilitated by DHZIF-8. • PEM displayed satisfactory proton conductivity stability. • Maximum power density and current density of PEM were obviously promoted.