Proton-conductive channels engineering of perfluorosulfonic acid membrane via in situ acid–base pair of metal organic framework for fuel cells

The development of rapid and dependable proton transport channels is crucial for proton exchange membrane fuel cells (PEMFCs) operating in low humidity conditions. Herein, a metal–organic framework (NH-Zr framework) consisting of 1H-pyrazole-3, 5-dicarboxylic acid (PZDC), and zirconium chloride octahydrate (ZrOCl2·8H2O) rich in basic sites was in situ constructed in a perfluorosulfonic acid (PFSA) solution, and hybrid proton exchange membranes were prepared (PFSA-NH-Zr). The introduced NH-Zr framework successfully induced proton conducting groups (-SO3H) reorganization along the NH-Zr framework, resulting in the formation of fast ion transport channels. Meanwhile, under low humidity, the acid–base pairs between N–H (NH-Zr framework) and -SO3H (PFSA) promoted the protonation/deprotonation and the subsequent proton leap via the Grotthuss mechanism. Especially, the hybrid membrane PFSA-NH-Zr-1 with suitable NH-Zr content had a promising proton conductivity of 0.031 S/cm at 80 °C, 40% relative humidity (RH), and 0.292 S/cm at 80 °C, 100% RH, which were approximately 33% and 40% higher than the pristine PFSA membrane (0.023 S/cm and 0.209 S/cm), respectively. In addition, the maximum power density of the hybrid proton exchange membrane was 0.726 W/cm2, which was nearly 20% higher than the pristine PFSA membrane (0.604 W/cm2) under 80 °C, 40% RH. Thus, PFSA-NH-Zr may be promising membrane materials for potential applications in fuel cells. This work established a referable strategy for developing high-performance proton exchange membranes under low RH conditions.