Short side chain perfluorosulfonic acid composite membrane with covalently grafted cup stacked carbon nanofibers for polymer electrolyte fuel cells

Abstract

Efficient proton conduction through polymer electrolyte membrane is critical in the performance of low temperature polymer electrolyte fuel cells (LT-PEFC). Herein, polystyrene sulfonic acid grafted cup stacked carbon nanofiber (PSSA-g-CSNF) incorporated short side chain (SSC)-perfluorosulfonic acid (PFSA) ionomer composite polymer electrolyte is discussed. An optimum level of PSSA-g-CSNF introduced as an additive to SSC-PFSA matrix exhibit higher proton conductivity, improved mechanical, chemical stability, and limited hydrogen crossover towards PEFC application in comparison to recast pristine SSC-PFSA membranes (Aquivion®-720). Maximum current density of 2.5 A cm−2 at 0.5 V and peak power density of 1.4 W cm−2 under H2 and O2 condition is seen for the optimized nanocomposite membrane. Besides, the peak power density of the nanocomposite membrane shows an enhancement higher than 22% and 42% in relation to recast pristine Aquivion and Nafion212 respectively. In addition to this, nanocomposite membrane shows higher chemical stability and retention of 80% initial OCV even after 100 h of accelerated stress test (AST) as compared to 73% for pristine Aquivion. Uniform dispersion of PSSA-g-CSNF in Aquivion facilitates facile proton transport by limiting fuel cross-over via hydrogen bonding interaction with closely spaced hydrophilic groups in the membrane matrix in LT-PEFC.