High proton conductivity dual modified ionic crosslink membrane for fuel cell application at low humidity condition with molecular dynamics simulations

Abstract

Dual modified ionic cross-link polysulfone (PSF) polymer-based proton-conducting membrane is synthesized with an aim to provide low methanol permeability without sacrificing the proton conductivity for direct methanol fuel cell application. The modification of pristine PSF membrane with aniline and further cross-linking by sulfuric acid was confirmed by its detailed characterization. The modified membrane achieved a high proton conductivity of 0.072 Scm (30 °C) and 0.178 Scm (110 °C) in low humidity condition (40%). The membrane exhibits low methanol permeability (2.5 × 10 cm s ) with high selectivity (28.4 × 10 Scm s ). The higher diffusivity of hydronium ion (H O ) with an increase in hydration level and temperature was studied by molecular dynamics simulation and well agrees with experimental results in terms of proton conductivity. The reduced electrostatic interactions between the sulfonic acid group and H O ion were confirmed by the radial distribution function analysis. These interaction pushes the H O ion that helps in the transfer of proton by increases their coordination with water. Moreover, the high interaction of amine group with H O ion also contributes to the proton conductivity enhancement. The dual modified membrane achived maximum power density of 0.19 Wcm at 45 mA cm and was 42% higher as compared to aniline treated polysulfone (APSF) membrane. −1 −1 −8 2 −1 5 3 −1 + + + + −2 −2 3 3 3 3