Highly proton conductive membranes based on lignin/ZrP/PTFE composite for high temperature PEM fuel cells

Abstract

Novel lignin/zirconium phosphate (ZrP) based membranes for proton exchange membrane fuel cells applications were synthesized and studied in this work. The effects of lignin along with other additives such as ionic liquids and glycerol were investigated in terms of proton conductivity. Lignin was found to enhance the proton conductivity of pure ZrP membranes by one order of magnitude from 0.1 to 1 mS/cm. The addition of glycerol to the lignin/zirconium phosphate enhanced the proton conductivity with the highest value to be 20.2 mS/cm at 1.0 %wt. glycerol. Among three different ionic liquids that were investigated in this work, the highest proton conductivity was obtained with 1-Hexyl-3-methylimidazolium tricyanomethanide [HMIM][C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> ] ionic liquid at 0.3 %wt. The addition of [HMIM][C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> ] to the lignin/ZrP based membranes gave a proton conductivity of 100 mS/cm.