Methanol permeability enhancement through heat treatment of Nafion-based composite membrane for direct methanol fuel cell application

• Published in: Fuel
• Main Author: Elham O.S.J.; Kamarudin S.K.; Shaari N.; Zainoodin A.M.; Yusof M.R.
• Format: Article
• Language: English
• Published: Elsevier Ltd 2024
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85195375811&doi=10.1016%2fj.fuel.2024.131839&partnerID=40&md5=8cb97a668dcccf6abc50e59e6bc357ae

In this study, the lignosulfonate-hydroxyapatite nanofillers (LS-HAP) were incorporated into a Nafion polymer matrix and annealed at different temperatures. The aim is to minimise the crossover of methanol and enhance the fuel cell performance. This study also investigates the synthesis of hydroxyapatite (HAP) from eggshell waste and evaluates the electrochemical properties of the synthesised HAP. The microstructure of the membranes produced is analysed in detail using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). The influence of annealing temperature on methanol crossover and proton conductivity was studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results reveal that annealing had significantly improved the crystallinity of the rN/LS-HAP membranes. Annealing at 160 °C had resulted in a methanol permeability of 2.4 × 10−6 cm2 s−1, combined with the highest proton conductivity of 18.82 mS cm−1; this outperforms Nafion 117, which possessed a methanol permeability of 8.91 × 10−6 cm2 s−1 and a proton conductivity of 3.28 mS cm−1. The proton conductivity experienced a downward trend in rN/LS-HAP 180 and rN/LS-HAP 200 due to the adverse effects of annealing at higher temperatures. In addition, rN-LS-HAP 160 showed superior performance under identical operating conditions, with the highest power density of 19.87 mW cm−2. With a power density of 9.67 mW cm−2, the use of 2 M methanol exceeded the performance of the commercial Nafion 117. The experimental results indicate that composite membranes annealed at 160 °C has effectively mitigated methanol crossover and improved the performance of passive DMFC. © 2024 Elsevier Ltd