Sustainable Plant-Based Biopolymer Membranes for PEM Fuel Cells

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Carboxycellulose nanofibers (CNFs) offer a sustainable, low-cost alternative to Nafion membranes for polymer electrolyte applications.
• Current limitations of CNFs include suboptimal performance and reduced mechanical strength under operational conditions.

Purpose of the Study:

• To enhance the performance and mechanical properties of carboxycellulose nanofibers (CNFs) for use as polymer electrolyte membranes.
• To investigate the efficacy of citric acid cross-linking for improving CNF membrane characteristics.

Main Methods:

• Carboxylation of wood pulp-derived cellulose via TEMPO oxidation.
• Preparation of citric acid cross-linked CNF membranes using a solvent casting method.
• Characterization using FT-IR, 13C NMR, XRD, FIB/SEM, SEM/EDX, TEM, AFM, and DMA.

Main Results:

• Successful chemical cross-linking between citric acid and CNFs confirmed by spectroscopic and crystallographic analyses.
• Optimal fuel cell performance achieved with a specific ratio of CNF suspension to citric acid solution.
• Citric acid cross-linked CNF membranes demonstrated significantly improved power density (27.7 mW cm-2) and current density (111.8 mA cm-2) at 80 °C and 100% RH.
• Proton conductivity reached 9.4 mS cm-1 at 80 °C with a minimum activation energy of 0.27 eV.

Conclusions:

• Citric acid cross-linking is an effective strategy to enhance the performance of carboxycellulose nanofiber membranes.
• The developed CNF membranes show promise as a superior, cost-effective alternative to commercial Nafion membranes for fuel cell applications.