Modification of nanocellulose membrane by impregnation method with sulfosuccinic acid for direct methanol fuel cell applications

Abstract

In this work, we aimed to investigate the potential use of nanocellulose as a solid electrolyte membrane for the direct methanol fuel cell application. Nanocellulose membrane was fabricated using the vacuum filtration of cellulose nanofiber suspension extracted from Para rubber wood sawdust. The membrane was impregnated with sulfosuccinic acid (SSA) and then activated at 120 °C for 1 h in hot pressing machine. The SSA concentrations used were in a range of 0.1–10.0%w/v. Effects of sulfosuccinic acid on methanol permeability, ion exchange capacities (IEC), water uptake, oxidative and thermal stabilities, and mechanical properties were also investigated. It was found from an FTIR technique and confirmed by a solid-state 13C CP-MAS NMR result that esterification between –COOH groups of SSA and –OH groups of nanocellulose occurred, leading to crosslinking of nanocellulose as well as the increased hydrophilic ionic domains (free –COOH and –SO3H) in the membrane. IEC of the neat nanocellulose and the nanocellulose membranes modified with SSA ranged from 0.005 to 0.069 mmol/g. The water uptake ranged from 28 to 61%. The results showed that the amounts of SSA used in modification influenced the proton conduction and methanol transport properties of nanocellulose. Based on our research, the sulfonate-modified nanocelluloses prepared by simple pre-impregnation with SSA showed better methanol barrier property and proton conductivity than the neat nanocellulose. Our SSA-modified nanocellulose membranes are promising to be developed and utilized as ionic biodegradable membranes in DMFA applications.