Proton Conductive, Low Methanol Crossover Cellulose-Based Membranes

Abstract

This work describes the development of sulfated cellulose (SC) polymer and explores its potential as an electrolyte-membrane for direct methanol fuel cells (DMFC). The fabrication of our membranes was initiated by the preparation of the novel sulfated cellulose solution via controlled acid hydrolysis of microcrystalline cellulose (MCC). Ion-conductive crosslinked SC membranes were prepared following a chemical crosslinking reaction. SC solution was chemically crosslinked with glutaraldehyde (GA) and cured at 30 °C to produce the aforementioned membranes. Effects of GA concentration on methanol permeability, proton conductivity, water uptake and thermal stabilities were investigated. The crosslinking reaction is confirmed by FTIR technique where a bond between the primary OH groups of cellulose and the GA aldehyde groups was achieved, leading to the increased hydrophobic backbone domains in the membrane. The results show that the time of crosslinking reaction highly affects the proton conduction and methanol permeability. The proton conductivity and methanol crossover (3M) of our GA crosslinked SC membranes are 3.7 × 10−2 mS cm−1 and 8.2 × 10−9 cm2 s−1, respectively. Crosslinked sulfated cellulose films have lower ion conductivity than the state-of-the-art Nafion (10.2 mS cm−1); however, the methanol crossover is three orders of magnitude lower than Nafion membranes (1.0 × 10−5 cm2 s−1 at 1 M). Such biofilms with high methanol resistivity address the major hurdle that prevents the widespread applications of direct alcohol fuel cells.

Glutaraldehyde-assisted crosslinking in regenerated cellulose films toward high dielectric and mechanical properties

“…The different variation trends of the dielectric properties are mainly related to the occurrence of the crosslinking reaction and the resultant molecular chain interaction. Generally, GA-induced crosslinking reaction occurs in the acidic condition (Aburabie et al 2021). For the CRC-I film, the crosslinking occurred in the LiOH/Urea solvent system and in this condition, to ensure the complete dissolution of cellulose and prevent the gelation of cellulose, the added amount of GA solution was relatively small, only 10 mL and therefore, the degree of the crosslinking is relatively small.…”

“…According to the literature (Aburabie et al 2021), GA-assisted crosslinking of cellulose molecular chains can be explained in Figure 2.…”

“…These changes confirm that crosslinking weakens the hydrogen bonding interaction between cellulose main chains. First, the occurrence of crosslinking consumes some hydroxy groups of cellulose molecular chains because the crosslinking occurs between the hydroxy groups of cellulose and aldehyde groups of GA (Aburabie et al 2021). Second, the presence of GA molecules possibly increases the distance between chain segments of cellulose, reducing the probability of forming intramolecular hydrogen bonding interaction.…”

Modified Cellulose Proton-Exchange Membranes for Direct Methanol Fuel Cells

“…The cross-linking of sulfated cellulose (SC) membranes by a combination of SC from acid hydrolysis MCC and Glutaraldehyde (GA) showed considerable performance improvement in DMFC applications [ 134 ]. An increase in the hydrophobic backbone domains and cross-linking confirmation was attributed to the connection between the GA aldehyde groups and cellulose primary −OH groups.…”

Breaking and Connecting: Highly Hazy and Transparent Regenerated Networked-Nanofibrous Cellulose Films via Combination of Hydrolysis and Crosslinking

“…Further chemical crosslinking of such material will improve such properties as well as film fabrication. Glutaraldehyde (GA) is one of the crosslinking agents that have been heavily researched for the crosslinking of cellulose; the reason is that dialdehydes improve resilience, mechanical properties, and thermal stability [ 25 ]. For the first time, we report the fabrication of a highly transparent and hazy substrate, composed of the abundant and biodegradable cellulose via a combination of controlled acid-hydrolysis (breaking chains) and chemical crosslinking (connecting chains).…”