High performance chitosan/nanocellulose-based composite membrane for alkaline direct ethanol fuel cells.

Polysaccharide anion exchange membranes (AEMs) containing chitosan (CS), cellulose nanofibrils (CNFs) and CNFs quaternized with poly(diallyldimethylammonium chloride) (CNF(P)s) were developed for use in alkaline direct ethanol fuel cells (ADEFCs). The resulting composite membranes prepared by the solvent casting process based on an experimental design were comprehensively assessed for morphology, KOH uptake, swelling ratio, EtOH permeability, mechanical properties, ionic conductivity, and cell performance. The fabricated CS-based composite membranes with CNF(P) fillers were superior to the commercial Fumatech FAA-3-50 membrane in terms of Young's modulus and tensile strength (69 % and 85 % higher, respectively), ion exchange capacity (169 % higher), and ionic conductivity (228 % higher). Single fuel cell tests have shown excellent performance of the CS-based membranes with CNF and CNF(P) fillers, as they exhibited up to 86 % improvement in power density at 80 °C compared to the commercial membrane (65.1 mW/cm2 vs. 35.1 mW/cm2) and higher maximum power density at all test conditions.

Study on Commercially Available Membranes for Alkaline Direct Ethanol Fuel Cells.

This study provides a comparison of different commercially available low-cost anion exchange membranes (AEMs), a microporous separator, a cation exchange membrane (CEM), and an anionic-treated CEM for their application in the liquid-feed alkaline direct ethanol fuel cell (ADEFC). Moreover, the effect on performance was evaluated taking two different modes of operation for the ADEFC, with AEM or CEM, into consideration. The membranes were compared with respect to their physical and chemical properties, such as thermal and chemical stability, ion-exchange capacity, ionic conductivity, and ethanol permeability. The influence of these factors on performance and resistance was determined by means of polarization curve and electrochemical impedance spectra (EIS) measurements in the ADEFC. In addition, the influence of two different commercial ionomers on the structure and transport properties of the catalyst layer and on the performance were analyzed with scanning electron microscopy, single cell tests, and EIS. The applicability barriers of the membranes were pointed out, and the ideal combinations of membrane and ionomer for the liquid-feed ADEFC achieved power densities of approximately 80 mW cm-2 at 80 °C.

Efficiency of Neat and Quaternized-Cellulose Nanofibril Fillers in Chitosan Membranes for Direct Ethanol Fuel Cells.

In this work, fully polysaccharide based membranes were presented as self-standing, solid polyelectrolytes for application in anion exchange membrane fuel cells (AEMFCs). For this purpose, cellulose nanofibrils (CNFs) were modified successfully with an organosilane reagent, resulting in quaternized CNFs (CNF (D)), as shown by Fourier Transform Infrared Spectroscopy (FTIR), Carbon-13 (C13) nuclear magnetic resonance (13C NMR), Thermogravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC), and ζ-potential measurements. Both the neat (CNF) and CNF(D) particles were incorporated in situ into the chitosan (CS) membrane during the solvent casting process, resulting in composite membranes that were studied extensively for morphology, potassium hydroxide (KOH) uptake and swelling ratio, ethanol (EtOH) permeability, mechanical properties, ionic conductivity, and cell performance. The results showed higher Young's modulus (119%), tensile strength (91%), ion exchange capacity (177%), and ionic conductivity (33%) of the CS-based membranes compared to the commercial Fumatech membrane. The addition of CNF filler improved the thermal stability of the CS membranes and reduced the overall mass loss. The CNF (D) filler provided the lowest (4.23 × 10-5 cm2 s-1) EtOH permeability of the respective membrane, which is in the same range as that of the commercial membrane (3.47 × 10-5 cm2s-1). The most significant improvement (~78%) in power density at 80 °C was observed for the CS membrane with neat CNF compared to the commercial Fumatech membrane (62.4 mW cm-2 vs. 35.1 mW cm-2). Fuel cell tests showed that all CS-based anion exchange membranes (AEMs) exhibited higher maximum power densities than the commercial AEMs at 25 °C and 60 °C with humidified or non-humidified oxygen, demonstrating their potential for low-temperature direct ethanol fuel cell (DEFC) applications.