Last modified: 2014-10-18
Abstract
Bacterial nanocellulose (BNC) is a kind of natural nano-structured macromolecular material obtained via fermentation of some microorganisms. Compared to the plant cellulose (PC), BNC is hemically same but distinguished by its special 3D nanostructure morphology, high tensile strength, high crystallinity, high chemical purity, high water binding capacity, low gas permeation and good biocompatibility. Hence, BNC has been studying in various fields, such as food additives, high quality audio membranes, functional papers, pervaporation membranes and biomedical materials [1-3]. This kind of nanocellulose material is capable of being produced in large scale with cost-effective feedstocks [4-10]. Most recently, the applications of BNC in key devices of proton exchange membrane fuel cell (PEMFC) including carbon support catalysts, gas diffusion layer (GDL) and proton exchange membranes [11-12] have been investigated. However, researches on fabricating the BNC-based proton exchange membranes that could be applied in PEMFC and direct methanol fuel cell (DMFC) are not systematic and in-depth. Therefore, aiming at utilization in PEMFC and DMFC, potential of BNC in fuel cells were evaluated, especially in methanol-resistant proton exchange membrane composites.
In this study, new highly proton-conductive, cost-effective and stable blend BNC composite membranes were prepared based on methods of doping BNC in Nafion solution or blending BNC with Nafion. The morphology, molecular structure and thermal stability were studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), dynamic mechanical analysis (DMA) and electrochemical impedance spectroscopy (EIS) along with water uptake, swelling behavior, dimensional stability, proton conductivity and methanol permeability tests. Experimental results showed that composite membranes had more compact structure, better thermal stability and greatly-improved methanol-resistant properties. The water uptake, area and volume swelling rates were all decreased and size stability of the composite membranes had been improved greatly compared to commercial Nafion membranes. The composite membranes showed excellent mechanical and thermal stability regardless of annealing. The performances of annealed membranes in PEMFC and DMFC showed much higher power densities than those of pristine membranes at 25oC. The results demonstrate that the composite membrane has a great potential in applications in direct methanol fuel cell as a novel proton-conducting membrane.
Keywords
References
[1] F. Hong, B. Wei, and L. Chen, “Preliminary study on biosynthesis of bacterial nanocellulose tubes in a novel double-silicone-tube bioreactor for potential vascular prosthesis,” BioMed Research International (2014), http://www.hindawi.com/journals/bmri/raa/560365/.
[2] G. Yang, C. Wang, F. Hong, X. Yang, and Z. Cao, “Preparation and characterization of BC/PAM-AgNPs nanocomposites for antibacterial applications,” Carbohydrate Polymers, 2015, 115(22): 636–642.
[3] B. Wei, G. Yang, and F. Hong, ”Preparation and evaluation of a kind of bacterial cellulose dry films with antibacterial properties,” Carbohydrate Polymers, 2011, 84(1): 533–538.
[4] F. Hong, X. Guo, S. Zhang, S. Han, G. Yang, and L. J. Jönsson, ”Bacterial cellulose production from cotton-based waste textiles: Enzymatic saccharification enhanced by ionic liquid pretreatment,” Bioresource Technology, 2012, 104: 503–508.
[5] F. Hong, Y. X. Zhu, G. Yang, and X. X. Yang, “Wheat straw acid hydrolysate as a potential cost-effective feedstock for production of bacterial cellulose,” Journal of Chemical Technology and Biotechnology, 2011, 86(5): 675–680.
[6] F. Hong and K. Qiu, ”An alternative carbon source from konjac powder for enhancing production of bacterial cellulose in static cultures by a model strain Acetobacter aceti subsp. xylinus ATCC 23770,” Carbohydrate Polymers, 2008, 72 (3): 545–549.
[7] A. Cavka, X. Guo, S. Tang, S. Winestrand, L. J. Jönsson, and F. Hong, “Production of bacterial cellulose and enzyme from waste fiber sludge,” Biotechnology for Biofuels, 2013, 6: 25.
[8] X. Guo, A. Cavka, L. J. Jönsson, and F. Hong, “Comparison of methods for detoxification of spruce hydrolysate for bacterial cellulose production,” Microbial Cell Factories, 2013, 12: 93.
[9] S. Zhang, S. Winestrand, X. Guo, L. Chen, and F. Hong, and L. J. Jönsson, “Effects of phenolic compounds on the production of bacterial nanocellulose by Gluconacetobacter xylinus. Microbial Cell Factories, 2014, 13: 62.
[10] S. Zhang, S. Winestrand, L. Chen, D. Li, L. J. Jönsson, and F. Hong, “Tolerance of the nanocellulose-producing bacterium Gluconacetobacter xylinus to lignocellulose-derived acids and aldehydes,” Journal of Agricultural and Food Chemistry, 2014, 62: 9792–9799.
[11] G. Jiang, J. Qiao, and F. Hong, “Application of phosphoric acid and phytic acid doped bacterial cellulose as novel proton-conducting membranes to PEMFC,” International Journal of Hydrogen Energy, 2012, 37(11): 9182–9192.
[12] G. Jiang, J. Zhang, J. Qiao, Y. Jiang, H. Zarrin, Z. Chen, and F. Hong. Bacterial nanocellulose/nafion composite membranes for low temperature polymer electrolyte fuel cells,” Journal of Power Sources, 2015, 273: 697–706.