Bacterial Cellulose Used In Proton Exchange Membranes

Bacterial cellulose prepared by Acetobacter xylinum is a versatile renewablebiomaterial in terms of its unique three-dimensional network structure, good thermalstability and good mechanical strength. This biopolymer has several practicalapplications in foods, paper, textiles, headphone membranes, medical fields includingwound dressing, artificial skins, artificial blood vessels and scanffold materials andpervaporative separation and so on. But there is few researches on the proton exchangemembrane fuel cells. In this paper, the preliminary researches on bacterial celluloseapplied in the proton exchange membrane fuel cells were studied. The main results wereas follows:1. BC (bacterial cellulose) membranes, which are a kind of proton exchange membrane,were produced by Acetobacter xylinum NUST4.2 in the static culture in 29℃for oneweek, and treated by purification. In order to enhance proton conductive property of theBC membranes, the membranes were modified by introducing carboxymethyl celluloseor adulterated by inorganic acids. FT-IR (Fourier-transformed infrared spectroscopy) wasemployed to characterize -COOH introduced in BC structure. The experimental datashow that the membrane modified by 5% H₃PO₄ has higher proton conductive propertythan those unmodified or modified by other methods.2. Platinum nanoparticles were precipitated from platinum salt solution on the BCmembrane. This material was termed as platinum-cellulose, whose structure anddistribution and amount of platinum precipitated was estimated by SEM(scanningelectron microscope) and X-ray energy spectroscopy. The thermal stability of bacterialcellulose membrane characterized show that it has superior properties for protonexchange membrane. Furthermore, another kind of catalyst layer was Pt/C catalyst layer,whose distribution of platinum on carbon carrier was observed by TEM (transmissionelectron microscope). The catalytic performance of platinum-cellulose membranes andPt/C catalyst layer were respectively tested by cyclic voltammetry. The results reveal thatboth of catalyst layers have good catalytic performance.3. A kind of MEA (membrane electrode assemblies) consisted of platinum-cellulose andelectrolyte layer consisting of the modified bacterial cellulose by 5% H₃PO₄. AnotherMEA consisted of Pt/C and modified bacterial cellulose. Both of the MEA wereassembled into fuel cells respectively. The performance and power density of the abovefuel cells were tested by voltammetry. The results showed that Pt/C-cellulose fuel cell has an output of 1.72mW/cm². Platinum-cellulose fuel cell has an output of 210μW/cm²,which is higher than that of American bacterial cellulose MEA fuel cell, 84.3μW/cm².