Fabrication of macroporous chitosan scaffolds doped with carbon nanotubes and their characterization in microbial fuel cell operation.

Hawaii Natural Energy Institute, University of Hawaii, Honolulu, HI 96822, USA.
Enzyme and Microbial Technology (Impact Factor: 2.97). 05/2011; 48(6-7):458-65. DOI: 10.1016/j.enzmictec.2011.02.006
Source: PubMed

ABSTRACT Chitosan (CHIT) scaffolds doped with multi-walled carbon nanotubes (CNT) were fabricated and evaluated for their utility as a microbial fuel cell (MFC) anodic material. High resolution microscopy verified the ability of Shewanella oneidensis MR-1 to directly colonize CHIT-CNT scaffolds. Cross-linking agents 1-ethyl-3-[3-dimethylaminopropyl] carbodimide hydrochloride (EDC), glutaraldehyde and glyoxal were independently studied for their ability to strengthen the CHIT-CNT matrix without disrupting the final pore structure. 2.5 vol% glyoxal was found to be the optimal cross-linker in terms of porosity (BET surface area=30.2 m(2) g(-1)) and structural stability. Glyoxyl and EDC cross-linked CHIT-CNT scaffolds were then studied for their ability to transfer electrons to underlying glassy carbon. Results showed an open circuit cell voltage of 600 mV and a maximum power density of 4.75 W/m(3) at a current density of 16 A/m(3) was achieved in non stirred batch mode, which compares well with published data using carbon felt electrodes where a power density of 3.5 W/m(3) at a current density of 7 A/m(3) have been reported. Additionally, CHIT-CNT scaffolds were impregnated into carbon felt electrodes and these results suggest that CHIT-CNT scaffolds can be successfully integrated with multiple support materials to create hybrid electrode materials. Further, preliminary tests indicate that the integrated scaffolds offer a robust macroporous electrode material that can be used in flow-through configurations.

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    ABSTRACT: This work describes electrochemical interfacial mechanisms under different flow conditions for glassy carbon scaffold electrodes (GCEs) modified with single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) dispersed within a chitosan (Chit) polymer. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize and assess the interfacial response. High-resolution techniques also revealed that carbon nanotubes dispersed within a Chit solution provide homogeneous distribution on glassy carbon substrates. The MWCNT-Chit scaffold CV response exhibited a six-fold increase in the redox peak currents (I-pa = 381 mu A versus 55 mu A for bare GCE). EIS was performed at different polarization potentials based on the results of the anodic peak potential, as measured by CV, in order to elucidate and characterize the charge and mass transfer mechanisms of the nanostructure-modified electrode surfaces so that the influence of flow conditions and redox potential on its performance, could be determined. The selected potentials were: open circuit potential (OCP), 0.2 V, 0.3 V, and 0.4 V. A combination of kinetic and diffusion processes resulted when Electrical analog element analysis was used to correlate the interfacial mechanisms at different flow and bias potential conditions. The EIS experiments demonstrated that Bode diagrams could be used to characterize the porous homogenous formation of layers in the scaffolds and provided new perspectives for those applications requiring flow-through conditions.
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