Microbial bioelectrochemical systems (BES) represent an upcoming technology for the exploitation and cleaning of waste water.¹ In addition, BES are gaining importance as bio-analytical devices like microbial fuel cell (MFC)-type sensors, e.g. for BOD in waste waters as well as for the analysis of microbial activity.^1,2 In BES, microorganisms are used as biocatalysts at the anode allowing the interception of electrons released during the oxidation of substrates. During the past decade, the average current densities of the biofilm anodes have already impressively increased from microampere per square cm level to between 0.7 and 1 mA cm^-2. Since the improvement of the biological component in BES becomes increasingly difficult, the improvement of the electrode materials becomes an important task. One strategy is the improvement of the electrode surface properties by surface treatment procedures such as ammonia treatment, polymer modification or surface oxidation.^3,4 Another promising path is to increase the active surface area by means of, e.g., brush or fiber electrodes^5,6 and 3D electrode materials - a path that already delivers promising results (about 2.4 mA cm^-2)⁷. The aim of the presented work was to exploit high surface area electrospun and solution blown fiber materials to enhance the microbial bioelectrocatalysis at BES anodes. Herein, three-dimensional electrospun and solution-blown carbon fiber nonwovens are shown to be excellent and promising anode materials for microbial BES such as MFCs. They combine the use of a minimum amount of carbon and great performance. The bioelectrocatalytic anode current density values reached up to 3 mA cm^-2, which represents to date, amongst the highest reported values for electrocatalytically active biofilms of Geobacter sulferreducens.⁸ These current densities were achieved without chemical surface modification, which may represent an advantage with respect to longevity. Based on this initial study, further and systematic investigations are proposed to fully exploit the potential of this class of materials. A special emphasis of further investigations must be on tests designed to elucidate the long-term behavior of these electrode materials and the resistivity against clogging of the pore structures.

References:

[1] K. Rabaey et al. (Eds.), Bioelectrochemical Systems: From Extracellular Electron Transfer to Biotechnological Application, IWA Publishing 2009.

[2] D. Odaci et al., Bioelectrochem. 2009, 75, 77-82.

[3] S. Cheng et al., Electrochem. Comm. 2007, 9, 492-496.

[4] X. Wang et al., Environ. Sci. Technol. 2009, 43, 17, 6870-6874.

[5] B.E. Logan et al., Environ. Sci. Technol. 2007, 41, 3341-3346.

[6] Y. Liu et al., Biosens. Bioelectron. 2010, 25, 2167-2171.

[7] Y. Zhao et al., Chem. Eur. J. 2010, 16, 4982-4985.

[8] S. Chen et al., Energy Environ. Sci. 2011, 4, 1417-1421.

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