The nanostructure of three-dimensional scaffolds enhances the current density of microbial bioelectrochemical systems

Bioelectrochemical systems encompass a range of electrochemical systems wherein microorganisms are used as biocatalysts. These range from classical microbial fuel cells to novel microbial electrosynthesis processes. The future of practical applications relies on increased performance. In all cases the development of new electrode materials is essential to overcome the low current densities of bioelectrochemical systems. Here we describe a new biocompatible, highly conductive three-dimensional scaffold electrode, NanoWeb-RVC, with a hierarchical porous structure, synthesized by direct growth of carbon nanotubes on a macroporous substrate. The nanostructure of these electrodes enhances the rate of bacterial extracellular electron transfer while the macrostructure ensures efficient mass transfer to and from the electrode surface. NanoWeb-RVC electrodes showed a current density of (6.8 ± 0.3) mA cm-2, almost three times higher than a control electrode with the same macroporous structure but lacking the nanostructure. This current density is among the highest reported to date for a microbial bioanode.