Nonwoven mats of N-doped carbon nanofibers as high-performing anodes in microbial fuel cells

The performances of single chamber microbial fuel cells (SCMFCs) can be drastically enhanced by using nitrogen-doped electrospun carbon nanofibers (N–CNFs) as a surface coating material in composite anodes. The crucial step is the fine-tuning of the surface properties to improve bacteria growth on the anodic electrode. Two different pyrolysis treatments, conducted under inert atmosphere at 600 °C and 900 °C are analyzed in order to optimize the thermal treatment able to balance the surface chemistry of N–CNFs with respect to their electrical conductivity. N–CNFs treated at 600 °C result to be the best performing surface coating material in composite anodes, minimizing the process costs together while keeping excellent properties towards application. Morphological, physical and chemical features of the material are analyzed. The optimized N-doped CNFs show good interaction with microorganisms. All these features enhance the SCMFC performances. The SCMFCs with composite anode achieve power densities of 2.153 ± 0.011 W m−2, an order of magnitude higher than the results reached by using commercial carbon fibers. These performances are better than the ones obtained with activated CNFs proposed in the literature, where maximum pyrolysis temperature is up to 1100 °C and further chemical treatments are needed to ensure optimal surface chemistry, improving biofilm growth.