Surface areas of the anode and cathode electrodes of a microbial fuel cell (MFC) affect the power production of the MFC. Increased surface area on the anode allows for more bacterial sites for biofilm buildup and electron transfer. Increased surface area on the cathode creates more sites for the combination of hydrogen protons, electrons, and oxygen to close the circuit of the MFC.
The first objective of this study was to test the effects of nano-structure enhanced cathodes on power production of MFC using graphite powder, carbon nanotube powder, and activated carbon granules. The second objective of this study was to develop and test new electrode construction methods and compare the results of the cathode enhancement using different current collectors; a graphite bar and a stainless steel mesh.
Graphite bar cathodes were coated with silver epoxy and then either graphite powder or carbon nanotube powder were attached. The cathode with only silver epoxy produced a power density of 3.71 mW/m2. The graphite powder and silver epoxy cathode produced the highest power density of 5.47 mW/m2. The carbon nanotube and silver epoxy cathodes managed only a maximum power density of 4.52 mW/m2.
Stainless steel mesh cathodes were coated with a graphite conductive paint and then had graphite powder, carbon nanotube powder, or activated carbon granules attached. The conductive paint cathodes produced a maximum power density of 7.68 mW/m2. Graphite powder and conductive paint cathodes produced 2.56 mW/m2 at maximum power density. Cathodes with carbon nanotube powder and conductive paint produced a powder density maximum of 3.24 mW/m2. The activated carbon and conductive paint cathodes produced 4.93 mW/m2 at maximum power density.
The carbon nanotubes did not prove to be the most helpful enhancement of the cathodes. The carbon nanotubes caused a major increase in the internal resistance of the fuel cell which may mean they need to be pretreated before use in an MFC. The activated carbon and graphite paint enhancements provided results that indicated that they deserve further research to obtain their true potential. The cost reduction from using stainless steel mesh and the power production associated with them show that they could make better choices for use as electrodes.