Microbial fuel cells offer an efficient and environmentally-friendly method of
producing electricity and as such are an attractive green energy source especially as they can potentially produce power whilst recycling waste. The first objective of this study was to test the possibility of generating electricity with Acidiphilium SJH
bacteria operating at a low pH as biocatalysts, with the ferric ion as the electron
shuttle and glucose as the electron donor in a two-compartment microbial fuel cell.
This study is focused on a comparison between different microbial fuel cell designs that were constructed to test their energy performances. The resulting power densities ranged from 18.3 mW/m² to 25 mW/m² and the coulombic efficiency based on the contained substrates is in the range of 6 % to 7 %. Unfortunately the design of microbial fuel cells and scale-up is limited by the large cost of the platinum electrodes. Hence the electrode material used in the design is an important parameter when deciding the performance and cost effectiveness of microbial fuel cell.
This work demonstrates a potentially large reduction in cost by utilising the catalytic activity of platinum nano-sized particles on a Ketjen Black cathode that is able to diffuse oxygen from the air, eliminating the need for an external oxygen supply. The low pH redox behaviour of the ferric ion has been paired with an iron-reducing Acidiphilium sp. to form an effective fuel cell. At room temperature a power output of 20.7 m W/m² was achieved with nano particulate platinum loading of 150 µg /cm² within a Ketjen Black cathode. The modified cathode retained an equivalent of 80 % efficiency when compared to a solid platinum electrode; which is significant considering that the mass of platinum used in the modified electrode was only 0.1 % of that in a solid platinum electrode. Platinum nanoparticles were electrodeposited on carbon felt from an aqueous electrolyte containing hydrogen hexachloroplatinate by a potential cycling method. The modified Pt/KB cathode achieved higher power density when compared with the platinum electrodeposition on the carbon felt cathode electrode.