Microbial fuel cell performance with a pressurized cathode chamber.

Microbial fuel cell (MFC) power densities are often constrained by the oxygen reduction reaction rate on the cathode electrode. One important factor for this is the normally low solubility of oxygen in the aqueous cathode solution, which creates mass transport limitation and hinders oxygen reduction at the electrocatalyst (platinum, Pt). Here, we increased the air pressure in the cathode chamber to increase the solubility and consequently the availability of oxygen, which is a function of the partial pressure. Under stable anode and cathode conditions, an MFC was tested with an anion-exchange membrane (AEM) and a cation-exchange membrane (CEM) at atmospheric pressure, +17.24 kPa (2.5 psig), and +34.48 kPa (5.0 psig) overpressure of air. The cell potential at an external resistance of 100 omega increased from 0.423 to 0.553 V by increasing the cathode pressure from atmospheric pressure to 17.24 kPa for an MFC with AEM, and this resulted in a 70% increase in the power density (4.29 vs 7.29 W/m3). In addition, the MFC produced 66-108% more power with AEM in comparison to CEM under the same operating conditions. We discussed the mechanisms that explain this. Results from this study demonstrate that higher MFC power densities can be realized by increasing the cathode air pressure if the membrane oxygen diffusion to the anode can be controlled.