Membrane-electrode assembly enhances performance of a microbial fuel cell type biological oxygen demand sensor

A membrane-electrode assembly (MEA) was applied to a microbial fuel cell (MFC) type biological oxygen demand (BOD) sensor and the performance of the sensor was assessed. To establish the optimal conditions for MEA fabrication, platinum-catalysed carbon cloth cathodic electrodes were assembled with cation exchange membranes under various temperatures and pressures. By analysing coulombs from the MFCs, it could be determined that the optimal hot-pressing conditions were 120 °C and 150 kg cm-2 for 30 s. When the MEA fabricated under optimal conditions and an air cathode were utilized for the construction of the MFC type BOD sensor, coulombs increased to 4.65 C from 0.52 C and power increased to 69,080 mW m-3 from 880 mW m-3 (at a BOD concentration of 200 mg L-1), respectively, compared with the conventional MFC lacking a MEA. The increased power improved the performance of the MFC type BOD sensor: sensitivity increased from 1.2 x 10-3 to 1.8 x 10-2 C per mg L-1 of BOD, with good linearity (r2 = 0.97) and over 97% repeatability. We conclude that the MEA can be successfully applied to MFCs to make them highly sensitive BOD sensors.