Carbon-supported zirconium oxide as a cathode for microbial fuel cell applications

Cost-effective electrode materials to be used as cathodes in lab-scale prototype microbial fuel cells (MFCs) were prepared from mixtures of carbon black (C) and zirconium oxide (ZrO2) of different composition. The catalytic activity of these cathodes in the oxygen reduction reaction (ORR) and their stability toward poisoning in typical MFC operative conditions were assessed by using electrochemical techniques. Scanning electron microscopy and Brunauer–Emmett–Teller measurements gave insights into sample morphology and surface area. The results indicated that the C/ZrO2 sample with a ZrO2 loading of 25 wt % (C/ZrO2_25) represents the best compromise in terms of ORR activity and stability. C/ZrO2_25 was assembled into cathodes of a prototype single-chamber MFC, which produced a maximum power density of 600 mW m−2. A comparative cost analysis of energy production indicated that the cost of energy delivered by MFCs assembled with a C/ZrO2 cathode was more than 15 times lower than that of MFCs assembled with a reference Pt/C cathode.