Use of carbon mesh anodes and the effect of different pretreatment methods on power production in microbial fuel cells

Flat electrodes are useful in microbial fuel cells (MFCs) as close electrode spacing improves power generation. Carbon cloth and carbon paper materials typically used in hydrogen fuel cells, however, are prohibitively expensive for use in MFCs. An inexpensive carbon mesh material was examined here as a substantially less expensive alternative to these materials for the anode in an MFC. Pretreatment of the carbon mesh was needed to ensure adequate MFC performance. Heating the carbon mesh in a muffle furnace (450°C for 30 min) resulted in a maximum power density of 922 mW/m² (46 W/m³) with this heat-treated anode, which was 3% more power than that produced using a mesh anode cleaned with acetone (893 mW/m²; 45 W/m³). This power density with heating was only 7% less than that achieved with carbon cloth treated by a high temperature ammonia gas process (988 mW/m²; 49 W/m³). When the carbon mesh was treated by the ammonia gas process, powerincreased to 1015 mW/m² (51 W/m³). Analysis of the cleaned or heated surfaces showed these processes decreased atomic O/C ratio, indicating removal of contaminants that interfered with charge transfer. Ammonia gas treatment also increased the atomic N/C ratio, suggesting that this process produced nitrogen related functional groups that facilitated electron transfer. These results show that low cost heat-treated carbon mesh materials can be used as the anode in an MFC, providing good performance and even exceeding performance of carbon cloth anodes.