Optimizing the electrode surface area of sediment microbial fuel cells

Sediment microbial fuel cells (SMFCs) is a promising technology for bioremediation, environmental monitoring and remote power supply in various water environments. Optimizing the anode/cathode surface area ratio (SAR(a/c)) is important to enhance the power and decrease the cost of SMFCs. However, in fact, little information has been reported to optimize the SAR(a/c) of SMFCs in individual or stacked mode. This study comparatively analyzed the effects of electrode surface areas on the performance of single SMFCs and serial SMFC-stacks under separated- and connected-hydraulic conditions. The results suggested an optimal SAR(a/c) of 1 to 1.33 for both single and serial stacked SMFCs. Voltage reversal occurred in serial SMFC stacks with unoptimal SAR(a/c) but not in optimized stacks. The more the SAR(a/c) deviated from the optimal SAR(a/c), the more easily the voltage reversal occurred (i.e. lower reversal current). Compared to a separated-hydraulic environment, a connected-hydraulic environment showed no effect on the power generation of anode-limiting SMFC stacks but decreased the power generation and reversal current of cathode-limiting SMFCs, probably due to larger parasitic current. The results are important for the scale-up and application of SMFCs.