Accelerated tests for evaluating the air-cathode aging in microbial fuel cells

Air-cathode stability is a key factor affecting the feasibility of microbial fuel cells (MFCs) in applications. However, there is no quick and effective method to evaluate the robustness and durability of the MFC air cathodes. In this study, a three-phase decrease of power density was observed in multiple MFCs that have been operated for about a year. Quantification of the contributions of cathode biofilm and salt accumulation to the current decrease suggested that the biofouling was the major contributor to the cathode aging during the first 200 days, and salt accumulation gradually outpaced biofouling afterward. An accelerated test method was then developed using fast-growing Escherichia coli, simulated soluble microbial products (SMPs), and a concentrated medium solution. Using this method, the cathode aging can be evaluated quickly within hours/days compared to over a year of operation, benefiting the development of high-performing and durable cathode materials.