Structure Evolution of Air Cathodes and Their Application in Electrochemical Sensor Development and Wastewater Treatment

Cathode structure and material are the most important factors to determine the performance and cost of single chamber air-cathode microbial fuel cell (MFC), which is the most promising type of MFC technology. Since the first air cathode was invented in 2004, five major structures (1-layer, 2-layer, 3-layer, 4-layer and separator-support) have been invented and modified to fit new material, improve power performance and lower MFC cost. This paper reviewed the structure evolution of air cathodes in past 18 years. The benefits and drawbacks of these structures, in terms of power generation, material cost, fabrication procedure and modification process are analyzed. The practical application cases (e.g., sensor development and wastewater treatment) employed with different cathode structures were also summarized and analyzed. Based on practical performance and long-term cost analysis, the 2-layer cathode demonstrated much greater potential over other structures. Compared with traditional activated-sludge technology, the cost of an MFC-based system is becoming competitive when employing with 2-layer structure. This review not only provides a detailed development history of air cathode but also reveals the advantages/disadvantages of air cathode with different structures, which will promote the research and application of air-cathode MFC technology.