Non-Platinum Group Catalysts to Improve Performance of a Membraneless Microbial Fuel Cell

Abstract

Over the last couple decades, microbial fuel cells (MFCs) have become a technology of interest for renewable energy production and waste treatment/reclamation. MFCs are flexible with fuel and, for this reason, have garnered interest as biosensors, unit operations in advanced wastewater treatment, and alternative power sources. MFCs oxidize organic matter at the anode where microbes perform anaerobic respiration to convert organic matter into simpler compounds (such as carbon dioxide, methane, etc.); however, the anode electrode serves as the final electron acceptor [1, 2]. The electrons produced at the anode are used at the cathode in oxygen reduction reaction (ORR), a reaction that requires the presence of a catalyst. The system design for MFCs can vary to meet different applications [3], but one of the more popular designs is a membrane less, single chamber, air cathode microbial fuel cell [4], which has the anode submerged in an oxygen-less, nutrient solution and has an air-exposed cathode. Although promising in concept, MFCs have very low power density, making them cost inefficient. A major performance limitation in MFCs has been identified in the cathode. Overall efficiency and power density a strongly influenced by cathode design and catalyst selection for the ORR [4, 5]. Previous modeling efforts have suggested oxygen crossover to the anode, oxygen diffusion to the ORR catalyst, and the catalyst used are major factors for low power density [6-8]. In this work, improved MFC performance is demonstrated using non-platinum group catalyst material. The novel catalyst was benchmarked against a platinum group catalyst. Using the novel non-platinum catalyst results in a modest increase in open circuit potential, and a significant increase in maximum current density and power density. In addition, we have investigated the influence of non-platinum catalyst loading on the overall performance. The novel catalysts used in this work demonstrated stability over months of operation. This suggests that the non-platinum group catalyst used in this work is more efficient than platinum group catalyst, improving the cell performance while simultaneously enabling lower cost. References Jr, L.B.W., C.H. Shaw, and J.F. Castner, Bioelectrochemical fuel cells. Enzyme and Microbial Technology, 1982. 4(3): p. 6.Kim, H.J., et al., A mediator-less microbial fuel cell using a metal reducing bacterium, Shewanella putrefaciens. Enzyme and Microbial Technology, 2002. 30(2): p. 8.He, Z., S.D. Minteer, and L.T. Angenent, Electricity Generation from Artificial Wastewater Using an Upflow Microbial Fuel Cell. Environmental Science and Technology, 2006. 39: p. 6.Liu, H. and B.E. Logan, Electricity Generation Using an Air-Cathode Single Chamber Microbial Fuel Cell in the Presence and Absence of a Proton Exchange Membrane. Environmental Science and Technology, 2004. 38: p. 6.Rismani-Yazdi, H., et al., Cathodic limitations in microbial fuel cells: An overview. Journal of Power Sources, 2008. 180: p. 12.Ou, S., et al., Full cell simulation and the evaluation of the buffer system on air-cathode microbial fuel cell. Journal of Power Sources, 2017. 347: p. 11.Ou, S., et al., Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition. Journal of Power Sources, 2016. 328: p. 12.Ou, S., et al., Multi-variable mathematical models for the air-cathode microbial fuel cell system. Journal of Power Sources, 2016. 314: p. 9. Figure 1