Microbial fuel cells (MFC) with 30% wet-proofed air cathodes have previously been optimized to have 4 diffusion layers (DLs) in order to limit oxygen transfer into the anode chamber and optimize performance. Newer MFC designs that allow close electrode spacing have a separator that can also reduce oxygen transfer into the anode chamber, and there are many types of carbon wet-proofed materials available. Additional analysis of conditions that optimize performance is therefore needed for separator-coupled MFCs in terms of the number of DLs and the percent of wet proofing used for the cathode. The number of DLs on a 50% wet-proofed carbon cloth cathode significantly affected MFC performance, with the maximum power density decreasing from 1427 to 855mW/m 2 for 1-4 DLs. A commonly used cathode (30% wet-proofed, 4 DLs) produced a maximum power density (988mW/m 2) that was 31% less than that produced by the 50% wet-proofed cathode (1 DL). It was shown that the cathode performance with different materials and numbers of DLs was directly related to conditions that increased oxygen transfer. The coulombic efficiency (CE) was more affected by the current density than the oxygen transfer coefficient for the cathode. MFCs with the 50% wet-proofed cathode (2 DLs) had a CE of >84% (6.8A/m 2), which was substantially larger than that previously obtained using carbon cloth air-cathodes lacking separators. These results demonstrate that MFCs constructed with separators should have the minimum number of DLs that prevent water leakage and maximize oxygen transfer to the cathode. © 2011 Elsevier B.V.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-I1-003-13
Acknowledgements: This research was supported by the 863 Project in China (2009AA06Z306), an award from Ministry of Education of the People's Republic of China, a scholarship from Shanghai Tongji Gao Tingyao Environmental Science and Technology Development Foundation, an award from Tsinghua University, and Award KUS-I1-003-13 from the King Abdullah University of Science and Technology (KAUST). We thank Dr. Shaoan Cheng at Zhejiang University for comments and suggestions.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.