Improved performance of microbial fuel cells using a gradient porous air cathode: An experiment and simulation study

High carbon catalyst loadings are commonly used for the catalyst layer (CL) in air-cathodes to obtain a performance comparable with that using platinum. This results in a much thicker CL, which severely limits mass transfer. In this study, we developed a porosity-gradient CL to passively enhance mass transfer in the air-cathode of microbial fuel cells (MFCs) for the first time. Computational results demonstrated that a cathode CL with increasing porosity (CL-IP) and decreasing porosity (CL-DP) from the water to the air-facing side exhibited improved transport of oxygen and OH-, respectively, alleviating concentration overpotentials in the CL Experimental results also showed that an MFC that included a cathode with CL-IP achieved a maximum power density of 1781 +/- 92 mW m(-2), which was higher than that achieved with CL-DP and a homogeneous CL (1614 +/- 72 and 1183 +/- 205 mW m(-2)). (C) 2019 Elsevier B.V. All rights reserved.