Effect of the oxygen reduction catalyst loading method on the performance of air breathable cathodes for microbial fuel cells

This paper presents three different methods of hydrothermal (HT), microwave (MW), and cyclic voltammetry (CV) used to load a catalyst on a cathode surface. In the HT and MW methods, a multiwall carbon nanotube (MWCNT) is used as a support material to fix the catalyst, while Nafion solution is used as a binder to load the catalyst on the cathode surface. For the third option, the CV method is used to directly load the catalysts on the cathode surface without any support material. The performances of the three cathodes are tested in an air breathable batch microbial fuel cell (MFC) and compared to that of a commercial carbon cloth cathode with platinum (Pt). The maximum power density of the MFC with the HT cathode is measured as 833 mW m−2, which is higher than those of the CV and MW cathodes and slightly smaller than the MFC with the Pt cathode. The open circuit voltage of the MFC with the HT cathode is 610 mV, which is higher than those of MFCs with other cathodes, while the power density is higher than the MFCs of the MW and CV cathodes. In the case of the HT cathode, a conductive MWCNT network is well formed and entangled with the catalyst nanostructure of the cathode surface while the small ohmic and activation resistances of the HT cathode contribute to the good MFC performance.