Microbial fuel cell performance with non-Pt cathode catalysts

Various cathode catalysts prepared from metal porphyrines and phthalocyanines were examined for their oxygen reduction activity in neutral pH media. Electrochemical studies were carried out with metal tetramethoxyphenylporphyrin (TMPP), CoTMPP and FeCoTMPP, and metal phthalocyanine (Pc), FePc, CoPc and FeCuPc, supported on Ketjenblack (KJB) carbon. Iron phthalocyanine supported on KJB (FePc-KJB) carbon demonstrated higher activity towards oxygen reduction than Pt in neutral media. The effect of carbon substrate was investigated by evaluating FePc on Vulcan XC carbon (FePcVC) versus Ketjenblack carbon. FePc-KJB showed higher activity than FePcVC suggesting the catalyst activity could be improved by using carbon substrate with a higher surface area. With FePc-KJB as the MFC cathode catalyst, a power density of 634 mW m^-2 was achieved in 50 mM phosphate buffer medium at pH 7, which was higher than that obtained using the precious-metal Pt cathode (593 mW m^-2). Under optimum operating conditions (i.e. using a high surface area carbon brush anode and 200 mM PBM as the supporting electrolyte with 1 g L^-1 acetate as the substrate), the power density was increased to 2011 mW m^-2. This high power output indicates that MFCs with low cost metal macrocycles catalysts is promising in further practical applications.