Effective Cathode Catalysts for Oxygen Reduction Reactions in Microbial Fuel Cell

Microbial fuel cells (MFCs) are bioelectrochemical systems that directly convert chemical energy contained in organic matters like wastewaters into electrical energy by utilizing the metabolic (catalytic) activity of microorganisms (Kim et al. 1999; Bond and Lovley 2003). In the anode chamber of MFC, the substrates are oxidized by electroactive bacteria to produce carbon dioxide with electrons (e−) and protons (H+) (Logan and Regan 2006). The generated e− get transported to the cathode through the outside circuit, while H+ will transfer through the electrolyte and reach the cathode. Additionally, the electrons and protons mix with the oxygen molecule and reduced to a water molecule on the cathode. The oxygen reduction reaction (ORR) at the cathode is considered a rate limiting step due to its heterogenic nature. An efficient catalyst is, therefore, required to reduce the cathodic overpotential (Chandrasekhar 2019). The costly noble metal dust platinum was used during the early phase of research; however, recently different types of nonmetal materials were applied such as metal-based catalysts, carbon-based catalysts, carbon–metal hybrid catalysts, and metal–nitrogen–carbon advanced catalysts for efficient ORR (Clauwaert et al. 2008). The performances of MFCs having different ORR catalysts were compared in terms of power output. In certain es, biocathode was utilized for ORR. The present chapter broadly discussed the varied cathode catalysts used for the oxidation–reduction reactions in MFCs. The chapter included the synthesis procedure of ORR catalyst, nature, stability, and electrochemical performance as cathode catalysts. This chapter is expected to deliver an understanding of the applications of cathode catalysts in MFCs to boost method efficiency furthermore as to build the method economically viable.