Multi-metal ferrite as a promising catalyst for oxygen reduction reaction in microbial fuel cell

Improving catalytic activity of cathode with noble metal-free catalysts can significantly establish microbial fuel cells (MFCs) as a sustainable and economically affordable technology. This investigation aimed to assess the viability of utilizing tri-metal ferrite (Co₀.₅Cu_0.5 Bi_0.1Fe_1.9O₄) as an oxygen reduction reaction (ORR) catalyst to enhance the performance of cathode in MFCs. Trimetallic ferrite was synthesized using a sol-gel auto-combustion process. Electrochemical evaluations were conducted to assess the efficacy of as-synthesized composite as an ORR catalyst, employing electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). This evaluation revealed that the impregnation of bismuth in the Co-Cu-ferrite structure improves the reduction current response and reduces the charge transfer resistance. Further experiments were conducted to test the performance of this catalyst in an MFC. The MFC with tri-metal ferrite catalyst generated a power density of 11.44 W/m³ with 21.4% coulombic efficiency (CE), which was found to be comparable with commercially available 10% Pt/C used as cathode catalyst in MFC (power density of 12.14 W/m³ and CE of 23.1%) and substantially greater than MFC having bare carbon felt cathode without any catalyst (power density of 2.49 W/m³ and CE of 7.39%). This exceptionally inexpensive ORR catalyst has adequate merit to replace commercial costlier platinum-based cathode catalysts for upscaling MFCs.