Cu-doped CaFeO₃ perovskite oxide as oxygen reduction catalyst in air cathode microbial fuel cells

Cathode electrocatalyst is quite critical to realize the application of microbial fuel cells (MFCs). Perovskite oxides have been considered as potential MFCs cathode catalysts to replace Pt/C. Herein, Cu-doped perovskite oxide with a stable porous structure and excellent conductivity was successfully prepared through a sol-gel method. Due to the incorporation of Cu, CaFe_0.9Cu_0.1O₃ has more micropores and a larger surface area, which are more conducive to contact with oxygen. Doping Cu resulted in more Fe³⁺ in B-site and thus enhanced its binding capability to oxygen molecules. The data from electrochemical test demonstrated that the as-prepared catalyst has good conductivity, high stability, and excellent ORR properties. Compared with Pt/C catalyst, CaFe_0.9Cu_0.1O₃ exhibits a lower overpotential, which had an onset potential of 0.195 V and a half-wave potential of -0.224 V, respectively. CaFe_0.9Cu_0.1O₃ displays an outstanding four-electron pathway for ORR mechanism and demonstrates superiors corrosion resistance and stability. The MFC with CaFe_0.9Cu_0.1O₃ has a greater maximum power density (1090 mW m^-3) rather than that of Pt/C cathode (970 mW m^-3). This work demonstrated CaFe_0.9Cu_0.1O₃ is an economic and efficient cathodic catalyst for MFCs.