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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 0.9 Cu 0.1 O 3 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 0.9 Cu 0.1 O 3 exhibits a lower overpotential, which had an onset potential of 0.195 V and a half-wave potential of −0.224 V, respectively. CaFe 0.9 Cu 0.1 O 3 displays an outstanding four-electron pathway for ORR mechanism and demonstrates superiors corrosion resistance and stability. The MFC with CaFe 0.9 Cu 0.1 O 3 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 0.9 Cu 0.1 O 3 is an economic and efficient cathodic catalyst for MFCs. • Cu-doped double B-site perovskite forms microporous structure. • Cu promotes the combination of Fe–O and O. • CaFe 0.9 Cu 0.1 O 3 shows outstanding and highly stable ORR catalytic performance. • CaFe 0.9 Cu 0.1 O 3 can be used as a highly efficient cathode catalyst in MFCs. [ABSTRACT FROM AUTHOR]

Stable perovskite oxide is considered as a potential cathode for microbial fuel cells (MFCs). Herein, Zn is used as an effective element to modify the micro-structure and oxygen vacancy of perovskite to be a novel cathode catalyst. Physical characterizations show that due to partial volatilization at high temperature of Zn, perovskite forms hierarchically porous structures. Moreover, Zn is precipitated in electrochemical reaction to generate Zn vacancy in situ; thus, the active center of Fe has a superior interaction with oxygen-containing species, promoting the production of oxygen vacancy and forms a mixed valence state of Fe2+/Fe3+. The Zn-doped perovskite material CaFe 0·7 Zn 0·3 O 3 exhibits remarkable oxygen reduction reaction (ORR) performances with outstanding onset potential (0.194 V vs. Ag/AgCl) and half-wave potential (−0.219 V vs. Ag/AgCl) under alkaline condition, which is better than Pt/C catalyst. Besides, CaFe 0·7 Zn 0·3 O 3 shows an excellent four-electron pathway of ORR mechanism with remarkable corrosion resistance and stability, which enables a more reliable cathode electrocatalyst. The maximum power density of CaFe 0·7 Zn 0·3 O 3 (892.10 ± 90.79 mW m−3) testing on microbial fuel cell is comparable to the maximum power density (1012.86 ± 84.03 mW m−3) of Pt/C. The findings of this work provide the feasibility of exploring inexpensive and high-performance cathode catalyst. Image 1 • Zn-doped CaFeO 3 promotes mesoporous formation. • The incorporation of Zn creates more oxygen vacancies. • CaFe 0·7 Zn 0·3 O 3 shows the remarkable catalytic activity and stability during ORR. • Applying as the cathode catalyst in microbial fuel cells. [ABSTRACT FROM AUTHOR]