CoO nanosheets in situ grown on nitrogen-doped activated carbon as an effective cathodic electrocatalyst for oxygen reduction reaction in microbial fuel cells

•CoO nanosheets were in suit successfully generated onto N-AC.•CoO@N-ACwasfirstutilizedascathodicelectrocatalystinMFCs.•The rate and kinetics constant for ORR were greatly enhanced.•The MPD was 1650.1±36.2mWm−2, 122.5% higher than that of the control.•CoO@N-AC is a promissing cathodic electocatalyst for MFCs. A low cost, naturally abundant, and highly active oxygen reduction reaction (ORR) electrocatalyst is essential for the commercialization of microbial fuel cells (MFCs). In this study, a promising strategy was proposed to prepare catalyst CoO nanosheets supported by nitrogen-doped activated carbon (CoO@N-AC) to achieve a synergetic effect between metallic oxide and heteroatom-doped carbon. The nanocomposites possess a large Brunauer–Emmett–Teller surface area (1577.2m2g−1), low total resistance (9.26Ω), and four-electron ORR pathway. These nanocomposites are utilized as the air-cathode catalysts in MFCs. CoO@N-AC remarkably increases the maximum power density by 122.5% from 741.5±8.5mWm−2 to 1650.1±36.2mWm−2, which is higher than that of Pt/C (1201.4±13.5mWm−2). The excellent catalytic activity makes CoO@N-AC a promising cathodic electrocatalyst for practical application of MFCs.