Carnation-like MnO2 modified activated carbon air cathode improve power generation in microbial fuel cells

•γ-MnO2 decorated AC air cathode was produced by using a simple potentiostatic method.•Carnation-like MnO2 crystals were formed on the cathode surface.•The mesopore structure plays an important role in the cathode performance.•The highest maximum power density of 1554 mW m−2 was achieved.•The simple cathode preparation method may promote the application of MFC technology.

Highly active and low-cost electrocatalysts are of great importance for large-scale commercial applications of microbial fuel cells (MFCs). In this work, we prepared an activated carbon (AC) air cathode containing electrodeposited γ-MnO2 using a potentiostatic method. The results indicated that carnation-like MnO2 crystals were bound to the surface of the AC air cathode after a deposition time of 10 min, which greatly improved the performance of the cathode. BET analysis results demonstrated that the electrodeposition of MnO2 decreased the micropore surface area of the cathode but increased the mesopore surface area. When compared with a bare AC air cathode, the electrodeposited MnO2 cathode exhibited higher catalytic activity for oxygen reduction reaction. The maximum power density of the MFC equipped with the electrodeposited MnO2 AC air cathode was 1554 mW m−2, which is 1.5 times higher than the control cathode.