The kinetics of oxygen reduction of cathode catalyst is a critical factor that limits the performance of microbial fuel cells (MFCs). The composite catalyst of three composite proportion(1:3

1:1 and 3:1)

which were prepared by reacting KMnO4 with supercapacitor activated carbon (S-AC)

were tested as air-cathode catalyst of microbial fuel cells (MFCs) for oxygen reduction. X-ray diffraction (XRD) was used to characterize the catalysts

energy dispersive X-Ray Spectroscopy to estimate the quality of MnO2

scanning electron microscopy (SEM) to observe the surface morphology

and BET method to examine surface area and pore distribution characteristics

to analyze the factors affecting the performance of the composite catalyst. With increasing of composite proportion

the MnO2 sheets gathered into nano-particles (300—500 nm) on the surface of S-AC. At the same time

there is the decrease of the internal and external surface area MnO2/S-AC. Nickel foam air-cathode was made with different catalysts

and tested in air-cathode MFCs to study the effect on MFC performance by linear sweep voltammetry (LSV)

polarization curves and power density curve. When the feeding ratio of KMnO4: S-AC is 1:3

the maximum power density was 321.2 mW·m-2

which was increased by about 20% over the S-AC loading MFC. However

when the feeding ratio was increased to 1:1 and 3:1

the maximum power density decreased to 240.9 and 160.3 mW·m-2. MnO2/S-AC composite catalyst within a certain ratio range could effectively improve the performance of air-cathode and MFC

which helps to the expansion application of air-cathode MFC.