Cathode electrodes for MFC studies were prepared using non
wet-proofed carbon paper (E-Tek). On the air facing side, four
poly-tetrafluoroethylene (PTFE) diffusion layers were applied
according to previously reported procedures (Cheng et al., 2006).The catalyst layer was prepared by mixing of Mn–Co oxide catalyst
with carbon Vulcan XC-72R and Nafion solution (5% Nafion solution
from Aldrich) to form catalyst ink which painted on the side
of the carbon paper exposed to solution. The catalyst ink formulation
was: 6.25 mg of catalyst, 16.66 mg of carbon Vulcan XC-72R,
270 lL of isopropyl alcohol, 217 lL of 5% Nafion solution and
135 lL of double distilled water. The mixture was ultrasonicated
for 30 min. For MFC cathode fabrication, the catalyst loading
(Mn–Co oxide) was 0.5 mg/cm2. The first layer was obtained by
spreading the ink on carbon paper electrode area, using amaskanda
brush. Several successive layers were then deposited on top of each
other to reach the loading of 0.5 mg/cm2. It was ascertained that
the previous layers were dry before adding another layer. Pt was
used as a control for the cathode catalysts. The platinum cathode
was made following the previously described method, in which
0.5 mg Pt/cm2 catalyst was bonded on a carbon paper electrode
using a Nafion solution. All electrodes were dried at room temperature
for 24 h before use.