Pyrazine-bridged Fe[M-C(CN)(4)] complexes (M-C = Pt2+ and Pd2+) with 3D porous structures were utilized as the cathode of one-compartment H2O2 fuel cells, which operated in 0.3 M H2O2, using a nickel mesh as an anode. The power density of a H2O2 fuel cell using pyrazine-bridged Fe[Pt(CN)(4)] reached 4.2 mW cm(-2), which is the highest value reported for the one-compartment H2O2 fuel cells. On the other hand, H2O2 fuel cells using pyrazine-bridged M-N[Pt(CN)(4)] (M-N = Co2+ and Mn2+) as the cathodes exhibited power densities lower than 0.01 mW cm(-2), indicating that Fe2+ ions are indispensable to achieve the high power density.