Electrochemical performance of iron redox flow batteries (RFBs) was improved through incorporating iron redox mediators into the electrodes. Unpurified carbon nanotubes electrodes containing ferrocene catalysts, from the carbon nanotubes synthesis, are activated to create “hotspots” for Faradaic charge transfer that reduces losses associated with activation, Ohmic, and mass transfer resistances. This permits higher discharge voltages at elevated discharge currents, which from Ohm’s Law (P = iE) establishes augmented power densities. Carbon nanotube electrodes are activated utilizing cyclic voltammetry, in an acidic environment, to initiate charge transfer interactions between redox electrolytes and iron nanoparticles in the electrode. Modified electrodes exhibited 141% gain in power density and a 56.5% improvement in energy density in coin cell devices. Economic value and ready availability of iron paired with enhanced performance makes iron RFBs a viable option for future RFB research. The highest peak power density reported for all-iron RFBs to the author’s awareness was accomplished at 176 mW cm^-2 with iron-modified electrodes under no electrolyte flow.