By using specially prepared Teflon‐bonded electrodes, it was possible to eliminate the internal IR drop across the porous electrode and the concentration overvoltage associated with diffusion of oxygen in the gas filled pores of the electrode structure. After this elimination, the apparent exchange current and kinetic parameters for the reduction of oxygen on Pt‐black in , , and electrolytes can be determined by using Tafel plots. The data indicate that although the rate of the transfer reaction is the same in the two acids, is the poorer electrolyte for an acid fuel cell because of the much slower transport of oxygen. The kinetic data differ only moderately from those reported for smooth Pt surfaces.