The electrocopolymerization of o-toluidine (OT) and p-phenylenediamine (PPDA) on a platinum electrode in a solution of 0.5 mol/dm3 H2SO4 with cyclic voltammetry was examined. The addition of PPDA to the solution of OT in 0.5 mol/dm3 H2SO4 accelerated the electrocopolymerization of OT and PPDA. Fourier transform infrared spectroscopy and ultravioletvisible spectra for the polymers showed that the unit of PPDA should have been integrated into the backbones of the copolymers to form phenazine-like ring structures, and the delocalization of electrons in the copolymer was better than that in poly(o-toluidine) (POT). The scanning electron microscopy (SEM) images for the polymers showed that the copolymers became more porous, and smaller particles, which made oxygen, oxidized the reduced copolymer more easily and faster. It was proven with SEM, energy-dispersive X-ray spectroscopy, and transmission electron microscopy that the size of the nanoplatinum particles deposited on the copolymer reached 10 nm and was much smaller than those on POT. They had better tolerance to the poisoning species arising from the intermediates of the dissociation of methanol on a platinum electrode during the electrocatalytic oxidation of methanol. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013