For the development of better cathode catalysts for use in polymer electrolyte fuel cells, Pt/C catalyst is modified with poly(melamine-co-formaldehyde) methylated (PMF) by simple coating treatment directly on an electrode. Although this modification almost halves the electrochemical surface area due to PMF covering the Pt surface, the mass activity of the oxygen reduction reaction (ORR) is increased ca. 2-fold. This indicates that the ORR activity of uncovered active sites of Pt is increased by ca. 4-fold by this modification. A similar improvement of ORR is also observed after a Pt/C catalyst electrode is dipped into aqueous solutions of some aminated 1,3,5-triazine derivatives including melamine. These aminated 1,3,5-triazine derivatives such as PMF and melamine positively shift the redox peaks of the adsorption/desorption of OHad which can act as an inhibitor of ORR on Pt. This could result in higher ORR activity. (C) 2019 The Electrochemical Society.