Deposition of small Pt nanoparticles of the order of 2–2.5 nm on carbon nanotubes (CNTs) grown directly on carbon paper is demonstrated in this work. Sulfonic acid functionalization of CNTs is used as a means to facilitate the uniform deposition of Pt on the CNT surface. The organic molecules attached covalently to the CNT surface via electrochemical reduction of corresponding diazonium salts are treated with concentrated sulfuric acid and the sulfonic acid sites thus attached are used as molecular sites for Pt ion adsorption, which are subsequently reduced to yield the small Pt nanoparticles. Cyclic voltammograms reveal that, after removal of the organic groups during high temperature reduction, these Pt nanoparticles are in electrical contact with the carbon paper backing. A typical Pt loading of 0.09 mg cm⁻² is achieved, that shows higher specific surface area of Pt than an E-TEK electrode with Pt loading of 0.075 mg cm⁻². A membrane and electrode assembly (MEA) is prepared with a Pt/CNT electrode as cathode and an E-TEK electrode as anode, and it offers better performance than a conventional E-TEK MEA.