Platinum particles electrodeposition on carbon substrates

Electrochemical deposition of platinum on different carbon substrates was applied to obtain supported submicroparticles to use as electrocatalysts for the oxidation of methanol in acid media. Particles with well-defined morphology and size can be obtained by this technique controlling electrodeposition potential and time. Glassy carbon and graphite fibers were used as substrates. Platinum particles were deposited from chloroplatinic acid solutions. Conventional electrochemical techniques were used to characterize supported platinum surface status. Particle size and catalyst mass were influenced by deposition potential and time. The application of double potential steps favored a more uniform dispersion of the particles and a general reduction in particle size. From specific surface area measurements particle diameters between 10 and 20 nm were estimated when glassy carbon was used as support. Differences in size and morphology were observed when Pt was deposited on graphite fibers. Notwithstanding using similar conditions, the particles on fibers were bigger and tending to coalesce. This behavior was ascribed to the highly hydrophobic surface of the fibers. The Pt deposits were tested as catalyst for electrochemical methanol oxidation. The Pt/GC electrocatalytic activity expressed as current per Pt mass was found to depend on the metal particle size, showing a decreasing activity when the catalyst diameter increase.