title: Platinum electrodeposition on unsupported carbon nano-onions.
abstract: An effort to develop smaller, well-dispersed catalytic materials electrochemically on high-surface-area carbon supports is required for improved fuel cell performance. A high-surface-area carbon material of interest is carbon nano-onions (CNOs), also known as multilayer fullerenes. The most convenient synthesis method for CNOs is annealing nanodiamond particles, thus retaining the size of the precursors and providing the possibility to prepare very small nanocatalysts using electrochemical techniques. In terms of pure metal catalysts, platinum is the most common catalyst used in fuel cells. The combination of Pt nanoparticles with CNOs could lead to new catalytic nanomaterials. In this work, this was accomplished by using a rotating disk-slurry electrode (RoDSE) technique. The Pt/CNO catalysts were prepared from slurries that contained functionalized CNOs and K(2)PtCl(6) as the platinum precursor in aqueous 0.1 M H(2)SO(4) solution. X-ray photoelectron spectroscopy results showed that 37% of the Pt on the CNOs is metallic Pt whereas 63% had higher binding energies, which is evidence of higher oxidation states or the presence of Pt atoms and clusters on CNOs. However, aberration-corrected scanning transmission electron microscopy of the Pt/CNOs confirmed the presence of Pt atoms and clusters on CNOs. Thermal gravimetric analysis showed the excellent thermal stability of the Pt/CNOs and a lower onset potential for the electrochemical oxidation of methanol compared to that of commercial Pt/Vulcan catalyst material. The computational method confirmed the Pt atoms' location at CNOs surface sites. Geometric parameters for distances between Pt atoms in the 3Pt/CNOs molecular system from our theoretical calculations are in agreement with the respective parameters obtained experimentally. The combination of CNO with RoDSE presents a new highly dispersed catalyst nanomaterial.
authors.affiliation: Center for Advanced Nanoscale Materials, Department of Chemistry, University of Puerto Rico, Rio-Piedras Campus, P.O. Box 23346, San Juan, Puerto Rico 00931.
authors.forename: Diana
authors.initials: D
authors.lastname: Santiago
authors.forename: Gabriel G
authors.initials: GG
authors.lastname: Rodríguez-Calero
authors.forename: Amit
authors.initials: A
authors.lastname: Palkar
authors.forename: Diana
authors.initials: D
authors.lastname: Barraza-Jimenez
authors.forename: D H
authors.initials: DH
authors.lastname: Galvan
authors.forename: Gilberto
authors.initials: G
authors.lastname: Casillas
authors.forename: Alvaro
authors.initials: A
authors.lastname: Mayoral
authors.forename: Miguel
authors.initials: M
authors.lastname: Jose-Yacamán
authors.forename: Luis
authors.initials: L
authors.lastname: Echegoyen
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Cabrera
mesh_terms: D002384:Catalysis; D004566:Electrodes; D004595:Electroplating; D037741:Fullerenes / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D010084:Oxidation-Reduction; D010316:Particle Size; D056951:Photoelectron Spectroscopy; D010984:Platinum / Q000737:chemistry*; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D037741:Fullerenes; D010984:Platinum; D000432:Methanol