Facet-Selective Platinum Electrodeposition at Free-standing Polycrystalline Boron-Doped Diamond Films
ABSTRACT In the present investigation, electrochemical deposition of platinum particles was carried out on boron doped diamond (BDD) films by using cyclic voltammetry at different potential sweep rates while maintaining the Pt concentration and number of potential cycles during the deposition as constant for all samples. The BDD film surfaces were studied using Raman spectroscopy, X-ray diffraction, and scanning electrochemical microscopy. The deposited particles were characterized by scanning electron microscopy/X-ray energy dispersive analysis, X-ray photoelectron spectroscopy, and cyclic voltammetry before and after methanol oxidation. The platinum nanoparticles are found to be selectively electrodeposited on the (111) facets of the BDD. In addition, the location of the Pt particles on the diamond facets was affected by the potential sweep rate. For higher sweep rates, the particle size was dependent on the facet on which the particles are electrodeposited with smooth (110) facets exhibiting a smaller number of particles but with a larger particle diameter. After methanol oxidation studies using cyclic voltammetry and controlled potential electrolysis for several hours, the platinum particles remained attached to the (111) facets of the BDD, while the particles on the (110) facets of the BDD became agglomerated along grain boundaries. Functional groups present on the (111) facet of the diamond surface play an important role on the stability of the particles attached to the diamond surface. After methanol oxidation, the particles deposited on other facets appeared to lose their adhesion leading to agglomeration on the grain boundaries. BDD appears to be a promising electrocatalyst support material that can help to resist platinum nanoparticle agglomeration in direct methanol and other low temperature fuel cell applications.
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ABSTRACT: The catalytic performance of nanoparticles can be tuned either by their composition, which mediates electronic structure, or by shape. The shape of a particle is determined by the surface atomic arrangement and coordination. This is affected by the chosen route to synthesize the particle. The route we employed for treating Pt nanoparticles through the application of a square-wave potential is presented. This treatment enhanced the ammonia oxidation stability at platinum modified boron-doped diamond electrodes. Starting from Pt nanoparticles electrodeposited on diamond substrate instead of bulk Pt, we obtained tetrahexahedral Pt nanoparticles. SEM images showed platinum particles with an irregular shape, close to it several regular sharp shaped platinum particles with a size regime of tenths (100-10 nm) of nanometers. Skeleton type particles appear to be the remains of the precursor platinum particles after the square wave treatment breaks down the platinum particles. Platinum features were not shown on the cyclic voltammograms for treatments longer than 30 minutes. This treatment debilitates the C-O-Pt interaction that provides the stability of the platinum particles on the diamond (111) surface. Non-treated particles show a higher current density for the oxidation of ammonia, than the treated particles. The decay of the current after the potential cycling was greater with the non-treated particles than on the particles, which were subjected to the square wave treatment. The chronoamperometry traces reflects similar behaviors.218th ECS Meeting; 01/2010
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ABSTRACT: Environmental compatibility, high flammability, richest in energy per mass unit, and easy conversion into thermal, mechanical and electrical energy are the key advantages of hydrogen fuel, which makes it an idealized vision for future energy as a promising alternative to the diminishing fossil fuels. Unlike the methods very well known in the literature, we used environmental benign photoelectrochemical (PEC) hydrogen production method. Pt is one of the promising electrode materials for PEC method, but high cost makes it impractical for commercialization. A methodology for low Pt loading (7.22 × 10−5 g cm−2) based on electrospray technique is explained for the preparation of hydrogen evolution electrode. The resulted films are annealed at different temperatures and investigated by different characterization techniques that showed surface morphological and compositional changes with annealing temperature. The pores-type structure is transformed to vertically aligned plate-like structure with annealing temperature. After annealing at 400 °C, Pt film is more oxidized and enriching about ∼30% of film surface area with oxidized Pt. The solar to hydrogen conversion efficiency in water splitting was raised from an initial value of 8.4–10.6% and Pt loading was reduced by approximately 1000-fold (from 0.07 to 7.22 × 10−5 g cm−2). Thus, present high efficient hydrogen electrode preparation method utilized less Pt material than the conventional Pt electrode and the efficiency was increased by 26%. This can be scaled up for becoming a volume production low-cost method.International Journal of Hydrogen Energy 07/2010; 35(13-35):6541-6548. DOI:10.1016/j.ijhydene.2010.02.028 · 2.93 Impact Factor
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ABSTRACT: Modified boron-doped diamond (BDD) surfaces supporting different, carefully selected types of metal nanoparticles on different types of crystal facets were fabricated via a self-assembly method. A hydrogen plasma-treated BDD surface was treated with UV/ozone for 10s followed by immersion in a Au nanoparticle (AuNP) solution to fabricate a BDD surface selectively and densely supporting AuNPs on the (111) facet (AuNP111-BDD). The AuNP111-BDD sample was then immersed in H2PtCl6/ascorbic acid or H2PdCl4/sodium citrate to cover the AuNP surface with Pt or Pd (Pt/AuNP111-BDD or Pd/AuNP111-BDD). These samples were treated with UV/ozone for 40s followed by re-immersion in the AuNP solution to immobilize AuNPs on the (100) facets (Pt/AuNP111–AuNP100-BDD or Pd/AuNP111–AuNP100-BDD). The metal nanoparticles supported on the BDD surface were confirmed by cyclic voltammetry to be electrochemically active. The crystal-facet-selective support of the metal nanoparticles was also confirmed by two-dimensional elemental mapping via field emission Auger electron spectroscopy. The macro procedures used for the crystal-facet-selective immobilization of the AuNPs was reproducible, and this technique should be applicable to the creation of a new class of advanced materials in such fields as optics, electronics, sensing, and (electro)catalysis.Diamond and Related Materials 08/2011; 20(8):1171-1178. DOI:10.1016/j.diamond.2011.06.033 · 1.57 Impact Factor