Electrodeposited PtCo and PtMn electrocatalysts for methanol and ethanol electrooxidation of direct alcohol fuel cells (original) (raw)
Related papers
Journal of Power Sources
Well-dispersed Pt nanoparticles with controlled size and narrow size distribution were prepared by polyalcohol reduction of platinum acetylacetonate, using oleylamine as a capping agent. The particle size was varied from 3.5 nm to 11.5 nm by decreasing the amount of oleylamine added in the synthesis. Size selection of the as-prepared particles by solvent fractionation yielded nearly monodispersed Pt particles. The as-prepared particles were loaded on a carbon support by physical deposition, but showed no electrocatalytic activity due to the oleylamine bound to the particle surface. The particles were activated for electrocatalysis after heating the particles in air at 185 • C for 5 h, conditions that gave no particle-sintering and no oxidation. Cyclic voltammetry showed that the particles after the heat treatment in air were electrocatalytically active for methanol oxidation. The smaller 3.5 nm and 4.0 nm Pt particles had a higher intrinsic activity for methanol oxidation, but a lower tolerance to CO poisoning, compared with 6.0 nm, 9.5 nm and 11.5 nm particles. CO-stripping results suggest that CO is more easily oxidized on larger Pt particles.
Synthesis and activation of Pt nanoparticles with controlled size for fuel cell electrocatalysts
Journal of Power Sources, 2007
ABSTRACT Well-dispersed Pt nanoparticles with controlled size and narrow size distribution were prepared by polyalcohol reduction of platinum acetylacetonate, using oleylamine as a capping agent. The particle size was varied from 3.5 nm to 11.5 nm by decreasing the amount of oleylamine added in the synthesis. Size selection of the as-prepared particles by solvent fractionation yielded nearly monodispersed Pt particles. The as-prepared particles were loaded on a carbon support by physical deposition, but showed no electrocatalytic activity due to the oleylamine bound to the particle surface. The particles were activated for electrocatalysis after heating the particles in air at 185 °C for 5 h, conditions that gave no particle-sintering and no oxidation. Cyclic voltammetry showed that the particles after the heat treatment in air were electrocatalytically active for methanol oxidation. The smaller 3.5 nm and 4.0 nm Pt particles had a higher intrinsic activity for methanol oxidation, but a lower tolerance to CO poisoning, compared with 6.0 nm, 9.5 nm and 11.5 nm particles. CO-stripping results suggest that CO is more easily oxidized on larger Pt particles.
Enhancing by Weakening: Electrooxidation of Methanol on Pt3Co and Pt Nanocubes
Angewandte Chemie International Edition, 2010
Direct methanol fuel cells (DMFCs) are attractive energy conversion devices for powering portable electronics by converting the chemical energy of methanol directly into electricity. To increase the methanol oxidation activity and to reduce platinum loading, bimetallic catalysts of platinum alloyed with a less expensive metal M are often used. Among different bimetallic catalysts, Pt/Ru has attracted most attention owing to its strong methanol oxidation enhancement. The improved catalytic activity is explained by the bifunctional mechanism and the electronic effect. In the bifunctional mechanism, the platinum sites are responsible for methanol oxidation to form adsorbed carbon monoxide (CO ads ), which poisons the catalyst surface for further fuel oxidation; the ruthenium sites provide adsorbed hydroxyl groups (OH ads ), which is the oxidant for the removal of CO ads , at a much lower potential than on platinum. In the electronic effect, the presence of ruthenium changes the electronic structure of platinum in such a way that it lowers the CO adsorption energy. These two mechanisms often operate concurrently and are often invoked to explain the activity enhancement of other Pt/M alloys. Herein we present methanol oxidation on Pt 3 Co nanocubes (NCbs), in which the enhanced methanol oxidation arises solely from the electronic effect.
The Journal of Physical Chemistry C, 2013
TiC, TiCN, and TiN supported Pt nanoparticles have been investigated as anode electrocatalytic materials for direct methanol fuel cells. The catalysts were studied in acidic and alkaline media and compared with platinum supported on carbon black. CO and methanol oxidation were studied by voltammetry and chronoamperometry techniques. Transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction analysis were employed to characterize the novel catalysts. Results show that a carbonsupported Pt catalyst is mainly formed by nanoparticles with long (111) domains, and those catalysts with a titanium-based support present a huge amount of defect sites with diverse symmetries. Additionally to geometric factors, an electronic effect by the Ti-based support leads to considerably enhanced CO electrooxidation with respect to carbonsupported catalysts, which is of special relevance in alkaline media. However, no such improvement is observed during the methanol oxidation reaction on Ti-based catalysts at high pH.
Journal of Electroanalytical Chemistry, 2012
One of the key objectives in fuel cell technology is to reduce Pt loading by the improvement of its catalytic activity towards alcohol oxidation. Here, a sol-gel based method was used to prepare ternary and quaternary carbon supported nanoparticles by combining PtARu with Mo, Ta, Pb, Rh or Ir, which were used as electro-catalysts for the methanol and ethanol oxidation reactions in acid medium. Structural characterization performed by XRD measurements revealed that crystalline structures with crystallites ranging from 2.8 to 4.1 nm in size and with different alloy degrees were produced. Tantalum and lead deposited as a heterogeneous mixture of oxides with different valences resulting in materials with complex structures. The catalysts activities were evaluated by cyclic voltammetry and by Tafel plots and the results showed that the activity towards methanol oxidation was highly dependent of the alloy degree, while for ethanol the presence of a metal capable to promote the break of CAC bond, such as Rh, was necessary for a good performance. Additionally, the catalysts containing of TaO x or PbO x resulted in the best materials due to different effects: the bi-functional mechanism promoted by TaO x and a better dispersion of the catalysts constituents promoted by PbO x .
Electrocatalysis, 2011
Size-controlled Pt nanoparticles embedded in TiO 2 were prepared by simultaneous dual-gun sputtering from pure targets of Pt and TiO 2. The mean diameter of the Pt nanoparticles, as confirmed by their transmission electron microscopic images, was varied from ∼2 to ∼4 nm by changing the RF power ratio of Pt and TiO 2. The transmission electron diffraction and X-ray diffraction patterns of the Pt nanoparticles embedded in TiO 2 confirmed that the Pt particles are polycrystalline, whereas the TiO 2 matrix is amorphous. The electrocatalytic properties of Pt/TiO 2 were strongly influenced by the particle size and the TiO 2 support. The presence of the TiO 2 support led to higher electronic density on Pt, changing its chemisorption properties, weakening the Pt-CO bonds, and increasing its CO oxidation activity. The high CO oxidation activity of the Pt nanoparticles embedded in TiO 2 can be also attributed to the ability of TiO 2 to provide highly reactive oxygen atoms. CO desorbed at higher onset potential with a decrease in the particle size, which is related to quantumsize effects in the Pt nanoparticles. The high activity of methanol oxidation on the Pt/TiO 2 electrode resulted from the homogeneous dispersion and the miniaturization of Pt. In addition, we found that the enhanced catalytic activity in the Pt/TiO 2 electrodes correlated to proton spillover phenomena in TiO 2 and was measured by performing an in situ electrochromic test.
iranian journal of catalysis, 2017
The impregnation method was used to synthesize Pt and Pt3Co supported on MWCNTs applying NaBH4 as the reducing agent. The structure, morphology, and chemical composition of the electrocatalysts were characterized through SEM, XRD, and EDX. X-ray diffraction showed a good crystallinity of the supported Pt nanoparticles on the composites and showed the formation of Pt3Co alloy. The SEM images revealed that the particles of Pt3Co were deposited uniformly on the surface of MWCNT with a diameter of 10 nm. EDX analysis confirmed the surface segregation of Co and Pt occurred (1:3 surface atomic ratio Pt-Co) for the Pt3Co/MWCNT nanocomposite. The Pt3Co/MWCNTs and Pt/MWCNTs electrocatalysts’ electrochemical performance was assessed against the methanol oxidation reaction (MOR) in 0.5 M H2SO4 solution using the chronoamperometry (CA) and the cyclic voltammetry (CV) methods. The minimum onset potential and the largest oxidation current density were obtained at Pt3Co/MWCNTs electrocatalyst. The...
Pt particles supported on conducting polymeric nanocones as electro-catalysts for methanol oxidation
Journal of Power Sources, 2004
The electrochemical synthesis of conducting nanocones of Pt incorporated poly(3-methyl) thiophene, employing alumina membrane templates and its use as an electrode material for methanol oxidation is reported. The activity (131 mA/cm 2 at +0.4 V versus Ag/AgCl for a Pt loading of 80 g/cm 2 ) of nanocone-based electrode was found to be more than one order of magnitude higher compared to the regular poly(3-methyl) thiophene electrode (12.2 mA/cm 2 at +0.4 V versus Ag/AgCl for a Pt loading of 80 g/cm 2 ). The chronoamperometric response confirms the better activity and stability of the nanocone-based electrode compared to the commercial 20 wt.% Pt/C (E-TEK) and template-free electrode. The XPS data confirmed the presence of Pt in the metallic state. The nanocone morphology of poly(3-methyl) thiophene, helps in the effective dispersion of Pt particles facilitating the easier access of methanol to the catalytic sites.