Electrochemical and in situ IR characterization of PtRu catalysts for complete oxidation of ethylene glycol and glycerol (original) (raw)
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Electrochimica Acta, 2009
Present paper reports kinetics of electro-oxidation of ethanol (EtOH) and ethylene glycol (EG) onto Pt and PtRu nanocatalysts of different compositions in the temperature range of 298-318 K. These catalysts have been characterized by SEM, EDX, XRD, CV and amperometry. It has been observed that apparent activation energies for oxidation of EtOH and EG pass through a minimum at about 15-20 at.% of Ru in the PtRu alloy catalysts. Anodic peak current vs. composition curve also shows a maximum around this composition. The results have been explained by a geometric model, which proposes requirement of an ensemble of three Pt atoms with an adjacent Ru atom onto PtRu surface for an efficient electro-oxidation of EtOH or EG. This is further supported from statistical data analysis of probability of occurrence of such ensembles onto PtRu alloy surface. Present results also suggest that electro-oxidation of EG onto nano-PtRu catalyst surfaces follows a different path from that of EtOH at alloy composition less than 15 at.% of Ru.
2012
ABSTRACT Spray pyrolysis of metal precursors was used to synthesize binary and ternary nano-structured Pt-based catalysts. Characterization of the catalysts was performed using SEM, TEM, and EDS to determine morphology, purity and composition. The electrochemical performance of synthesized Pt84Ru16, Pt96Sn4, and Pt88Ru6Sn6 was evaluated via cyclic voltammetry and steady state polarization for oxidation of ethylene glycol and glycerol. The binary Pt84Ru16 and Pt96Sn4 catalysts had higher maximum currents and better stability than a templated Pt catalyst and templated ternary Pt88Ru6Sn6 catalyst. All binary and ternary catalysts had less adsorbed reaction products during potential cycling than the templated platinum electrocatalyst. In situ infrared reflection absorption spectroscopy (IRRAS) analysis showed complete oxidation of ethylene glycol and glycerol with the binary and ternary catalysts by CO2 generation. This work emphasizes the benefits provided by adding Ru and Sn to Pt catalysts for oxidation of complex alcohols.
Journal of New Materials for Electrochemical Systems
In this work, unsupported Pt, Pt-Ru (1:1 wt. % Pt:Ru ratio) and Pt-CeO2 (1:1 wt. % Pt:CeO2 ratio) electrocatalysts were synthesized and evaluated as anodes for the ethylene glycol oxidation reaction (EGOR) in out in H2SO4 electrolyte. The nanomaterials were prepared by slowly dropping the precursors in a NaBH4 solution, in a reduction process of 10 min. Analysis by XRD showed the formation of polycrystalline electrocatalysts, while the chemical composition characterization indicated a ratio between the different elements in the bimetallic materials close to the stoichiometric value. Selected area electron diffraction patterns evaluation carried out in the TEM apparatus helped in the identification of Pt (1 1 1) in the three anodes, Ru (1 0 0) in Pt-Ru, and CeO2 (1 1 1) in Pt-CeO2, confirming the formation of Ru and CeO2 phases. The results from the electrochemical characterization by Linear Scan Voltammetry (LSV) showed that the Pt-Ru material possess a higher mass catalytic activit...
Journal of Colloid and Interface Science, 2008
The synthesis and characterization of catalysts based on nanomaterials, supported on multi-walled carbon nanotubes (CNT) for ethylene glycol (EG) oxidation is investigated. Platinum (Pt) and platinum–ruthenium (Pt–Ru) nanoparticles are deposited on surface-oxidized multi-walled carbon nanotubes [Pt/CNT; Pt–Ru/CNT] by the aqueous solution reduction of the corresponding metal salts with glycerol. The electrocatalytic properties of the modified electrodes for oxidation of ethylene glycol in acidic solution have been studied by cyclic voltammetry (CV), and excellent activity is observed. This may be attributed to the small particle size of the metal nanoparticles, the efficacy of carbon nanotubes acting as good catalyst support and uniform dispersion of nanoparticles on CNT surfaces. The nature of the resulting nanoparticles decorated multiwalled carbon nanotubes are characterized by scanning electron microscopy (SEM) and transmission electron microscopic (TEM) analysis. The cyclic voltammetry response indicates that Pt–Ru/CNT catalyst displays a higher performance than Pt/CNT, which may be due to the efficiency of the nature of Ru species in Pt–Ru systems. The fabricated Pt and Pt–Ru nanoparticles decorated CNT electrodes shows better catalytic performance towards ethylene glycol oxidation than the corresponding nanoparticles decorated carbon electrodes, demonstrating that it is more promising for use in fuel cells.TEM images of nanoparticles decorated MWCNT obtained by glycerol as reducing agent.
Electrochemical study of PtRh/C and PtRhNi/C electrocatalysts for ethylene glycol oxidation
Journal of Solid State Electrochemistry, 2017
In the last decades, the ethylene glycol has been considered as another option of fuel, in both acid and alkaline solutions, for fuel cells application. Pt-based electrocatalysts are used in this type of technology but it is necessary to add a second or third oxophilic metal to form bimetallic or trimetallic alloys. Alloys with a second or a third metal modify electrocatalytic properties of Pt in order to overcome poisoning effects and enhancement of the ele ctro catalytic activity of platinu m-b ased electrocatalyst. PtRh/C and PtRhNi/C electrocatalysts were prepared by alcohol reduction method, and their catalytic activity and stability were evaluated by cyclic voltammetry and chronoamperometry, in alkaline medium using a KOH solution with ethylene glycol in concentrations of 0.5 and 1.0 mol L −1. The results showed that the binary electrocatalyst has a higher electrocatalytic performance and obtain about 90% more energy density than PtRhNi/C. This result indicates that the higher amount of Rh in the alloy presents a synergistic effect with Pt. Chronoamperometry tests show that both electrocatalysts have an active surface and tolerance to poisoning by intermediate products, and the presence of Ni in the ternary electrocatalyst contributes to raise this tolerance.
Glycerol and Ethanol Oxidation in Alkaline Medium Using PtCu/C Electrocatalysts
International Journal of Electrochemical Science, 2018
The performance of platinum-copper electrocatalysts synthesized in different ratios (100:0, 90:10, 70:30, 50:50, and 0:100), using a borohydride reduction method for electrochemical oxidation of different fuels, was evaluated in an alkaline direct alcohol fuel cell. X-ray diffraction of Pt/C and PtCu/C showed a face-centered cubic structure (fcc) of the platinum and its alloys. Transmission electron microscopy analysis allowed us to see a good dispersion of metallic particles with some regions with clusters of nanoparticles, for all the synthesised materials in the presence of copper. Cyclic voltammetry and chronoamperometry tests demonstrated that the PtCu/C (50:50) and PtCu/C (70:30) electrocatalysts exhibited the highest activity and stability for the glycerol and ethanol oxidation, respectively. The tests made in fuel cells, directly fed with glycerol and ethanol, presented the PtCu/C (90:10) electrocatalyst as the most effective on the oxidation reaction of the fuels when compared with Pt/C and Cu/C.
Journal of Power Sources, 2006
We present results of a comparative study on the interaction of ethylene glycol (EG) with carbon supported Pt, PtRu and Pt 3 Sn nanoparticle catalysts, employing electrochemical and quantitative differential electrochemical mass spectroscopy (DEMS) measurements under continuous reaction and continuous electrolyte flow conditions. For all three catalysts EG adsorption is inhibited at very cathodic adsorption potentials, dissociative adsorption starts above 0.06 V and increases with increasing potential. Based on the electron yield per formed CO 2 molecule and on the similarity with the CO ad stripping characteristics CO ad is identified as the main stable adsorbate; the relative coverage in terms of adsorbed C1 species, relative to that of a saturated CO adlayer on the respective catalyst, reaches a maximum of ca. 0.6 at around 0.4 V on Pt/Vulcan, ca. 0.2 at around 0.2 V on PtRu/Vulcan and ca. 0.4 at around 0.35 V on Pt 3 Sn/Vulcan. Bulk EG electrooxidation under steady-state conditions shows a very small current efficiency for CO 2 formation of below 6% for 0.1 M EG on all three catalysts, the oxidation of EG mainly generates partly oxidized C2 by-products. Catalyst modification by Ru or Sn improves the activity for EG oxidation at low potentials (≤0.56 V), but does not lead to better selectivities for complete EG oxidation to CO 2 at potentials with significant oxidation rates. Hence, CC bond breaking is rate limiting for complete oxidation under present reaction conditions for all three catalysts. The data are consistent with a parallel pathway reaction mechanism, with formation and subsequent oxidation of CO ad in the one pathway and partial oxidation, via a sequence of reaction steps, to increasingly oxidized C2 species in the other pathway.
PtRu/C and PtSn/C electrocatalysts were prepared by the alcohol-reduction process with different atomic ratios. The electrocatalysts were characterized by EDAX, XRD, TEM and cyclic voltammetry and the electro-oxidation of ethylene glycol was studied by cyclic voltammetry and chronoamperometry using the thin porous coating technique. PtRu/C and PtSn/C electrocatalysts were found to be active for ethylene glycol oxidation, which starts at lower potentials by increasing the ruthenium and tin content. In the region of interest for direct alcohol fuel cell applications PtSn/C electrocatalysts were more active than PtRu/C electrocatalysts.
Electrochimica Acta, 2011
Electrocatalytic activities of Pt/C, Pt-Ru/C, and Pt-Ni/C for the oxidation of ethylene glycol in a basic solution are evaluated by cyclic voltammetry and quasi-steady state polarization. Based on the results of Tafel slopes from quasi-steady state polarization, the catalytic activities for ethylene glycol oxidation are in the order of Pt-Ru/C > Pt-Ni/C > Pt/C. The analysis of intermediate products for ethylene glycol oxidation by higher performance liquid chromatograph (HPLC) demonstrates that the degree of ethylene glycol oxidation is dependent on catalysts. Pt-Ru/C shows the highest current densities for ethylene glycol oxidation, but shows lower fuel utilization. On the other hand, Pt-Ni/C shows higher ability to cleavage CC bonds, but is suffered from catalyst poisoning. To improve the tolerance for catalyst poisoning, we construct a novel Pt-Ni-SnO 2 /C catalyst, compare its catalytic activities, and evaluate the intermediates. Pt-Ni-SnO 2 /C shows superior catalytic activities for ethylene glycol oxidation, resulting in the highest degree of complete electro-oxidation of ethylene glycol to CO 2 .
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 .