Innovative functionalization of Vulcan XC-72 with Ru organometallic complex: Significant enhancement in catalytic activity of Pt/C electrocatalyst for the methanol oxidation reaction (MOR) (original) (raw)
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Journal of Power Sources, 2006
Carbon fibers with dangling bonds lined up in an orderly way on the wall of the carbon tube and with an average tube diameter of about 25 nm were studied as support for Pt-Ru nanoparticles. These nanoparticles were prepared using a non-ionic water-in-oil microemulsion (w/o) formed by polyethylenglycol-dodecylether, n-heptane, and water. To evaluate the electrochemical performance of this novel catalyst, Pt-Ru nanoparticles supported on carbon Vulcan XC were also prepared by the microemulsion method for comparison. Transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, and nitrogen adsorption were used to investigate the carbon-supported Pt-Ru catalysts. The microemulsion method furnished Pt 50 -Ru 50 particles with average particle sizes of 4.0 ± 0.8 nm, for both carbon supports. The electrocatalytic activity of the supported alloys in methanol oxidation was investigated by cyclic voltammetry and chronoamperometry. Results reveal that the catalytic activity is enhanced by a factor of two when the carbon nanofibers are used as support for the Pt-Ru nanoparticles. The electronic conductivity of the carbon fibers and dangling bonds seem to be the factors responsible for the excellent performance exhibited by the electrodes.
ChemElectroChem, 2019
An efficient route to chemically functionalize reduced graphene oxide (rGO) with ruthenium organometallic compounds and the subsequent anchorage of Pt nanoparticles is reported. Two organometallic complexes, [(η 6-C 6 H 5 OCH 2 CH 2 OH) RuCl 2 ] 2 (Rudim) and [(η 6-C 6 H 4 (CHMe 2)Me)RuCl 2 ] 2 (Ru-cym), as well as commercial RuCl 3 • XH 2 O (Ru-com) have been synthetized an used as functionalizing agents. By implementing a conventional polyol synthesis method, the Pt/rGO Ru-dim , Pt/rGO Ru-cym , Pt/rGO Rucom and Pt/rGO nanocatalysts have been synthetized. Characterization by XRD indicates that the presence of Ru leads to the formation of PtÀ Ru alloyed phases due to overlapping of Pt fcc and Ru hcp reflections. When characterized for the methanol oxidation reaction (MOR) in acid media, Pt/rGO Ru-dim reached a mass current density of 491.49 mA mg Pt À 1 , higher than those generated by the other nanocatalysts. The results show that the functionalization of rGO with Ru-dim remarkably increases the catalytic activity of Pt for the MOR, suggesting PtÀ Ru metalÀ metal interactions that promotes the anodic reaction.
Journal of Electroanalytical Chemistry, 2011
Carbon-supported Pt, Pt-Ru, Pt 3 -Sn electrocatalysts have been synthesized by a modified polyol method. Energy dispersive spectroscopic (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopic (XPS) analyses reveal that the as-prepared samples are composed of mainly Pt and RuO 2 or SnO 2 and the formation of alloys is found only after heat-treatment at 200°C in a flowing 10% H 2 -90% Ar atmosphere. The activity and durability for the methanol electro-oxidation reaction (MOR) have been evaluated by accelerated durability test (ADT) carried out by scanning the electrode potential for extended number of cycles in the potential ranges of 0.02-0.6, 0.02-0.8, and 0.02-1.2 V vs. NHE. Regardless of heat-treatment, the initial activity for MOR decreases in the order Pt-Ru/C > Pt 3 -Sn/C > Pt/C and the durability decreases in the order Pt/C > Pt 3 -Sn/C > Pt-Ru/C. During the ADT of the as-prepared Pt-Ru/C and Pt 3 -Sn/C, no detectable amount of dissolved Sn ions was found in the electrolyte solution, while almost 40% of Ru could be found in the electrolyte solution after ADT between 0.02 and 1.2 V vs. NHE. With MOR activity comparable to and durability better than that of Pt-Ru, the Pt-Sn based catalysts offer the potential to be employed as anode catalysts in direct methanol fuel cells.
Methanol electro-oxidation on Pt-Ru-P/C and Pt-Ru-P/MWCNT in acidic medium
Pt-Ru-P was prepared by the chemical reduction method using sodium hypophoshite as a reducing agent on Vulcan XC 72 and multi-walled carbon nano-tubes (MWCNTs). Sodium citrate was added as the stabilizer during electro-catalyst preparation. The electro-catalytic activity towards methanol oxidation in acidic medium was studied by cyclic voltammetry and linear sweep voltammetry. Pt-Ru-P/MWCNT showed excellent activity than Pt-Ru-P/C. This may be attributed to the effectiveness of the MWCNTs acting as good catalyst support material. The particle size of both electro-catalysts obtained with the transmission scanning electron microscopy (TEM) ranged between 2-4nm desirable for the direct methanol fuel cells.
Effect of third metal on the electrocatalytic activity of PtRu/Vulcan for methanol electro-oxidation
Journal of Solid State Electrochemistry, 2008
The effect of a third metal on the activity of PtRu/ Vulcan toward methanol oxidation reaction (MOR) is studied. An efficient method to prepare ternary catalysts was used, which allows the introduction of the third metal to PtRu/ Vulcan without altering its particle size or dispersion. Ni, Mo, Co, and Ir were chosen and added to PtRu/Vulcan, based on theoretical and experimental literature results, anticipating enhancement in the catalytic activity of PtRu/Vulcan. The composition of the third metal can be varied from trace to considerable amounts. Transmission electron microscopy and energy-dispersive X-ray analysis were used to determine the particle size, dispersion, and the composition of the ternary catalysts. Cylic voltammetry, chronoamperometry, and COstripping voltammetry were used to analyze and compare the activities of the catalysts at 25°C. It has been found that the addition of even trace amounts of third metal significantly affects the catalytic activity of PtRu toward MOR.
Electrochimica Acta, 2006
The methods developed and described in paper-part I are employed to prepare nanometer size Pt-Ru particles on a Vulcan ® XC72R substrate with controlled metal loading. Transmission Electron Microscopy (TEM) confirmed uniform particles size (average diameter 2 nm) and homogeneous dispersion of the particles over the substrate. Energy Dispersive X-ray absorption (EDX) analysis confirmed the compositional homogeneity. The catalytic activity of these supported nanoparticles with regard to methanol electrooxidation is investigated using cyclic voltammetry (CV), chronoamperometry (CA) and CO-stripping voltammetry techniques at temperatures between 25 and 60 • C. Such investigation concerns supported catalysts prepared with ca. 10 and 18 wt.% overall metal loading (Pt + Ru) onto the Vulcan ® XC72R substrate. Comparative testing of our catalysts and a commercial Pt-Ru/Vulcan reveals markedly superior activity for our catalysts. In fact, we observe for the latter a five-fold increase of the oxidation current as compared to a commercial Pt-Ru/Vulcan with equal metal loading. One of the reasons for the greater activity is found to be the very high dispersion of the metals over the substrate, i.e. the large surface area of the active phase. Other reasons are plausibly ascribable to the varied Pt/Ru composition and/or reduced presence of contaminants at the catalyst surface. (V. Tricoli). with respect to state of the art nanocatalysts based on binary Pt-Ru alloy.
Different carbon-supported Pt-Mo and Pt-Ru materials were synthesized and a systematic study was carried out in order to evaluate their catalytic activity towards methanol oxidation. Direct current methods were applied in sulfuric acid and methanolcontaining electrolytes, in order to evaluate the electrochemical response of the studied electrodes. Pt-Mo catalysts reveal similar performances and, in some cases, higher than Pt-Ru materials. For both catalysts series, it was found that low loadings of the promoting metal (Ru or Mo) improve the methanol oxidation activity. Characterizations by means of transmission electron microscopy and X-Ray Diffraction allowed to measure mean particle sizes below 10 nm for all phases. The Pt-Ru catalysts consist of metallic Pt and metallic ruthenium, while in the The Pt-Mo materials platinum is present in its metallic state and MoO 3 is the predominant molybdenum species.
Carbon supported Pt, Ru and Mo catalysts for methanol electrooxidation
International Journal of Hydrogen Energy, 2012
Methanol electrochemical oxidation on carbon supported electrocatalysts was studied on platinum, ruthenium and molybdenum as active phases. Pt/C, PtRu/C, PtMo/C and PtRuMo/ C catalysts were synthesized with 20% metal loading by chemical reduction. These catalysts were physical and electrochemical characterized by Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), cyclic voltammetry and CO anodic stripping voltammetry. Chronoamperometry was used to analyze and compare the catalysts activities after an electrochemical surface activation. The platinum active area was determined by anodic stripping CO voltammetry, exhibiting a different electrochemical profile for each catalyst. PtMo/C CO oxidation profile exhibited two peaks and clearly depicted the lowest onset potential value. The electrochemical methods revealed an enhanced performance of PtMo/C catalysts for methanol oxidation in comparison with the others catalysts studied. After the integration of chronoamperometric plots over 20 min in methanol acid media at 450 mV, PtMo/
Journal of Power Sources, 2008
A novel catalyst, polyoxometallate-stabilized platinum-ruthenium alloy nanoparticles supported on multiwalled carbon nanotubes (Pt-Ru-PMo 12-MWNTs), was synthesized by a microwave-assisted polyol process. The effects of microwave reaction time, microwave reaction power, and pH value of the reaction solution on the electrocatalytic properties of Pt-Ru-PMo 12-MWNTs catalysts were also investigated. The polyoxometallate (PMo 12) formed a self-assembled monolayer on the surface of the Pt/Ru nanoparticles and MWNTs, which effectively prevented the agglomeration of Pt, Ru nanoparticles and MWNTs, due to the electrostatic repulsive interactions between the negatively charged PMo 12 monolayers. Energy dispersive spectroscopy examination and electrochemical measurements showed that the loading content of Pt/Ru and their electrochemical activity vary with the synthesis conditions, such as pH, reaction time, and microwave power. It was found that the a Pt-Ru-PMo 12-MWNTs electrocatalyst with high Pt loading content, small crystallite size, and good electrocatalytic activity could be synthesized using a long reaction time, intermediate microwave power, and a pH value of 7. The electrocatalysts obtained were characterized using X-ray diffraction, and scanning and transmission electron microscopy. Their electrocatalytic properties were also investigated by using the cyclic voltammetry technique.