Current-Time Behavior of Smooth and Porous PtRu Surfaces for Methanol Oxidation

Hoster, Harry E.; Iwasita, T.; Baumgärtner, H.; Vielstich, W.

doi:10.1149/1.1365142

Cited by 105 publications

(84 citation statements)

References 39 publications

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“…The observed current decay is not uncommon in chronoamperometry studies of methanol oxidation at Pt-and PtRubased electrocatalysts and could be ascribed to catalyst poisoning, due, in turn, to chemisorbed methanol dehydrogenation fragments ͑mainly CO͒ 12,13 or to formation of Ru oxides. 14 The presence of surface active impurities 15 or anions 13 in the electrolyte solution that may slowly adsorb onto the catalyst surface during long-term experiments, thereby determining loss of activity, has also been adduced as a possible further reason for the current decay. In agreement with cyclic voltammetry results, the Pt-Ru-Ir/2 catalyst displays the highest current density ͑i.e., apparent activity͒ in Fig.…”

Section: A168mentioning

confidence: 99%

Pt-Ru-Ir Nanoparticles Prepared by Vapor Deposition as a Very Efficient Anode Catalyst for Methanol Fuel Cells

Pasupathi

Tricoli

2006

Electrochem. Solid-State Lett.

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Preparation of Pt-Ru-Ir nanoparticle catalysts on carbon black by a novel vapor deposition method is reported. Particle size as assessed by transmission electron microscopy is ca. 2.5 nm with narrow distribution. Moreover, they are homogeneously dispersed on the substrate. The electrocatalytic activity of the particles toward methanol electro-oxidation was investigated by cyclic voltammetry, chronoamperometry at constant potential, and adsorbed CO-stripping voltammetry. It was found that these catalysts possess outstanding activity for methanol electro-oxidation. This is over one order of magnitude higher than in state of the art catalysts. The novel catalysts have the potential to bear significant performance improvement of direct methanol fuel cells. Fuel cells bring the promise of clean electrical energy generation with high efficiency. The polymer electrolyte fuel cell operating at relatively low temperature ͑typically from 25 to 130°C͒ with liquid methanol feed ͑direct methanol fuel cell, DMFC͒ is particularly promising for mobile applications, such as cars and mobile telephones. One major technical problem affecting up-to-date DMFCs is the low activity of the anode catalyst. Thus, in order to attain adequate power density and efficiency, a burdensome amount of catalyst is required. The latter is made out of metals such as platinum and ruthenium that are also very costly. Methanol electro-oxidation at Pt-Ru catalysts proceeds through several elementary steps. At first, methanol molecules are dehydrogenated, thereby producing organic fragments, mainly carbon monoxide ͑CO͒, that chemisorb and build up at the catalyst surface. CO fragments are subsequently oxidized to CO 2 by adjacent hydroxyl groups ͑-OH͒ that also form at the catalyst surface in the presence of water.1 Finally, CO 2 is liberated, thereby allowing turnover of the catalytic sites. To some extent, depending on the anodic potential, methanol may not be fully dehydrogenated to CO. In this case, further oxidation of the resulting dehydrogenation fragments generates formic acid or methylformate in place of CO 2 .2,3 Many investigators believe that methanol electro-oxidation occurs through a bi-functional mechanism: methanol molecules are adsorbed and dehydrogenated at Pt sites, whereas surface bonded-OH groups are preferentially formed at the Ru sites by water dissociation ͗PtCO ads + Ru − OH → Pt + Ru + CO 2 ↑ + H + + 1e − ͘ A good review on the bifunctional mechanism can be found in Ref. 1. Other investigations, however, suggest that the main role of ruthenium in the alloyed catalyst is a modification in the platinum electronic structure, which causes significant weakening of the CO chemisorption bond at Pt sites thereby enhancing the turnover rate. 4 Whether the promoting effect of Ru can be ascribable to a bifunctional mechanism or to weakening of the Pt-CO chemisorption bond, it is clear that the most effective catalysts for methanol electro-oxidation must be based on Pt-Ru combinations. Despite considerable advance in development of these ele...

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Section: A168mentioning

confidence: 99%

Pt-Ru-Ir Nanoparticles Prepared by Vapor Deposition as a Very Efficient Anode Catalyst for Methanol Fuel Cells

Pasupathi

Tricoli

2006

Electrochem. Solid-State Lett.

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“…As in CO tolerance, the increased activity for methanol oxidation could be attributed to the differences in the degree of alloying or the particle morphology differences in the catalysts due to the decomposition phase of the precursors. Hoster et al [26] established that rough Pt-Ru surfaces, surfaces with many defects such as steps and kinks, and surfaces formed by electrodeposition are more resistant to poisoning than smooth Pt-Ru surfaces of the same composition. The higher current density seen on the argon atmosphere prepared catalyst confirms the higher activities of this catalyst for methanol oxidation; once again, this could be due to the formation of Ru-OH from Ru on the surface of the catalyst.…”

Section: Effect Of Catalyst Preparation Atmospherementioning

confidence: 99%

“…Once again, this is likely due to morphology and ruthenium oxidation state changes as the operation temperature increases. The particle size decreased as temperature is decreased; therefore, following with the CO tolerance, the Pt(111)/Ru catalyst has shown increased methanol oxidation performance [26] and these particle sizes are known to have the highest Pt(111) surface coverage [30]. Additionally, the oxidation of methanol has been shown to take place preferably on rough surfaces [26]; this type of surface could be produced at low temperatures rather than high temperatures, since smaller particles contain more corner and edge sites.…”

Section: Effect Of Catalyst Preparation Temperaturementioning

confidence: 99%

Systematic Study of Pt-Ru/C Catalysts Prepared by Chemical Deposition for Direct Methanol Fuel Cells

2017

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In this research, the activity and stability for methanol electro-oxidation on Pt-Ru/C catalysts was increased by optimising the catalyst preparation method. The Pt-Ru/C catalysts were synthesised using Pt(acac) 2 and Ru(acac) 3 precursors for chemical deposition of the metals. Performance of the catalyst was examined by cyclic voltammetry and chronoamperometry in a methanolcontaining electrolyte. TEM, EDS, X-ray photoelectron spectroscopy and XRD were used to physically characterise the catalysts. The parameters investigated were precursor decomposition phase, synthesis temperature and Pt/Ru ratio. Precursor deposition from the liquid phase was more active for methanol electro-oxidation, predominantly due to particle size and degree of alloying achieved during this precursor decomposition phase. Synthesis temperature affected the particle size, active surface area, ruthenium oxidation state and degree of alloying which in turn affected catalyst stability and activity for methanol electro-oxidation. The Pt/Ru ratio greatly affects the performance of the catalyst. The catalyst with the highest activity for methanol electro-oxidation was the catalyst synthesised at 350°C with a Pt/Ru ratio of 50:50.

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“…4. The initial deactivation of the catalyst is a quasi-reversible process and partial recovery of catalytic activity may be obtained by cycling to a lower potential periodically [47,48]. The long term poisoning rate from these adsorbed species, δ, can be described as the linear decay of the current density obtained from chronoamperometry after 500 s and is given by [49]:…”

Section: Electrocatalytic Stability-chronoamperometry and Long Cycle mentioning

confidence: 99%

Palladium Nanoparticles Loaded on Carbon Modified TiO2 Nanobelts for Enhanced Methanol Electrooxidation

Liang

Persic³

et al. 2013

Nano-Micro Lett.

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Abstract:Carbon modified TiO2 nanobelts (TiO2-C) were synthesized using a hydrothermal growth method, as a support material for palladium (Pd) nanoparticles (Pd/TiO2-C) to improve the electrocatalytic performance for methanol electrooxidation by comparison to Pd nanoparticles on bare TiO2 nanobelts (Pd/TiO2) and activated carbon (Pd/AC). Cyclic voltammetry characterization was conducted with respect to saturated calomel electrode (SCE) in an alkaline methanol solution, and the results indicate that the specific activity of Pd/TiO2-C is 2.2 times that of Pd/AC and 1.5 times that of Pd/TiO2. Chronoamperometry results revealed that the TiO2-C support was comparable in stability to activated carbon, but possesses an enhanced current density for methanol oxidation at a potential of −0.2 V vs. SCE. The current study demonstrates the potential of Pd nanoparticle loaded on hierarchical TiO2-C nanobelts for electrocatalytic applications such as fuel cells and batteries.

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Current-Time Behavior of Smooth and Porous PtRu Surfaces for Methanol Oxidation

Cited by 105 publications

References 39 publications

Pt-Ru-Ir Nanoparticles Prepared by Vapor Deposition as a Very Efficient Anode Catalyst for Methanol Fuel Cells

Pt-Ru-Ir Nanoparticles Prepared by Vapor Deposition as a Very Efficient Anode Catalyst for Methanol Fuel Cells

Systematic Study of Pt-Ru/C Catalysts Prepared by Chemical Deposition for Direct Methanol Fuel Cells

Palladium Nanoparticles Loaded on Carbon Modified TiO2 Nanobelts for Enhanced Methanol Electrooxidation

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