Potential Application of Tungsten Carbides as Electrocatalysts:  4. Reactions of Methanol, Water, and Carbon Monoxide over Carbide-Modified W(110)

Hwu, Henry H.; Chen, Jingguang G.

doi:10.1021/jp0269118

Cited by 72 publications

(63 citation statements)

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“…Recently our group has published a series of papers on surface science and electrochemical studies aimed at evaluating the feasibility of using tungsten carbides as fuel cell anode electrocatalysts for direct methanol fuel cell (DMFC) [1][2][3][4][5][6][7][8]. In this manuscript we will provide an overview of these studies, as well as some recent results on this subject.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…These studies examined the surface reactions of methanol, water, and CO on carbidemodified W(111) and W(110) single crystal surfaces, with and without submonolayer coverages of Pt [1,[3][4][5]8]. It was found that methanol readily decomposed on C/W(111) and C/W(110), although a fraction of methanol underwent a reaction pathway producing undesired gas-phase CH 4 . Further investigation found that modifying the C/W(111) and C/W(110) surfaces with submonolayer coverages of Pt eliminated the reaction pathway for gas-phase CH 4 , indicating a synergistic effect by supporting low coverages of Pt on the carbide surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…It was found that methanol readily decomposed on C/W(111) and C/W(110), although a fraction of methanol underwent a reaction pathway producing undesired gas-phase CH 4 . Further investigation found that modifying the C/W(111) and C/W(110) surfaces with submonolayer coverages of Pt eliminated the reaction pathway for gas-phase CH 4 , indicating a synergistic effect by supporting low coverages of Pt on the carbide surfaces. Compared to Pt, the C/W(111), C/W(110), Pt/C/W(111), and Pt/C/W(110) surfaces also showed significant increases in activity toward the dissociation of water and a reduction in the CO desorption temperatures, both of which would be very desirable for the DMFC application.…”

Section: Introductionmentioning

confidence: 99%

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A Combined Surface Science and Electrochemical Study of Tungsten Carbides as Anode Electrocatalysts

et al. 2007

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An effective anode electrocatalyst in direct methanol fuel cell (DMFC) should have high activity for the oxidation of methanol and the decomposition of water, while remaining stable under the relatively harsh anode environment. Although the Pt/Ru bimetallic alloy is currently the most effective anode electrocatalyst, both Pt and Ru are expensive due to limited supplies and both are susceptible to CO poisoning. Consequently, the discovery of less expensive and more CO tolerant alternatives to the Pt/Ru catalysts would help facilitate the commercialization of DMFC. In this paper we will discuss the possibility of using tungsten carbides (WC) and Pt-modified WC as potential anode electrocatalysts in DMFC. We will provide an overview of our recent work, using a combined approach of fundamental surface science studies and in-situ electrochemical evaluation of the activity and stability of tungsten carbides. We will demonstrate the feasibility to bridge fundamental surface science studies on single crystals with the electrochemical evaluation on polycrystalline WC films. We will also discuss the synergistic effect by supporting low coverages of Pt on the WC substrate to further enhance the electrochemical performance of WC.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Combined Surface Science and Electrochemical Study of Tungsten Carbides as Anode Electrocatalysts

et al. 2007

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“…These results confirm the higher stability of carbide supported Pt-Ru in relation to carbon-supported Pt-Ru towards methanol electro-oxidation reaction. This stability may be due to the excellent corrosiontolerance of carbide in comparison to carbon black in acidic medium [23,24]. The improved durability of carbide-supported electro-catalysts may also be due to the strong interaction between Pt-Ru nanoparticles and carbide support.…”

Section: Resultsmentioning

confidence: 99%

Durable Transition‐Metal‐Carbide‐Supported Pt–Ru Anodes for Direct Methanol Fuel Cells

et al. 2012

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Molybdenum carbide (MoC) and tungsten carbide (WC) are synthesized by direct carbonization method. Pt–Ru catalysts supported on MoC, WC, and Vulcan XC‐72R are prepared, and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission electron microscopy in conjunction with electrochemistry. Electrochemical activities for the catalysts towards methanol electro‐oxidation are studied by cyclic voltammetry. All the electro‐catalysts are subjected to accelerated durability test (ADT). The electrochemical activity of carbide‐supported electro‐catalysts towards methanol electro‐oxidation is found to be higher than carbon‐supported catalysts before and after ADT. The study suggests that Pt–Ru/MoC and Pt–Ru/WC catalysts are more durable than Pt–Ru/C. Direct methanol fuel cells (DMFCs) with Pt–Ru/MoC and Pt–Ru/WC anodes also exhibit higher performance than the DMFC with Pt–Ru/C anode.

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Pseudomorphic Transformation of Inverse Opal Tungsten Oxide to Tungsten Carbide

Lytle¹,

Denny²,

Turgeon³

et al. 2007

Advanced Materials

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Scientists continue to place a strong emphasis on fabricating functional nanostructured materials. The ability to maintain intricate structural features on a nanometer length scale is frequently limited by the excessive sintering and crystallite growth that occurs in direct syntheses of many useful oxides, metals, and other compositions. An alternate synthetic approach that may overcome these structural challenges involves pseudomorphic transformations, reactions which alter the chemical composition of a preform but retain its original outward appearance and/or morphological features.[1] We are currently investigating the pseudomorphic transformation of three-dimensionally ordered macroporous (3DOM or inverse opal) tungsten oxide (WO 3 ) into tungsten carbide because of the advantages that nanostructured macroporous tungsten carbides can bring to catalytic and electrocatalytic applications. Tungsten carbides are low-cost substitutes for precious metal catalysts in the dehydrogenations of butane and cyclohexane; the isomerizations of 2,2-dimethylpropane to 2-methylbutane, neopentane to isopentane, and n-hexane; the hydrogenolysis of n-alkanes, and the electrocatalysis of methanol, water, and carbon monoxide. [2,3] 3DOM tungsten carbides would enhance catalytic activity by providing relatively numerous reaction sites on abundant, easily accessible macropore wall surfaces, and by permitting high flow-through capability within a low-density structure. As an example, nanostructured tungsten carbides are particularly promising as high-surface-area fuel cell catalysts that are significantly less prone to carbon monoxide poisoning than Pt.[4] Here we demonstrate the pseudomorphic fabrication of 3DOM tungsten carbides from 3DOM WO 3 and precursor-infiltrated colloidal crystal composite preforms, achieving morphological retention on a sub-100 nm length scale. Previous reports of tungsten carburization are based on reactions with bulk WO 3 or W preform powders, and do not show evidence for pseudomorphism on a sub-micrometer length scale.[ after carburization, but morphological retention on a sub-micrometer length scale was not examined. Boudart also presented pseudorphism for the stepwise conversion of MoO 3 via nitride to carbide, which was both topotactic (on the crystallographic level) and pseudomorphic, in that plates were maintained that were several micrometers in edge length. The direct conversion from molybdenum oxide to carbide was pseudomorphic at this length scale, but only if a Pt, Pd or MoO 3 catalyst was added. Relatively few studies have demonstrated pseudomorphism on a sub-micrometer length scale.[7] We recently achieved sub-100 nm pseudomorphism via multistep transformation reactions of 3DOM silica preforms into 3DOM titania.[8] The broad range of feature sizes available in inverse opal materials makes the 3DOM geometry well-suited for studying the morphological replication capabilities/limitations of pseudomorphic transformation reactions. Colloidal crystal templates, which are close-packed assemblies of ...

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Potential Application of Tungsten Carbides as Electrocatalysts: 4. Reactions of Methanol, Water, and Carbon Monoxide over Carbide-Modified W(110)

Cited by 72 publications

References 30 publications

A Combined Surface Science and Electrochemical Study of Tungsten Carbides as Anode Electrocatalysts

A Combined Surface Science and Electrochemical Study of Tungsten Carbides as Anode Electrocatalysts

Durable Transition‐Metal‐Carbide‐Supported Pt–Ru Anodes for Direct Methanol Fuel Cells

Pseudomorphic Transformation of Inverse Opal Tungsten Oxide to Tungsten Carbide

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