Preparation and performance of nanosized tungsten carbides for electrocatalysis

Shen, Pei Kang; Yin, Shibin; Li, Zihui; Chen, Chan

doi:10.1016/j.electacta.2010.03.025

Cited by 71 publications

(42 citation statements)

References 62 publications

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“…700 8C) required to overcome the thermodynamic and kinetic barriers for carbon incorporation into the metal lattice induce uncontrollable particle sintering, generating particles with exceedingly low surface areas that are not suitable for commercial applications (Supporting Information , Figure S1). [1,2] Although alternative synthesis methods with unconventional heating [20][21][22][23] and carbon sources [11,17,19,24,25] have been developed to mitigate sintering, the resulting particles are extensively coked and do not feature metalterminated surfaces. Current methods either partially mitigate sintering while generating thick surface oxide layers with excess surface carbon or fully mitigate sintering by embedding carbides within high excesses of carbon.…”

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confidence: 99%

Engineering Non‐sintered, Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

2014

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Transition-metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide-scale use as catalysts. A method is presented for the production of metal-terminated TMC nanoparticles in the 1-4 nm range with tunable size, composition, and crystal phase. Carbon-supported tungsten carbide (WC) and molybdenum tungsten carbide (Mo x W 1Àx C) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100-fold higher than commercial WC and within an order of magnitude of platinumbased catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.Early transition-metal carbides (TMCs) are earth-abundant materials with established commercial use in a variety of applications owing to their favorable optical, electronic, mechanical, and chemical properties. [1][2][3] Tungsten carbide (WC) has garnered much attention for its catalytic similarities to the platinum group metals [4] (PGMs) in several thermoand electrocatalytic reactions, such as biomass conversion, [2,5,6] hydrogen evolution and oxygen reduction, [7][8][9][10][11] and alcohol electrooxidation. [12,13] The reactivity of WC has been partially attributed to the intercalation of C to the W lattice, which gives rise to a "Pt-like" d-band electronic density states (DOS). [14] Peppernick et al. demonstrated that WC À ions exhibit isoelectronic correspondence with Pt À ions.[15] Because WC exhibits high thermal and electrochemical stability while resisting common catalyst poisons such as carbon monoxide and sulfur, [1][2][3] it has been identified as a suitable candidate to replace PGM catalysts in emerging renewable energy technologies, such as fuel cells and electrolyzers. [7][8][9][10][11][16][17][18] While there are many methods to synthesize WC nanoparticles (NPs), none of the current methods can simultaneously prevent sintering of the WC nanoparticles while also mitigating surface impurity deposition. Thus, despite the promising catalytic properties of model WC surfaces, the lack of synthesis methods to produce metal-terminated WC NPs of controlled sizes has prevented its wide-spread use as an earthabundant catalyst. [1,2,7,19] The high carburization temperatures (> ca. 700 8C) required to overcome the thermodynamic and kinetic barriers for carbon incorporation into the metal lattice induce uncontrollable particle sintering, generating particles with exceedingly low surface areas that are not suitable for commercial applications (Supporting Information , Figure S1). [1,2] Although alternative synthesis methods with unconventional heating [20][21][22][23] and carbon sources [11,17,19,24,25] have been developed to mitiga...

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confidence: 99%

Engineering Non‐sintered, Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

2014

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“…The commonly used Vulcan XC-72R is electrochemically unstable at high potential, leading to corrosion after extended operation in acidic media. As the carbon corrodes, Pt nanoparticles agglomerate into larger particles and / or detach from the support material, consequently reducing the electrochemical surface area (ECSA) and catalytic activity ( 21 , 22 (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). Various graphitized carbon support materials with special pore structures have also been explored, such as carbon nanotubes (CNT), nanofibers (CNF), nanohorns (CNH) and nanocoils, all showing promising results, although the costly and complex synthesis methods employed constitute a barrier to their introduction into market (34)(35)(36)(37)(38)(39)(40).…”

Section: Introductionmentioning

confidence: 99%

Graphitic Carbon Nitride Materials for Energy Applications

et al. 2015

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Polymeric layered carbon nitrides were investigated for use as catalyst support materials for proton exchange membrane fuel cells (PEMFCs) and water electrolyzers (PEMWEs). Three different carbon nitride materials were prepared: a heptazine-based graphitic carbon nitride material (gCNM), poly (triazine) imide carbon nitride intercalated with LiCl component (PTI-Li+Cl-) and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials were found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported Pt, Pt/PTI-Li+Cl- exhibited the best durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan. Superior methanol oxidation activity was observed for all gCNM supported Pt catalysts on the basis of the catalyst ECSA. Preliminary results on IrO2 supported on gCNM using a PEMWE cell revealed an enhancement in the charge-transfer resistance as the current density increases when compared to unsupported IrO2. This may be attributed to a higher active surface area of the catalyst nanoparticles on the gCNM support.

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“…5. To ensure complete dissolution of the silica and good dispersion of the nanoparticles on the catalyst support, stop the reaction after 16 hr by adding reagent-grade NH 4 OH dropwise to neutralize the ABF solution to a pH of 6-7. Caution: this reaction is exothermic.…”

Section: Removing the Silica Shells And Supporting The Nanoparticlesmentioning

confidence: 99%

“…Several newer methods involve mixing a metal precursor with a carbon precursor and applying conventional and unconventional heating techniques. [11][12][13][14][15][16][17][18] Excess carbon is used to prevent sintering, but this excess carbon results in extensive surface carbon, making these materials not suitable for catalytic applications.…”

Section: Introductionmentioning

confidence: 99%

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

Hunt

Román‐Leshkov

2015

JoVE

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A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The silica-encapsulated metal oxide nanoparticles are then carburized in a methane/hydrogen atmosphere at temperatures over 800 °C to form silica-encapsulated early transition metal carbide nanoparticles. During the carburization process, the silica shells prevent the sintering of adjacent carbide nanoparticles while also preventing the deposition of excess surface carbon. Alternatively, the silica-encapsulated metal oxide nanoparticles can be nitridized in an ammonia atmosphere at temperatures over 800 °C to form silica-encapsulated early transition metal nitride nanoparticles. By adjusting the reverse microemulsion parameters, the thickness of the silica shells, and the carburization/nitridation conditions, the transition metal carbide or nitride nanoparticles can be tuned to various sizes, compositions, and crystal phases. After carburization or nitridation, the silica shells are then removed using either a room-temperature aqueous ammonium bifluoride solution or a 0.1 to 0.5 M NaOH solution at 40-60 °C. While the silica shells are dissolving, a high surface area support, such as carbon black, can be added to these solutions to obtain supported early transition metal carbide or nitride nanoparticles. If no high surface area support is added, then the nanoparticles can be stored as a nanodispersion or centrifuged to obtain a nanopowder. Video LinkThe video component of this article can be found at

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Preparation and performance of nanosized tungsten carbides for electrocatalysis

Cited by 71 publications

References 62 publications

Engineering Non‐sintered, Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

Engineering Non‐sintered, Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

Graphitic Carbon Nitride Materials for Energy Applications

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

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