Metal Nitride and Metal Carbide Nanoparticles by a Soft Urea Pathway

Giordano, Cristina; Erpen, Christian; Yao, Weitang; Milke, Bettina; Antonietti, Markus

doi:10.1021/cm9018953

Cited by 230 publications

(225 citation statements)

References 17 publications

(29 reference statements)

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“…Additionally, our Ti-Ta-ON catalyst was also synthesized using a more benign, ammonia-free synthesis route. 40 Admittedly, we still cannot pinpoint the nature of the ORR sites in the Ta oxynitrides. This is in part because we cannot independently Table I).…”

Section: Resultsmentioning

confidence: 99%

“…46 Having established that the tantalum oxide and tantalum nitride are not active, we now focus on the tantalum oxynitride catalysts. To synthesize TaON, we employed an ammonia-free synthesis route 40,47,48 by using urea as the nitrogen source. The XRD patterns for the synthesized tantalum oxynitrides are presented in Figure 3.…”

Section: Resultsmentioning

confidence: 99%

“…40 The obtained powders are represented as Ta-ON (3 h) or (6 h). We controlled the molar ratio between urea and the metal precursors of 5 to ensure the nitrogen excess.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Influence of Aliovalent Substitutions on Oxygen Reduction on Tantalum Oxynitrides

Pasqualeti

Padgett

Kuo

et al. 2017

J. Electrochem. Soc.

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The development of active and stable oxygen reduction reaction (ORR) electrocatalysts using low-cost, abundant elements is of critical importance to the widespread adoption of proton-exchanged membrane fuel cells (PEMFCs). Tantalum-containing compounds, such as tantalum oxynitrides, can catalyze ORR in acid, with the degree of oxidation proposed to play a central role in controlling the ORR activity. Herein, we report the incorporation of aliovalent ions in tantalum oxynitrides (Ta-ON) and their effect on the ORR activity in acid. We synthesize Ta-ON by utilizing urea as the nitrogen source and use aliovalent (Ti 4+ ) and isovalent (Nb 5+ ) substitutions to evaluate the influence of the aliovalent substitution on the ORR activity. We found that an aliovalent Ti 4+ substitution increases the ORR activity by 3x, which we attribute to improved electrical conductivity and increased ORR active sites. In comparison, isovalent Nb 5+ substitution or carbon inclusion as oxycarbonitride did not positively affect the ORR activity. Our finding points to the important role of defects and conductivity in the Ta Active, acid-stable, and cost-effective cathodes for the oxygen reduction reaction (ORR) play an enabling role in the commercialization of proton-exchanged membrane fuel cells (PEMFCs). Platinum nanoparticles supported on high surface-area carbon supports (Pt/C) are currently the most active ORR electrocatalyst; 1 however, there are concerns with the scalability and stability 2 of Pt. 3,4 To identify alternatives, many groups have examined non-Pt ORR electrocatalysts made of inorganic, organic, and hybrid organic-inorganic materials. Examples include Fe-N-C, 5 and polyaniline (PANI)-Fe/Co-C, 6,7 some of which have ORR kinetics almost already comparable to Pt/C. 8,9 However, these electrocatalysts are not yet stable under longterm operations.3 While many efforts have been made to improve the stability 10 and identify the active sites, 11 long-term stability of these carbon-based electrocatalysts remains a challenge.Valve metal compounds such as tantalum-based compounds are among a few classes of non-precious-metal materials that are stable in acid.12 Their exceptional stability has spurred investigations of how they can be used as electrocatalysts. Examples include tantalum oxynitride (TaON) and tantalum nitride (Ta 3 N 5 ), which have also been investigated for solar-driven water splitting. [13][14][15][16] However, most valvemetal oxides are not active toward the ORR. As a result, significant efforts have been devoted to activating these materials for the ORR. Ota et al. have shown that controlling the degree of oxidation can improve the ORR in tantalum oxynitrides.17,18 By surveying TaC x N y , 17Ta-CNO 17,19 and TaO x N y /Ti, 20 they have proposed that an ideal interaction between the oxygen molecule and the surface tantalum must be optimized via this degree of oxidation to improve the ORR activity. 21The same group has also demonstrated correlations between the ORR and oxygen vacancies, which they proposed as the ...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Influence of Aliovalent Substitutions on Oxygen Reduction on Tantalum Oxynitrides

Pasqualeti

Padgett

Kuo

et al. 2017

J. Electrochem. Soc.

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“…Component and morphology analysis of Li 4 Ti 5 O 12 /TiN composites Titanium oxides can be thermally transformed into pure metal nitrides in the presence of urea as the nitrogen source [26,27]. In this case, the extent of the nitridation was carefully regulated by the relative amount of urea under the controlled experimental conditions, ensuring the nitridation reaction to occur only on the surface region of the oxides.…”

Section: Resultsmentioning

confidence: 99%

Surface nitridation induced high electrochemical performance of Li4Ti5O12 using urea as a nitrogen source

Zhao

Zhou

Ming

et al. 2013

Ionics

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“…This method is very flexible and has been used to synthesize nanostructures of many different nitrides, e.g. GaN, WN, TiN and Fe 3 N [16][17][18]. The advantage of the gel precursor is that reagents can be mixed on a molecular level, which leads to lower reaction temperatures and a much smaller particle size.…”

Section: Introductionmentioning

confidence: 99%

One-step route to a hybrid TiO₂/Ti_xW_1−xN nanocomposite byin situselective carbothermal nitridation

Schnepp

Hollamby

Tanaka

et al. 2012

Science and Technology of Advanced Materials

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Metal oxide/nitride nanocomposites have many existing and potential applications, e.g. in energy conversion or ammonia synthesis. Here, a hybrid oxide/nitride nanocomposite (anatase/Ti x W 1−x N) was synthesized by an ammonia-free sol-gel route. Synchrotron x-ray diffraction, complemented with electron microscopy and thermogravimetric analysis, was used to study the structure, composition and mechanism of formation of the nanocomposite. The nanocomposite contained nanoparticles (<5 nm diameter) of two highly intermixed phases. This was found to arise from controlled nucleation and growth of a single oxide intermediate from the gel precursor, followed by phase separation and in situ selective carbothermal nitridation. Depending on the preparation conditions, the composition varied from anatase/Ti x W 1−x N at low W content to an isostructural mixture of Ti-rich and W-rich Ti x W 1−x N at high W content. In situ selective carbothermal nitridation offers a facile route to the synthesis of nitride-oxide nanocomposites. This conceptually new approach is a significant advance from previous methods, which generally require ammonolysis of a pre-synthesized oxide.

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Metal Nitride and Metal Carbide Nanoparticles by a Soft Urea Pathway

Cited by 230 publications

References 17 publications

Influence of Aliovalent Substitutions on Oxygen Reduction on Tantalum Oxynitrides

Influence of Aliovalent Substitutions on Oxygen Reduction on Tantalum Oxynitrides

Surface nitridation induced high electrochemical performance of Li4Ti5O12 using urea as a nitrogen source

One-step route to a hybrid TiO₂/Ti_xW_1−xN nanocomposite byin situselective carbothermal nitridation

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Metal Nitride and Metal Carbide Nanoparticles by a Soft Urea Pathway

Cited by 230 publications

References 17 publications

Influence of Aliovalent Substitutions on Oxygen Reduction on Tantalum Oxynitrides

Influence of Aliovalent Substitutions on Oxygen Reduction on Tantalum Oxynitrides

Surface nitridation induced high electrochemical performance of Li4Ti5O12 using urea as a nitrogen source

One-step route to a hybrid TiO2/TixW1−xN nanocomposite byin situselective carbothermal nitridation

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One-step route to a hybrid TiO₂/Ti_xW_1−xN nanocomposite byin situselective carbothermal nitridation