Hydrogen as a reducing agent: Thermodynamic possibilities

Luidold, Stefan; Antrekowitsch, H.

doi:10.1007/s11837-007-0133-1

Cited by 22 publications

(8 citation statements)

References 20 publications

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“…29 Consistent with this, we found that catalyst annealing in H 2 at high temperatures and a pressure of 30 Torr is a necessary condition to obtain a high yield of NWs on the substrate. In addition, annealing at high temperatures is necessary for the reduction of Bi 2 O 3 , but this treatment should be kept as short as possible in order to avoid the evaporation of the liquid Bi droplets formed.…”

supporting

confidence: 80%

Synthesis parameter space of bismuth catalyzed germanium nanowires

Xiang

Cao

Arbiol

et al. 2009

Applied Physics Letters

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The synthesis parameter space of bismuth catalyzed germanium nanowires by chemical vapor deposition is determined. The process window for high aspect ratio nanowires is found to be extremely narrow. The optimal conditions are found to be 300 °C and 150 Torr gas pressure. For lower temperatures, the solubility of Ge in Bi is too low for the nucleation of Ge nanowires to occur. For higher temperatures, small Bi droplets tend to evaporate leading to an extreme reduction in the nanowire density. The extremely low process temperature makes Bi a good candidate for its growth on low cost and low thermal budget substrates such as plastics.

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supporting

confidence: 80%

Synthesis parameter space of bismuth catalyzed germanium nanowires

Xiang

Cao

Arbiol

et al. 2009

Applied Physics Letters

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“…Additionally, by simply altering the reduction temperature, H 2 can be used to reduce the salts of many metals including Ni, Co, Fe, and Ag. 53 Using H 2 as the reducing agent is highly beneficial when compared to other routes. This is attributed to the relative ease of producing pure metals that require no further purification as well as the rapid reaction times because of better gas−solid interactions.…”

Section: Methodsmentioning

confidence: 99%

Copper-Encapsulated Vertically Aligned Carbon Nanotube Arrays

Stano

Chapla

Carroll

et al. 2013

ACS Appl. Mater. Interfaces

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A new procedure is described for the fabrication of vertically aligned carbon nanotubes (VACNTs) that are decorated, and even completely encapsulated, by a dense network of copper nanoparticles. The process involves the conformal deposition of pyrolytic carbon (Py-C) to stabilize the aligned carbon-nanotube structure during processing. The stabilized arrays are mildly functionalized using oxygen plasma treatment to improve wettability, and they are then infiltrated with an aqueous, supersaturated Cu salt solution. Once dried, the salt forms a stabilizing crystal network throughout the array. After calcination and H2 reduction, Cu nanoparticles are left decorating the CNT surfaces. Studies were carried out to determine the optimal processing parameters to maximize Cu content in the composite. These included the duration of Py-C deposition and system process pressure as well as the implementation of subsequent and multiple Cu salt solution infiltrations. The optimized procedure yielded a nanoscale hybrid material where the anisotropic alignment from the VACNT array was preserved, and the mass of the stabilized arrays was increased by over 24-fold because of the addition of Cu. The procedure has been adapted for other Cu salts and can also be used for other metal salts altogether, including Ni, Co, Fe, and Ag. The resulting composite is ideally suited for application in thermal management devices because of its low density, mechanical integrity, and potentially high thermal conductivity. Additionally, further processing of the material via pressing and sintering can yield consolidated, dense bulk composites.

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“…Reduced hydrogen is readily adsorbed on atomic Pd through an exothermic process. , The generated hydrogen (either Volmer hydrogen atoms or Heyrovsky and Tafel hydrogen molecules) is a moderate reductant , with a standard reduction potential of 0 V (vs standard hydrogen electrode, SHE) which can reduce many high-valent metallic compounds, such as Pd(II) with a standard reduction potential of 0.83 V (vs SHE). We performed an additional experiment to show that gaseous hydrogen could reduce the Pd(II)−Cl complex in acidic solution, which was confirmed by the observation of a quick and noticeable color transition from bright yellow to dark black when hydrogen gas was introduced into the solution (Figure panels A and B, before and after H 2 gas bubbling).…”

Section: Resultsmentioning

confidence: 99%