Solid state studies on Bi1.7−xHgxV8O16 (x≤0.4) and magnetic properties of alkali metal inserted AxBi1.7V8O16 (A=Li and Na) hollandite type phases

Marimuthu, Karthikeyan; Varadaraju, U.V.

doi:10.1016/j.matchemphys.2005.06.030

Cited by 3 publications

(2 citation statements)

References 11 publications

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“…This configuration allows for the desired electrical properties in the catalyst because the cation freely gives its electrons to the surrounding ring resulting in mixed (+3/+ 4) valences on the Ru sites [29]. The details of the tunnel-like structure of hollandites can be found in several previous studies [29][30][31][32][33][34][35][36][37]. Conversely, if the hollandite itself is not active, then it is reasonable to conclude that the hollandite acts as precursor from which Ru and K are placed in close proximity following decomposition; this may be responsible for the enhanced performance of these catalysts.…”

Section: Discussionmentioning

confidence: 98%

Characterization of K-Promoted Ru Catalysts for Ammonia Decomposition Discovered Using High-Throughput Experimentation

et al. 2008

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We obtain H 2 from low temperature NH 3 decomposition using a new hollandite (KRu 4 O 8 ) catalyst supported on c-Al 2 O 3 discovered using high-throughput experimentation and advanced TEM/SEM characterization. Relative to the base Ru°catalyst, this new catalyst shows NH 3 conversion enhancements of 30-50% at T = 350°C and decomposition activity at temperatures decreased by 50-100°C. TEM analysis over the lifetime of the catalyst shows multiple phases and morphologies suggesting that the KRu 4 O 8 behaves either as a new low-temperature decomposition catalyst or as a precursor to the active catalyst.

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Section: Discussionmentioning

confidence: 98%

Characterization of K-Promoted Ru Catalysts for Ammonia Decomposition Discovered Using High-Throughput Experimentation

et al. 2008

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“…Based on TEM/SEM characterization of these catalysts (see below), it was identified that the 4Ru/12K catalyst is present in the form of a complex tubular structure assigned to KRu 4 O 8 . It has been earlier reported that such tubular structure is characteristic of a family of compounds called hollandites [17][18][19][20][21][22][23][24][25]. Due to their peculiar 1D tunnel like structure, hollandites have extensively been studied for use as 1D ionic conductors [18].…”

Section: Promotion Of Ru Catalystmentioning

confidence: 99%

Hydrogen initiative: An integrated approach toward rational nanocatalyst design for hydrogen production. Technical Report-Year 1

Vlachos¹,

Buttrey²,

Lauterbach³

2007

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The overall objective of this grant is to develop a rational framework for the discovery of low cost, robust, and active nano-catalysts that will enable efficient hydrogen production. Our approach will be the first demonstration of integrated multiscale model, nano-catalyst synthesis, and nanoscale characterization assisted high throughput experimentation (HTE). We will initially demonstrate our approach with ammonia decomposition on noble metal catalysts. Our research focuses on many elements of the Hydrogen Initiative in the Focus Area of "Design of Catalysts at the Nanoscale'. It combines high-throughput screening methods with various nanostructure synthesis protocols, advanced measurements, novel in situ and ex situ characterization techniques, and multiscale theory, modeling and simulation. This project directly addresses several of the long-term goals of the DOE/BES program. In particular, new nanoscale catalytic materials will be synthesized, characterized and modeled for the production of hydrogen from ammonia and a computational framework will be developed for efficient extraction of information from experimental data and for rational design of catalysts whose impact goes well beyond the proposed hydrogen production project. In the first year of the grant, we have carried out HTE screening using a 16 parallel microreactor coupled with an FTIR analysis system. We screened nearly twenty single metals and several bimetallic catalysts as a function of temperature, catalyst loading, inlet composition, and temperature (order of 400 experiments). We have found that Ru is the best single metal catalyst and no better catalysts were found among the library of bimetallics we have created so far. Furthermore, we have investigated promoting effects (i.e., K, Cs, and Ba) of the Ru catalyst. We have found that K is the dominant promoter of increased Ru activity. Response surface experimental design has led to substantial improvements of the Ru catalyst with promotion, especially at lower temperatures. It has been found that the promoting effect is not limited to K but extendible to some other alkaline metals. In addition, we have studied a number of synthesis variables, including the effects of support, solvent used, calcination temperature and time. It has been found that solvent and support could have an important effect on activity. Advanced characterization of the Ru/K promoted catalyst has been carried via SEM, TEM, selected-area electron diffraction, and energy dispersive x-ray spectroscopy.

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Fabrication and Characterization of Silver/Polyaniline Composite Nanowires in Porous Anodic Alumina

et al. 2007

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Silver/polyaniline (Ag/PANI) nanowires are prepared by electropolymerization of aniline in porous anodic aluminum oxide (AAO) from an acidic electrolyte containing silver metal ions and aniline. Ag nanowires, PANI nanowires, and PANI thin films are made for comparative purposes. The nanowires are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction. The HRTEM images illustrate that the composite nanowires consist of core Ag nanowires sheathed by polymer; i.e., they are nanocables. UV-visible absorption spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy are done to investigate the chemical structure of the nanocables and any interaction between Ag and PANI. The Raman spectra indicate that the polymer is in the conducting emeraldine salt form and FTIR shows that there is some interaction between Ag and the acid protonated NH groups of polyaniline.

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Solid state studies on Bi1.7−xHgxV8O16 (x≤0.4) and magnetic properties of alkali metal inserted AxBi1.7V8O16 (A=Li and Na) hollandite type phases

Cited by 3 publications

References 11 publications

Characterization of K-Promoted Ru Catalysts for Ammonia Decomposition Discovered Using High-Throughput Experimentation

Characterization of K-Promoted Ru Catalysts for Ammonia Decomposition Discovered Using High-Throughput Experimentation

Hydrogen initiative: An integrated approach toward rational nanocatalyst design for hydrogen production. Technical Report-Year 1

Fabrication and Characterization of Silver/Polyaniline Composite Nanowires in Porous Anodic Alumina

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