Controllable assembly of Ag/C/Ni magnetic nanocables and its low activation energy dehydrogenation catalysis
29 May 2012-Journal of Materials Chemistry (The Royal Society of Chemistry)-Vol. 22, Iss: 24, pp 11988-11993
TL;DR: In this paper, double-shelled Ag/C/Ni nanocables have been synthesized through a deposition covering process of Ni nanoparticles (NPs) onto Ag/c pentagonal prism nanowires (NWs).
Abstract: Double-shelled Ag/C/Ni nanocables have been synthesized through a deposition covering process of Ni nanoparticles (NPs) onto Ag/C pentagonal prism nanowires (NWs). The proposed synthesis mechanism is corroborated by scanning electron microscopy, transition electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-vis absorption spectroscopy. The resulting Ag/C/Ni nanocables with an average diameter of ∼270 nm are made up of Ag NW core (∼200 nm diameter) with internal amorphous C layer (∼10 nm thickness) and outer Ni shell (∼25 nm thickness). The UV-vis absorption spectroscopy analysis indicates that the covering of the Ni shell on the Ag/C nanowire can dampen the surface plasmon resonance (SPR) of Ag wire core and lead to a red-shifted SPR absorption peak. In particular, compared with Ni NPs, the resultant double-shelled Ag/C/Ni magnetic nanocables exhibits higher catalytic activity for the dehydrogenation toward aqueous ammonia borane under ambient atmosphere, and its calculated activation energy is lower than those of many bimetallic catalysts.
Citations
More filters
TL;DR: Well-dispersed magnetically recyclable core-shell Ag@M (M = Co, Ni, Fe) nanoparticles supported on graphene have been synthesized via a facile in situ one-step procedure, indicating that MeAB could be used as not only a potential hydrogen storage material but also an efficient reducing agent.
Abstract: Well-dispersed magnetically recyclable core–shell Ag@M (M = Co, Ni, Fe) nanoparticles (NPs) supported on graphene have been synthesized via a facile in situ one-step procedure, using methylamine borane (MeAB) as a reducing agent under ambient condition. Their catalytic activity toward hydrolysis of ammonia borane (AB) were studied. Although the Ag@Fe/graphene NPs are almost inactive, the as-prepared Ag@Co/graphene NPs are the most reactive catalysts, followed by Ag@Ni/graphene NPs. Compared with AB and NaBH4, the as-synthesized Ag@Co/graphene catalysts which reduced by MeAB exert the highest catalytic activity. Additionally, the Ag@Co NPs supported on graphene exhibit higher catalytic activity than the catalysts with other conventional supports, such as the SiO2, carbon black, and γ-Al2O3. The as-synthesized Ag@Co/graphene NPs exert satisfied catalytic activity, with the turnover frequency (TOF) value of 102.4 (mol H2 min–1 (mol Ag)−1), and the activation energy Ea value of 20.03 kJ/mol. Furthermore, the ...
159 citations
TL;DR: Two-dimensional (2D) heterostructured Ni/graphene nanocomposites were constructed via electrostatic-induced spread by following in situ-reduction growth process for magnetically recyclable catalysis of p-nitrophenol to p-aminophenol.
Abstract: Two-dimensional (2D) heterostructured Ni/graphene nanocomposites were constructed via electrostatic-induced spread by following in situ-reduction growth process for magnetically recyclable catalysis of p-nitrophenol to p-aminophenol. The heterostructures with large 2D surface and moderate inflexibility enable the superior catalytic activity and selectivity toward hydrogenation reaction for p-nitrophenol. On the basis of high-efficiency utilization of Ni Nps catalysis activity and electron-enhanced effect from graphene, the coupling effect of Ni/graphene magnetic nanocomposites can lead to highly catalytic activity for the hydrogenation reaction of p-nitrophenol with the pseudo-first-order rate constants of 11.7 × 10–3 s–1, which is over 2-fold compared to Ni Nps (5.45 × 10–3 s–1) and higher than reported noble metal nanocomposites. Complete conversion of p-nitrophenol was achieved with selectivity to p-aminophenol as high as 90% under atmosphere and room temperature. Additionally, this heterostructured ma...
150 citations
TL;DR: In this paper, the roles of catalysts in controlling the dehydrogenation process of different liquid chemical hydrides as well as their synthetic strategies are evaluated for developing affordable and sustainable hydrogen storage systems to achieve the requirements for further industrial applications.
129 citations
TL;DR: Nickel nanoparticles immobilized on three-dimensional nitrogen-doped graphene-based frameworks (NiNPs@3D-(N)GFs) were synthesized and examined for hydrogen generation from the hydrolytic dehydrogenation of ammonia borane as discussed by the authors.
Abstract: Nickel nanoparticles immobilized on three-dimensional nitrogen-doped graphene-based frameworks (NiNPs@3D-(N)GFs) were synthesized and examined for hydrogen generation from the hydrolytic dehydrogenation of ammonia borane. The high dispersion of NiNPs over the 3D-(N)GFs and consolidated interaction between the 3D-(N)GFs and NiNPs catalyzes the dissociation of hydrogen molecules and the subsequent migration of hydrogen atoms on the 3D-(N)GFs. Due to the unique properties of the as-prepared material such as porous structure and existence of nitrogen and nickel to have interaction with molecular hydrogen, it has high potential to be employed in hydrogen storage. The as-prepared catalyst is an ideal candidate for developing highly efficient portable hydrogen generation, which can be useful for various applications such as fuel cells, metal/air batteries, etc.
120 citations
TL;DR: In this article, a facile one-step in situ procedure using methylamine borane (MeAB) as the reducing agent was used to synthesize Ag@CoNi/graphene NPs.
Abstract: Well dispersed magnetically recyclable trimetallic core–shell Ag@CoNi nanoparticles (NPs) supported on graphene have been synthesized via a facile one-step in situ procedure using methylamine borane (MeAB) as the reducing agent. The as-synthesized NPs exhibit much higher catalytic activities for hydrolytic dehydrogenation of ammonia borane (AB) than the monometallic, bimetallic, trimetallic alloy (AgCoNi/graphene), and graphene free (Ag@CoNi) counterparts. Moreover, compared with NaBH4 and AB, the weaker reducing agent MeAB has much better control during the synthesis of the graphene supported Ag@CoNi NPs, which resulted in the highest catalytic activity. Kinetic studies indicate that the catalytic hydrolysis of AB by the Ag@CoNi/graphene NPs is first order, with the activation energy measured to be 36.15 kJ mol−1. Furthermore, the as-prepared NPs exert good catalytic activities and recycle stabilities towards the hydrolysis of AB and MeAB. Hence, this general method indicates that MeAB can be used as both a potential hydrogen storage material and an efficient reducing agent, and can be easily extended to facile preparation of other graphene supported multi-metal NPs.
114 citations
References
More filters
TL;DR: A method of constructing <30-nanometer structures in close proximity with precise spacings is presented that uses the step-by-step application of organic molecules and metal ions as size-controlled resists on predetermined patterns, such as those formed by electron-beam lithography.
Abstract: The present invention is a method and apparatus relating to manufacturing nanostructure patterns and components using molecular science. The method includes overlaying a multilayer organic molecule resist on at least a portion of a parent structure selectively deposited on a substrate, depositing a layer over the parent structure and in contact with at least a portion of the multilayer organic resist, and removing the multilayer organic molecule resist to leave a residual structure.
2,301 citations
TL;DR: Density functional theory studies suggest that the enhanced catalytic activity for the core-shell nanoparticle originates from a combination of an increased availability of CO-free Pt surface sites on the Ru@Pt nanoparticles and a hydrogen-mediated low-temperature CO oxidation process that is clearly distinct from the traditional bifunctional CO oxidation mechanism.
Abstract: Most of the world’s hydrogen supply is currently obtained by reforming hydrocarbons. ‘Reformate’ hydrogen contains significant quantities of CO that poison current hydrogen fuel-cell devices. Catalysts are needed to remove CO from hydrogen through selective oxidation. Here, we report first-principles-guided synthesis of a nanoparticle catalyst comprising a Ru core covered with an approximately 1–2-monolayer-thick shell of Pt atoms. The distinct catalytic properties of these well-characterized core–shell nanoparticles were demonstrated for preferential CO oxidation in hydrogen feeds and subsequent hydrogen light-off. For H2 streams containing 1,000 p.p.m. CO, H2 light-off is complete by 30 ∘C, which is significantly better than for traditional PtRu nano-alloys (85 ∘C), monometallic mixtures of nanoparticles (93 ∘C) and pure Pt particles (170 ∘C). Density functional theory studies suggest that the enhanced catalytic activity for the core–shell nanoparticle originates from a combination of an increased availability of CO-free Pt surface sites on the Ru@Pt nanoparticles and a hydrogen-mediated low-temperature CO oxidation process that is clearly distinct from the traditional bifunctional CO oxidation mechanism. To produce hydrogen by reforming hydrocarbons, efficient catalysts capable of removing carbon monoxide are needed. This can now be achieved via a preferential oxidation mechanism using nanoparticle catalysts consisting of a ruthenium core covered with platinum.
1,111 citations
TL;DR: The different behaviors in restructuring and chemical response of Rh.5.5Pd0.5 and Pt.5 nanoparticle catalysts under the same reaction conditions illustrates the flexibility and tunability of the structure of bimetallic nanoparticles catalysts during catalytic reactions.
Abstract: Heterogeneous catalysts that contain bimetallic nanoparticles may undergo segregation of the metals, driven by oxidizing and reducing environments. The structure and composition of core-shell Rh 0.5 Pd 0.5 and Pt 0.5 Pd 0.5 nanoparticle catalysts were studied in situ, during oxidizing, reducing, and catalytic reactions involving NO, O 2 , CO, and H 2 by x-ray photoelectron spectroscopy at near-ambient pressure. The Rh 0.5 Pd 0.5 nanoparticles underwent dramatic and reversible changes in composition and chemical state in response to oxidizing or reducing conditions. In contrast, no substantial segregation of Pd or Pt atoms was found in Pt 0.5 Pd 0.5 nanoparticles. The different behaviors in restructuring and chemical response of Rh 0.5 Pd 0.5 and Pt 0.5 Pd 0.5 nanoparticle catalysts under the same reaction conditions illustrates the flexibility and tunability of the structure of bimetallic nanoparticle catalysts during catalytic reactions.
1,085 citations
TL;DR: Current progress in catalysis research to control the rate and extent of hydrogen release and preliminary efforts at regeneration of H3NBH3 are discussed.
Abstract: Ammonia–borane, H3NBH3, is an intriguing molecule for chemical hydrogen storage applications. With both protic N–H and hydridic B–H bonds, three H atoms per main group element, and a low molecular weight, H3NBH3 has the potential to meet the stringent gravimetric and volumetric hydrogen storage capacity targets needed for transportation applications. Furthermore, devising an energy-efficient chemical process to regenerate H3NBH3 from dehydrogenated BNHx material is an important step towards realization of a sustainable transportation fuel. In this perspective we discuss current progress in catalysis research to control the rate and extent of hydrogen release and preliminary efforts at regeneration of H3NBH3.
911 citations
TL;DR: It is demonstrated on the example of ammonia borane infused in the nanoporous silica that the kinetics of hydrogen release is improved while the purity of hydrogen is increased in comparison with the release from bulk ammoniaborane.
Abstract: One of the imposing barriers to realizing the promise of an energy economy based on hydrogen is onboard hydrogen storage for fuel-cell-powered vehicles. New materials that enable the release of dense, plentiful and pure hydrogen at temperatures less than 85 oC are necessary to move the world from an oil-based economy to a hydrogen economy. We report a novel approach in which we deposit a hydrogen-rich material into a nanoporous scaffold. The role of the scaffold is to impose a nano-phase structure on the hydrogen-rich material thus providing an additional handle on the kinetics and thermodynamics of hydrogen release. We demonstrate on the example of ammonia borane infused in the nanoporous silica that the kinetics of hydrogen release is improved while the purity of hydrogen is increased in comparison with the release from bulk ammonia borane. These findings suggest that hydrogen rich materials infused in nanoscaffolds offer the most promising approach to date for onboard hydrogen storage
769 citations