6 results on '"Patel, N. A."'
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2. Improved H2 production rate by hydrolysis of Ammonia Borane using quaternary alloy catalysts
- Author
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Fernandes, R., Patel, N., Paris, A., Calliari, L., and Miotello, A.
- Subjects
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HYDROGEN production , *HYDROLYSIS , *AMMONIA , *BORANES , *CHROMIUM-cobalt-nickel-molybdenum alloys , *CATALYSTS , *TRANSITION metals - Abstract
Abstract: Co–M–B–P quaternary alloy catalyst powders (where M = Cr, Mo, W, and Cu) were synthesized by chemical reduction method to improve the catalytic performance of Co–B catalyst for hydrogen production by hydrolysis of Ammonia Borane (AB). The catalytic activity increases significantly due to the combined promoting effects induced by M and P in quaternary alloy as compared to binary Co–B catalyst. The promoting roles of each doping element in Co–B catalyst during AB hydrolysis were studied using XPS, XRD, SEM, and BET surface area analyses. Each transition element, present in the form of either oxides or metal, acts as an atomic barrier to prevent Co–B particle agglomeration to increase the effective surface area. At the same time these species also act as Lewis acid sites to improve the absorption of the reactants on to the surface. Inclusion of phosphorous, in addition, is able to create higher number of Co-active sites on the surface, which was inferred from XPS analysis. Among all the alloy catalysts, Co–Cr–B–P showed the highest H2 generation rate, which was mainly attributed to the collective effects of Cr and P in forming the catalyst surface having higher surface area and more Co-active sites. On the contrary, in the case of Cu doped Co–B catalyst, the inclusion of P considerably lowers the surface area, which decreases the catalytic activity. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
- View/download PDF
3. Co-Mo-B-P Alloy with Enhanced Catalytic Properties for H Production by Hydrolysis of Ammonia Borane.
- Author
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Fernandes, R., Patel, N., Miotello, A., and Calliari, L.
- Subjects
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COBALT alloys , *HYDROGEN production , *CHEMICAL systems , *METAL catalysts , *HYDROLYSIS , *BORANES , *AMMONIA , *CHEMICAL reduction - Abstract
Systematic studies of Co-Mo-B-P alloy catalysts, synthesized by chemical reduction methods, were conducted for H generation by hydrolysis of ammonia borane (AB). The molar concentrations of Mo and P were optimized in the alloy to obtain the best catalytic activity. The combined promoting effects induced by Mo and P in the quaternary alloy caused the H generation rate to increase by ~7.5 times as compared to the undoped-Co-B catalyst. XPS, XRD, SEM, and BET surface area analyses were carried out to understand the promoting role of each dopant element during AB hydrolysis. In the Co-Mo-B-P alloy catalyst, Mo in form of oxides acts as an atomic barrier to avoid Co-B particles agglomeration to preserve the effective surface area. These oxidized species also act as Lewis acid sites to enhance the absorption of reactant to further assist the hydrolysis reaction over alloy catalysts. The role of P in the alloy catalyst is to create a higher number of Co active sites on the catalyst surface as confirmed by XPS. These combined promoting effects provided by P and Mo doping in the Co-B catalyst reduce the activation energy to the lowest value (23 kJ/mol) in the hydrolysis of AB. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
4. Superior hydrogen production rate by catalytic hydrolysis of ammonia borane using Co-B nanoparticles supported over mesoporous silica particles
- Author
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Patel, N., Fernandes, R., Edla, R., Lihitkar, P.B., Kothari, D.C., and Miotello, A.
- Subjects
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HYDROGEN production , *HYDROLYSIS , *BORANES , *NANOPARTICLES , *SILICA , *CATALYSTS - Abstract
Abstract: Catalyst in the form of Co-B nanoparticles supported on mesoporous silica particles (MSP) was synthesized by chemical impregnation–reduction method. This catalyst powder was used for hydrogen production by hydrolysis of Ammonia Borane (AB) and was compared with Co-B catalyst supported on non-porous silica particles (NSP) and unsupported Co-B powder. It was found that the MSPs synthesized in the present studies have average pore size of about 3.1nm which were efficient to anchor the Co-B particles with average size of ~8nm on the surface to provide high active surface area and improved degree of dispersion. MSP-supported Co-B catalyst was able to produce expected amount of H2 gas from hydrolysis of AB with significantly superior generation rate, about 3 times higher than that produced by unsupported and NSP-supported Co-B catalyst. Availability of a large number of under-coordinated Co active atoms owing to the size of nanoparticles, better dispersion, high surface area and good stability against agglomeration during the reaction are the main features acquired by the Co-B nanoparticles supported on MSP that exhibit high catalytic efficiency. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
5. Co–B nanoparticles supported on carbon film synthesized by pulsed laser deposition for hydrolysis of ammonia borane
- Author
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Patel, N., Fernandes, R., Santini, A., and Miotello, A.
- Subjects
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NANOPARTICLES , *CARBON , *THIN films , *PULSED laser deposition , *HYDROLYSIS , *BORANES , *CATALYSTS , *HYDROGEN production - Abstract
Abstract: Thin films of Carbon-supported Co–B nanoparticles were synthesized by using Pulsed Laser Deposition (PLD) and used as catalysts in the hydrolysis of Ammonia Borane (AB) to produce molecular hydrogen. Amorphous Co–B-based catalyst powders, produced by chemical reduction of cobalt salts, were used as target material for nanoparticles-assembled Co–B film catalysts preparation through PLD. Various Ar pressures (10–50 Pa) were used during deposition of carbon films to obtain extremely irregular and porous carbon support with high surface area prior to Co–B film deposition. Surface morphology of the catalyst films was studied using Scanning Electron Microscopy, while structural characterization was carried out using X-Ray diffraction. The hydrogen generation rate attained by carbon-supported Co–B catalyst film is significantly higher as compared to unsupported Co–B film and conventional Co–B powder. Almost complete conversion (95%) of AB was obtained at room temperature by using present film catalyst. Morphological analysis showed that the Co–B nanoparticles produced after the laser ablation process act as active catalytic centers for hydrolysis while the carbon support provides high initial surface area for the Co–B nanoparticles with better dispersion and tolerance against aggregation. The efficient nature of our carbon-supported Co–B film is well supported by the obtained very low activation energy (∼29 kJ (mol)−1) and exceptionally high H2 generation rate (13.5 L H2 min−1 (g of Co)−1) by the hydrolysis of AB. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
6. Nanoparticle-assembled Co-B thin film for the hydrolysis of ammonia borane: A highly active catalyst for hydrogen production
- Author
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Patel, N., Fernandes, R., Guella, G., and Miotello, A.
- Subjects
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THIN films , *NANOPARTICLES , *COBALT catalysts , *HYDROLYSIS , *AMMONIA , *BORANES , *HYDROGEN production , *PULSED laser deposition , *CHEMICAL reduction , *LASER ablation - Abstract
Abstract: Nanoparticle-assembled Co-B thin films were synthesized by Pulsed Laser Deposition (PLD) and used as catalysts for the hydrolysis of NH3BH3 (ammonia borane, AB) to produce molecular hydrogen. Amorphous Co-B-based catalyst powders, produced by chemical reduction of cobalt salts, were used as target material for Co-B thin film catalysts preparation through PLD. Surface morphology of Co-B powder and film catalyst was studied using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Compositional and structural characterizations were carried out using X-photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques, respectively. The efficiency of both powder and film catalysts was tested by comparative kinetic analysis of the AB hydrolysis for hydrogen production. It was observed that nanoparticles produced during the laser ablation process act as active catalytic centers to produce significantly higher rate (about 6 times) of H2 than the same amount of the corresponding Co-B powders. Almost complete conversion (95%) of AB was obtained, as confirmed by 11B NMR, by using Co-B films at room temperature. Active Co-B nanoparticles on the surface of the PLD-deposited films is able to decrease the activation energy, for hydrolysis of AB, to the very low value of 34kJmol−1. We also found that by adding small amount of NaBH4 to the NH3BH3 solution increases the efficiency of the Co-B catalyst films, thus generating H2 with higher rate. Maximum H2 generation rate of about ∼8.2LH2 min−1 (g of Co)−1 and ∼13LH2 min−1 (g of Co)−1 was measured by hydrolysis of AB and mixture of (AB+NaBH4) solutions, respectively. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
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