Magnesium alanate Mg(AlH4)2 is one promising material for H2 storage because it has 9.3 wt % H2 s... more Magnesium alanate Mg(AlH4)2 is one promising material for H2 storage because it has 9.3 wt % H2 storage capacity and decomposition temperature close to 160 °C. In this paper we present a study on the structural characterization and thermal stability of Mg alanate thin films. Samples in form of Mg/Al multilayer thin films prepared by electron beam deposition and then
ABSTRACT Here we describe the apparatus developed in our laboratory for carbon monoxide (CO) oxid... more ABSTRACT Here we describe the apparatus developed in our laboratory for carbon monoxide (CO) oxidation studies dedicated to test thin film catalysts deposited on flat substrates. Our apparatus is original for its unique technical solutions, especially in continuous gas flow mode, and specifically as: (i) the sample holder is designed such that it can allow the gas flow to interact with the entire surface of the catalyst film to be utilized for the CO oxidation reaction, (ii) three different mass flow controllers permit a gas mixture of any composition during the measurement, (iii) CO to CO 2 conversion is continuously monitored for long periods of time and can be tested in a wide range of temperatures (30–500 • C) with high accuracy on-line gas chromatography, and (iv) several security measures are guaranteed during the handling of CO gas. To test the efficiency of the apparatus, an experiment for CO oxidation was carried out at various temperatures using cobalt oxide cluster-assembled thin films synthesized by pulsed laser deposition over a glass substrate.
ABSTRACT TiO2 films codoped with V cations and N anions were synthesised by RF-magnetron sputteri... more ABSTRACT TiO2 films codoped with V cations and N anions were synthesised by RF-magnetron sputtering. The incorporation of V and N in TiO2 lattice produces isolated energy levels near the conduction and valence bands, respectively, causing an effective narrowing of the band gap to 2.5 eV. Recombination of photo-charges was reduced by depositing multilayer films of indium tin oxide (ITO)/V-N-codoped TiO2 with different numbers of bilayers. In multilayer structure, the generated photoelectrons, travelling into TiO2 film of limited thickness, rapidly enter the space charge interface of the ITO/TiO2 films from where they are instantaneously injected into the ITO layer and then removed towards the cathode. The synergic effects created by band narrowing and enhanced charge separation by using codoping and multilayer structure strategy in TiO2 generate higher photocurrent for water splitting under visible light which definitely exceeds that obtained by doping TiO2 with a single, V or N, element.
ABSTRACT The effect of Zinc Oxide Nanoparticles (ZnO NPs) on functional properties of Bovine Seru... more ABSTRACT The effect of Zinc Oxide Nanoparticles (ZnO NPs) on functional properties of Bovine Serum Albumin (BSA) protein was studied. ZnO NPs were synthesized with average size of ̃7.5 nm as obtained from TEM analysis. The catalytic conversion of p-nitrophenylacetate (PNPA) to p-nitrophenol in the presence of BSA attached with ZnO NPs was examined by UV-Vis spectroscopy at room temperature. The result suggests that esterase activity of BSA is significantly enhanced (6 times) due to the ground state BSA-ZnO complex formation.
ABSTRACT Ruthenium nanoparticles (NPs) supported over carbon thin films (Ru/C thin films) catalys... more ABSTRACT Ruthenium nanoparticles (NPs) supported over carbon thin films (Ru/C thin films) catalysts were synthesized by pulsed laser deposition and used as catalysts for hydrolysis of ammonia borane (AB). Highly irregular and porous carbon films with high surface area were deposited by varying Ar gas pressures during the deposition. By taking the advantage of phase explosion phenomena, occurring at high laser fluence, the surface of the carbon films were decorated with crystalline Ru NPs with size below ∼10 nm. Ru/C thin film catalyst produced H2 with 6 times higher H2 generation rate as compared to unsupported Ru NPs assembled film, and with a high turnover frequency value of 70.5 mol H2 mol−1 Ru min−1. A combination of morphological features and high content of sp2 bonded C atoms provides good dispersion of Ru NPs over a large surface area. Both these features contribute in generating large number of active sites leading to the increase in catalytic efficiency. A possibility of using the present form of catalyst as an ON/OFF switch for H2 production was also tested. Although the catalytic activity decreased with the number of hydrolysis cycles, Ru/C thin film catalyst was able to generate the expected amount of H2 gas in each cycle when it was reused several times. The observed low activation energy (∼28 kJ mol−1) and high H2 generation rate (15.5 L H2 min−1 g−1 of Ru) by hydrolysis of AB suggest that Ru/C thin film catalyst is highly efficient.
ABSTRACT We show that Pb nanowires may grow by co-sputtering of Al–Pb target. During sputter depo... more ABSTRACT We show that Pb nanowires may grow by co-sputtering of Al–Pb target. During sputter deposition, stress is generated inside the deposited film. Because Pb is immiscible in Al, stress relaxation occurs through Pb segregation along the aluminum grain boundary. Extrusion of Pb is inhibited if a few layers of Al oxide are formed on the surface of the film. However, if the surface oxide is broken by external perturbations, for example air-operated corrosion or electron beam, then segregated Pb extrudes in form of nanowires.
ABSTRACT Boron-hydrides are the most promising source to produce clean H2 gas with very high rate... more ABSTRACT Boron-hydrides are the most promising source to produce clean H2 gas with very high rate at room temperature. To increase and control the H2 generation rate through hydrolysis of boron-hydrides an efficient and robust catalyst is necessary, made up of elements that are abundant in our earth. Interest in Co-based catalysts, mainly cobalt boride (Co–B), arises by their special features that make them potential substitute of noble metal catalyst for H2 production. Even economically this catalyst best suits the scenario for the future systems. The present review exhaustively and systematically highlights the progress made in the development of Co-based catalyst towards hydrogen production by hydrolysis of various boron-hydrides. Various strategies for synthesizing such catalysts and improving their activity and stability, including optimizing preparation conditions, nanostructuring, alloying, supporting on various materials, and exploiting hybrid systems, are discussed. Finally, by summarizing the successful and efficient routes, future challenges and perspectives to design a novel single catalyst for direct application are presented, along with the problems that must be resolved on a theoretical level to understand the mechanisms that govern the process of catalysis: this is an area of research that usually affects all catalysts.
A porous coating assembled with hierarchical 3D Co3O4 urchin-like particles was synthesized by Pu... more A porous coating assembled with hierarchical 3D Co3O4 urchin-like particles was synthesized by Pulsed Laser Deposition (PLD) and thermal oxidation. Laser ablation of Cosingle bondB powder, used as the target material, in oxygen atmosphere formed core–shell particles on the coating surface with mainly a metallic Co core and a mixture of Co, B and O accommodating the shell. The thermal oxidation of these core–shell particles in air at 600 °C induces the morphological transformation to urchin-like particles consisting of nanowires (NWs) (diameter: 30–60 nm and length 1–3 μm) grown radially from the core surface. The extrusion marks on the surface of NWs indicate that the stress induced growth process is caused by difference in the thermal expansion coefficient. XRD, Raman, EXAFS and HRTEM analysis confirmed that the NWs are polycrystalline consisting of pure Co3O4 phase. A wet-chemistry hydrothermal procedure was also employed to synthesize nanostructured urchin-like particles which are hollow and the structure is held together by the radially oriented nanorods (diameter: 40–150 nm). During photocatalysis, urchin-like particles synthesized by PLD displayed significantly higher (∼5 times) degradation rates when compared to chemical urchins for degradation of methylene blue dye via a photo-Fenton reaction in presence of H2O2 and visible light. This is mainly attributed to poor stability of the nanorods in the chemical urchin structure. Features such as high surface area, enhanced stability against agglomeration, polycrystalline nature of the NWs, porous surface and superior adhesion, are responsible for the enhanced photocatalytic activity of Co3O4 urchin-like particles assembled in a porous coating synthesized by PLD and thermal oxidation. Reusability tests also demonstrate the robust nature of the catalyst coating.
Magnesium alanate Mg(AlH4)2 is one promising material for H2 storage because it has 9.3 wt % H2 s... more Magnesium alanate Mg(AlH4)2 is one promising material for H2 storage because it has 9.3 wt % H2 storage capacity and decomposition temperature close to 160 °C. In this paper we present a study on the structural characterization and thermal stability of Mg alanate thin films. Samples in form of Mg/Al multilayer thin films prepared by electron beam deposition and then
ABSTRACT Here we describe the apparatus developed in our laboratory for carbon monoxide (CO) oxid... more ABSTRACT Here we describe the apparatus developed in our laboratory for carbon monoxide (CO) oxidation studies dedicated to test thin film catalysts deposited on flat substrates. Our apparatus is original for its unique technical solutions, especially in continuous gas flow mode, and specifically as: (i) the sample holder is designed such that it can allow the gas flow to interact with the entire surface of the catalyst film to be utilized for the CO oxidation reaction, (ii) three different mass flow controllers permit a gas mixture of any composition during the measurement, (iii) CO to CO 2 conversion is continuously monitored for long periods of time and can be tested in a wide range of temperatures (30–500 • C) with high accuracy on-line gas chromatography, and (iv) several security measures are guaranteed during the handling of CO gas. To test the efficiency of the apparatus, an experiment for CO oxidation was carried out at various temperatures using cobalt oxide cluster-assembled thin films synthesized by pulsed laser deposition over a glass substrate.
ABSTRACT TiO2 films codoped with V cations and N anions were synthesised by RF-magnetron sputteri... more ABSTRACT TiO2 films codoped with V cations and N anions were synthesised by RF-magnetron sputtering. The incorporation of V and N in TiO2 lattice produces isolated energy levels near the conduction and valence bands, respectively, causing an effective narrowing of the band gap to 2.5 eV. Recombination of photo-charges was reduced by depositing multilayer films of indium tin oxide (ITO)/V-N-codoped TiO2 with different numbers of bilayers. In multilayer structure, the generated photoelectrons, travelling into TiO2 film of limited thickness, rapidly enter the space charge interface of the ITO/TiO2 films from where they are instantaneously injected into the ITO layer and then removed towards the cathode. The synergic effects created by band narrowing and enhanced charge separation by using codoping and multilayer structure strategy in TiO2 generate higher photocurrent for water splitting under visible light which definitely exceeds that obtained by doping TiO2 with a single, V or N, element.
ABSTRACT The effect of Zinc Oxide Nanoparticles (ZnO NPs) on functional properties of Bovine Seru... more ABSTRACT The effect of Zinc Oxide Nanoparticles (ZnO NPs) on functional properties of Bovine Serum Albumin (BSA) protein was studied. ZnO NPs were synthesized with average size of ̃7.5 nm as obtained from TEM analysis. The catalytic conversion of p-nitrophenylacetate (PNPA) to p-nitrophenol in the presence of BSA attached with ZnO NPs was examined by UV-Vis spectroscopy at room temperature. The result suggests that esterase activity of BSA is significantly enhanced (6 times) due to the ground state BSA-ZnO complex formation.
ABSTRACT Ruthenium nanoparticles (NPs) supported over carbon thin films (Ru/C thin films) catalys... more ABSTRACT Ruthenium nanoparticles (NPs) supported over carbon thin films (Ru/C thin films) catalysts were synthesized by pulsed laser deposition and used as catalysts for hydrolysis of ammonia borane (AB). Highly irregular and porous carbon films with high surface area were deposited by varying Ar gas pressures during the deposition. By taking the advantage of phase explosion phenomena, occurring at high laser fluence, the surface of the carbon films were decorated with crystalline Ru NPs with size below ∼10 nm. Ru/C thin film catalyst produced H2 with 6 times higher H2 generation rate as compared to unsupported Ru NPs assembled film, and with a high turnover frequency value of 70.5 mol H2 mol−1 Ru min−1. A combination of morphological features and high content of sp2 bonded C atoms provides good dispersion of Ru NPs over a large surface area. Both these features contribute in generating large number of active sites leading to the increase in catalytic efficiency. A possibility of using the present form of catalyst as an ON/OFF switch for H2 production was also tested. Although the catalytic activity decreased with the number of hydrolysis cycles, Ru/C thin film catalyst was able to generate the expected amount of H2 gas in each cycle when it was reused several times. The observed low activation energy (∼28 kJ mol−1) and high H2 generation rate (15.5 L H2 min−1 g−1 of Ru) by hydrolysis of AB suggest that Ru/C thin film catalyst is highly efficient.
ABSTRACT We show that Pb nanowires may grow by co-sputtering of Al–Pb target. During sputter depo... more ABSTRACT We show that Pb nanowires may grow by co-sputtering of Al–Pb target. During sputter deposition, stress is generated inside the deposited film. Because Pb is immiscible in Al, stress relaxation occurs through Pb segregation along the aluminum grain boundary. Extrusion of Pb is inhibited if a few layers of Al oxide are formed on the surface of the film. However, if the surface oxide is broken by external perturbations, for example air-operated corrosion or electron beam, then segregated Pb extrudes in form of nanowires.
ABSTRACT Boron-hydrides are the most promising source to produce clean H2 gas with very high rate... more ABSTRACT Boron-hydrides are the most promising source to produce clean H2 gas with very high rate at room temperature. To increase and control the H2 generation rate through hydrolysis of boron-hydrides an efficient and robust catalyst is necessary, made up of elements that are abundant in our earth. Interest in Co-based catalysts, mainly cobalt boride (Co–B), arises by their special features that make them potential substitute of noble metal catalyst for H2 production. Even economically this catalyst best suits the scenario for the future systems. The present review exhaustively and systematically highlights the progress made in the development of Co-based catalyst towards hydrogen production by hydrolysis of various boron-hydrides. Various strategies for synthesizing such catalysts and improving their activity and stability, including optimizing preparation conditions, nanostructuring, alloying, supporting on various materials, and exploiting hybrid systems, are discussed. Finally, by summarizing the successful and efficient routes, future challenges and perspectives to design a novel single catalyst for direct application are presented, along with the problems that must be resolved on a theoretical level to understand the mechanisms that govern the process of catalysis: this is an area of research that usually affects all catalysts.
A porous coating assembled with hierarchical 3D Co3O4 urchin-like particles was synthesized by Pu... more A porous coating assembled with hierarchical 3D Co3O4 urchin-like particles was synthesized by Pulsed Laser Deposition (PLD) and thermal oxidation. Laser ablation of Cosingle bondB powder, used as the target material, in oxygen atmosphere formed core–shell particles on the coating surface with mainly a metallic Co core and a mixture of Co, B and O accommodating the shell. The thermal oxidation of these core–shell particles in air at 600 °C induces the morphological transformation to urchin-like particles consisting of nanowires (NWs) (diameter: 30–60 nm and length 1–3 μm) grown radially from the core surface. The extrusion marks on the surface of NWs indicate that the stress induced growth process is caused by difference in the thermal expansion coefficient. XRD, Raman, EXAFS and HRTEM analysis confirmed that the NWs are polycrystalline consisting of pure Co3O4 phase. A wet-chemistry hydrothermal procedure was also employed to synthesize nanostructured urchin-like particles which are hollow and the structure is held together by the radially oriented nanorods (diameter: 40–150 nm). During photocatalysis, urchin-like particles synthesized by PLD displayed significantly higher (∼5 times) degradation rates when compared to chemical urchins for degradation of methylene blue dye via a photo-Fenton reaction in presence of H2O2 and visible light. This is mainly attributed to poor stability of the nanorods in the chemical urchin structure. Features such as high surface area, enhanced stability against agglomeration, polycrystalline nature of the NWs, porous surface and superior adhesion, are responsible for the enhanced photocatalytic activity of Co3O4 urchin-like particles assembled in a porous coating synthesized by PLD and thermal oxidation. Reusability tests also demonstrate the robust nature of the catalyst coating.
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