Electrospun Bimetallic NiCr Nanoparticles@Carbon Nanofibers as an Efficient Catalyst for Hydrogen Generation from Ammonia Borane

In this study, we report on the fabrication and utilization of NiCr alloy nanoparticles (NPs)-decorated carbon nanofibers (CNFs) as efficient and competent non-precious catalysts for the hydrolytic dehydrogenation of ammonia borane (AB) at 25 ± 2 °C. The introduced NFs have been fabricated in one step using a high-temperature thermal decomposition of the prepared electrospun nanofiber mats (nickel acetate tetrahydrate, chromium acetate dimer, and polyvinyl alcohol) in an inert atmosphere. The chemical composition of the NFs with different proportions of Ni1−xCrx (x = 0.0, 0.1, 0.15, 0.2, 0.25, 0.3) was established via standard characterization techniques. These techniques proved the formation of disorder Cr2Ni3 alloy and carbon for all the formulations. The as-synthesized composite NFs exhibited a higher catalytic performance for AB dehydrogenation than that of Cr-free Ni–CNFs. Among all the formulations, the sample composed of 15% Cr shows the best catalytic performance, as more H2 was released in less time. Furthermore, it shows good stability, as it is recyclable with little decline in the catalytic activity after six cycles. It also demonstrates the activation energy, entropy (ΔS), and enthalpy (ΔH) with 37.6 kJ/mole, 0.094 kJ/mole, and 35.03 kJ/mole, respectively. Accordingly, the introduced catalyst has a lower price with higher performance encouraging a practical sustainable H2 energy application from the chemical hydrogen storage materials.

Síntesis y caracterización de un compuesto semiconductor NiO-ZnO dopado con nanopartículas de Au por el método sol-gel para aplicación como sensores de gas

Síntesis y caracterización de un compuesto semiconductor NiO-ZnO dopado con nanopartículas de Au por el método sol-gel para aplicación como sensores de gas Alex Díaz, Dionicio Otiniano, E. Della Gaspera, Alessandro Martucci Departamento de Ingeniería de Materiales, Universidad Nacional de Trujillo-Perú Dipartimento d’Ingegneria Meccanica – Settore Materiali, Universita di Padova, 35131 Padova-Italia DOI: https://doi.org/10.33017/RevECIPeru2012.0002/ RESUMEN Láminas porosas de un compuesto semiconductor formado por NiO-ZnO (%mol) dopado con nanopartículas de Au (3% mol) fueron preparados por el método sol-gel usando acetato de níquel tetrahidratado (NiC4H6O4.4H2O) y acetato de zinc dihidratado (C4H6O4Zn.2H2O) como precursores, metanol (CH6OH) y etanol (C2H6O) como solventes, monoetanolamina (C2H7NO) y dietanolamina (C4H11NO2) como ligantes funcionales, y ácido cloroaúrico HAuCl4 como precursor. Las muestras se caracterizaron por espectroscopias Infrarrojo (IR), ultravioleta (UV-VIS), microscopía SEM, difracción de rayos X (XRD), y ensayos de sensores gaseosos. Las muestras semiconductoras fueron depositadas sobre substratos de silicio por el método de spin-coating a 2000 rpm, posteriormente fueron tratadas a 500 y 600 ºC. Los efectos de las composiciones de NiO-ZnO y el porcentaje de dopaje también se discuten en este argumento. El espesor de la capa fue determinado por elipsometria aproximado a 75 nm. Estos compuestos fueron ensayados para sensores gaseosos de H2 y CO (1% V/V) a 300ºC, demostrando óptimos resultados para el H2, pero no así para el CO. Descriptores: NiO, ZnO, semiconductores, sensor gaseoso. ABSTRACT Porous films formed by a semiconductor ZnO-NiO (% mol) doped with Au nanoparticles (3% mol) were prepared by sol-gel method using nickel acetate tetrahydrate (NiC4H6O4.4H2O) and zinc acetate dihydrate (C4H6O4Zn.2H2O) as precursors, methanol (CH6OH) and ethanol (C2H6O) as solvents, monoethanolamine (C2H7NO) and diethanolamine (C4H11NO2) as functional chelants, and chloroauric acid (HAuCl4) as gold precursor. The samples were characterized by infrared (IR) and ultraviolet (UV-VIS) spectroscopy, microscopy SEM, X-ray diffraction (XRD) and gas sensing tests. The semiconductor samples were deposited on silicon substrates by spin-coating method at 2000 rpm, subsequently annealing at 500 and 600 °C. The effects of the compositions of NiO-ZnO and the percentage of doping are also discussed. The layer thickness was determined by ellipsometry in approximately 75 nm. These compounds were tested for gas sensors for H2 and CO (1% V/V) at 300 °C, showing excellent results for H2, but not for the CO. Keywords: NiO, ZnO, semiconductors, gas sensor.

The Formation of Carbon Nanostructures via Catalytic Pyrolysis of Naphthalene under Its Autogenic Pressure

The formation of carbon nanotubes (CNTs), spherical carbon nanocapsules (CNCs), and carbon spheres (CSs) is accomplished by using the method of reactions under autogenic pressure at elevated temperatures (RAPET). A powder mixture of naphthalene and nickel acetate tetrahydrate is dissociated under its autogenic pressure. The resultant CNTs and CNCs exhibit good graphitic quality, and the diameters range from 50~200 nm. Smooth and monodisperse CSs with the diameter ranging from 5~10 μm can be obtained by pyrolysis of pure naphthalene. Our results show that the reaction temperature and catalyst proportion play a key role in the formation of carbon nanostructures with RAPET method.

Fuel Cell Electrodes Based on Carbon Nanotube/Metallic Nanoparticles Hybrids Formed on Porous Stainless Steel Pellets

The preparation of carbon nanotube/metallic particle hybrids using pressed porous stainless steel pellets as a substrate is described. The catalytic growth of carbon nanotubes was carried out by CVD on a nickel catalyst obtained by impregnation of pellets with a highly dispersive colloidal solution of nickel acetate tetrahydrate in ethanol. Granular polyethylene was used as the carbon source. Metallic particles were deposited by thermal evaporation of Pt and Ag using pellets with grown carbon nanotubes as a base. The use of such composites as fuel cell electrodes is discussed.

Preparation and Crystal Structure Nickel Acetate Tetrahydrate

The crystals of nickel acetate tetrahydrate have been obtained in the existence of 4-amino-2-methylquinoline. The crystal structure of the nickel acetate tetrahydrate was determined by X-ray single crystal diffraction analysis. The crystal data for nickel acetate tetrahydrate: monoclinic, space group P2(1)/c, a = 0.48319(9) nm, b = 1.1900(2) nm, c = 0.85531(17) nm, V = 0.49064(16) nm3, Z=2, M r= 248.86, De = 1.685 g/cm3, T = 298(2) K, F (000) = 260, R = 0.0756 and wR = 0.1662. The complex forms three-dimensional network structure through hydrogen bonds.