Alfonso Policicchio

Cu-BTC/Aminated Graphite Oxide Composites As High-Efficiency CO2 Capture Media

CO2 adsorption isotherms on Cu-BTC/aminated graphite oxide composites were measured in the pressure range up to 1.5 MPa at three different temperatures close to ambient. Adsorption capacity, isosteric heat of adsorption, and regenerability were investigated. They are considered as significant factors determining the practical application of materials for CO2 capture. The results indicate a significant improvement in the performance of the composites as CO2 adsorbents in comparison with the parent Cu-BTC MOF. Among all samples analyzed, the composite of Cu-BTC and modified graphite oxide with the highest N content (MOF/GO-U3) is the best performing sample. On its surface 13.41 mmol/g CO2 was adsorbed at room temperature and 1.5 MPa. A high selectivity for CO2 adsorption over that of CH4 was found. The selectivities for CO2 adsorption over N2 are governed by the properties of the MOF phase. A relatively low heat of CO2 adsorption and the high degree of surface homogeneity cause that the composites can be fully regenerated and used in multicycle adsorption with the minimum energy demand.

Thermally induced modifications of the optic properties of lead zirconate titanate thin films obtained on different substrates by sol-gel synthesis

Lead zirconium titanate PbZr0.53Ti0.47O3 (PZT) thin films have been obtained by sol-gel synthesis, deposited on different substrates [float glass, indium tin oxide (ITO)-coated float glass, and intrinsic silicon wafer], and later subjected to different thermal treatments. The morphologic and the structural properties of both PZT thin films and substrates have been investigated by scanning electron microscope and their composition was determined by energy dispersive x-ray (EDX) analysis. Moreover, variable angle spectroscopic ellipsometry provides relevant information on the electronic and optical properties of the samples. In particular, the optical constant dispersion of PZT deposited on ITO-coated float glasses shows a small absorption resonance in the near IR region, not observed in PZT films deposited on the other substrates, so that such absorption resonance can be explained by interfacial effects between ITO and PZT layers. This hypothesis is also supported by EDX measurements, showing an interdiffu...

Metallic Tin-Filling Effects on Carbon Nanotubes Revealed by Atomically Resolved Spectro-Microscopies

The identification of features in the Local Density of States (LDOS) of carbon nanotubes (CNTs) obtained by Scanning Tunneling Spectroscopy (STS) is of great importance in order to understand their properties. In this work, Single- and Multi-Wall Carbon Nanotubes are compared with Multi-Wall CNTs filled with tin nanowires (Sn@CNTs) in order to investigate the effect on morphological and electronic properties of the CNTs metallic filling. The LDOS of CNTs, together with topology changes, is investigated by using spatially resolved STM/STS at room temperature and in air and compared to the LDOS of highly oriented pyrolitic graphite (HOPG). The LDOS of CNTs is dominated from different electronic states filling the C 2pσ-2pσ* band gap. The appearance of those states is linked to the diameter and the defects of the CNTs. In fact, Snnanowires encapsulation induces changes in the structure of the CNTs and the appearance of electronic states in the LDOS inside the band gap. A more extensive description of the samples is obtained depicting the morphological features and the vibrational structure on wider areas using Scanning Electron Microscopy (SEM) and Raman spectroscopy, respectively.

Enhanced hydrogen and methane storage of hybrid mesoporous organosilicas

In this study, hybrid mesoporous organosilicas (HMOs) were synthesized by using tetraethyl orthosilicate (TEOS) as the silica source and 1,4-bis(triethoxysilyl)benzene (BTB) in various ratios of BTB to TEOS. The two extreme cases of 0 and 100 mol% BTB were compared with the partial addition of BTB (25 mol%) and the partial absence of TEOS (75 mol% BTB). The synthesized mesoporous materials were characterized by means of powder X-ray diffraction (PXD), scanning electron microscopy (SEM) and helium pycnometry for the determination of skeletal density. The Brunauer–Emmett–Teller (BET) method was used for the determination of the specific surface area (SSA) and non-local density functional theory (NLDFT) calculations were employed for the determination of the pore size distribution (PSD). The hydrogen and methane sorption properties were investigated using a Sieverts apparatus under isothermal sorption equilibrium conditions at cryogenic and close to ambient temperatures, respectively. For hydrogen, the combination of phenyl rings with pores at the micro/mesopore border resulted in an increase in sorption capacity. The simultaneous presence of two different precursors increased the surface inhomogeneity, which led to a wider distribution of adsorption sites close to the micro/mesopore border, which favored the hydrogen sorption properties. The presence of the phenyl rings doubled the number of methane molecules that the material surface could accommodate. The partial substitution of TEOS by BTB (25 mol%) gave the same density of adsorbed methane as the non-hybrid material, which consisted of 100% BTB. The materials exhibited excellent reversibility and sorption stability upon aging. Their sorption performance was evaluated using the Toth model and was correlated with their structural characteristics. The fraction of micropores among the total number of pores was quantitatively correlated with the maximum storage capacity and the adsorbate–adsorbent interaction strength. Finally, for a low coverage of methane the enthalpy of adsorption was calculated by the Clausius–Clapeyron equation.

Activated carbon and metal organic framework as adsorbent for low-pressure methane storage applications: an overview

The aim of this comprehensive review on materials for methane storage application is to understand which are the best conditions and the best materials for their use for the implementation of storage tank. The research was focused on two different families of samples that up to now appear like the most promising. In particular, Activated carbon and metal organic framework were analyzed and an overall picture was extrapolated. Analysis of the structural parameters and adsorption capacities were evaluated and relation between them were obtained. A comparison of values available in literature was done and, when possible, laboratory tests were performed. The presented results allow to identify potential materials with high specific storage capacity and to verify their performances in optimized conditions. This work represents the starting point for a real and efficient method to the methane storage as a starting point for the development of Adsorbed Natural Gas technology for static and/or automotive applications.