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Mananghaya M.,De La Salle University - Manila | Mananghaya M.,National Research Council of the Philippines
International Journal of Hydrogen Energy | Year: 2015

The implementation and effectiveness of the ability of Nitrogen doped Carbon Nanotube with divacancy (4ND-CNxNT) that is decorated with Sc for Hydrogen adsorption was evaluated with the aide of spin-unrestricted Density Functional Theory formalism. The composite material Sc/4ND-CNxNT has an excellent quality as a media for hydrogen storage characterized by strong binding such that each Sc can hold up to five hydrogen molecules. Detailed structural and electronic properties were reported starting from one up to five hydrogen molecules absorbed. © 2015 Hydrogen Energy Publications, LLC.


Enriquez J.I.G.,De La Salle University - Manila | Villagracia A.R.C.,De La Salle University - Manila | Villagracia A.R.C.,National Research Council of the Philippines
International Journal of Hydrogen Energy | Year: 2016

The effects of different crystallographic defects and substitutional doping of 3d-block transition metals (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) on the electronic properties and hydrogen molecule (H2) interaction of penta-graphene (PG) were investigated using density functional theory calculations. Electronic properties of PG show strong dependence on PG's structural configuration and the type of metal dopants used. Doping PG with transition metals (TM) may be used to change PG from being a wide band gap semiconductor to a narrow band gap semiconductor or a semimetal. PG have H2 adsorption energies (Eads) that are superior to graphene, with Eads between -0.7 eV and -0.9 eV depending on the adsorption site. Transition metals act as proton rich dopant, and induced positive electrostatic potential in its adjacent regions. Thus, doping improve H-2 adsorption, especially when substituted on sp2 hybridized carbon site. The V-doped and Ti-doped sheets, with Eads of -0.351 eV and -0.319 eV, respectively, show the greatest potential for on-board reversible solid-state hydrogen molecule storage application. © 2016 Hydrogen Energy Publications LLC.


Mananghaya M.,De La Salle University - Manila | Mananghaya M.,National Research Council of the Philippines
Journal of the Korean Chemical Society | Year: 2015

The binding ability and hydrogen storage capacity of nitrogen doped carbon nanotube with divacancy (4ND-CNxNT) that is decorated with transition metals was investigated based on density functional theory calculations. Results indicate that scandium shows an ideal reversible hydrogen binding capability with promising system-weight efficiency compared with other transition metals when functionalized with 4ND-CNxNT. The (Sc/4ND)10-CNxNT can store up to 50H2 molecules, corresponding to a maximum gravimetric density of 5.8 wt%. Detailed structural stability and electronic properties were reported as hydrogen molecules were absorbed. It takes about 0.16 eV/H2 to add one H2 molecule, which assures reversible storage of H2 molecules under ambient conditions.


Mananghaya M.,De La Salle University - Manila | Mananghaya M.,National Research Council of the Philippines
Journal of Molecular Liquids | Year: 2015

The paper discusses the impact of functionalization on understanding the solubility of a single-walled carbon nanotube (SWCNT) to increase its dispersion in water, with the aide of spin-unrestricted density functional theory (DFT). A finite (10, 0) zigzag nanotube model containing 80 C atoms saturated with hydrogen at the ends was investigated with DFT. The (10, 0) SWCNTs were functionalized with: (a) carboxylic acid, (b) aromatic dicarboxylic acid and (c) aminotriethylene glycol, which can be derived from the carboxylic acid. The functionalization is thermodynamically stable and bonding is favorable. The results show an enhancement in the solubility of the nanotubes in water due to increased dipole moment as visualized in the HOMO-LUMO surface plots. Further as the degree of sidewall functionalization increases, the SWCNT sample becomes more soluble as assessed by the calculated Gibbs free energies of solvation. © 2015 Elsevier B.V. All rights reserved.


Villagracia A.R.C.,De La Salle University - Manila | Villagracia A.R.C.,National Research Council of the Philippines | Mayol A.P.,De La Salle University - Manila | Ubando A.T.,De La Salle University - Manila | And 11 more authors.
Clean Technologies and Environmental Policy | Year: 2016

Algal biofuels serve as a promising alternative energy source for liquid fuels. However, one of the bottlenecks in the conversion of microalgae to biofuels is the drying process. A moisture content of at most 10 % is desired for algal biomass prior to oil extraction to maximise biofuel yield. Conventional means of drying results to longer drying time and uneven drying of algal biomass. This study investigated the drying characteristics of microwave for microalgae (Chlorella vulgaris). Three microwave intensity levels (300, 600, and 900 W) were considered to dry 10, 20, and 30 of algal mass. Page model gave a better fit on the moisture ratio with time of microwave drying than the exponential model. Furthermore, the specific energy requirement was computed, and a relationship was found between moisture ratio with power and mass. Fourier transform infrared spectroscopy results showed significant reduction of infrared signal intensities of the functional groups present in the algae after drying at higher microwave power level. It was concluded that the 20 W/g microwave drying setting gave a lower specific energy requirement with good quality of remaining high lipid content qualitatively. Furthermore, it was recommended to use gas chromatography mass spectroscopy to further quantify the algal lipids and other functional groups. © 2016 Springer-Verlag Berlin Heidelberg

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