Hydrogen storage in Ca-decorated carbyne C10-ring on either Dnh or D(n/2)h symmetry. DFT study

Ab Initio Study on the Potential of Metal-Decorated Pristine and Activated Carbyne for Hydrogen Storage Applications

“…The HOMO–LUMO spatial distribution exhibited a uniform orbital formation, which promoted easier metal atom binding . The next step was to evaluate the stability of the pristine and activated carbyne-doped complexes by determining the binding energy E b M using eq . ,, E normalb normalM = 1 x [ E C 12 + x E M − E M x C 12 ] where E C 12 is the total energy of the carbyne molecule (pristine or activated), E M is the total energy per metal atom (AM, AEM, and TM), and E M x C 12 is the total energy of one carbyne molecule decorated with x metal atoms.…”

“…Analysis of H 2 adsorption properties on the pristine and activated carbyne complexes was done by adding one atom at a time around the alkali, alkaline-earth, and transition metals (Li, Na; Sr, Ba; Sc, Ti, Ni, Y). The average binding energy of n H 2 molecules adsorbed by the MC 12 complex was calculated using eq . ,,− E ave = false[ E false( normalM x normalC 12 false) + n E false( normalH 2 false) − E false( normalM x normalC 12 − n normalH 2 false) false] n where E (M x C 12 ) and E (H 2 ) are the total energies of the MC 12 complex (M = AM, AEM, and TM) and E (M x C 12 – n H 2 ) is the total energy of the M x C 12 system with n H 2 molecules adsorbed on decorated complexes.…”

Carbyne Ring Activated Using ZnCl2 for Hydrogen Adsorption: DFT Study

“… 21 Nevertheless, only a single Ca atom might be bound to the carbyne molecule with binding energy ( E b Ca ) higher than 2 eV, reaching 6.16 wt % for the gravimetric hydrogen storage. Even for cluster C 10 -rings 24 in polyyne and cumulenic forms, only a single Ca atom might be chemisorbed with binding energies greater than 2.5 and 2.33 eV for GGA-PW91 and GGA-PBE functionals, respectively. Up to either six or seven H 2 molecules are physisorbed by Ca atom, with average energies of 0.22 eV per H 2 (PW91) and 0.263 eV per H 2 (DFT-D) for cumulene and polyyne molecules, respectively.…”

“…Alkaline-earth metal dopants, especially Ca atoms, show better hydrogen storage performance. 4 , 16 − 24 Ca atom is selected as the main dopant because of not only its lower cohesive energy (1.84 eV) compared with the transition metals (∼4 eV) but also its lightness in weight, its lower trend to aggregate on the host material whenever they are deposited, and its ability to retain the hydrogen content after doping. 20 − 22 Carbyne is composed of sp-hybridized carbon atoms.…”

“…Metal doping is one of the effective methods to upgrade the strength of binding between hydrogen molecules and carbon-based nanomaterials. Alkaline-earth metal dopants, especially Ca atoms, show better hydrogen storage performance. ,− Ca atom is selected as the main dopant because of not only its lower cohesive energy (1.84 eV) compared with the transition metals (∼4 eV) but also its lightness in weight, its lower trend to aggregate on the host material whenever they are deposited, and its ability to retain the hydrogen content after doping. − Carbyne is composed of sp-hybridized carbon atoms. − The material has been proposed as nanoelectronic and also is likely to be used for hydrogen storage owing to an effective surface area around 13,000 m 2 g –1 , four times larger than theoretical graphene values. , The carbyne-ring structure is the base state of small carbon clusters (up to about 20 atoms) and an alternative form of linear chains, which are obtained by laser vaporization of graphite. − Between carbon clusters that result beginning with this technique in which carbyne has been found, ring structures are comparatively the most stable compared to other configurations and are the principal precursors of fullerenes and nanotubes . Two carbyne structures might be defined as cumulene (equal double bonds) and polyyne (alternative single/triple bonds). − Previous research has shown theoretical estimation of Ca-decorated pristine carbyne for hydrogen storage on linear chains and rings, which meet the U.S. Department of Energy target requirement of 5.5 wt % .…”