Understanding the structure and electronic properties of N-doped graphene nanoribbons upon hydrogen saturation

Abstract

Structures and electronic properties of zigzag graphene nanoribbon (ZGNR) with pyridine (3NV-ZGNR) functionalized by Scandium (Sc) at the edge were studied through quantum chemical calculations in the formalism of density-functional theory (DFT). Pyridine-like nitrogen defects is very crucial for enhancing the Sc atom binding to the defects and is thermodynamically favoured. During Sc decoration of ZGNR there is a shift from 0.35 eV small gap semiconductor regime to that of a metal which can be used for band gap tuning by controlled saturation of Sc. ZGNR decorated with Sc can attract H 2. Upon saturation of multiple H 2 in quasi-molecular fashion, the metallic character is converted to semiconductors of small gap of 0.10 eV, which are predicted to be interesting materials not only for hydrogen storage but also for their band gap engineered properties.

Scandium and Titanium Containing Single-Walled Carbon Nanotubes for Hydrogen Storage: a Thermodynamic and First Principle Calculation

“…The calculated adsorption energies for n H 2 is summarized in Table S1 together with the other parameters for maximal n H 2 adsorption. The E ads in the Sc-4ND-CN x NT complex are larger than those in Sc + pure CNT complex27282930. Remarkably, it is also energetically favorable for the group to complex with additional hydrogen molecules as shown in Fig.…”

“…It can be noted though that the adsorption energies, E ads, are still within the right range for room temperature storage for both Sc a Ti. For the number of H 2 to be adsorbed on each metal atom, it is similar to that in Sc/Ti - pure CNT or other Sc/Ti-dispersed graphitic materials, such as graphene or nanoribbons (for example, five H 2 /Sc and four H 2 /Ti)272829303132. Based from previous discussions, Sc is the transition metal of choice in designing advance composite material for reversible hydrogen adsorption and desorption with promising system-weight efficiency evaluated at room temperature.…”

“…For efficient hydrogen storage at ambient conditions, the consecutive adsorption energy (ΔE) should be in the range of 0.16–0.42 eV/H 2 intermediate between physiosorption and chemisorptions for realizable reversible adsorption and desorption 20 30 34 35 36 . The ΔE is calculated based on the following formula…”

“…A linear regression model expressed in the form of E f (n) = 3.149n + 0.458 can fit the formation energy (E f ) vs. n porphyrin defects data with r 2 = 0.996. The physical and chemical structure of the synthesized highly nitrogen-enriched graphitic carbon was investigated experimentally by powder X-ray diffraction, scanning and transmission electron microscopy, selected area electron diffraction, energy dispersive spectroscopy, elemental analysis, Fourier transform infrared spectroscopy, X-ray photoemission spectroscopy, and electron energy loss spectroscopy and theoretically by using DFT formalisms 24 25 26 27 28 29 30 31 32 33 34 35 36 . The analysis confirmed that the product has a highly crystalline nitrogen-enriched graphitic structure with a carbon-to-nitrogen ratio of 1:1.12 corresponding to a maximum of n = 10 defects.…”

Solubility of aminotriethylene glycol functionalized single wall carbon nanotubes: A density functional based tight binding molecular dynamics study

“…Interestingly, further studies would indicate that if polar molecules will be added (OH, NH 2 ) in the simulation the overall result still gives the same pattern if the concentration of the polar solutes are not that high (to be published). Also, the (n,n) fSWCNT does not exhibit this kind of periodicity in its adsorption and solubility; it is quite interesting to find out if other nanomaterials such as graphene, nanoribbons and metal oxide/graphene composite exhibit kind of adsorption pattern that is diameter dependent . The CNTs hollow structure and large specific surface area facilitates the accommodation of biomolecules and drug molecules.…”