arXiv subjects

Nacir Tit

Publications and source records attributed to Nacir Tit.

6 recordsLinked to original sources

arXiv2026

N-Graphdiyne as a Tunable Platform for Stabilizing Light Metals toward High-Capacity Reversible Hydrogen Storage

Hydrogen (H2) is a promising carbon-neutral energy carrier. However, its deployment is limited by the lack of lightweight, reversible storage media that operate under practical conditions. Here, we establish nitrogen-doped graphdiyne (N-GDY) as a programmable two-dimensional platform for stabilizing dispersed light-metal dopants and enabling high-capacity physisorption of molecular H2. The computational package involves density functional theory (DFT) combined with ab initio molecular dynamics (AIMD) and Langmuir-based statistical thermodynamic modeling. The results revealed that N-sites of N-GDY bind up to five Li, Na, K, and Ca atoms per primitive cell with binding energies of -2.27, -1.57, -1.80, and -2.13 eV, respectively, exceeding their respective bulk cohesive energies. AIMD simulations at 400 K further confirm the structural robustness of the decorated frameworks and the absence of metal aggregation. The polarised metal centres activate reversible H2 adsorption through electrostatic and dispersion interactions, with average adsorption energies falling within the optimal window (-0.15 to -0.35 eV per H2). Sequential adsorption analysis reveals uptake of up to 25 H2 molecules per primitive cell, achieving intrinsic gravimetric capacities of 13.08, 10.82, 9.23, and 9.15 wt% for Li-, Na-, K-, and Ca-functionalized systems, respectively. Thermodynamic analysis indicates favorable adsorption-desorption behavior under near-ambient conditions, with Li- and Ca-functionalized systems exceeding the 6.5 wt% U.S. Department of Energy's ultimate system-level target when considering intrinsic material capacity. These results identify N-GDY as a chemically tunable scaffold for dispersing lightweight metals and provide a mechanistic design strategy for achieving high-capacity, reversible hydrogen storage in porous two-dimensional materials.

cond-mat.mtrl-sci↗

arXiv2026

Defect-Engineered Beryllium Dinitride (BeN2) Monolayer with Light-Metal Decoration for Reversible High-Capacity Hydrogen Storage

Hydrogen (H2) possesses the highest gravimetric energy density of any chemical fuel and is the most abundant element in the universe. However, its extremely low volumetric energy density at standard conditions imposes a fundamental materials challenge for safe, efficient, and reversible storage. Here, we report a defect-engineered 2D beryllium dinitride (BeN2) monolayer that enables stable light-metal functionalization for high-capacity H2 storage. A 2 x 2 supercell containing two intrinsic beryllium vacancies accommodates four Li, Na, and K atoms without clustering, exhibiting strong average metal-vacancy binding energies of -3.80, -2.94, and -3.18 eV, respectively. Ab initio molecular dynamics simulations at 400 K confirm the thermal stability of the metal-decorated frameworks and the suppression of metal aggregation. The vacancy-stabilized alkali-metal centers generate localized charge polarization that facilitates the adsorption of up to 20 H2 molecules per supercell, with average adsorption energies of -0.182 eV (Li), -0.191 eV (Na), and -0.171 eV (K), making the adsorption reversible under near-ambient conditions. The corresponding gravimetric H2 storage capacities reach 11.64, 9.82, and 8.49 wt percent, respectively, significantly exceeding the US Department of Energy (DOE) ultimate target of 6.50 wt percent. Moreover, thermodynamic analysis further confirms favorable adsorption-desorption behavior within practical operating windows. These results establish vacancy-defected light-metal decorated BeN2 as a viable design strategy for high-density, reversible H2 storage, providing a scalable framework for engineering polar lightweight materials for energy storage applications.

cond-mat.mtrl-sci↗

arXiv2026

Pentagonal PdTe2 Monolayer for Sustainable Solar-driven Hydrogen Production

This investigation demonstrates that the pentagonal PdTe$_2$ (penta-PdTe$_2$) monolayer is a highly tunable two-dimensional (2D) photocatalyst, characterized by a bandgap of 1.87~eV and high hole mobility. Using density functional theory (DFT) calculations with the HSE06 functional, we show that tensile strain engineering, particularly at $+2%$ and $+3%$, is essential for enabling spontaneous water splitting. At these strain values, the valence-band maximum (VBM) and conduction-band maximum (CBM) straddle the water redox potentials ($\mathrm{H^+/H_2}$ and $\mathrm{O_2/H_2O}$) under both acidic ($\mathrm{pH}=0$) and neutral ($\mathrm{pH}=7$) conditions. The monolayer's low hole effective mass facilitates rapid charge extraction, mitigating electron--hole recombination and promoting the oxygen evolution reaction (OER) more effectively than many hexagonal and pentagonal counterparts. The Gibbs free energy ($\Delta G$) pathways indicate that the overpotentials for the hydrogen evolution reaction (HER) and OER are highly sensitive to mechanical deformation, specifically biaxial strain. In particular, a tensile strain of $+3%$ yields an optimized balance of overpotentials, with $\eta_{\mathrm{HER}} = 0.70~\mathrm{V}$ at $\mathrm{pH}=0$ and $\eta_{\mathrm{OER}} = 0.72~\mathrm{V}$ at $\mathrm{pH}=7$. Finally, integrating optical absorption with thermodynamic driving forces results in a solar-to-hydrogen (STH) efficiency of $20.40%$ at $\mathrm{pH}=7$. This performance exceeds that of several previously reported two-dimensional catalysts, positioning penta-PdTe$_2$ as a superior candidate for sustainable, solar-driven hydrogen production.

cond-mat.mtrl-sci↗

arXiv2024

Vacancy-Induced Boron Nitride Monolayers as Multifunctional Materials for Metal Ion Batteries and Hydrogen Storage Applications

This study comprehensively examined the structural, electronic, electrochemical, and energy storage properties of boron-vacancy induced porous boron nitride monolayers (BN:VB) as multifunctional materials, anodes for MIBs and H2 storage applications. Our computational approaches, density functional theory (DFT), ab initio molecular dynamics (AIMD), and thermodynamic analysis, revealed exceptionally high energy and gravimetric densities for MIBs and H2 storage, respectively. We investigated the interactions of Li, Na, and K atoms on BN:VB, which strongly bonded with binding energies stronger than their bulk cohesive energies, which ensured structural stability and the absence of metal clustering. Electronic properties, analyzed through spin-polarized partial density of states (PDOS), band structure, and Bader charge analysis, revealed significant charge transfers from the metal atoms to BN:VB, enhancing the electronic conductivity of the latter. Theoretical specific capacities were calculated as 1821.53, 786.11, and 490.51 mA h/g for Li, Na, and K, respectively, which comfortably exceeded the conventional anodes, such as graphite. Average open-circuit voltages (OCVs) were found as 0.15, 0.25, and 0.32 V, for Li, Na, and K, respectively, indicating strong electrochemical stability. Diffusion studies showed lower barriers of 0.47, 0.08, and 0.60 eV for Li, Na, and K, respectively, with increased metal loadings, suggesting enhanced mobilities and charge/discharge rates. On the other side, the metal-functionalized BN:VB monolayers exhibited remarkably high H2 gravimetric capacities, supported by Langmuir adsorption model-based statistical thermodynamic analysis. Average adsorption energies of H2 on 4Li-, 4Na-, and 4K@BN:VB, were found in perfect range for practical storage applications.

cond-mat.mtrl-sci↗

arXiv2024

Light-Metal Functionalized Boron Monoxide Monolayers as Efficient Hydrogen Storage Material: Insights from DFT Simulations

Exceptionally high energy density by mass, natural abundance, widespread applications, and environmental friendliness make hydrogen (H2) a front-runner among clean energy options. However, the transition toward clean and renewable energy applications and the actualization of H2 economy require an efficient H2 storage medium. Material-based H2 storage is a viable option, as liquefaction and storage under pressure require ultra-low temperature (-253{\deg}C) and tremendously high pressure (700 atm), respectively. In this work, we highlight the exceptional H2 storage capabilities of recently synthesized boron monoxide (BO) monolayer functionalized with light metals (Li, Na, K, and Ca). Our computational approach, employing density functional theory (DFT), ab initio molecular dynamics (AIMD), and thermodynamic analysis, reveals promising results. We found that up to four metal dopants (Li, Na, K, and Ca) can be adsorbed onto BO monolayer with significantly strong binding energies. Importantly, these bindings surpass the cohesive counterparts of the parental metal bulks, consequently stabilizing the crystal integrities, as confirmed by AIMD simulations. Each metal dopant on BO efficiently adsorbs multiple H2 molecules through electrostatic and van der Waals interactions. Interestingly, the metal-functionalized BO monolayers exhibit exceptionally high H2 gravimetric capacities up to 11.75 wt%. These promising capacities exceed the 5.50 wt% target set by the US Department of Energy for 2025. Following the same guidelines, the average binding energy per H2 molecule is within the range of -0.17 to -0.32 eV. The adsorption and desorption of H2 under practical working conditions are investigated by Langmuir adsorption model based statistical thermodynamic analysis, further supporting the potential of metal-functionalized BO monolayers for material-based H2 storage applications.

cond-mat.mtrl-sci↗

arXiv2002

Superconductivity in carbon nanotubes coupled to transition metal atoms

The electronic structures of zig-zag and arm-chair single-walled carbon nanotubes interacting with a transitional-metal atomic nanowire of Ni have been determined. The Ni nanowire creates a large electron density of states (DOS)at the Fermi energy. The dependence of the enhanced DOS on the spin state and positioning of the transition-metal wire(inside or outside the nanotube) is studied. Preliminary estimates of the electron-phonon interaction suggest that such systems may have a superconducting transition temperature of $\sim$ 10-50 K. The signs of superconductivity seen in ``ropes'' of nanotubes may also be related to the effect of intrinsic transition-metal impurities.

cond-mat.supr-con↗