Kamal A. Soliman

Efficient and reversible hydrogen storage remains a major challenge for clean energy technologies. Here, DFT-D3 calculations combined with PDOS, TD-DFT, QTAIM, and RDG analyses were used to evaluate a Na-decorated Al₄N₄O₂ nanocluster as a solid-state hydrogen storage material. The optimized Al–N–O framework is structurally stable, with a formation energy of − 4.645 eV, and shows strong electronic polarization due to charge redistribution between Na and O/N sites. Ab initio molecular dynamics simulations at 600 K predict high thermal stability of the Al₄N₄O₂Na₄ nanocluster during the simulated hydrogen adsorption–desorption process. The resulting electropositive Na and electron-rich O/N regions create dual adsorption sites that promote polarization-induced physisorption of H₂. Upon successive hydrogenation, adsorption energies range from − 0.470 to − 0.309 eV per H₂, with desorption enthalpies of − 28.56 to − 21.45 kJ mol^-1 per H₂, suggesting reversible hydrogen release at 244–347 K. The predicted gravimetric capacity reaches 20.13 wt%, exceeding the DOE 2025 target.

The inhibitory performance of two polymeric compounds, polythiophene (PT) and polypyrrole (PPy), on the corrosion behavior of mild steel (MSt) in 1.0 M H₂SO₄ solution was systematically investigated using potentiodynamic polarization, potentiodynamic anodic polarization, electrochemical impedance spectroscopy (EIS), and weight loss measurements. The novelty of this study lies in its integrated approach, which correlates experimental chemical and electrochemical analyses with quantum chemical calculations and Monte Carlo simulations to provide a comprehensive understanding of the inhibition mechanism. The results demonstrate that both PT and PPy act as mixed-type inhibitors, significantly reducing corrosion through adsorption onto the MSt surface in accordance with the Langmuir adsorption isotherm. The inhibition efficiency increases with increasing inhibitor concentration, while it decreases with rising temperature, suggesting that the adsorption process is predominantly physical in nature. Polarization measurements further confirm that PT and PPy behave as mixed-type inhibitors and exhibit pitting inhibition behavior, as evidenced by the positive (noble) shift in the pitting corrosion potential with increasing inhibitor concentration. Thermodynamic parameters associated with activation and adsorption processes were determined and discussed in detail. In addition, a comparative study of PT and PPy adsorption on the Fe (110) surface was conducted using quantum chemical descriptors and Monte Carlo simulations. The combined electronic structure analysis and adsorption results consistently indicate that PPy forms a more stable and protective adsorbed layer, in excellent agreement with experimental findings, thereby identifying it as the more effective polymeric inhibitor for mild steel corrosion protection.

The development of efficient anode materials is essential for calcium‐ion batteries (CaIBs). Using density functional theory (DFT‐D3) calculations with Grimme's D3 dispersion correction, we investigated pristine borospherene (B ₄₀ ), heteroatom‐doped (B ₃₉ N, B ₃₉ Si, B ₃₉ Ti), and halide‐encapsulated nanocages (F ^– B ₄₀ , Cl ^– B ₄₀ , Br ^– B ₄₀ , and F ^– B ₃₉ X). Calcium and Ca ²⁺ interactions were analyzed via binding energy, charge transfer, and conductivity. Ti‐doping enhanced Ca storage with favorable adsorption (−2.15 eV), high voltage (4.45 V), and strong reactivity. Fluoride encapsulation further strengthened Ca binding, reaching −3.626 eV in Ca/F ^– B ₃₉ Ti. Molecular dynamics (MD) simulations confirmed structural stability, and theoretical capacities of 441.2–477.9 mAh g ⁻¹ compare well with reported CaIB anodes. Significant bandgap reductions (e.g., 57.88% in Ca/F ^– B ₃₉ N, 51.99% in Ca/F ^– B ₃₉ Ti) indicate improved conductivity. Spin‐polarized PDOS for Ca/B ₃₉ Ti and Ca/F ^– B ₃₉ Ti revealed asymmetric spin states, suggesting net magnetism. Quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) analyses highlighted electrostatic and partial covalent interactions. Notably, Ca adsorption on fluoride‐encapsulated B ₃₉ X produced the highest hyperpolarizability ( β ₀ ), indicating potential for optoelectronic use. Open‐circuit voltages of Ca ₆ /B ₄₀ , Ca ₆ /Br ^– B40, and Ca ₆ /F ^– B ₃₉ Ti (0.1–1 V) confirm stability at high Ca content. Overall, borospherene nanocages, particularly fluoride‐encapsulated and Ti‐doped systems, emerge as promising CaIB anodes and multifunctional materials for energy and photonic devices.

DFT study of graphene functionalized via carbene was performed to identify the preferred –OH adsorption sites and to assess how hydroxylation affects adsorption of NH₃ gas. The carbene attaches to the graphene basal plane through a [2+1] cycloaddition, producing a local cyclopropane-like motif with a C–C bond. This modification introduces localized mid-gap states and asymmetric charge redistribution that create chemically active anchoring sites for –OH groups. We systematically scanned possible –OH adsorption sites and identified site-dependent binding energies. NH₃ preferentially anchors at the carbene center and is further stabilized by multidentate hydrogen bonding with neighboring –OH groups. Calculated NH₃ adsorption energies range from moderate values (single –OH and some two –OH symmetric sites, E_ads ≈ −0.64 to −0.75 eV) to strong interaction for selected through-plane two –OH pairs (E_ads ≈ −1.78 to −1.83 eV), where synergistic hydrogen bonding amplifies the NH₃ interaction. Charge density difference and Bader analyses indicate polarization-dominated binding with minimal net charge transfer, consistent with hydrogen bonding rather than covalent bond formation. Desorption time estimation shows that moderate binding motifs provide rapid recovery at room temperature. We conclude that targeted placement of paired –OH groups on carbene-functionalized graphene offers a tunable route to balance sensitivity and reusability for NH₃ sensing.

This study investigates the hydrogen storage capacity of co-doped graphene with non-bonded B and N atoms (BC₄N) using density functional theory (DFT). The optimized structure reveals the introduction of co-doping ripples the surface, enhancing potential hydrogen storage applications. The adsorption behavior of Li and Na atoms on the BC₄N surface is examined, demonstrating a higher binding energy, surpassing their cohesive energies. Density of State (DOS), Partial Density of State (PDOS), and charge transfer analyses indicate electron donation from Li and Na to BC₄N monolayer, establishing BC₄N as an electron acceptor. The investigation extends to H₂ adsorption on Li/BC₄N and Na/BC₄N systems, revealing a non-dissociative form and a cooperative effect with increasing H₂ molecules. The hydrogen storage gravimetric density is calculated, and desorption temperatures are determined, highlighting the potential of Li/BC₄N and Na/BC₄N as promising candidates for efficient hydrogen storage.

This study explores the adsorption properties of Li‐ and Na‐decorated C ₂₄ N ₂₄ nanocages and their interactions with SO ₂ , SCO, H ₂ S, CS ₂ , HCHO, and CH ₄ gas molecules. The introduction of Li and Na atoms significantly enhances gas adsorption due to increased binding energies and modified electronic properties. The adsorption of SO ₂ , SCO, H ₂ S, CS ₂ , HCHO, and CH ₄ on Li‐and Na‐decorated C ₂₄ N ₂₄ demonstrates varying interaction strengths compared to pristine C ₂₄ N ₂₄ . The decorated nanocages exhibit altered electronic structures, with changes in energy gaps and charge transfer upon gas adsorption. Frontier molecular orbital analysis indicates improved reactivity, suggesting potential suitability for gas sensing applications. However, recovery times reveal limitations in sensing abilities for certain gases. The ΔG for all gases adsorbed on C ₂₄ N ₂₄ , Li‐ and Na‐decorated C ₂₄ N ₂₄ at 298.15 K and 1 atm are nonspontaneous, except for SO ₂ and HCHO on Li‐ and Na‐decorated C ₂₄ N ₂₄ . The results demonstrate that Li‐ and Na‐decorated C ₂₄ N ₂₄ nanocages exhibit high sensitivity and fast desorption for SO ₂ , highlighting their potential for practical gas sensing applications.