Structural and electronic properties of Li-adsorbed single and bilayer porphyrin sheets as an electrode material for energy storage devices - a DFT analysis.

In this study, we adopt density functional theory (DFT) to investigate the structural and electronic properties of monolayer and bilayer 2-D porphyrin sheets (PS) of covalent organic frameworks (COFs) upon interaction with Li atoms as an electrode material for Li-ion batteries. Based on their mechanical properties, our systems exhibit remarkable stability. The adsorption of Li at various sites in the monolayer, including over and between the bilayers of PS, is investigated. Our results indicate that Li at site S3 has the highest adsorption energy, and Li is energetically preferred to intercalate within the bilayer rather than monolayers due to its high adsorption energies. Notably, the charge transfer remains consistent for both systems. The density of state distribution, charge density difference plots, spin density and the band structure results show that the PS has high electrical conductivity. Additionally, the reaction potential was carried out, and the negative reaction potential results demonstrate that the system undergoes a reduction reaction. The resultant theoretical capacity and the open circuit voltage highlight that the PS materials of COFs are an important step for use in the next generation high-performance lithium-ion batteries.

Superatom molecular orbital in C80.

The Superatom Molecular Orbitals (SAMO) in fullerene derivatives are of great interests which gives a wide basement for many electronic applications. In this work, the Density Functional Theory reveals the SAMO states of endohedrally doped C80 derivatives with Li, Sc, Mn, Ti, Ca, Fe, and Co atoms in molecular and periodic structures. The choice and position of metal atoms in endohedrally doped C80 derivatives largely affects the orientation of SAMO energies and wavefunction distributions. Among various derivatives, the Co-substituted C80 constitutes the lowest SAMO energy. The charge transfer study infers the influence of metal atoms inside the cage on SAMO energies. At higher energies, pz-, 2s-, and pxy- SAMO bands have been overlapped with higher dispersion bands which depict the increased intermolecular interaction in delocalized bands causing a larger dispersion. These results give new insights for future studies on lowering SAMO energy nearly to the fermi level in higher fullerenes.

Reinforcing the tetracene-based two-dimensional C48H16 sheet by decorating the Li, Na, and K atoms for hydrogen storage and environmental application -A DFT study.

To meet the increasing need of energy resources, hydrogen (H2) is being considered as a promising candidate for energy carrier that has motivated research into appropriate storage materials among scientists. Thus, in this study for the first time, zig-zag and armchair edged tetracene based porous carbon sheet (C48H16) is investigated for H2 storage using the density functional theory. To explore the hydrogen storage capacity, the hydrogen molecule is initially positioned parallel to the C48H16 sheet at three different sites, resulting in lower adsorption energies of -0.020, -0.024, and -0.015 eV respectively. The Li, Na, and K atoms are decorated to improve H2 adsorption on the C48H16 sheet. The Li atom decorated C48H16 sheet has a higher binding energy value of -2.070 eV than the Na and K atom decorated C48H16 sheet. The presence of Li, Na, and K atoms on the C48H16 sheet enhance the H2 adsorption energy than the H2 on the pristine C48H16 sheet. The decrease of Mulliken charge in alkali metal atoms (Li, Na, and K atom) on the C48H16 sheet reveal that the electron is transferred from H-σ orbital to s orbital of alkali metal atoms on the C48H16 sheet, leads to the enhancement of H2 binding. Compared to H2 adsorption on Na and K atom decorated C48H16 sheet, the H2 adsorption on Li atom decorated C48H16 sheet has the maximum adsorption energy value of -0.389 eV. The obtained hydrogen storage capacity of Li, Na, and K atoms decorated C48H16 sheets are about 7.49 wt%, 7.31 wt%, and 7.14 wt% respectively for four H2 molecules, which is greater than the targeted hydrogen storage capacity of the United States Department of Energy (DOE). Thus the obtained results in this work reveal that the decorated C48H16 sheets with Li, Na, and K atom plays the potential role in the H2 storage.

A first principle study of heme molecule as an active adsorbent for halogenated hydrocarbons.

Heme, a biomolecule with complex structure and unique properties and strong adsorption of oxygen, is utilized as an adsorbing material for haloalkene gas molecules. It has been systematically investigated employing density functional theory. Among the haloalkene gases chosen in the present study, the interaction energy is maximum for CDFM (-10.66 kcal/mol) and lowest for TFM (-5.02 kcal/mol). The calculated bond stabilization energy for heme-haloalkene complexes correlates with findings of interaction energy. The noncovalent interaction between heme and haloalkenes is confirmed from the topological analysis. The energy gap values decrease on adsorption of haloalkenes along with a decrease in reactivity of the complexes.

Kinetics and degradation of camphene with OH radicals and its subsequent fate under the atmospheric O2 and NO radicals - A theoretical study.

Camphene (C10H16) is an abundant bicyclic monoterpene in the atmosphere which can be easily oxidized by the atmospheric OH radicals. In this study, the oxidation of camphene with OH radicals and its subsequent reactions are studied using quantum chemical method. Thermochemical parameters show that the addition of OH radicals to the terminal C10 atom of camphene is thermodynamically more stable than the addition of OH radicals to the internal C7 atom of camphene. The reaction force profile demonstrates that the formation of two hydroxyalkoxy radical intermediates (I1a and I2a) are mainly dominated by the structural rearrangement with 94.28% and 99.43% of the total energy, respectively. The overall reaction rate coefficient for camphene + OH radical is 2.1⨯10-12 cm3 molecule-1 sec-1 at 298 K and 1 atm which agree well with the experimental reaction rate coefficient (5.58⨯10-11 cm3 molecule-1 sec-1) for the reaction of camphene with OH radical. The branching ratio for the addition of OH radical to the C10 position of camphene is 68.32%, and the C7 position of camphene is 31.68% at 298 K. The calculated lifetime reveals that camphene degrades quickly in the atmosphere owing to its short lifetime of 5.3 h. The obtained mechanistic and kinetic results reveal that the addition of OH radical to the C10 position is more dominant than the C7 position, and it is more stable and spontaneous in the atmosphere.

Impact of Oxygen Functional Groups on Reduced Graphene Oxide-Based Sensors for Ammonia and Toluene Detection at Room Temperature.

The chemically reduced graphene oxide (rGO) was prepared by the reduction of graphene oxide by hydrazine hydrate. By varying the reduction time (10 min, 1 h, and 15 h), oxygen functional groups on rGO were tremendously controlled and they were named RG1, RG2, and RG3, respectively. Here, we investigate the impact of oxygen functional groups on the detection of ammonia and toluene at room temperature. Their effect on sensing mechanism was analyzed by first-principles calculation-based density functional theory. The sensing material was fabricated, and the effect of reduction time shown improved the recovery of ammonia and toluene sensing at room temperature. Structural, morphological, and electrical characterizations were performed on both RG1 and RG3. The sensor response toward toluene vapor of 300 ppm was found to vary 4.4, 2.5, and 3.8% for RG1, RG2, and RG3, respectively. Though RG1 shows higher sensing response with poor recovery, RG3 exhibited complete desorption of toluene after the sensing process with response and recovery times of approximately 40 and 75 s, respectively. The complete recovery of toluene molecules on RG3 is due to the generation of new sites after the reduction of oxygen functionalities on its surface. It could be suggested that these sites provided anchor to ammonia and toluene molecules and good recovery under N2 purge. Both theoretical and experimental studies revealed that tuning the oxygen functional groups on rGO could play a vital role in the detection of volatile organic compounds (VOCs) on rGO sheets and was discussed in detail. This study could provoke knowledge about rGO-based sensor dependency with oxygen functional groups and shed light on effective monitoring of VOCs under ambient conditions for air quality monitoring applications.