Stone-Wales Defect in Graphene

2D graphene the most investigated structures from nanocarbon family studied in the last three decades. It is projected as an excellent material useful for quantum computing, artificial intelligence, and next generation advanced technologies. Graphene exists in several forms and its extraordinary thermal, mechanical, and electronic properties, principally depend on the kind of perfection of the hexagonal atomic lattice. Defects are always considered as undesired components but certain defects in graphene could be an asset for electrochemistry and quantum electronics due to the engineered electronclouds and quantum tunnelling. The authors carefully discuss the Stone-Wales imperfections in graphene and its derivatives comprehensively. A specific emphasis is focused on the experimental and theoretical aspects of the Stone-Wales defects in graphene with respect to structure-property relationships. The corroboration of extrinsic defects like external atomic doping, functionalization, edge distortion in the graphene consisting of Stone-Wales imperfections, which are very significant in designing graphene-based electronic devices, are summarized.

Ab Initio Investigation of the Adsorption of CO2 Molecules on Defect Sites of Graphene Surfaces: Role of Local Vacancy Structures

An in-depth investigation into the adsorption of CO₂ on graphene vacancies is essential for the understanding of their applications in various industries. Herein, we report an investigation of the effects of vacancy defects on CO₂ gas adsorption behavior on graphene surfaces using the density functional theory. The results show that the formation of vacancies leads to various deformations of local carbon structures, resulting in different adsorption capabilities. Even though most carbon atoms studied can only trigger physisorption, there are also carbon sites that are energetically favored for chemisorption. The general order of the adsorption capabilities of the local carbon atoms is as follows: carbon atoms with dangling bonds > carbon atoms shared by five- and six-membered rings and a vacancy > carbon atoms shared by two six-membered rings and a vacancy. A stronger interaction in the adsorption process generally corresponds to more obvious changes in the partial density of states and a larger amount of transferred charge.

A density functional theory study on the adsorption reaction mechanism of double CO2 on the surface of graphene defects

Much research has been done on reactions of a single CO₂ molecule with a graphene surface. In this paper, density functional theory calculations are used to investigate the adsorption and reaction of double CO₂ on the surface of single vacancy (SV) and divacancy (DV) defect graphene. The study found that due to the mutual repulsion between CO₂ and the size of the SV defect, it is difficult for two CO₂ molecular to be adsorbed directly above the SV defect at the same time. Regardless of SV or DV, the adsorption of the first CO₂ in the defect center will have a beneficial effect on the adsorption of the second CO₂. In addition, the transition state calculation of the CO₂ reaction on the DV plane was carried out, and the adsorption behavior was analyzed and studied. This in-depth study is helpful to the understanding of the reaction behavior of CO₂ on graphene, and further exploration in the direction of the effective application of graphene to the reaction and adsorption of CO₂. Our work explores the adsorption behavior of CO₂ on graphene surfaces, the physical and chemical adsorption of double CO₂ at the defect was studied and analyzed.

Adsorption and reaction mechanisms of single and double H2O molecules on graphene surfaces with defects: a density functional theory study

More attention needs to be drawn to the high application value of the gasification reaction between carbonaceous materials and water in industry. In this study, density functional theory is used to investigate the adsorption and reaction mechanism of water molecules on graphene surfaces with various kinds of defects. The desorption mechanism of the reaction product is also analyzed. The optimal and stable physical adsorption configuration of water molecules on the pristine graphene and various defects graphene surface has been determined. Chemisorption configurations of a single water molecule and double water molecules on the graphene surface with single vacancy defects are discussed and used as reaction precursors to explore the reaction path of water molecules in the process of desorbing hydrogen at active sites. The whole process of the reaction is largely exothermic and the thermodynamic advantages of double water molecules participating in the reaction are determined. The two reaction mechanisms of two-steps or co-adsorption and desorption of double water molecules are compared, and the lowest energy barrier advantage of the latter is determined.

Modeling of Si-B-N Sheets and Derivatives as a Potential Sorbent Material for the Adsorption of Li+ Ion and CO2 Gas Molecule

In the present exploration, a few Si-B-N derivatives are derived to adsorb Li ions and CO₂ gas molecules for the potential application of metal-air batteries. The newly derived structure's bond lengths are as follows: Si=Si, 2.2 Å; Si-B, 1.9 Å; Si-N, 1.7 Å; and B-N, 1.4 Å, consistent with the experimental results of relevant structures. The stability of the newly derived structures is examined by the atom-centered density propagation study by varying the temperature from 270 to 400 K, and no structural variations are observed throughout the dynamics. Li adsorption on the Si₄B₂ ring has the maximum binding energy of -3.9 eV, and the result is consistent with the previous results. The rings with the 2:1 silicon-boron ratio provide strong adsorption for Li atoms. The calculated maximum electromotive force of the newly derived sheets is 0.56 V with the maximum theoretical density of 783 Wh/kg. Similarly, the maximum adsorption of CO₂ on the sheet is -0.106 eV, which is considerably higher than that on graphene and its derivatives. CO₂ adsorption has been carried out in the presence of water molecules to investigate the change in CO₂ adsorption with the moisture (water) content, and the results show no significant change in the adsorption of CO₂ with moisture. However, water has a strong interaction with the maximum interaction energy of -0.72 eV. Further, to explore the potential ability of the sheets, each sheet's edges are examined as hydrogen storage expedient and the surface as an artificial photosynthesis platform. The Si₄B₂ ring is more favorable for the adsorption of H atom with the chemisorption of -7.138 eV. Similarly, all of the major UV-absorption spectral peaks fall between 450 and 800 nm, which shows that the sheet can be used as an artificial photosynthesis platform.

Gas adsorption efficacy of graphene sheets functionalised with carboxyl, hydroxyl and epoxy groups in conjunction with Stone–Thrower–Wales (STW) and inverse Stone–Thrower–Wales (ISTW) defects

The complete reduction of graphene oxide is difficult to achieve, and hence oxygen-containing functional groups do exist in graphene, along with structural defects.

Mechanistic insights into biomimetic carbonic anhydrase action catalyzed by doped carbon nanotubes and graphene

Density functional theory shows transition metal doped carbon nanotubes and graphene to be active and biomimetic for carbon capture.

Sensing Characteristics of a Graphene-like Boron Carbide Monolayer towards Selected Toxic Gases

By using first-principles calculations based on density functional theory, we study the adsorption efficiency of a BC3 sheet for various gases, such as CO, CO2, NO, NO2, and NH3. The optimal adsorption position and orientation of these gas molecules on the BC3 surface is determined and the adsorption energies are calculated. Among the gas molecules, CO2 is predicted to be weakly adsorbed on the graphene-like BC3 sheet, whereas the NH3 gas molecule shows a strong interaction with the BC3 sheet. The charge transfer between the molecules and the sheet is discussed in terms of Bader charge analysis and density of states. The calculated work function of BC3 in the presence of CO, CO2, and NO is greater than that of a bare BC3 sheet. The decrease in the work function of BC3 sheets in the presence of NO2 and NH3 further explains the affinity of the sheet towards the gas molecules. The energy gap of the BC3 sheets is sensitive to the adsorption of the gas molecules, which implies possible future applications in gas sensors.