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The electrochemical synthesis of hydrogen peroxide (H2O2) provides a greener and more efficient method compared with classic catalysts containing toxic metals. Herein, we used first-principles density functional theory (DFT) calculations to investigate 174 different single-atom catalysts with graphyne substrates, and conducted a three-step screening strategy to identify the optimal noble metal-free single atom catalyst. It is found that a single Ni atom loaded on γ-graphyne with carbon vacancies (Ni@V-γ-GY) displayed remarkable thermodynamic stability, excellent selectivity, and high activity with an ultralow overpotential of 0.03 V. Furthermore, based on ab-initio molecular dynamic and DFT calculations under the H2O solvent, it was revealed that the catalytic performance for H2O2 synthesis in aqueous phase was much better than that in gas phase condition, shedding light on the hydrogen bond network being beneficial to accelerate the transfer of protons for H2O2 synthesis.

As a new carbon allotrope, graphyne (GY) has been predicted with singular and abundant electrochemical capabilities. Although it is difficult to prepare GY directly, the preparation of GY derivatives can help us to understand the properties of GY from another perspective. Herein, we developed a facile strategy to prepare GY derivatives such as nitrogen (N) substituted GYs which are comprised by azaaromatic rings and acetylene bonds. Their band gap and lithium storage properties have been tuned by presetting the number of N atoms in the benzene ring. Both properties and applications of the as-prepared GYs have been studied and compared with the calculation results of GY. With the increase of N content in GY, the charge concentration and the conductivity have been improved, while the band gap has been decreased and lithium storage capability has been enhanced, demonstrating the property and performance of GY can be well regulated by precise N introduction. Notably, all these experimental and theoretical results suggested a universal avenue for the preparation of GY based versatile materials with regulated properties by tuning the composition of benzene rings.

The high cost and relative scarcity of platinum (Pt) restrict large-scale commercialization of fuel cells, which has spurred researchers to develop low-cost alternatives integrating with high hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) catalytic activity. Herein, we performed density functional theory (DFT) calculations to explore the electrocatalytic activity of graphyne nanotubes (GyNTs). Several GyNTs were found to be potential metal-free electrocatalysts, with both HER and ORR activity superior to Pt. Moreover, we revealed a linear relationship between the Gibbs free energy change of O2 adsorption (ΔGOOH) and binding energy of H adsorption (ΔEH), which could be attributed to the fact that both the C O bond of OOH adsorption and the C H bond of H adsorption are single bonds. Therefore, ΔEH is proposed as a general descriptor for the rational design of bifunctional graphyne materials toward HERs and ORRs. Our findings provide a simple strategy for the rational design of bifunctional materials.

In this paper, the thermal conductivity characteristics of the α2-graphyne nanotubes are investigated. Molecular dynamics simulations are used for this purpose. The influences of chirality, diamete...

In this paper, we perform a systematical investigation on searching for defect γ -graphyne nanoribbons ( γ -GYNRs) with optimal thermoelectric performance by utilizing nonequilibrium Green’s function combined with Bayesian optimization. The calculations show that Bayesian optimization could quickly and accurately identify the optimal structure with best thermoelectric efficiency. Even in the worst round of optimization, optimal structure could be obtained by only calculating 719 structure candidates (merely 4.35% of all the 16512 candidates). The room temperature thermoelectric figure of merit of optimal defect γ -GYNR (length 11.846 nm, width 1.453 nm) could approach 2.315, which is 5 times of that of pristine γ -GYNR. The obvious advantage of optimal defect γ -GYNR is mainly attributed to the maximum balance of weakening of thermal power factor (side effect) and suppression of thermal conductance (positive effect). Through analyzing the pair correlation function, we also find that the correlations between perfect (defect) unit and perfect (defect) unit are both extremely low for defect γ -GYNRs with high thermoelectric conversion efficiency. The findings presented in this work indicate the effectiveness and superiority of Bayesian optimization in designing defect γ -GYNRs, and could provide new insights for exploring other low-dimensional materials with excellent thermoelectric properties.

The fabrication of solid surfaces with distinct wettability has critical implications in both science and technology. Recently, coatings have been widely employed to modulate the wettability of sol...

To obtain high hydrogen storage performance, Li and Na co-decorated T4,4,4-graphyne have been studied by the method of first-principles calculations in this paper. Li and Na atoms are bound on hexagonal ring and acetylenic ring included in T4,4,4-graphyne, with the average adsorption energy of 1.73 and 2.38 eV, respectively. Our calculations show that the maximum gravimetric density of H2 uptake is 10.46 wt%, and an appropriate adsorption energy is reached. Moreover, by plotting charge density differences, it is found that the induced electric field between Li/Na and T4,4,4-graphyne can enhance the adsorption for hydrogen molecule. Furthermore, this complex is thermodynamic stable at room temperature, which is certificated by molecule dynamics simulation. Our results demonstrate that Li and Na co-decorated T4,4,4-graphyne is an alternative material for hydrogen storage.

Graphyne, a new two-dimensional carbon allotrope containing both sp and sp2 hybridized states, is a current topic of focus in nanomaterial research community. Taking gamma (γ)-graphyne as an exampl...

Monte Carlo simulation has been used to study the behavior of the magnetization plateaus of the bi-layer graphyne like-structure with spin-2 and spin-5/2 by varying different physical parameters. W...

Among all the 2D-carbon materials, graphyne is currently one of the most interesting carbon allotropes besides graphene. It has potential applications in a wide variety of scientific fields owing to its unique sp–sp2 hybrid network, which endows desirable electronic properties towards energy-related applications. In this review, we summarize the recent progress in graphynes for electronic and energy applications from a theoretical point of view. The intrinsic electronic structure of graphyne and its chemical and mechanical properties are comprehensively described. It is hoped that this review could provide a strong theoretical understanding of graphynes, thus accelerating the design of robust and efficient graphyne-based advanced energy and electronic devices in the future.

In this paper, we propose a new acetylenic carbon material called pyridyne, which is composed of acetylenic linkages and pyridine rings. From first-principles calculations, we investigate the structural, elastic and electronic properties of pyridyne. It is found that the structure of pyridyne is stable at 300 K and its stability is comparable to experimentally synthesized graphdiyne and graphtetrayne. Compared with graphene or graphyne, pyridyne possesses more diverse pores and reduced delocalization of electrons. The in-plane stiffness of pyridyne is 183 N m-1 with a Poisson's ratio of 0.304. Pyridyne is found to be a semiconductor with a direct band gap of 0.91 eV. The intrinsic electron mobility can reach 6.08 × 104 cm2 V-1 s-1, while the hole mobility can reach 1.82 × 104 cm2 V-1 s-1.

In the light of ultrahigh atom utilization, high catalytic activity and low cost, single-atom catalysts (SACs) have been garnering extensive attention in the field of electrochemistry. In recent studies, however, bifunctional SACs for water splitting are rare, and face the challenge of high overpotential. In this work, a series of transition metal (TM) atoms supported on two-dimensional (2D) H4,4,4-graphyne monolayer were verified to be bifunctional SACs for HER/OER and OER/ORR by first-principles calculations. It is interesting that Co@H4,4,4-GY and Pt@H4,4,4-GY could be applied as high-efficiency catalysts for water splitting with low overpotentials of 0.04/0.45 and 0.17/0.69 V for HER/OER, respectively. In addition, Ni@H4,4,4-GY as bifunctional SACs also exhibits desirable catalytic activity for OER/ORR with low overpotentials of 0.34/0.29 V, even superior to commercial IrO2 and RuO2. Our results reveal that TM–substrate coordination and local electronic property show significant effects on the catalytic properties for HER/OER/ORR, and the d band center as an effective descriptor could be adopted to optimize the catalytic performance of the catalysts.

Zero valence palladium (Pd(0)) nanoparticles have been reported to be more favorable to the oxygen reduction reaction (ORR) than palladium oxide (PdO). However, PdO is normally concomitant in Pd(0) nanoparticles. Herein, we developed an inventive method to prepare pure Pd(0) nanoparticles supported with hydrogen-substituted graphyne (Pd/HsGY) and its nitrogen-doped sample (Pd/N–HsGY). Pd(0) nanoparticles were obtained by reducing the atomically dispersed bivalent Pd, which is easy to be anchored on HsGY. The unique sp-hybridized carbon atoms in HsGY exhibited obvious extrinsic charge compensation to maintain the supported Pd nanoparticles to zero valence state. The as-prepared samples, especially Pd/N–HsGY, displayed excellent activity for ORR, higher than that of commercial Pd/C and Pt/C. In an alkaline medium, the mass activity of Pd/N–HsGY at 0.8 V (vs. RHE) was 2.1 times higher than that of Pd/C, and 1.7 times higher than that of Pt/C. While in an acidic medium, the mass activity of Pd/N–HsGY was 17.7 and 1.6 times Pd/C and Pt/C, respectively. Pd/N–HsGY based Zn–air battery exhibited higher power density than Pt/C-based battery and superior stability for more than 300 hours. Density functional theory calculations confirmed that Pd(0) nanoparticles, Pd/HsGY and Pd/N–HsGY were favorable to ORR. This method brings new perspectives for designing zero valence metal nanoparticles for electrocatalytic applications.

Porous hydrogen substituted graphyne (HsGY) has been considered as a promising candidate for anode material due to its excellent electrochemical properties. In this work, we found that monolayer and bilayer HsGY are good electrodes for high charge capacity lithium-ion batteries based on density functional theory calculations. Mechanical tests reveal that monolayer and bilayer HsGY exhibit excellent mechanical properties, including large critical strains (>25%) and high in-plane stiffness (>200 N m−1). The bilayer HsGY displays ultrahigh stiffness (400.27 N m−1). Li adsorption on bilayer HsGY is stronger than that on the monolayer HsGY. Moreover, Li diffusion on the surfaces of monolayer and bilayer HsGY has low energy barriers (

Graphyne-based two-dimensional (2D) carbon allotropes feature extraordinary physical properties; however, their synthesis as crystalline single-layered materials has remained challenging. We report on the fabrication of large-area organometallic Ag−bis-acetylide networks and their structural and electronic properties on Ag(111) using low-temperature scanning tunneling microscopy combined with density functional theory (DFT) calculations. The metalated graphyne-based networks are robust at room temperature and assembled in a bottom-up approach via surface-assisted dehalogenative homocoupling of terminal alkynyl bromides. Large-area networks of several hundred nanometers with topological defects at domain boundaries are obtained due to the Ag–acetylide bonds’ reversible nature. The thermodynamically controlled growth mechanism is explained through the direct observation of intermediates, which differ on Ag(111) and Au(111). Scanning tunneling spectroscopy resolved unoccupied states delocalized across the network. The energy of these states can be shifted locally by the attachment of a different number of Br atoms within the network. DFT revealed that free-standing metal−bis-acetylide networks are semimetals with a linear band dispersion around several high-symmetry points, which suggest the presence of Weyl points. These results demonstrate that the organometallic Ag−bis-acetylide networks feature the typical 2D material properties, which make them of great interest for fundamental studies and electronic materials in devices.

Adsorption of NOx and COx (x = 1, 2) molecules on T4,4,4-graphyne sheet is studied using density functional theory. The most stable adsorption configurations, adsorption energies, binding distances, charge transfers, electronic band structures and density of states are calculated. Our results show that CO, CO2, NO and NO2 molecules are weakly physisorbed on T4,4,4-graphyne sheet. T4,4,4-graphyne is a direct band gap semiconductor. The electronic properties of T4,4,4-graphyne show no sensitivity to the presence of CO and CO2 molecules, while the changes in the electronic properties are observed after NO and NO2 adsorption. The electronic properties of T4,4,4-graphyne are sensitive to the concentration of molecular adsorption. Our findings show immense potential of T4,4,4-graphyne as a highly sensitive gas sensor for NO and NO2 detection.

The adsorptions of hydrogen on Li-decorated nitrogen-substituted graphyne are investigated by density functional theory. The substitutional doping of nitrogen atoms can change the electronic struct...

Motivated by novel graphyne-like carbon nanostructure C68-GY, spin-polarized DFT calculations with dispersion-correction were performed to investigate the hydrogen adsorption capacity of Li decorated C68-GY nanosheet. The binding energy between Li and C68-GY was larger than the cohesive energy of bulk metal, indicating Li atoms would prefer to separately attached on C68-GY. The ab initio molecular dynamics simulation has been performed to confirm the stability of Li/C complex. When five Li atoms decorated on C68-GY, 14H2 molecules were captured. The maximum hydrogen storage density was 8.04 wt% with an average hydrogen adsorption energy of −0.227 eV per H2. The positively charged Li atoms aroused electrostatic field and induced the polarization of H2. It was notable to observe strong hybridization between the main peak of H-1s orbitals with Li below Fermi level, which was responsible for the enhancement of hydrogen binding energy, indicating its potential application on hydrogen storage.

In contrast to the energy-extensive Haber–Bosch process, green production of ammonia (NH3) at ambient conditions remains as one of the main goals of the 21st century. In this work, we systematicall...

Graphyne sheets and nanotubes (GyNTs) are known as novel low-dimensional, i.e., two-dimensional (2D) and one-dimensional (1D), semiconducting carbon allotropes that can be used in nanoelectronics and therefore merit fundamental investigation. Among such materials, attention is currently focused on γ-graphyne-1, a member of the graphyne family that exhibits a maximum cohesive energy of −8.37 eV and chemical stabilityhas been focused. In this research density functional tight binding (DFTB) method in the investigation of electrical property under geometrical variation is reported and a detailed description of electrical as well as stability properties for γ-graphyne-1 in uniform strain is illustrated. It is concluded that the γ-graphyne-1 family of materials exhibit semiconducting properties with large bandgap values from 1.34 eV for the sheet structure to 1.93 eV for (3,0) armchair γ-graphyne-1 nanotubes. The γ-graphyne-1 family also displays elastic properties, enabling the modulation of the bandgap and engineering of the effective mass using homogeneous strain. These properties, along with the nonmetallic behavior of GyNTs, make them perfect materials for the design of novel electronic devices.

Similar to graphene, the absence of band gap limits applications of the recently proposed α2-graphyne sheet. We have investigated tuning the energy band of α2-graphyne through functionalization with carbene groups. The effect of carbene group CR2 (R = Cl, H, CN, CH3, and NO2) on the structural and electronic properties of α2-graphyne is studied by density functional theory study. The binding energy, charge transfer, equilibrium geometries, electronic band structures, and density of states of pure and functionalized α2-graphyne sheets are calculated. It is found that the chemical functionalization of α2-graphyne with carbene groups causes the structural deformation and opens the band gap. The energy band gap of α2-graphyne increases by 0.48 eV as the concentration of carbene groups varies. Our results indicate that chemical functionalization is an effective way to tune the electronic properties of α2-graphyne.

The hydrogen storage capacity of yttrium decorated graphyne nanotubes is calculated using spin polarized DFT method. The stabilities, electronic properties and the structures of Y attachment on graphyne tube are investigated. It is revealed that Y can be separately adsorbed on graphyne tube with the binding energy of 6.76 eV and the clustering of metal atoms is hindered. The geometry optimization shows that Y atoms decorated graphyne tube can capture 42H2 molecules through Dewar-Kubas like interaction and the polarization under the electrostatic potential formed by Y and graphyne tubes. The weight percent capacity is 5.71 wt%, with an average hydrogen adsorption energy of −0.153 eV per H2, indicating its potential application on hydrogen storage candidates.

Lattice strain, either tensile or compressive, can fine-tune the electronic structure of surfaces via altering the distances between surface atoms, thereby modifying the catalytic activity of catalysts. Numerous examples of strain engineering have been applied to various electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), but strain-optimized 2D carbon-based single-atom electrocatalysts for catalyzing the overall water splitting reaction have received little attention. Here, we applied the lattice strain of Co,N co-decorated graphyne (Co@N1-GY) to directly optimize its catalytic activity for the overall water splitting reaction based on first-principles calculations. Our calculations suggest that compressive strain and tensile strain lead to less stability of Co@N1-GY and the distances between C and Co atoms increase linearly with the strain changing from compressive to tensile, thus linearly upshifting the p-band center of C atoms and the d-band center of Co atoms. In addition, biaxial strain has more remarkable effects on these properties than uniaxial strain. From compressive to tensile strain, the chemisorption of electrochemically generated intermediates in both HER and OER becomes weaker and weaker. A tensile strain of 0.5% on Co@N1-GY gives an ideal HER performance, while the OER reaches the minimum overpotential of 0.33 V under the biaxial tensile strain of 3%.

The instinctive chemical inertia of CO2 impedes its electrochemical reduction by high energy input. Single atom catalysts (SACs) on supports are considered as a class of excellent electrocatalysts with high activity, selectivity and atomic efficiency for CO2 electrochemical reduction. Supports for single atoms are believed to greatly impact the electrocatalytic activity of SACs. However, further research on the relationship between the structure of supports for SACs and CO2 electroreduction is still needed. Herein, density functional theory (DFT) calculations are performed to investigate the role of supports in tuning the CO2 electrocatalytic activity of SACs. Graphynes with different pore sizes (graphyne, graphdiyne, graphyne-3 and graphyne-4) are taken into account to unveil the effect of their skeleton structure on the anchored Cu single atoms. We found that support skeletons could greatly impact the coordination configuration of metal atoms and the steric repulsion of support skeletons to intermediates. These two factors jointly result in different electrocatalytic performances of SACs. The comparative analysis proves that the graphynes with large pores are appropriate supports for Cu adatoms for CO2 electroreduction due to the low-coordinated Cu atoms and weak-steric-repulsion carbon skeleton. Such SACs exhibit much enhanced activity and selectivity as compared with the Cu(111) surface and monoatomic Cu on nitrogen-doped graphene. This work provides a new insight into the rational design of supports for SACs.

From an interplay of high-resolution UHV-STM imaging and DFT calculations, we have achieved on-surface synthesis of graphyne nanowires through stepwise reactions involving two different types of dehalogenative homocoupling reactions (i.e., C(sp3)-Br and C(sp2)-Br). This study would further supplement our database of on-surface synthesis and provide us with an alternative and efficient strategy for the fabrication of desired nanostructures/nanomaterials.

Graphynes (GYs) are the new star carbon isomers with two-dimensional layered in-plane porous structures, which are composed of sp- and sp2-hybrid carbon atoms. These special features result in their unique topological and electronic structures, high charge mobility and excellent electronic transport properties. All of these advanced properties of GYs make them promising in various applications. In the GY family, graphdiyne (GDY) was the first successfully prepared member, so it attracted the most attention. In this review, the recent progress on the synthetic strategies, functional mechanisms and applications of GDY and other GYs in the fields of energy storage/conversion are summarized, and the challenges hindering their large-scale fabrication toward practical applications are analyzed. Finally, the possible research directions for overcoming the challenges are proposed based on the development trend and perspectives of GYs. It is hoped that this review is helpful for deeply understanding GYs and GY-based materials.

By applying non-equilibrium Green's functions (NEGF) in combination with tight-binding (TB) model, the electronic transport properties of pristine and defected zigzag α-graphyne nanotubes (Z-α-GYNTs) are studied under finite bias. We have considered single vacancy (SV) and double vacancy (DV) and also the effect of tube size. Depending on the position of absent atom(s), different modes arise. Initially the formation energy is calculated for each mode and we observed that in all cases an endothermic process in needed. Moreover by studying the band structure we found that all defects cause gap closing, but not enough to change the semiconducting nature of Z-α-GYNTs entirely. Considering p as a positive integer, I-V characteristics show that for (3p-1, 0) tubes, all defects are found to increase the current but on the contrary presence of them in a (3p, 0) tube results in current reduction. (3p + 1, 0) tubes does not show a defined and specific reaction to the defects. Band structure of electrodes, transmission spectrum, Density of states, molecular energy spectrum and molecular projected self-consistent Hamiltonian (MPSH) are analyzed subsequently to make the electronic transport properties of GYNT devices clearer. Our results can be used in developing nano-scale devices.

The effect of BN nanodots with hexagonal shape on the electronic properties of α- and β-graphyne sheets is investigated. The structural and electronic properties of α- and β-graphyne sheets doped with BN nanodots are studied by using density functional theory. The cohesive energies of the systems indicate all considered structures are thermally stable. It is found that hexagonal BN nanodots can effectively open the band gap in α- and β-graphyne sheets. It means BN nanodots change α- and β-graphyne sheets from semimetal to semiconductor. The BN nanodots with different sizes are considered. It is found that band gaps of the studied α- and β-graphyne sheets doped with BN nanodots increase with the increase in the size of BN nanodots. Hence, α- and β-graphyne sheets doped with BN nanodots are promising materials for use in nanoelectronic devices based on semiconductors.

Developing highly active and non-precious-metal single-atom catalysts (SAC) for electrochemical water splitting is of great significance to the development of renewable energy technology in future. Herein, 10 first-row transition-metal (TM, from Sc to Zn) single atoms anchored on a graphyne (GY) nanosheet (TM@GY) as electrocatalysts for water splitting are explored through computational screening approach. It is found that the single atoms prefer to tightly bind at the acetylenic-ring center of GY. Meanwhile, these TM@GY catalysts show metallic properties or reduced band gap, favoring electron transfer during the electrochemical processes. Moreover, both Co@GY and Mn@GY catalysts present good catalytic performance for hydrogen evolution reaction (HER) with both the acetylenic C and TM atoms being highly active sites. However, only the Co@GY catalyst shows good oxygen evolution reaction (OER) activity with an overpotential of 0.55 V. Thus, Co@GY could serve as a potential bifunctional electrocatalyst for water splitting. Besides, the d-band center of TM atoms on TM@GY can be turned through controlling TM atoms with different d-electron number and be used to predict the OER performance. This work highlights that GY doped with single non-precious-metals can be considered for designing high-active and low-cost bifunctional electrocatalysts for practical electrochemical reactions.

We design novel graphyne/blue phosphorene van der Waals (vdW) heterostructures (G/BP) under the external electric fields (Efield) and strains. It is demonstrated that the G/BP is a type-I semiconductor with a direct band gap of approximately 0.378 eV. The external Efield and strains not only have important effects on the band structure which undergoes a fascinating direct-indirect and semiconductor-metal transitions, but also influence the band alignment which experiences transition from type-I to type-II. In brief, the features of tunable bandgap and controllable band alignment endow G/BP with potential for application in future optoelectronic devices.

In this work, electronic and structural properties of single Al or N atom doped and Al-N co-doped graphyne (GY) toward hydrogen storage were investigated using DFT-D calculations. Results show that N and Al atoms energetically prefer to lie instead of Csp in the chain and Csp2 in the hexagonal ring, respectively. Al or N doping changes conducting nature of GY from semiconductor to metallic. Pristine GY and more stable structures of Al doped, N doped and Al-N co-doped GY were examined for H2 adsorption. Adsorption energies for the first H2 molecule are about −0.140, −0.224, −0.141 and −0.288 eV/H2, respectively. They can hold 4, 9, 7 and 16 H2 molecules with average adsorption energy of ~−0.089, −0.158, −0.144 and −0.161 eV/H2, respectively. Also, the calculated corresponding hydrogen storage capacities reach up to 5.26, 10.17, 8.75 and 16.67 wt%, respectively. Although, effect of Al atom is more than N atom, when both of them co-doped in GY, its electronic and structural properties, as well as hydrogen storage capacity improve, extremely and they have a synergistic effect onto hydrogen adsorption. These findings show that N-Al co-doped GY can be used for designing new hydrogen storage materials in the future.

Many layered graphene and graphene-like two-dimensional carbon materials have been successively proposed in theory and experiment owing to their exceptional properties and potential applications. By employing the first-principles study, we find that a new graphene-like material, δ -graphyne, whose properties of the zigzag-edged nanoribbon are very similar to those ones of zigzag-edged graphene case. The band structure clearly exhibits a metallic property in non-magnetic state. And we can see a visible spin splitting within the ferromagnetic state, however, spin degeneracy within the antiferromagnetic state. To this end, here we propose a molecular junction based on the zigzag- δ -graphyne nanoribbon symmetrically with additional phenyl rings at both edges. The computational results imply that the device has many good electron transport performances, such as negative differential resistance, spin-filtering and rectification effects, and so on. In particular, the spin-filtering efficiency can be up to 99%, and the maximum of the rectification ratio reaches up to 106%. The mechanisms for these effects are revealed and discussed in terms of the band structure, spin-resolved electron transmission spectrum, the local density of state and the transmission pathway. Therefore, our research results can provide a basis for the experimental preparation of the δ -graphyne-based junction.

The mechanism of the adsorption and grafting of diazonium cations onto the surface of graphyne and graphdiyne was investigated using Density Functional Theory (DFT). The adsorption energy (both in vacuum and water as solvent) of the phenyl diazonium cation was evaluated at three different positions of the graphyne and graphdiyne surface. Moreover, the lowest energy adsorption sites were used to calculate and plot Non-covalent Interactions (NCI). The Bond Dissociation Energy (BDE) results (up to 66 kcal/mol) for the scission of the phenyl group support the remarkable stability of the grafted layer. As both of these materials are non-dispersible in aqueous solution, in this work through the use of Molecular Mechanics (MM) and Molecular Dynamics (MD) we explored also the effect of the grafted substituted aryl groups derived from aryldiazonium salts onto the solvation properties of these materials.

Two-dimensional (2D) carbon nitrides are drawing increasing interests due to the structural diversities and unique electronic properties, superiors to the pure 2D carbon materials. Motivated by the recent experimental progresses, we investigated from first-principles a new family of 2D carbon nitrides composed of sp- and sp2-hybridized carbon atoms and with kagome, rhombic and hexagonal lattices. The kagome and rhombic lattices exhibit moderate electronic band gaps (0.98–3.34 eV), high carrier mobility in the order of 3 × 105 cm2V−1s−1, high flexibility with critical strain up to 44%–47%, and type-II band alignment which are desired for applications in electronic devices and solar cells. Our findings are expected to offer theoretical bases for synthesis and applications of these novel 2D carbon nitrides and promote the following experimental exploration.

The effect of 3D-transition metal doping concentration on electronic structure and magnetic properties of γ-graphyne are investigated by density functional theory. We have investigated the ...

The discovery of graphene has triggered the explosive development of two-dimensional (2D) nanomaterials, including both inorganic and organic species. Benefiting from the simple elemental composition, inorganic 2D nanomaterials were the center research in the past decade, which has long shadowed the research of 2D organic (or soft) nanomaterials. Although many kinds of 2D soft nanomaterials have been successfully prepared, a unified definition for them is still impossible due to the complicate and quite different chemical structures between each other and even relying on totally different techniques to distinguish them. Since our first review on 2D soft nanomaterials in 2015, this field has moved forward with big success. In this review, we will focus on the development of 2D soft nanomaterials after 2015. In order to deliver better overview of this field, new and comprehensive classification is used in this review: 2D aromatic molecules, graphene and graphene nanoribbons, graphyne and graphdiyne, B x C y N z nanosheets, 2D polymers, 2D supramolecules, crystalline 2D assemblies, 2D covalent organic frameworks, 2D metal-organic frameworks, sandwich-like 2D porous polymers, 2D polymer nanosheets, etc. The focus of this review lies on synthetic strategies and the challenges of characterization, definition and fundamental understanding.

Through Density Functional Theory Simulations we predict that a Ytrrium atom attached on graphyne surface can adsorb up to a maximum of 9 molecular hydrogens (H2), with a uniform binding energy of ∼0.3 eV/H2 and an average desorption temperature of around 400 K (ideal for fuel cell applications), leading to 10 wt% of hydrogen, substantially higher than the requirement by DoE. The higher hydrogen wt% in Y doped graphyne compared to Y doped Single Walled Carbon Nanotubes (SWNT) and graphene is due to the presence of sp hybridized C atoms (in the acetylene linkage) supplying additional in-plane px-py orbitals leading to π (π*) bonding (antibonding) states. Charge transfer from metal to carbon nanostructure results in a redistribution of s, p, d orbitals of the metal leading to a non - spin polarized ground state in Y doped graphyne, due to the presence of the acetylene linkage, whereas Y doped SWNT and graphene remain magnetic like the isolated metal atom. In the non-magnetic graphyne + Y system, the net charge transfer from Y to successive H2 molecules is less than in magnetic Y + graphene and Y + SWNT systems, enabling Y + graphyne to store a larger number of H2 molecules. Furthermore, our ab initio MD simulations show that the system is stable even at room temperature and there is no dissociation of H2 molecules, enabling the system to achieve 100% desorption. So Y doped graphyne is found to be a promising hydrogen storage device with high wt%, 100% recyclability and desirable desorption temperature.

Carbon nanomaterials are receiving an increasingly large interest in a variety of fields, including also nanomedicine. In this area, much attention is devoted to investigating and modeling the behavior of these nanomaterials when they interact with biological fluids and with biological macromolecules, in particular proteins and oligopeptides. The interaction with these molecules is in fact crucial to understand and predict the efficacy of nanomaterials as drug carriers or therapeutic agents as well as their potential toxicity when they occupy the active site of a protein or severely affect the secondary and tertiary structure, or even the local dynamics, thus inhibiting their biological function. In this review, therefore, we describe the most recent work carried out in the last few years to model the interaction between carbon nanomaterials, either pristine or functionalized, and proteins or oligopeptides using classical atomistic methods, mainly molecular dynamics simulations. The attention is focused on 0-dimensional fullerenes, mainly C60, on 1-dimensional carbon nanotubes, mostly the single-walled armchair and some chiral ones, and on 2-dimensional graphene and graphyne, the latter containing also sp hybridized atoms in addition to the sp2 ones common to the other carbon nanomaterials.

By using of the first-principles calculations based on density functional theory, a novel monolayer planar structure named C64-graphyne is predicted. Tetratomic and hexatomic rings, as well as C C triple bonds exist in this new stable structure with the lattice parameter of 9.291 A. The carbon hexatomic ring in C64-graphyne contains two quite distinct C C bonds, which is known as cyclohexatriene. Its electronic band structures show a semiconductor nature with a narrow direct band gap of 0.35 eV. Interestingly, by substituting a carbon atom with one nitrogen atom either in the hexatomic ring or in the chain of C64-graphyne, two stable planar structures are obtained. Such doping with nitrogen atom induced metallic properties in this monolayer structure. Further investigation shows that the alternating substitution of boron and nitrogen atoms for all carbon atoms in C64-graphyne also induced a new stable structure, the (BN)64 structure. The electronic studies proved its insulator property with the band gap of 4.08 eV.

Graphyne, a single atomic layer structure of the carbon six-member rings connected by one acetilenic linkage, is a promising anode of rechargeable batteries. In this paper, a first-principle study has been carried out on graphyne as a new candidate for the anode material of magnesium-ion batteries, using density functional theory calculations. The main focus is on the magnesium adsorption on graphyne surface. The structural properties such as adsorption height and energy, the most stable adsorption sites, the Band structure and DOS of the pristine graphyne the diverse Mg-decorated graphyne structures, and energy barrier against Mg diffusion are also calculated. As a consequence of the band structure and DOS of graphyne structures, it is found that the pristine graphyne and the Mg-decorated graphyne structures show a semiconducting nature and metallic behavior, respectively. Moreover, the migration behavior of Mg on graphyne for the main diffusion paths is determined by the Nudged Elastic Band (NEB) method., 7 pages, 5 figures

Desalination of sea saline water seems a successful solution to supply clean water. For desalination, novel nanoporous membranes have been proposed as a substitute for the classic reverse osmosis (RO) membranes. The one-atom-thick graphyne membrane has shown great potential in water desalination. By applying functional groups (FGs) into the pores of the monolayer graphyne membranes, the water permeability and the ion rejection were passively increased. The effects of applying various FGs such as Hydrogen, Fluorine, Carboxyl and Amine, effect of the salt concentration, the applied pressure, and the effective diameter of the graphyne pores were determined by molecular dynamics (MD) simulations. Also, the distribution of water density and hydrated ions structure were discussed. The results revealed that graphyne-4 with F FGs may be the best membrane for desalination. Compared with bare graphyne, this membrane increased the water permeability and the ion rejection for the various applied pressures of salt concentrations.

α-Graphyne nanotubes as quasi-one-dimensional structures could have interesting electronic and optical properties in comparison to graphene. In this work, we have calculated electronic band structure, density of states and optical absorption spectrum of some single-wall zigzag α-graphyne nanotubes by using a simple tight-binding method in a reduced lattice. The results show that two-thirds of nanotubes have semi-conductive behavior accompanied with an oscillatory decreasing band gap, while the rest presented metallic characteristics. The outcome reveals the optical gap fluctuates per different incremental nanotube diameters; in addition, the highest amount of optical absorption occurs when emission energies exceed 4 eV.

A novel two-dimensional (2D) structurally stable carbon allotrope is proposed using first-principles calculations, which is a promising material for water purification and for electronic devices due to its unique porous structure and electronic properties. Rectangular and hexagonal rings are connected with acetylenic linkages, forming a nanoporous structure with a pore size of 6.41 angstrom, which is known as T-4,T-4,T-4-graphyne. This 2D sheet exhibits a direct bandgap of 0.63 eV at the M point, which originates from the p(z)( )atomic orbitals of carbon atoms as confirmed by a tight-binding model. Importantly, T-4,T-4,T-4-graphyne is found to be energetically more preferable than the experimentally realized beta-graphdiyne, it is dynamically stable and can withstand temperatures up to 1500 K.

Graphdiyne possesses not only high strength but also excellent ductility, making it possible to be used in future high-performance protective structures. In this paper, the mechanical properties of graphdiyne were firstly measured by AFM experiments, and the failure behavior during low velocity perforation was also investigated by molecular dynamics (MD) simulations. Firstly, the elastic modulus was measured to be about 218.5 GPa by AFM experiments, which is about half of its ideal value due to various defects and the layer numbers of the synthesized graphdiyne film. Then, the nanoindentation processes of graphdiyne films were investigated by MD simulations, and the elastic modulus and strength were simulated to be about 489.04 GPa and 33.95 GPa, respectively. The failure behavior of the graphdiyne film was also studied in atomic level. Sequential broken of C C, C C and C C bonds and recombination of the broken bonds were observed to form a unique lathy crack. Furthermore, the effects of loading speed and indenter radius on the mechanical response of graphdiyne were investigated. A revised formula was developed for analyzing the mechanical properties of films in AFM experiments under various loading conditions.

In this paper, the structural and electronic properties of atomic oxygen and hydrogen adsorption on graphdiyne (GDY) and its BN analog (BNdiyne) has been studied by the first-principles calculations. The calculated results show that the most stable adsorption positions of atomic hydrogen (oxygen) for GDY and BNdiyne monolayer are the top site (T2) and the hollow site (H2), respectively. The strong interaction (chemisorption) between atomic hydrogen and the monolayers leads to a decrease of 0.1 eV in the band gap of GDY, while an increase of 0.15 eV in BNdiyne. The shallow impurity energy level introduced by oxygen enhances the conductivity of GDY which could be indicated from the non-zero transmission coefficient at zero bias as well. In addition, a tiny magnetic has occurred in the oxygenated GDY while it has not occurred in the hydrogenated GDY which is different from the graphyne.

Recently, Shang et al. (Angew Chem Int Ed 57(3):774–778, 2018) have developed a method to synthesize ultrathin (around 1.9 nm) graphyne nanosheets. We reported here the mixed-mode I–II fracture toughnesses and crack growth angles of single-layer graphyne sheets using molecular dynamics (MD) simulations and the finite element (FE) method based on the boundary layer model, respectively. The various carbon–carbon bonds of graphyne sheets in the FE method are equated with the nonlinear Timoshenko beams based on the Tersoff–Brenner potential, where all the parameters of the nonlinear beams are completely determined based on the continuum modeling. All the results from the present FE method are reasonable in comparison with those from our MD simulations using the REBO potential. The present results show that both the critical stress intensity factors (SIFs) and the crack growth angle strongly depend on the chirality and loading angle $$\varphi $$ ( $$\varphi =90^{\circ }$$ and $$\varphi =0^{\circ }$$ representing pure mode I and pure mode II, respectively). Meanwhile, the fracture properties of single-layer cyclicgraphene and supergraphene sheets are also studied in order to compare with those of the graphyne sheets. The critical equivalent SIFs are derived as $$1.55

By performing molecular dynamics, the thermal transport properties of seven type graphyne (GY) with different structures (nanosheet, nanotube and GY/graphene (GR) heterojunction) are investigated. It can be observed comparing with other six GY, the thermal conductivity (TC) of (14,14,14)-GY shows unexpectedly significant anisotropy, which is consistent with previous study in Phys. Chem. Chem. Phys. 2016, 18, 24210. This anisotropy is mainly due to the lower contribution of high-frequency and short-wavelength phonons weakened by armchair (14,14,14)-GY. Moreover, when GY is rolled up to GY nanotubes (NTs), it is interesting to discover TC of GYNT, especially (14,14,14)-GYNT, shows a diameter-dependent anisotropy. For large-diameter NT, the TC of zigzag model is higher, however, an opposite phenomenon is obtained with small-diameter model. This phenomenon can be explained by the relative alternation of phonon group velocity and phonon lifetime and the appearance of band gap with the change of diameter. At last, we also notice the GY/GR heterojunctions express much lower thermal resistance (TR) comparing with other carbon based heterojunctions, and the in-plane TR of GY/GR heterojunction is two orders of magnitude lower than that of out-of-plane TR. Further, the alternation of TR can be well explained by the coupling degree of different type phonons.

The development of direct methanol fuel cells is hindered by the issue of methanol crossover across membranes, despite the remarkable features resulting from the use of liquid fuel. Here we investigate the proton-selective conduction behavior across 2D graphyne in an aqueous environment. The aqueous proton conduction mechanism transitions from bare proton penetration to a mixed vehicular and Grotthuss transportation when the side length of triangular graphyne pores increases to 0.95 nm. A further increase in the side length to 1.2 nm results in the formation of a patterned aqueous/vacuum interphase, enabling protons to be conducted through the water wires via Grotthuss mechanism with low energy barriers. More importantly, it is found that 2D graphyne with the side length of less than 1.45 nm can effectively block methanol crossover, suggesting that 2D graphyne with an appropriate pore size is an ideal material to achieve zero-crossover proton-selective membranes., Aqueous proton-selective membranes are vital for methanol fuel cells and flow batteries, but suffer from crossover issues. Here the authors use ab initio molecular dynamics simulations to show that graphyne is an ideal candidate for a proton-selective membrane that can be tailored for methanol impermeability

The modeling and simulation of γ-graphyne under monotonic and hysteretic in-plane loading is presented. An atomistic finite element model of γ-graphyne was developed. Four different loading tests w...

Different sites for K adsorption in γ-graphyne were investigated using density functional theory (DFT) calculations and optical and structural properties of the structures were examined. For the most stable structures, we put one H2 molecule in different directions on the various sites to evaluate the hydrogen adsorption capability of them. Then, one to nine H2 molecules in sequence were added to the best structure. Results show that clustering of the K atoms is hindered on the graphyne surface and the most desirable adsorption site for K atom is the hollow site of 12-membered ring with adsorption energy of 5.86 eV. Also, this site is the best site for H2 adsorption onto K-decorated graphyne with Edas of −0.212 eV. Adding of number of H2 molecule on this site shows that K atom can bind nine H2 molecules at one side of the graphyne with the average adsorption energy of 0.204 eV/H2. Therefore, for one side ca. 8.95 wt % and for both sides of the graphyne with a K atom in each side ca. 13.95 wt % of the hydrogen storage capacity can be achieved. This study shows that K-decorated graphyne can be a promising candidate for the hydrogen storage applications.