Acetylenic Linkages Research Articles

Three-dimensional acetylenic modified graphene for high-performance optoelectronics and topological materials

Seeking carbon phases with versatile properties is one of the fundamental goals in physics, chemistry, and materials science. Here, based on the first-principles calculations, a family of three-dimensional (3D) graphene networks with abundant and fabulous electronic properties, including rarely reported dipole-allowed truly direct band gap semiconductors with suitable band gaps (1.07–1.87 eV) as optoelectronic/photovoltaic materials and topological nodal-ring semimetals, are proposed through stitching different graphene layers with acetylenic linkages. Remarkably, the optical absorption coefficients in some of those semiconducting carbon allotropes express possibly the highest performance among all of the semiconducting carbon phases known to date. On the other hand, the topological states in those topological nodal-ring semimetals are protected by the time-reversal and spatial symmetry and present nodal rings and nodal helical loops topological patterns. Those newly revealed carbon phases possess low formation energies and excellent thermodynamic stabilities; thus, they not only host a great potential in the application of optoelectronics, photovoltaics, and quantum topological materials etc., but also can be utilized as catalysis, molecule sieves or Li-ion anode materials and so on. Moreover, the approach used here to design novel carbon allotropes may also give more enlightenments to create various carbon phases with different applications.

Grain Boundary Perfection Enabled by Pyridinic Nitrogen Doped Graphdiyne in Hybrid Perovskite

AbstractThe solution processing in hybrid perovskite films inevitably results in the formation of detrimental defects at grain boundaries (GBs) that deteriorate the optoelectronic properties and bring about severe hysteresis as well as operational instability. Here, an effective scenario to alleviate the imperfection issue at perovskite GBs via incorporating pyridinic nitrogen‐doped graphdiyne (N‐GDY) is proposed. Taking full advantage of periodic acetylenic linkages and introduced pyridinic N atoms, the deep‐level trap states like Pb–I antisite defects and under‐coordinated Pb atoms are considerably passivated, thus diminishing the undesired non‐radiative recombination. Additionally, the spatial confinement coupling with electrostatic repulsion effect originated from the intrinsic 2D structure of N‐GDY, has been identified to deal with the halide ion migration behavior. Such contributions are further theoretically evidenced with the charge density delocalization as well as the ion migration energy barrier elevation. The authors unprecedentedly verified the superiorities based on the flexible chemical‐tailorability of atomic crystal GDY materials toward polycrystalline perovskite related energy conversion devices.

Supertetrahedraphene: A novel quasi 2D carbon allotrope with controllable thickness and electronic properties

A novel all-carbon material with quasi 2D character, supertetrahedraphene, was proposed using carbon tetrahedron as the starting material. The geometry and electronic properties were investigated via density functional theory (DFT) calculations. Supertetrahedraphene was confirmed to be an energetically meta-stable and dynamically stable semiconductor with an indirect band gap of 2.80 eV. An acetylenic linkage ( C C ) was inserted to change the height of supertetrahedraphene, resulting in a new sp + sp 3 hybrid system. Insertion of C C can further stabilize supertetrahedraphene and transform it to a semiconductor with direct band gaps. These band gaps steadily decrease as the number of C C increases, and the supertetrahedraphene is predicted to be metallic if the C C is of sufficient length. Our results suggest a strategy to design novel carbon materials with desired properties.

Theoretical design of all-carbon networks with intrinsic magnetism

To induce intrinsic magnetism in the nominally nonmagnetic carbon materials containing only s and p electrons is an intriguing yet challenging task. Here, based on first-principles electronic structure calculations, we propose a universal approach inspired by Ovchinnikov’s rule to guide us the design of a series of imaginative magnetic all-carbon structures. The idea is to combine the differently stacked graphene layers via the acetylenic linkages (−C≡C−) to obtain a class of two-dimensional (2D) and three-dimensional (3D) carbon networks. With first-principles electronic structure calculations, we confirm the effectiveness of this approach via concrete examples of double-layer ALBG-C14, triple-layer ALTG-C22, and bulk IALG-C30. We show that these materials are antiferromagnetic (AFM) semiconductors with intralayer Néel and interlayer AFM couplings. According to the above idea, our work not only provides a promising design scheme for magnetic all-carbon materials, but also can apply to other π-bonding network systems.

A two-dimensional porous conjugated porphyrin polymer for uniform lithium deposition.

Uniform lithium deposition is a benefit to achieving high-energy-density lithium metal batteries. There are many effective methods to suppress the dendritic growth of metallic lithium and promote the application of the lithium anode. However, the designation of lithiophilic sites at the atomic level remains a huge challenge. Herein, a two-dimensional porous conjugated porphyrin polymer linked by two acetylenic linkages from an in situ coupling reaction has been prepared on copper foil and employed as the lithiophilic host. The four electron-rich pyrrolic nitrogen atoms in the porphyrin building block and the linkage electron-rich sp-hybridized carbon atoms were regarded as precise lithiophilic sites, resulting in a decreased nucleation overpotential and dendrite free morphology. With uniform lithium deposition, the electrochemical performance of the electrode was significantly improved in regard to the overpotential, coulombic efficiency and lifespan. This work expands the precise construction of lithiophilic sites at the atomic level and benefits to further development of high-energy density lithium metal batteries.

Structural, elastic and electronic properties of atomically thin pyridyne: theoretical predictions.

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.

Correlation between surface topological defects and fracture mechanism of γ-graphyne-like boron nitride nanosheets

The fracture mechanism of γ-graphyne-like boron nitride (GYBNN) and its analogous nanosheets, sp-GYBNNS (sp-C atoms situated at acetylenic linkages) and sp2-GYBNNS (sp2-C atoms situated in hexagonal rings) was patterned as a function of temperature in both the zigzag and armchair directions via Molecular Dynamic Simulation. Next, the effect of acetylenic chain length on the Young’s modulus and failure stress was studied. The applied stress was distributed on both hexagonal rings and acetylenic chains in the zigzag direction. However, in the direction of armchair the stress was mainly concentrated on the acetylenic chains. The failure stress varied less considerably by increasing the acetylenic chains’ length in zigzag direction than in armchair. The sp2-GYBNNS and GYBNNS had the highest and lowest tensile strength in both zigzag and armchair directions, respectively. The crack length increase from L/12 (25 Å) to L/2 (150 Å) led to a significant reduction in the Young’s modulus of sp2-GYBNNS from 270.05 to 177.25 GPa. The stress intensity factor for crack-contained sp2-GYBNNS (length = L/12) was declined from the value of 2.622 to 2.212 by increasing the temperature from 200 to 900 K.

Ab-initio investigation of hydrogen sorption in Ti functionalized modified calix[4]pyrrole-benzene

Hydrogen is an ecofriendly and affordable alternative for fossil fuels. Storage of hydrogen with high hydrogen weight percentage is the prime obstacle to use it as a fuel. The hydrogen storage capacity in Ti functionalized modified calix[4]pyrrole-benzene is explored using density functional theory. Hydrogens are sequentially adsorbed over functionalized Ti atoms as well as over the π−complexes of acetylenic linkages and pyrrole rings. The host stores 28 H2 with a maximum H wt% of 10.1 and sorption energies in the range of 0.50–0.25 eV. Mechanism of the quasi-molecular adsorption is explained through the analyses of electrostatic potential, distance parameters, and charges. Findings of molecular dynamics, van ‘t Hoff desorption analysis, and the occupation number prove that the host is thermally stable and stores H2 reversibly. Ti functionalized modified calix[4]pyrrole-benzene proves to be a potential hydrogen storage candidate fulfilling the 2020 targets set by the US, DOE.

A novel two-dimensional sp-sp2-sp3 hybridized carbon nanostructure with a negative in-plane Poisson ratio and high electron mobility

A novel two-dimensional (2D) semiconducting carbon allotrope is proposed by inserting alkyne into tetrahexcarbon. This new carbon allotrope consists of tetra-rings and acetylenic linkages and is called TAL-carbon. To the best of our knowledge, this is the first 2D carbon allotrope composed of sp-sp2-sp3 hybridized carbon atoms. Due to its unique puckered structure, TAL-carbon is the fourth 2D carbon material with an intrinsic in-plane negative Poisson ratio (NPR) reported after graphene, penta-graphene, and tetrahexcarbon. Materials with NPR exhibit a wide range of potential applications in biomedicine, aerospace industries, and precision instruments. TAL-carbon has an indirect band gap of 1.614 eV. At room temperature, it exhibits high in-plane electron mobility of up to ~3.5 × 104 cm2V−1s−1, which is 30 times higher than monolayer black phosphorus and two orders of magnitude higher than monolayer MoS2. The phonon dispersion curves and in-plane elastic constants indicate that TAL-carbon is dynamically and mechanically stable. Its equibiaxial strain limit reaches 13.7%, similar to that of graphene. An ab initio molecular dynamics (AIMD) simulation demonstrates that TAL-carbon is thermally stable at 300 K and 1000 K. The results show that TAL-carbon is a promising 2D auxetic material for applications in nanomechanics and nanoelectronics.

A comprehensive study on the mechanical properties and failure mechanisms of graphyne nanotubes (GNTs) in different phases

The mechanical properties, failure mechanisms of one-dimensional carbon allotropes including α, β, γ graphyne nanotubes (GNTs) and also conventional carbon nanotubes (CNTs) were calculated by using classical molecular dynamics simulations. The GNTs was showed unique properties due to the presence of single, double and triple bonds in their crystal lattice compared to CNTs. It was found that the α-GNT phase has had an ability for typical plastic behavior due to the presence of the acetylenic linkages and the atoms reconstruction processes. The effects of acetylenic linkages on the mechanical properties of different phases of GNTs including fracture behavior, Young’s modulus, and Poisson’s ratio were also investigated under uniaxial tension. Among GNTs, α-GNTs exhibited the lowest fractures stresses and Young’s modulus, while γ-GNTs showed the highest fractures stress and Young’s modulus. Moreover, GNTs had a higher Poisson’s ratio due to possessing a higher variety of pore sizes compared to CNTs. These features made the GNTs suitable for many different applications and open up a novel view for the study of plastic carbon-based nanomaterials. As well as, based on the visualization of the nanotubes fractures, the failure mechanism of the nanotubes was analyzed and discussed.

Elastic, electronic and optical properties of boron- and nitrogen-doped 4,12,4-graphyne nanosheet

The effects of boron (B) and nitrogen (N) dopants on 4,12,4-graphyne have been systematically investigated with density functional theory (DFT) calculations. The charge density analysis reveals that the N dopant at the sp-site destroys the acetylenic linkage in 4,12,4-graphyne, but instead tends to form a polar bond. The B- and N-doped 4,12,4-graphyne systems exhibit p- and n- semiconductor characters, respectively. Some obvious spin splitting polarizations can be observed in their band structures and DOS. Moreover, there is a giant difference in effective masses between electrons and electron holes , especially for B-doped 4,12,4-graphyne at C5 site. The directional electron and electronic thermal conductivities at C5 site are also estimated by performing the Boltzmann’s semiclassical transport calculations. In addition, both B- and N-doped systems are highly sensitive to light from the infrared to the ultra-violet regions under parallel polarization. However, the photoresponse is very weak under perpendicular polarization. • N dopant at the sp-site tends to form a polar bond in 4,12,4-graphyne. • Some obvious spin splitting polarizations can be observed in their band structures. • Giant differences between electrons and holes can be found at C5 site for B dopant. • Dopant at C5 site induces directional electron and electronic thermal conductivity. • The B- and N-doped 4,12,4-graphyne systems exhibit strong anisotropy photoresponse.

Metal-Tuned Acetylene Linkages in Hydrogen Substituted Graphdiyne Boosting the Electrochemical Oxygen Reduction.

Different from graphene with the highly stable sp2 -hybridized carbon atoms, which shows poor controllability for constructing strong interactions between graphene and guest metal, graphdiyne has a great potential to be engineered because its high-reactive acetylene linkages can effectively chelate metal atoms. Herein, a hydrogen-substituted graphdiyne (HsGDY) supported metal catalyst system through in situ growth of Cu3 Pd nanoalloys on HsGDY surface is developed. Benefiting from the strong metal-chelating ability of acetylenic linkages, Cu3 Pd nanoalloys are intimately anchored on HsGDY surface that accordingly creates a strong interaction. The optimal HsGDY-supported Cu3 Pd catalyst (HsGDY/Cu3 Pd-750) exhibits outstanding electrocatalytic activity for the oxygen reduction reaction (ORR) with an admirable half-wave potential (0.870 V), an impressive kinetic current density at 0.75 V (57.7 mA cm-2 ) and long-term stability, far outperforming those of the state-of-the-art Pt/C catalyst (0.859 V and 15.8 mA cm-2 ). This excellent performance is further highlighted by the Zn-air battery using HsGDY/Cu3 Pd-750 as cathode. Density function theory calculations show that such electrocatalytic performance is attributed to the strong interaction between Cu3 Pd and CC bonds of HsGDY, which causes the asymmetric electron distribution on two carbon atoms of CC bond and the strong charge transfer to weaken the shoulder-to-shoulder π conjugation, eventually facilitating the ORR process.

Palgraphyne: A Promising 2D Carbon Dirac Semimetal with Strong Mechanical and Electronic Anisotropy

For next‐generation carbon‐based nanoelectronics, it is highly desirable to search for easily obtained 2D carbon allotropes with various appealing properties. Herein, based on first‐principles calculations, a new 2D carbon Dirac semimetal with orthorhombic symmetry is identified, which is composed of a carbon skeleton of para‐xylene and acetylenic linkages, and is thus termed palgraphyne [pæl'græfain]. The calculations of stability reveal not only that palgraphyne is dynamically, thermally (above 1000 K), and mechanically stable, but also that it is energetically more preferable to the recently synthesized β‐graphdiyne and γ‐graphdiyne. Due to the particular atomic‐framework, the calculations of Young's modulus and Poisson's ratio show that palgraphyne is mechanically anisotropic with a sizable ratio between the maximum and minimum value up to 3.29. Remarkably, unlike the case of graphene, the Dirac cones of palgraphyne are distorted. As a result, its electronic transport properties also exhibit anisotropy, with different Fermi velocities along diverse orientations. The highest Fermi velocity reaches up to 8.89 × 105 m s−1 in the kx + ky direction, which is very close to that of prominent graphene (9.0 × 105 m s−1). The findings highlight a distinct 2D anisotropic Dirac semimetal, which has great potential applications in nanodevices.

The effect of doping on adsorption of Xe and Kr on graphyne and graphdiyne

Sequestration of radioactive noble gases xenon (Xe) and krypton (Kr) from off-gas streams of nuclear reactors and spent nuclear fuel reprocessing plants are essential. The Generally employed cryogenic distillation process for Xe/Kr separation is expensive and adsorption based techniques using porous materials are viable alternative. Recently, carbon allotropes such as graphynes (Gyn) and graphdiynes (Gdyn) attained importance due to their significance in many applications similar to graphene. In both graphyne and graphdiyne, the carbon atoms are sp-sp2 hybridized where benzene rings are linked through acetylenic and diacetylenic linkages respectively. They are good candidates for gas adsorption/separation due to their chemical stability and large surface area. In this regard, we have investigated the noble gas adsorption properties of doped/undoped graphyne and graphdiyne materials using density functional theory calculations. The graphyne and graphdiyne display enhanced adsorption affinity for Xe and Kr when doped with selective heteroatoms.

The nano gold rush: Graphynes as atomic sieves for coinage and Pt-group transition metals

Graphyne two-dimensional materials have been envisaged as potential useful membranes for applications such as gases separation and water desalination with very high salt rejection rates. The graphyne acetylenic linkages length defines its acetylenic holes size, thus offering a way of tuning their membrane permeability. The present study evaluates, based on density functional theory simulations, the possible use of γ-graphyne, the graphyne with the smallest acetylenic hole, to sieve Transition Metal (TM) atoms. The systematic study comprises obtaining adsorption minima for the 30 3d, 4d, and 5d TMs along with transition states for the diffusion across the γ-graphyne layer. The study reveals very small penetration barriers, below 0.5 eV, for late 3d, Pt-group, and coinage metals, whereas water molecules are found to display high penetration energy barriers above 5 eV, even when accounting for possible γ-graphyne out-of-plane deformations facilitating the water trespassing. The adsorption energy distribution of the adsorbed TMs shows that Pd and Au sieving by γ-graphyne would be specially enhanced versus their anchoring on the γ-graphyne carbon framework, thus pointing γ-graphyne as a possible effective membrane to sieve, particularly, late transition metals.

Giant piezoelectricity in B/N doped 4,12,2-graphyne

The effects of boron (B) and nitrogen (N) substitutions in 4,12,2-graphyne on its geometric structure and mechanical as well as electronic properties have been systematically investigated with the aid of density functional theory (DFT). The trend in the elastic properties of the substituted systems is determined by the doping positions and the type of the dopants. The Bader charge analysis reveals that the N dopant at the sp-site destroys the acetylenic linkage in 4,12,2-graphyne, but instead tends to form a polar bond, or even possibly a charge-shift bond. In particular, an obvious in-plane piezoelectricity is induced by foreign atom substitutions owing to the deformation of the pristine square symmetry. The electron and electronic thermal conductivities are also estimated by performing the Boltzmann's semiclassical transport calculations.

Three-dimensional graphene networks modified with acetylenic linkages for high-performance optoelectronics and Li-ion battery anode material

Searching for three-dimensional (3D) semiconducting carbon allotropes with proper bandgaps and excellent optoelectronic properties is always the chasing goal for the new emerging all-carbon optoelectronics. On the other side, 3D carbon materials have also been recognized as promising anode materials superior to commercialized graphite in Li-ion batteries (LIBs). Here, using first-principles calculations, we propose two novel 3D carbon allotropes through acetylenic linkages modification of two structurally intimately correlated 3D carbon structures — carbon kagome lattice (CKL) and interpenetrated graphene network (IGN). The modified CKL is a truly direct-gap semiconductor and possibly possesses the strongest optical transition coefficient amongst of all semiconducting carbon allotropes. The suitable bandgap and small effective masses also imply it can be a good electron transport material (ETM) for perovskite solar cells. As for the modified IGN, it is a topological nodal line semimetal and shows greatly enhanced specific capacity as anode materials in LIBs comparing to that of IGN. Our work not only find two new 3D carbon phases with fabulous physical and chemical properties for high-performance optoelectronics and Li-ion anode material, we also offer a fresh view to create various carbon structures with versatile properties.

Lithium Storage on Extended Graphynes: Predicted by DFT Calculations†

Graphyne,which contains planar sheets equally occupied by sp2 and sp carbon atoms,is a layered carbon allotrope. Since the length of the acetylene chains within graphyne can be variable by adjusting the number of acetylenic linkages( —C ≡ C—) between carbon hexagons,resulting in a family of graphyneextended graphynes( i. e. graph-n-ynes). In this work,density functional theory( DFT) calculations were carried out to investigate the adsorption of lithium atoms on extended graphynes monolayers,and the results were compared to extrapolate the potential relationship between lithium storage capacity and the number of acetylenic linkages. The results show that further extending the acetylenic chains might not be helpful in achieving higher capacity. The longer acetylene chains result in the lower carbon atom density,as well as the lower stability of the carbon networks,which should be taken into consideration seriously. High-capacity Li storage as LiC3 in graphdiyne and graph-5-yne,was achieved,and the preferred adsorption sites for Li were identified computationally. With high Li storage capacity and structural advantages,these porous carbon materials are expected to be applied in efficient lithium storage.

T4,4,4-graphyne: A 2D carbon allotrope with an intrinsic direct bandgap

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 Å, which is known as T4,4,4-graphyne. This 2D sheet exhibits a direct bandgap of 0.63 eV at the M point, which originates from the pz atomic orbitals of carbon atoms as confirmed by a tight-binding model. Importantly, T4,4,4-graphyne is found to be energetically more preferable than the experimentally realized β-graphdiyne, it is dynamically stable and can withstand temperatures up to 1500 K.

Multiscale Design of Graphyne-Based Materials for High-Performance Separation Membranes.

By varying the number of acetylenic linkages connecting aromatic rings, a new family of atomically thin graph-n-yne materials can be designed and synthesized. Generating immense scientific interest due to its structural diversity and excellent physical properties, graph-n-yne has opened new avenues toward numerous promising engineering applications, especially for separation membranes with precise pore sizes. Having these tunable pore sizes in combination with their excellent mechanical strength to withstand high pressures, free-standing graph-n-yne is theoretically posited to be an outstanding membrane material for separating or purifying mixtures of either gases or liquids, rivaling or even dramatically exceeding the capabilities of current, state-of-art separation membranes. Computational modeling and simulations play an integral role in the bottom-up design and characterization of these graph-n-yne materials. Thus, here, the state of the art in modeling α-, β-, γ-, δ-, and 6,6,12-graphyne nanosheets for synthesizing graph-2-yne materials and 3D architectures thereof is discussed. Different synthesis methods are described and a broad overview of computational characterizations of graph-n-yne's electrical, chemical, and thermal properties is provided. Furthermore, a series of in-depth computational studies that delve into the specifics of graph-n-yne's mechanical strength and porosity, which confer superior performance for separation and desalination membranes, are reviewed.