氮掺杂的石墨烯作为钠离子电池负极材料的第一性原理研究

采用基于密度泛函理论的第一性原理方法,研究了本征石墨烯、氮掺杂的石墨烯和叽咯石墨烯吸附钠原子的电荷密度、吸附能、态密度和储存量.结果表明,三种石墨烯中,钠原子的最佳吸附位置为H位.与本征石墨烯相比,氮掺杂的石墨烯对钠原子的吸附能提高,叽咯石墨烯对钠原子的吸附能是-3.274 eV,约为本征石墨烯对钠原子吸附能的1.7倍.钠原子与叽咯石墨烯中的氮原子发生轨道杂化,而与本征石墨烯和氮掺杂的石墨烯没有发生轨道杂化现象.叽咯石墨烯能够吸附10个钠原子,与本征石墨烯相比显著提高,氮掺杂的石墨烯只能吸附4个钠原子.因此,叽咯石墨烯有望成为一种潜在的储钠材料.     

过渡金属Pd掺杂AsP结构及其吸附甲醛和一氧化碳的性能研究

基于第一性原理方法,研究了单层本征磷砷AsP和过渡金属钯（Pd）掺杂磷砷AsP的结构,并对比研究了本征和掺杂后的AsP吸附甲醛（HCHO）和一氧化碳（CO）气体分子的稳定性、能带结构、态密度以及电荷差分密度。研究结果表明：经Pd掺杂后AsP由半导体转变为导体;本征AsP吸附一氧化碳最稳定的位置为P-As键顶上,吸附甲醛最稳定的位置为P原子顶上;本征吸附时气体分子与基底之间的距离在3 Å左右,气体分子与基底之间未形成化学键。过渡金属Pd原子掺杂AsP后形成两种结构,分别为Pd原子替换超胞结构中的As原子或P原子。两种掺杂结构分别吸附一氧化碳或甲醛气体分子时,除了Pd原子替换AsP中的As原子形成的结构吸附甲醛的吸附能未明显增加外,其余掺杂结构吸附一氧化碳或甲醛的吸附能和电荷转移较本征吸附时均显著增强,吸附CO分子时,C原子与Pd原子之间形成了化学键。特别是,Pd原子替换AsP中的P原子形成的结构对一氧化碳和甲醛气体分子的吸附性能明显强于Pd原子替换AsP中的As原子所形成的结构。     

B掺杂的石墨烯作为钠离子电池负极材料的研究

采用基于密度泛函理论的第一性原理方法,研究了本征石墨烯及缺陷石墨烯对钠原子的吸附行为.主要研究了三种石墨烯:本征石墨烯(P-graphene)、硼掺杂的石墨烯(Defect-Ⅰ)和硼掺杂的叽咯石墨烯(Defect-Ⅱ).结果表明,与P-graphene相比,Defect-Ⅰ和Defect-Ⅱ在吸附能、电荷密度、态密度和储钠量方面表现出很大的差异.Defect-Ⅰ和Defect-Ⅱ对钠原子的吸附能分别是-3.250 eV和-2.332 eV,约为P-graphene对钠原子吸附能的1.71倍和1.23倍.态密度计算结果表明,Defect-Ⅰ和Defect-Ⅱ中钠原子与硼原子发生轨道杂化,而P-graphene中不存在轨道杂化现象.Defect-Ⅰ和Defect-Ⅱ对钠原子的吸附量分别是9和8个,与P-graphene相比提高.因此,石墨烯中掺杂硼有望成为一种新型的储钠材料.     

B、N掺杂对钠在石墨烯上吸附性能的影响

采用基于密度泛函理论的第一性原理方法,研究了本征石墨烯及缺陷石墨烯对Na原子的吸附行为.主要研究了三种石墨烯:本征石墨烯、B掺杂的石墨烯和N掺杂的石墨烯.结果表明,与本征石墨烯相比,B掺杂的石墨烯和N掺杂的石墨烯在吸附能、电荷密度、态密度和储钠量方面表现出很大的差异.B掺杂的石墨烯对Na原子的吸附能是-1.93 e V,约为本征石墨烯对Na原子吸附能的2.7倍;与本征石墨烯相比,N掺杂的石墨烯对Na原子的吸附能明显增大.态密度计算结果表明,Na原子与B掺杂的石墨烯中的B原子发生轨道杂化,而本征石墨烯和N掺杂的石墨烯中不存在轨道杂化现象.B掺杂的石墨烯对Na原子的吸附量是3个,与本征石墨烯相比显著提高.因此,B掺杂的石墨烯有望成为一种新型的储钠材料.     

基于密度泛函理论研究掺杂Pd石墨烯吸附O2及CO

基于第一性原理的密度泛函理论研究了单个O₂和CO气体分子吸附于本征石墨烯和掺杂钯(Pd)的石墨烯的体系, 通过石墨烯掺Pd前后气体分子的吸附能、电荷转移及能带和态密度的计算, 发现掺Pd后气体分子吸附能和电荷转移显著增大, 这是由于Pd的掺杂, 在本征石墨烯能带中引入了杂质能级, 增强了石墨烯和吸附气体分子间的相互作用; 氧化性气体O₂和还原性气体CO吸附对石墨烯体系能带结构和态密度的影响明显不同, 本征石墨烯吸附O₂后, 费米能级附近态密度变大, 掺Pd后在一定程度变小; 吸附还原性的CO后, 石墨烯费米能级附近态密度几乎没有改变, 表明掺杂Pd不会影响石墨烯对CO的气体灵敏度, 但由于CO对石墨烯的吸附能增大, 可以提高石墨烯对还原性气体的气敏响应速度.     

Fe,Co,Ni掺杂石墨烯表面吸附C_2H_4的第一性原理研究

基于密度泛函理论(DFT)的广义梯度近似(GGA),本文对本征石墨烯以及掺杂Fe,Co,Ni石墨烯的几何结构和电子性质进行了优化计算,并计算了C_2H_4在本征石墨烯以及掺杂石墨烯表面的吸附过程,讨论了体系的吸附能、稳定性、DOS及掺杂对键长的影响.结果表明C_2H_4在本征石墨烯B位的吸附和掺杂石墨烯的吸附为化学吸附,在本征石墨烯T和H位的吸附为物理吸附;掺杂后石墨烯的比表面积增大,与本征石墨烯相比,掺杂使费米能级附近的态密度积分显著提高,表明掺杂石墨烯的电导性会发生变化,从而影响对C_2H_4的气敏度..C_2H_4在Fe、Co、Ni分别掺石墨烯的最佳吸附位为T位、H位和B位;掺杂Fe,Ni后体系的吸附能力显著提高,且掺杂Ni时体系的吸附能力最好.     

B、N掺杂对钠在石墨烯上吸附性能的影响

采用基于密度泛函理论的第一性原理方法,研究了本征石墨烯及缺陷石墨烯对Na原子的吸附行为。主要研究了三种石墨烯：本征石墨烯、B掺杂的石墨烯和N掺杂的石墨烯。结果表明,与本征石墨烯相比,B掺杂的石墨烯和N掺杂的石墨烯在吸附能、电荷密度、态密度和储钠量方面表现出很大的差异。B掺杂的石墨烯对Na原子的吸附能是-1.93 eV,约为本征石墨烯对Na原子吸附能的2.7倍;与本征石墨烯相比,N掺杂的石墨烯对Na原子的吸附能明显增大。态密度计算结果表明,Na原子与B掺杂的石墨烯中的B原子发生轨道杂化,而本征石墨烯和N掺杂的石墨烯中不存在轨道杂化现象。B掺杂的石墨烯对Na原子的吸附量是3个,与本征石墨烯相比显著提高。因此,B掺杂的石墨烯有望成为一种新型的储钠材料。     

石墨烯吸附钛原子的第一性原理计算

基于密度泛函理论研究了单个钛原子分别位于本征石墨烯(GR)、点缺陷石墨烯(包括空位石墨烯(DGR)和氮掺杂石墨烯(N-GR))薄片表面的吸附机理.通过计算钛原子在本征石墨烯表面不同位置时的吸附结构和吸附能,发现最稳定吸附位置是碳六元环的中心;计算了各个吸附体系的吸附能、态密度和差分电荷密度,研究表明三个吸附体系碳钛间均产生了电子轨道杂化,掺氮后的石墨烯对钛原子的吸附性能略微增强,而空位石墨烯对钛的吸附能是本征石墨烯的4倍,费米能级附近电子态局域化程度最大,吸附效果最好.     

Na在B掺杂的空位石墨烯上吸附性能的第一性原理研究

采用基于密度泛函理论的第一性原理方法,研究了本征石墨烯和B掺杂的空位石墨烯吸附Na原子的电荷密度、吸附能、态密度、储存量以及电极电压.结果表明,两种石墨烯中,Na原子的最佳吸附位置都是H位.B掺杂的空位石墨烯对Na原子的吸附能是-2.08 eV,比本征石墨烯对Na原子的吸附能(-0.71eV)低很多.B掺杂的空位石墨烯中Na原子与B原子发生轨道杂化,本征石墨烯中没有杂化现象.B掺杂的空位石墨烯能够吸附12个Na原子,较本征石墨烯多.因此,B掺杂的空位石墨烯更适合储钠.     

石墨烯吸附钛原子的第一性原理研究

基于密度泛函理论研究了单个钛原子分别位于本征石墨烯GR、点缺陷石墨烯（包括空位石墨烯DGR和氮掺杂石墨烯N-GR）薄片表面的吸附机理。通过计算钛原子在本征石墨烯表面不同位置时的吸附结构和吸附能,发现最稳定吸附位置是碳六元环的中心;计算了各个吸附体系的吸附能、态密度和差分电荷密度,研究表明三个吸附体系碳钛间均产生了电子轨道杂化,掺氮后的石墨烯对钛原子的吸附性能略微增强,而空位石墨烯对钛的吸附能是本征石墨烯的4倍,费米能级附近电子态局域化程度最大,吸附效果最好。     

N-doped graphene as a nanostructure adsorbent for carbon monoxide: DFT calculations

ABSTRACT

This work reports the physisorption of carbon monoxide (CO) on the surface of N-doped graphene. To study the adsorption of CO on N-doped graphene, some quantum chemical calculations were used through density functional theory. Based on our results, it can be found that the CO molecule could be adsorbed on the surface of N-doped graphene physically with the adsorption energies (E_ads) of ?2.9 and ?0.8 kcal mol^?1 (depends on the kind of configuration) while positive adsorption energies were calculated upon adsorption of CO on pristine graphene. We used the charge analysis for calculation of the net transferred charge of adsorbed CO on pristine and N-doped graphene sheets to evaluate the sensing ability of surface. The global indices of reactivity were calculated from the differences of the lowest unoccupied molecular orbital and highest occupied molecular orbital energies. Graphs for density of states point to some orbital hybridisation between CO molecule and N-doped graphene. Consequently, the N-doped graphene transforms the existence of CO molecules into electrical signal, and it may be potentially used as a sensor for CO.     

Sulfur dioxide adsorbed on graphene and heteroatom-doped graphene: a first-principles study

The adsorption of sulfur dioxide (SO₂) on intrinsic graphene and heteroatom-doped (B, N, Al, Si, Cr, Mn, Ag, Au, and Pt) graphene samples was theoretically studied using first-principles approach based on density functional theory to exploit their potential applications as SO₂ gas sensors. The structural and electronic properties of the graphene-molecule adsorption adducts are strongly dependent on the dopants. SO₂ molecule is adsorbed weakly on intrinsic graphene, and B-, N-doped graphene; in general, strong chemisorption is observed on Al-, Si-, Cr-, Mn-, Ag-, Au-, and Pt-doped graphene. The adsorption mechanisms are discussed from charge transfers and density of states. This work reveals that the sensitivity of graphene-based chemical gas sensors for SO₂ can be drastically improved by introducing appropriate dopant, and Cr, as well as Mn, may be the best choices among all the dopants.     

Lewis acid-base surface interaction of some boron compounds with N-doped graphene; first principles study

We studied density functional theory (DFT) calculations in terms of energetic and electronic properties toward adsorption of some boron compounds (B(OCH₃)₃, BF₃ and BC1₃) on the surface of pristine as well as N-doped graphene using WB97XD/6-31 + G(d,p) level of theory. The net charge transfer of mentioned molecules on the surface of pristine and N-doped graphene was calculated with above-mentioned basis set using natural bond orbital and Mulliken charge analysis during complex formation. The computed dipole moment shows when above-mentioned molecules approach to the surface of N-doped graphene, the amount of the dielectric (μD) will change depending on the kind of molecule. Our calculations reveal that N-doped graphene system has much higher adsorption energy, higher net charge transfer value than pristine graphene due to Lewis acid-base interaction. Comparing B(OCH₃)₃ as an organic boron derivative with boron trihalides (BF₃ and BCl₃), the Lewis acidity increases in the order of BF₃ < BC1₃< B(OCH₃)₃ with adsorption energies (E_ads) of −8.7, −18.3 and −26.5 kJ/mol (BSSE) respectively, while low adsorption energies were calculated on pristine graphene for mentioned molecules.     

Geometric stability and adsorption property of hydroxyl group on graphene sheets

The stable geometrics and adsorption behaviors of hydroxyl (OH) groups on graphene sheets are investigated using the first-principles calculations. The single hydroxyl adatom has small adsorption energy and diffusion barrier on pristine graphene. The binding strength of the hydroxyl group increases with the coverage, and the aggregations of the hydroxyl groups reduce the structural bucking of graphene sheet. On the graphene with single vacancy (SV-graphene), the large trapping zones mean the adsorbed OH would be easily trapped at the vacancy site. The hydroxyl groups prefer to aggregate on graphene surfaces and form the water molecule, leaving the epoxy group on pristine graphene or oxygen dopant in SV-graphene, which is used to constitute the structural model of oxidized graphene. These results would provide us a useful reference to understand the atomic structure and adsorption property of functional groups on graphene sheets.     

Density functional theory study on the adsorption of alkali metal ions with pristine and defected graphene sheet

The graphene-based materials along with the adsorption of alkali metal ions are suitable for energy conversion and storage applications. Hence in the present work, we have investigated the structural and electronic properties of pristine and defected graphene sheet upon the adsorption of alkali metal ions (Li⁺, Na⁺, and K⁺) using density functional theory (DFT) calculations. The presence of vacancies or vacancy defects enhances the adsorption of alkali ions than the pristine sheet. From the obtained results, it is found that the adsorption energy of Li⁺ on the vacancies defected graphene sheet is higher (3.05?eV) than the pristine (2.41?eV) and Stone–Wales (2.50?eV) defected sheets. Moreover, the pore radius of the pristine and defected graphene sheets are less affected by metal ions adsorption. The increase in energy gap upon the adsorption of metal ions is found to be high in the vacancy defected graphene than that of other sheets. The metal ions adsorption in the defective vacancy sheets has high charge transfer from metal ions to the graphene sheet. The bonding characteristic between the metal ions and graphene sheet are analysed using QTAIM analysis. The influence of alkali ions on the electronic properties of the graphene sheet is examined from the Total Density of States (TDOS) and Partial Density of States (PDOS).     

Decorated graphyne and its boron nitride analogue as versatile nanomaterials for CO detection

The sensitivity of a new two-dimensional (2D) carbon allotrope built from sp- and sp²-hybridised carbon atoms, graphyne (GY), as well as its boron nitride analogue (BN-yne) towards CO molecule has been theoretically investigated. Indeed, a theoretical understanding of the interaction between gas molecules and extended carbon-based network structures is crucial for developing new materials that could have a wide range of applications. Here, we report our first-principles calculations to explore the impact of metal decoration on the GY and BN-yne upon the CO adsorption. We predict that Ca and Li decorations significantly enhance the CO-sensing ability of the GY and BN-yne compared to that of their pristine sheets. Owing to strong interactions between CO and the decorated GY and BN-yne, dramatic changes in the electronic properties of the sheets together with large band gap variations were observed. The present study sheds a deep insight into the sensing properties of the novel carbon-based 2D structures beyond the graphene sheet.     

第一性原理研究气体小分子吸附的石墨烯负载金属原子体系

石墨烯负载的单个金属原子体系(M-gra)具有高的结构稳定性,显正电性的金属原子可作为活性位用在气敏器件和催化材料.本文采用基于密度泛函理论的第一性原理方法研究单个有毒气体小分子(NO和CO)在M-gra表面的吸附特性.研究结果表明:单个NO分子吸附的稳定性高于CO分子,由于其能够从反应衬底获得更多的转移电荷,因此,M-gra衬底对NO分子表现出高的灵敏度.此外,不同小分子吸附能够改变M-gra体系的电荷密度和自旋电荷分布,进而使得气体分子吸附体系表现出不同大小的磁矩.通过对比气体分子吸附前后M-gra体系的磁矩变化,能够有效判断吸附分子和反应衬底的类型.     

The adsorption behaviours of Pt adatom on pristine and defective bilayer graphene

The structural stability and electronic property of metal Pt atom anchors on two typical substrates (including the pristine and defective bilayer graphene, PBG and DBG) are studied using the first-principles calculations. For the PBG sheets, the Pt atom at the bridge site of bottom layer has only one stable adsorption, which is more stable than other sites of the top layer. For the DBG sheets, the doped Pt below defective site has the larger adsorption energy than that of the upper one. Compared to the isolated graphene films, the Pt(111) substrate-supported graphene systems have effect on the adsorption energies of Pt adatom to some extent, but it does not affect the most preferable configurations. Moreover, the diffusion pathways and energy barriers of Pt adatom on PBG and DBG substrates are comparatively investigated. For the DBG sheets, the Pt dopant has smaller diffusion barrier on upper layer than that of the intercalation process through the defective site. Therefore, the Pt dopant prefers to diffuse on the top layer and then forms the metal impurity. This work provides valuable information on understanding the formation process and intercalation mechanism of metal adatom on graphene sheets.