金属和非金属原子间协同效应调控气体小分子的吸附特性研究

采用基于密度泛函理论方法系统地研究了单个NO和CO小分子在非金属(B和N)与金属Ni原子共掺杂石墨烯(Bx-Ny-gra-Ni,x+y=0,1,2,3)表面的吸附特性,分析了吸附气体小分子的几何结构,吸附能,电荷转移量以及引起体系磁性变化等情况.研究结果表明：NO和CO倾向于吸附在Ni原子的顶位,B和N掺杂原子的数量和比例能够有效地调制小分子的吸附强度;与吸附的CO分子相比,Bx-Ny-gra-Ni表面吸附的NO分子能获得较多的电荷,进而表现出高的稳定性.此外,利用吸附的气体小分子与衬底间相互作用强度和灵敏性的差异、以及引起反应衬底的磁性变化将为设计石墨烯基气敏、催化和电子器件提供重要参考.     

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.     

理论研究过渡金属原子修饰石墨炔材料的功能性

采用基于密度泛函理论中第一性原理方法分别对石墨炔负载过渡金属原子(M-gra)体系的稳定构型以及对多种气体小分子的灵敏度和选择性进行理论研究.计算结果表明金属原子吸附在孔洞结构的H2位具有高稳定性,不同种类的金属原子能够有效调控石墨炔体系的电子特性和具有不同的磁矩.比较气体分子的吸附能大小,M-gra衬底对O和OH表现出高的灵敏度,单个NO、NO₂和O₂的稳定性高于CO分子.此外,小分子吸附的M-gra体系具有金属、半金属和半导体特性,在电子和气敏器件领域具有潜在应用.     

气体分子在Co-BN表面吸附的第一性原理研究

采用包含色散力校正的密度泛函理论(DFT-D)方法系统地研究了气体分子(O2, H2, NO, CO, CO2, SO2, H2S, H2O)在Co掺杂单层BN(Co-BN)表面的吸附, 分析了吸附小分子的几何结构, 吸附能, 电荷转移等情况. 结果表明: 1) CO等气体分子主要吸附在Co及其近邻六元环的顶位, 吸附结构的电荷转移表明掺杂原子Co对BN衬底的气敏特性有较好的调制作用; 2) 在Co-BN表面吸附的O2和CO较易被活化, 表明Co-BN可能是一种对CO氧化有较好催化活性的新型催化材料.     

气体分子在Co-BN表面吸附的第一性原理研究

采用包含色散力校正的密度泛函理论(DFT-D)方法系统地研究了气体分子(O_2,H_2,NO,CO,CO_2,SO_2,H_2S,H_2O)在Co掺杂单层BN(Co-BN)表面的吸附,分析了吸附小分子的几何结构,吸附能,电荷转移等情况.结果表明:1)CO等气体分子主要吸附在Co及其近邻六元环的顶位,吸附结构的电荷转移表明掺杂原子Co对BN衬底的气敏特性有较好的调制作用;2)在Co-BN表面吸附的O_2和CO较易被活化,表明Co-BN可能是一种对CO氧化有较好催化活性的新型催化材料.     

非金属与金属原子共掺杂石墨烯体系的气敏特性研究

采用基于密度泛函理论的第一性原理方法研究了非金属N原子和金属原子(M=Mo,Al,Co,Fe,Au和Pt)共掺杂石墨烯体系(M-GN4)的电子结构和表面活性.研究发现:单个金属原子掺杂的GN4体系表现出不同的稳定性,相比掺杂的Au原子,其它的金属原子都具有很高的稳定性( 6. 0 e V).掺杂的金属原子失去电荷显正电性将有助于调控气体分子的吸附特性. Mo-GN4和Al-GN4衬底对吸附的O_2表现出较高的灵敏性,单个CO和O_2分子在Co-GN4和Fe-GN4衬底的吸附能差别较小.此外,吸附不同的气体分子能够有效地调控M-GN4体系的电子结构和磁性变化.     

金属原子修饰石墨烯体系催化性能的理论研究

采用基于密度泛函理论的第一性原理方法研究了单个CO 和O2气体分子在金属原子修饰石墨烯表面的吸附和反应过程. 结果表明: 空位缺陷结构的石墨烯能够提高金属原子的稳定性, 金属原子掺杂的石墨烯体系能够调控气体分子的吸附特性. 通入混合的CO和O2作为反应气体, 石墨烯表面容易被吸附性更强的O2分子占据, 进而防止催化剂的CO 中毒. 此外, 对比分析两种催化机理(Langmuir-Hinshelwood和Eley-Rideal)对CO氧化反应的影响. 与其它金属原子相比, Al原子掺杂的石墨烯体系具有极低的反应势垒(< 0.4 eV), 更有助于CO氧化反应的迅速进行.     

金属原子修饰石墨烯体系催化性能的理论研究

采用基于密度泛函理论的第一性原理方法研究了单个CO和O2气体分子在金属原子修饰石墨烯表面的吸附和反应过程.结果表明:空位缺陷结构的石墨烯能够提高金属原子的稳定性,金属原子掺杂的石墨烯体系能够调控气体分子的吸附特性.通入混合的CO和O2作为反应气体,石墨烯表面容易被吸附性更强的O2分子占据,进而防止催化剂的CO中毒.此外,对比分析两种催化机理(Langmuir-Hinshelwood和Eley-Rideal)对CO氧化反应的影响.与其它金属原子相比,Al原子掺杂的石墨烯体系具有极低的反应势垒(0.4 e V),更有助于CO氧化反应的迅速进行.     

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.     

小分子吸附调控Ti掺杂石墨烯电子结构和磁性的密度泛函理论研究

本文采用基于密度泛函理论的第一性原理方法,研究了气体分子CO、NO、NO_2和SO_2吸附对Ti掺杂石墨烯(Ti G)电子结构和磁性的调制.研究表明:Ti G对CO、NO、NO_2和SO_2分子的吸附作用较强,各分子与Ti原子键合并形成Ti-X键(X代表C、O、N原子);各分子的吸附可导致Gas@Ti G体系电磁性质明显改变:CO分子吸附基底后,虽未能引起CO@Ti G体系电子性质改变和磁性的产生,却能够有效调控该体系的带隙宽度;不同于CO分子,NO、NO_2和SO_2分子的吸附使得半导体性的Ti G基底转变为金属特性,但各体系磁性表征不同:NO@Ti G发生完全自旋极化,即NO分子与基底上均有自旋分布,且二者的自旋方向相同;顺磁性的NO_2分子吸附于Ti G基底时磁性消失;SO_2分子吸附于Ti G基底后自身产生磁性,但基底几乎未发生自旋极化,SO_2@Ti G呈现自旋极化的局域分布特征.由此,依据分子吸附后体系电磁性质特征的不同,可辨识被测气体分子.此项研究结果为高灵敏度和高选择性的石墨烯基气体传感器的设计提供理论参考.     

A first-principles study on the interaction of CO molecules with VIII transition metals-embedded graphitic carbon nitride as an excellent candidate for CO sensor

We studied the adsorption behavior of CO molecules over graphitic carbon nitride (gCN) and VIII transition metals (TM)-embedded gCN systems (TM=Ni, Pd, and Pt atoms) using density functional theory. The results indicated that the Pt-embedded gCN is excellent candidate for adsorption of CO molecules with adsorption energy of −2.77 eV, which is much better than those of the other adsorbents. Furthermore, it was observed that the band gap energies of TM-embedded systems were less than that of pristine gCN and decoration of transition metal atoms leads to the formation of mid gap impurity states, resulting in increase of electrical conductivity. Additionally, the Lowdin charges displayed that upon adsorption of CO molecules, this molecule acts as an electron acceptor and gCN systems behave as an electron donor with electron transfer from d-orbitals of transition metal atoms to the states of CO molecule. The results of spin polarized band structure indicated that the pristine gCN, Ni and Pd-embedded systems are non-magnetic, whereas Pt-embedded gCN induces non-zero magnetic moment equal to 1.35 μB. Therefore, our results revealed that among the TM-embedded systems, Pt-embedded gCN is more effective than those of the other adsorbents in sensing and removing of this gas from the atmosphere.     

Spin polarization and charge transfer of Co nanoclusters coated with CO molecules

We have investigated magnetic properties of Co clusters coated with CO molecules by first-principles density functional calculations. Total magnetic moment of the system decreases with the increase of CO molecule concentration regardless of adsorption sites for CO molecules. Spin polarization slightly increases as CO molecules are adsorbed on the most stable sites of Co cluster, which is caused by the increased local spin polarization of p-electrons due to charge transfer from Co clusters to CO molecules.     

Effect of the electronic structure of a substrate on the photoinduced behavior of adsorbed NO and CO molecules

Photoprocesses in systems produced by adsorption of NO and CO molecules on the Pt(111) and Ni(111) surfaces, as well as on the (111) surface of Pt-Ge alloy, is studied by the IR absorption spectroscopy, resonant multiphoton ionization, and UV photoelectron spectroscopy methods. The energy of photons varies between 2.3 and 6.4 eV. The character of the processes depends on the type of the metallic substrate. On the Pt(111) surface, NO molecules dissociate or are desorbed, depending on the degree of coverage. On the Ni(111) surface, the molecules only dissociate. Conversely, NO molecules adsorbed on the (111) surface of the Pt-Ge alloy are only desorbed from the surface. In the CO/Pt(111) and CO/Pt(111)-Ge systems, CO molecules adsorbed on on-top adsorption sites are desorbed under the action of the photons, while those occupying bridging adsorption sites change their properties insignificantly. A model of photoinduced processes is suggested. According to this model, the lifetime of a state excited by charge transfer between the valence band of the metal and the 2π-antibonding molecular orbital plays a decisive part in the occurrence of one or the other of these processes.     

TiC-和TiN-(001)表面吸附性能的密度泛函理论研究

基于密度泛函理论系统研究了碳化钛(TiC)和氮化钛(TiN)非极性(001)表面吸附气体分子和原子的性能。鉴于这些材料拥有不同的电子结构特征,发现受电子的CO分子或未饱和的O和H原子在TiC(001)和TiN(001)表面吸附于不同的活性位点,而供电子的NH3和H2O气体分子或完全饱和的O2和H2分子仅倾向与两个表面的金属原子位点结合。这些吸附特性可能与此类材料表面的电子结构有关。     

Controlling spin off state by gas molecules adsorption on metal-phthalocyanine molecular junctions and its possibility of gas sensor

Employing Green's function (GF) technique in combination with spin-polarized density functional theory (DFT), we study the electronic structure and magnetic properties of metal phthalocyanine (MPc) (M?=?Mn, Fe, Co, Ni, Cu, Zn) with or without four different gas molecules (NO, CO, O₂ and NO₂) adsorbing on the M atom of MPc molecule. The corresponding stable adsorption structural configurations and transport properties of MPc molecular junctions are also investigated. Our results indicate that the magnetic moment of MPc for M?=?Mn, Fe and Co can be modified by the specific gas molecule adsorption, which is mainly ascribed to competitive relation of HOMO-LUMO Gap and Hund's rules. However, for M?=?Ni, Cu and Zn, it is difficult to detect gas molecule because the interaction of M atom and these gases is most of weak van der Waals interaction. Remarkably, the spin of MPc molecule can be switched to a magnetic off-state by specific gas absorption, giving rise to a potential application on controllable spintronic devices. In addition, CO, NO, O₂ and NO₂ gas molecules can be detected selectively by measuring spin filter efficiency of these MPc molecular junctions. On the basis of our results, MPc (M?=?Mn, Fe, Co) molecular junctions can be considered as a promising nanosensor device to detect individual gas molecules.