石墨烯吸附甲醛的第一性原理研究

采用第一性原理研究了甲醛分子吸附于本征石墨烯、缺陷石墨烯和掺杂石墨烯的体系.通过计算石墨烯掺杂前后对甲醛气体的吸附能、电荷转移及能带和态密度,发现掺杂Pt后甲醛分子吸附能和电荷转移显著增大,这是由于Pt的掺杂在本征石墨烯能带中引入了杂质能级,增强了石墨烯和甲醛分子间的相互作用,可以提高石墨烯对甲醛气体的气敏响应速度和吸附能力.     

4d过渡金属掺杂石墨烯对HCN吸附行为的第一性原理研究

采用第一性原理的密度泛函理论方法研究了掺杂Y、Zr、Nb、Mo、Tc和Ru的石墨烯体系对氰化氢(HCN)的吸附作用。首先考察了HCN分子中H、C或N原子分别靠近吸附点的三种吸附构型。然后比较了吸附HCN前后掺杂石墨烯的能带变化。研究结果表明,掺杂Mo和Ru的石墨烯吸附HCN后的带隙大小变化大于20%,并表现为半导体行为,说明吸附后掺杂石墨烯的电导性能受影响较大。此外,进一步研究了掺杂Mo和Ru的石墨烯吸附HCN的过程,讨论了吸附能、带隙、晶格常数、HCN电荷和键长的变化,并分析了掺杂Mo和Ru的石墨烯的振动特性。研究表明,掺杂Mo和Ru的石墨烯对HCN的吸附非常敏感,这可能是开发HCN传感器的有用材料。     

Li在石墨烯表面吸附与迁移的第一性原理研究

本工作研究了Li在石墨烯表面的吸附和迁移行为。基于密度泛函理论(DFT)的第一性原理方法,计算了Li在本征石墨烯表面的吸附特性和迁移行为以及石墨烯吸附Li前后的能带结构、态密度、电荷转移、差分电荷密度。Li在4×4石墨烯表面的扩散能垒为0.336 eV,其在C6环芯位的吸附能为1.569 eV,电荷转移量为0.870 7e,Li原子的2p轨道和C原子的2p轨道出现杂化。Li主要通过跨越C-C键桥位而在相邻C_6环芯位间实现平行于石墨烯表面的连续扩散,Li原子在石墨烯表面的最稳定吸附位为C_6环芯位,吸附Li后的石墨烯+Li体系显示出金属性,且Li与石墨烯间同时存在离子键和共价键。     

金原子修饰的石墨烯片对半胱氨酸的响应机理的第一性原理研究

使用密度泛函理论研究了本征石墨烯和经过金原子修饰的石墨烯吸附半胱氨酸的构型和电子性质.对比本征石墨烯,修饰金原子后的石墨烯与半胱氨酸之间有较强的结合能力和较短的连接距离,发生的是化学吸附.态密度的计算结果也显示半胱氨酸与金修饰后的石墨烯轨道之间存在显著的杂化现象,而本征石墨烯轨道杂化现象不明显.本征石墨烯与半胱氨酸发生的是物理吸附.预测相比于本征石墨烯,金修饰后的石墨烯是一种潜在的、更高灵敏度的半胱氨酸检测材料.     

Li吸附对石墨烯、BC_3、C_3N电学性质影响的第一性原理研究

基于密度泛函理论(DFT)的第一性原理方法,对Li在未掺杂和B(N)掺杂浓度为25%(原子分数)的石墨烯表面最稳定位置的吸附进行了结构优化,计算了本征石墨烯及B(N)掺杂石墨烯吸附Li前后的能带结构、态密度、电荷转移、差分电荷密度和结合能。计算结果表明,B掺杂浓度为25%(原子分数)时可显著提高石墨烯的Li吸附能,N掺杂浓度为25%(原子分数)时减弱了石墨烯的Li吸附能。吸附Li后的石墨烯、BC3和C3N体系均显示出金属性。     

Si表面吸附GaN的第一性原理研究

为了更好地了解Si表面对CaN的吸附,利用基于密度泛函理论的第一性原理平面波赝势方法,计算了Si(100)和Si(111)弛豫表面分别吸附GaN的电子结构、吸附能大小以及其态密度图.计算结果表明,相对于Si(111)表面,Si(100)表面更容易吸附GaN,在同等实验条件下,在Si(100)表面应更容易沉积GaN薄膜.采用ECR-MOPECVD工艺,于低温下在Si(100)衬底上沉积得到了GaN薄膜,XRD谱图表明该薄膜是一种晶体结构和无定形结构的混合结构.     

空位和Si掺杂对In在石墨烯上吸附的影响

利用第一性原理方法计算了空位和Si(硅)替位掺杂对In(钢)原子在石墨烯上吸附的影响.结果表明:在低覆盖度下,空位比Si替位掺杂更能增强In在石墨烯上的吸附,主要原因在于空位引入更多的悬挂键,加强了In和石墨烯之间相互作用.而对于较高覆盖度,Si替位掺杂却比空位对In吸附在石墨烯上的影响更强.无论是较高覆盖度还是低覆盖度,空位和Si替位掺杂均增强了In在石墨烯上的吸附.     

In-As共掺杂GaSb的第一性原理研究

采用基于密度泛函理论的第一性原理平面波超软赝势法,计算未掺杂,In、As单掺及In-As共掺GaSb的晶格参数、能带结构、态密度和吸收光谱。结果表明:掺杂后GaSb晶格发生畸变,As单掺GaSb的晶格常数增大,带隙减小,导致吸收光谱蓝移;而In单掺和In-As共掺GaSb晶格常数变大,且禁带宽度均减小,致使吸收光谱红移,这也是实验上造成掺杂GaSb热光伏电池吸收光谱扩展的原因。     

Mn掺杂单空位缺陷碳纳米管吸附NH3分子的第一性原理研究北大核心CSCD

研究本征碳纳米管、单空位缺陷碳纳米管、Mn掺杂碳纳米管和Mn掺杂单空位缺陷碳纳米管对NH3分子的吸附效果。采用基于密度泛函理论的第一性原理方法,对各个模型的吸附能、吸附距离、电荷转移量、电子密度等的分析后发现:单空位缺陷有利于提高碳纳米管对NH3分子的吸附效果,但碳纳米管未能与NH3分子形成化学吸附;掺杂Mn原子能大大提高单空位缺陷碳纳米管与NH3间的吸附能和电荷转移量,同时减小其吸附距离,说明Mn原子掺杂的单空位缺陷碳纳米管能够对NH3分子产生化学吸附。Mn原子掺杂单空位缺陷碳纳米管作为NH3气敏材料值得后续深入研究。     

基于石墨烯吸附净化材料的研究进展

石墨烯是一种片层状高比表面积碳材料,理论比表面积可达2 630 m2/g,具有非常高的吸附容量、良好的化学稳定性及机械性能等。有关石墨烯的发展和应用已成为当前的热点研究课题之一。详细讨论了石墨烯及其复合物在吸附重金属离子、有机污染物、有毒气体中的研究进展。最后对石墨烯及其复合物在吸附方面中的发展与应用做出了评价,同时对它们在吸附上的应用前景做了展望。     

Preparation of large-sized graphene from needle coke and the adsorption for malachite green with its graphene oxide

With needle coke (NC) as an initial material, large-sized graphene was successfully prepared through an oxidation–exfoliation–thermal reduction process. The prepared graphene was characterized by SEM, TEM, AFM, FTIR, XRD, Raman, and XPS, respectively. Results showed that the morphology of graphene from NC was different from that of natural graphite although the spectroscopic properties of graphene from NC are very similar to those from natural graphite. The lateral size of the prepared graphene is concentrated in 3–8?µm, which was considerably larger than that of natural graphite, multiwalled carbon nanotubes (MWCNTs) and stacked graphene nanofibers (SGNFs). In addition, the adsorption capacity of graphene oxide from NC for malachite green was investigated to confirm the size of graphene indirectly. The equilibrium adsorption capacity of 437.7?mg/g for malachite green was considerably higher than that from natural graphite whose adsorption capacity was 209.5?mg/g under identical conditions. All results confirm that NC is a better alternative for the preparation of graphene than natural graphite.     

B或N掺杂端部封闭碳纳米管吸附Pt的第一性原理计算

由于碳纳米管（CNTs）载Pt催化剂中,CNTs与Pt纳米颗粒间的交互作用弱,导致两者间导电性较差,并且容易引起Pt脱落或团聚。本文采用第一性原理对Pt原子在CNTs封闭端部的吸附行为进行了研究,发现B掺杂可以使（5,5）型和（9,0）型CNTs与Pt间的平均吸附能分别提高12.7%和19.6%,N掺杂可以使（5,5）型和（9,0）型CNTs与Pt间的平均吸附能分别提高22.4%和18.4%,并且CNTs与Pt间的电荷转移量较管壁吸附也得到了明显提升,同时B或N掺杂使CNTs-Pt体系的稳定性最高可分别提升133.8%和237.3%,说明在CNTs端部掺杂B或N可提高CNTs载Pt催化剂的性能。     

壳聚糖对氯离子的吸附作用研究

研究了壳聚糖对氯离子的吸附,结果表明脱乙酰度为95%的壳聚糖对Cl-的吸附可达到64.8%。     

不同染料吸附状态下染料敏化太阳能电池电化学阻抗谱研究

研究了TiO2表面染料的吸附状态不同时,染料敏化太阳能电池(DSC)的光电转换性能,并采用电化学交流阻抗技术(EIS)考察了不同染料吸附状态下DSC中的电子界面复合效应。结果表明,在非饱和吸附染料状态下,通过调整TiO2薄膜表面染料分子吸附量,可以降低界面电荷复合效应,使电子在TiO2薄膜的传输过程中寿命增加,从而提高DSC的填充因子。     

Experimental investigation on hydrogen adsorption performance of composite adsorbent in the tank with high vacuum multilayer insulation

Hydrogen is one of the main residual gases in the high vacuum multilayer insulated tank. H₂ adsorption performance of the composite adsorbent was investigated by using a test bench, an X-ray diffraction and a scanning electron microscopy.The composite adsorbent is composed of molecular sieve 5A and getter that includes the different proportion of PdO and Ag₂O. The getter shall is laid as flat as possible when fed into the tank. Leakage and outgassing rate can be decreased by 64% after placing getter. The crystal phase structure of PdO and Ag₂O in getter is unchanged by adsorption performance. Experimental results showed that the H₂ adsorption rate is high at the initial stage, and then it starts to become slow during a relatively long period. The type IV isotherms were obtained with these samples, and the H₂ adsorption principle is also discussed. The optimum percentage content of Ag₂O in the getter is 22%. Under the allowed highest pressure, the composite adsorbent that includes 15% Ag₂O, 85% PdO and molecular sieve 5A is preferentially used in the tank interlayer. The experimental results and performance analyses can be used in the design of the high vacuum multilayer insulated tank.     

稀土La掺杂Mg2Si的几何结构、弹性性能和电子结构的第一性原理研究EI北大核心CSCD

采用密度泛函理论(DFT)的第一性原理平面波赝势方法对稀土元素镧(La)掺杂Mg2Si的几何结构、弹性性能和电子结构进行计算与分析。首先,结合形成焓、Born力学稳定性以及差分电荷密度的结果可知,掺杂稀土元素La之后,形成的Mg8Si4La和Mg8Si3La均不能稳定存在,La掺杂的Mg2Si优先占据体系Mg原子的位置;其次,晶体的体模量(B),剪切模量(G),杨氏模量(E),泊松比(ν),以及各向异性系数(A)的计算结果表明本征Mg2Si为脆性相,而Mg7Si4La为韧性相,掺杂La可以提高Mg2Si的延展性;最后,态密度、Mulliken布居数和电荷差分密度的计算结果表明掺杂稀土镧后费米面向高能级区域偏离,进入导带,提高了Mg2Si的导电性。     

Adsorption of formaldehyde molecule on the intrinsic and Al-doped graphene: A first principle study

To search for a high sensitivity sensor for formaldehyde (H₂CO), we investigated the adsorption of H₂CO on the intrinsic and Al-doped graphene sheets using density functional theory (DFT) calculations. Compared with the intrinsic graphene, the Al-doped graphene system has high binding energy value and short connecting distance, which are caused by the chemisorption of H₂CO molecule. Furthermore, the density of states (DOS) results show that orbital hybridization could be seen between H₂CO and Al-doped graphene sheet, while there is no evidence for hybridization between the H₂CO molecule and the intrinsic graphene sheet. Therefore, Al-doped graphene is expected to be a novel chemical sensor for H₂CO gas. We hope our calculations are useful for the application of graphene in chemical sensor.     

Growth of Cu2O nanoparticle on reduced graphene sheets with high photocatalytic activity for degradation of Rhodamine B

Cu₂O–reduced graphene oxide (RGO) nanocomposite was synthesized by a simple one-pot solvothermal method. The morphology and properties of Cu₂O/RGO nanocomposites were characterized by scanning electron microscope, Raman spectroscopy, X-ray diffraction, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activities of the as-prepared nanocomposites were investigated by photodegrading Rhodamine B under visible light. Results show that Cu₂O/RGO nanocomposites exhibited a remarkably enhanced photocatalytic efficiency compared with pure Cu₂O nanoparticles and commercial P25. Moreover, we found that the content of graphene oxide introduced into composite material was a crucial factor for its improved photocatalytic performance.     

固体氧化物燃料电池Sr系钙钛矿电极B位元素成分优化规律

采用第一性原理, 对元素周期表中3~6周期52种元素作为固体氧化物燃料电池(SOFC) Sr为A位系列钙钛矿结构电极材料B位替换元素的相关结构相的结合能进行了系统计算, 据此分析了各元素对生成立方相和六方相结构稳定性影响的趋势。通过对相关体系的成分比例进行推算, 讨论了这些实验体系在稳定性趋势图中的分布规律, 进一步对上述体系的实验数据进行分析, 得到了以Mo-Fe-Co连线为中心的成分优化区域。根据相关氧离子扩散模型的计算, 结果显示该区域形成的原因与氧空位形成能、迁移能以及禁带宽度均较为适中有关。以上理论结合实验的研究为电极材料的成分优化提供了理论指导。