笼型Li6Si5团簇的结构和储氢性能研究

利用密度泛函M06方法,在6-311+G(d, p)基组水平上对Si_5和Li修饰的Si_5团簇的几何结构和电子性质及储氢性能进行理论计算研究.结果表明, Si_5团簇最低能量构型为笼型结构,纯Si_5团簇不能有效吸附氢分子. Li原子的引入显著改善了Si_5团簇的储氢能力.以六个Li原子穴位修饰Si_5团簇为载体,每个Li原子周围可以有效吸附三个氢分子,其氢分子的平均吸附能为2.395 kcal/mol,储氢密度可达16.617 wt%.合适的吸附能和较高储氢密度表明Li修饰Si_5团簇有望成为理想的储氢材料.     

硫酸铝在纤维增强轻质硅酸钙材料中的作用机理

通过试验证明，加入适量硫酸铝对于溶解乙气瓶填料具有如下作用：在料浆阶段能够促进料浆凝胶化，防止物料下沉；在蒸压过程中能够产生微膨胀，防止填料收缩，并能够使填料强度显著提高。同时，采用ＤＴＡ、ＸＲＤ、ＳＥＭ方法对其作用机理进行了研究。     

Recent advances in hydrogen storage technologies based on nanoporous carbon materials

Hydrogen is a promising energy carrier that can potentially facilitate a transition from fossil fuels to sustainable energy sources without producing harmful by-products. Prior to realizing a hydrogen economy, however, viable hydrogen storage materials must be developed. Physical adsorption in porous solids provides an opportunity for hydrogen storage under low-stringency conditions. Physically adsorbed hydrogen molecules are weakly bound to a surface and, hence, are easily released. Among the various surface candidates, porous carbons appear to provide efficient hydrogen storage, with the advantages that porous carbon is relatively low-cost to produce and is easily prepared. In this review, we summarize the preparation methods, pore characteristics, and hydrogen storage capacities of representative nanoporous carbons, including activated carbons, zeolite-templated carbon, and carbide-derived carbon. We focus particularly on a series of nanoporous carbons developed recently: metal–organic framework-derived carbons, which exhibit promising properties for use in hydrogen storage applications.     

铝掺杂富勒烯储氢研究:氢分子形成双层结构

利用密度泛函理论对铝(Al)掺杂富勒烯(C_(60))体系的储氢性能进行研究.计算结果显示单个Al原子吸附的最佳位置是在C_(60)表面碳五元环的中心位置,并形成稳定的Al-C_(60)团簇结构.当多个Al原子掺杂C_(60)时,12个Al原子吸附在C_(60)的碳五元环正上方具有最低的吸附能,并形成稳定的Al12-C_(60)团簇结构.当氢气与Al掺杂C_(60)的团簇相互作用时,C_(60)上碳原子的吸附使得氢气吸附在Al原子的侧位比吸附在Al原子的顶位更稳定.当多个氢气分子吸附时,102个氢分子形成稳定的双层结构并吸附在Al12-C_(60)上,体系的储氢质量分数能达到16.44%,其中第一层氢分子主要同两个临近的Al原子以及C_(60)相互作用,第二层氢气分子同近邻的Al原子和第一层氢气分子相互作用.     

BLim1/2+(m=6、7)团簇的结构及储氢性能的研究

为开发新型储氢材料提供更为丰富的理论基础,采用B3LYP泛函在6-311++G(d,p)基组水平上对BLi₆⁺超碱团簇和BLi₇²⁺超碱土团簇的稳定性结构、电荷分布等方面进行理论研究,进而研究团簇的储氢性能。结果表明：两个离子团簇均比它们所对应的中性团簇均具有较高的动力学稳定性。两个离子团簇中的每个Li原子同时有效吸附2个氢分子,BLi₆⁺团簇中氢分子在团簇表面平均吸附能为0.969~2.162kCal/mol,储氢质量分数达31.56wt%。而BLi₇⁺团簇中氢分子在团簇表面平均吸附能为1.764~3.714kCal/mol,储氢质量分数达32.21wt%。它们的储氢性能表明BLi₆⁺团簇和BLi₇²⁺团簇均有望成为良好的储氢媒介。     

A titanosilicate molecular sieve with adjustable pores for size-selective adsorption of molecules

Zeolites and related crystalline microporous oxides-tetrahedrally coordinated atoms covalently linked into a porous framework-are of interest for applications ranging from catalysis to adsorption and ion-exchange. In some of these materials (such as zeolite rho) adsorbates, ion-exchange, and dehydration and cation relocation can induce strong framework deformations. Similar framework flexibility has to date not been seen in mixed octahedral/tetrahedral microporous framework materials, a newer and rapidly expanding class of molecular sieves. Here we show that the framework of the titanium silicate ETS-4, the first member of this class of materials, can be systematically contracted through dehydration at elevated temperatures to 'tune' the effective size of the pores giving access to the interior of the crystal. We show that this so-called 'molecular gate' effect can be used to tailor the adsorption properties of the materials to give size-selective adsorbents suitable for commercially important separations of gas mixtures of molecules with similar size in the 4.0 to 3.0 A range, such as that of N2/CH4, Ar/O2 and N2/O2.     

Li原子修饰一维六角硼烯链团簇的结构及储氢性能研究

采用密度泛函理论(DFT)方法研究Li原子修饰一维六角硼烯链团簇的结构及其储氢性能。结果表明,氢分子能在Li原子修饰一维六角硼烯链团簇表面吸附,每个Li原子周围可以有效吸附两个H2,几何结构和电子性质的稳定性及合适的吸氢条件表明Li原子修饰一维六角硼烯链团簇材料在常温常压条件下可以作为有效储氢媒介。     

基于SiC和BC5的多孔材料设计及储氢性能研究

基于金刚石结构的SiC晶体和类似金刚石结构的BC5晶体设计了多孔材料,并用分子力学方法对其进行优化得到平衡态结构.利用GCMC对其在温度为298 K和77 K,压强为0-100 bar的条件下的储氢量、氢分子密度分布和等量吸附热进行了讨论.考虑孔内壁以化学吸附的氢在内,基于SiC晶体设计的多孔材料储氢量比Si C纳米管的结果更理想.氢分子密度分布图表明氢分子在孔道中的分布距孔道边缘有一定的距离,此距离与氢分子动力学直径2.89A相当.等量吸附热表明材料在温度为298 K和77 K对氢分子的吸附都是物理吸附.     

碱金属锂原子修饰硅原子链团簇的结构和储氢性能

采用密度泛函理论(DFT)方法研究Li2Sim(m=2,4,6)链状团簇结构及其储氢性能。研究结果表明,氢分子在碱金属Li原子修饰的三种硅链结构中均发生吸附,并且每个Li原子都可以吸附多个氢分子,其中两个Li原子修饰Si2链的结构能够吸附氢分子的储氢质量分数达18.6 wt%,氢分子的平均吸附能为1.850 kcal/moL。结果表明,碱金属Li原子修饰的硅链在室温条件下可作为氢气的存储媒介。     

化学活化法制备酚醛基活性炭纤维及其吸附性能

以酚醛纤维为原料、KOH为活化剂,采用化学活化法制备酚醛基活性炭纤维（PACF）,并以亚甲基蓝（MB）染料溶液作为吸附对象,对其吸附性能和吸附机理进行研究,同时采用扫描电子显微镜和比表面积及孔隙度分析仪对其微观形貌和比表面积及孔结构进行分析。结果表明：所制备的PACF得率高达47.01%,比表面积为1 378.48 m2/g,总孔容为0.60 cm3/g,平均孔径为1.52 nm,微孔率为90.62%,是一种以微孔为主的多孔性高吸附材料。当MB染料溶液的初始质量浓度为300 mg/L、pH为5时,最有利于PACF对其吸附,此时吸附量高达468.52 mg/g。吸附平衡和吸附动力学研究表明：PACF对MB染料溶液的吸附过程更符合Langmuir等温线模型和准二级动力学模型。此外,颗粒内扩散模型分析表明：外扩散和粒子内扩散都是PACF对MB染料分子吸附过程速率的控制步骤。     

A mesoporous germanium oxide with crystalline pore walls and its chiral derivative

Microporous oxides are inorganic materials with wide applications in separations, ion exchange and catalysis. In such materials, an important determinant of pore size is the number of M (where M = Si, Ge and so on) atoms in the rings delineating the channels. The important faujasite structure exhibits 12-ring structures while those of zeolites, germanates and other materials can be much larger. Recent attention has focused on mesoporous materials with larger pores of nanometre scale; however, with the exception of an inorganic-organic hybrid, these have amorphous pore walls, limiting many applications. Chiral porous oxides are particularly desirable for enantioselective sorption and catalysis. However, they are very rare in microporous and mesoporous materials. Here we describe a mesoporous germanium oxide, SU-M, with gyroidal channels separated by crystalline walls that lie about the G (gyroid) minimal surface as in the mesoporous MCM-48 (ref. 9). It has the largest primitive cell and lowest framework density of any inorganic material and channels that are defined by 30-rings. One of the two gyroidal channel systems of SU-M can be filled with additional oxide, resulting in a mesoporous crystal (SU-MB) with chiral channels.     

Recent advances in improving performances of the lightweight complex hydrides Li-Mg-N-H system

A brief review of state-of-the art advances in improving performances of the lightweight complex hydrides Li-Mg-N-H system is reported. Among the hydrogen storage materials, Li-Mg-N-H combination systems are regarded as one of the most potential candidates for the vehicular applications owing to their high hydrogen storage capacity (>5 wt% H) and a more appropriate thermodynamic properties of hydrogen absorption and desorption. In the Li-Mg-N-H systems, tremendous efforts have been devoted to improving the hydrogen storage properties by adjusting composition, revealing reaction mechanisms, adding catalysts and refining the microstructures, etc. During the studies, different mechanisms, such as the coordinated two-molecule or multimolecule reaction mechanism and the ammonia-mediated mechanism, are proposed and applied under some certain conditions. Catalysis and nanosizing are very effective in enhancing the kinetic properties and thermodynamic destabilization of Li-Mg-N-H systems. Due to nano effects, the space-confinement and nanoconfinement seems to be more effective for improving the hydrogen storage performance, and it is great significant to develop hydrogen storage materials by studying the nanoconfined effects on the Li-Mg-N-H systems.     

Mechanism of forming an ink-bottle-like pore structure based on SBA-15 by a novel MOCVD technique

Metallorganic chemical vapor deposition is used as a novel simple pore tailoring method to fine-tune the pore opening size of SBA-15 materials without significant loss in pore volume and surface area. By using acetylene as carbon source and copper (II) acetylacetonate as precursor, the poremouth of SBA-15 is effectively reduced from 5.78 nm to 3.67 nm while maintaining the pore body at 5.78 nm. The effect of four pore modification factors-the ratio of acetylene/nitrogen, the feeding time of carbon precursor, the ratio of SBA-C/Cu(acac)₂ and the cycles of MOCVD on the final pore structure of the SBA-15/carbon/copper composite is studied. The morphology and microstructure of the resulting product SBA-C-Cu are characterized by XRD patterns, TEM images and EDS analysis. The XRD and TEM reveal that the SBA-C-Cu composite is highly hexagonally ordered and has similar particle morphology as the original SBA-15.     

半经验分子轨道方法计算吸附分子几何构型的可靠性

运用半经验分子轨道AM1方法计算了金刚石（111）面上乙炔吸附分子的几何构型，通过与相似结构的丙烯分子实验参数的比较，分析论证了半经验分子轨道方法用于碳氢化合物吸附分子几何构型计算的可靠性．     

胞核嘧啶氢键二聚体的电子拓扑性质研究

采用GAUSSIAN程序包,在B3LYP/6-311++G**水平下,对胞核嘧啶及其7种氢键二聚体进行了结构优化和能量分析.使用AIM2000程序,在分子中的原子理论框架下对这些体系进行了详尽的电子拓扑性质的理论研究.从理论的角度证明了这些氢键的存在并探讨了其性质,比较了各种不同类型的氢键及二聚体的稳定性,为实验研究提供了一定的理论参考数据.     

Li原子修饰缺陷蓝磷单层储氢性能的第一性原理研究

本文基于第一性原理计算,系统地研究了碱金属Li原子修饰缺陷蓝磷单层体系的储氢性能. 研究结果表明,双空位缺陷DV2的引入可以有效增强Li原子与蓝磷单层间的相互作用,能够有效阻止单层表面Li团簇的形成. 单个Li原子可以稳定吸附3个H2分子,H2分子平均吸附能为0.248 eV/H2. 电子结构分析表明,H2分子主要通过极化机制和轨道杂化作用吸附在Li修饰的缺陷蓝磷单层体系上. 此外,本文还研究了温度和压强对Li/DV2体系储氢性能的影响. 结果表明,在室温和低压条件下,H2分子可以稳定吸附在Li/DV2体系表面,从而实现室温条件下的可逆储氢.     

三个磷酰化香豆素的合成及单晶结构

以二烷基亚磷酸酯和香豆素为原料,通过Atherton-Todd反应合成了3个新型含有磷酰基的香豆素类化合物,7-磷酰二乙基香豆素(2a)、4-甲基-7-乙酰氧基-6-磷酰二乙基香豆素(2b1)和7-羟基-4-甲基-6-磷酰二异丙基香豆素(2b2).单晶结构显示:化合物2a、2b1均为三斜晶系,P-1空间群,分子间有弱的π-π堆积,分子间主要靠范德华力紧密结合在一起.化合物2b2为单斜晶系,空间群为P2(1)/n,P=O的O原子和羟基氢原子之间存在分子间氢键,每一个分子分别与另外两个分子相连形成链状结构,由堆积图可以看到分子间有弱的π-π堆积,分子间主要靠范德华力紧密结合在一起.     

基于密度泛函理论的KDP(100)表面吸附水分子研究

基于密度泛函理论中的第一性原理计算方式,开展KDP(100)面表面吸附水分子的性质研究。结合Bader电荷、电子密度、差分电子密度和电子局域函数等参数进行电子密度拓扑分析,结果显示水分子在KDP(100)表面的最佳吸附位点为氢钾桥位,吸附能为–0.809eV,表明KDP(100)表面可以自发地吸附水分子;水分子中的氧原子通过吸附,与KDP(100)表面磷酸根基团上的氢原子形成含共价效应的强氢键O—H...O_w,拟合键能为–18.88 kcal/mol。     

氯化锌活化大麻布活性炭纤维的孔结构

以大麻布为原料,氯化锌为活化剂,在不同活化温度下制备大麻布活性炭纤维样品。采用低温氮气吸附和密度函数理论(DFT)等对样品的孔结构和表面能量分布等表面织构特征进行了研究。结果表明,样品BET比表面积随活化温度的升高呈现先增大后减小的变化趋势,800℃时达到最大值915 m2/g;样品是典型的微孔材料,孔分布集中于2 nm以下的微孔范围内,只有极少部分的中孔,基本没有大孔;样品的表面能量分布较宽,为不均匀性表面;随活化温度的升高,样品碘吸附量呈先增大后减小的变化趋势,与微孔孔容、总孔容以及由BET比表面积的变化趋势一致。     

SiLi5+团簇的结构及储氢性能理论研究

SiLi_5~+团簇由于具有高稳定特性,并且SiLi_5~+可以最多有效绑定15个氢分子,其理论质量储氢密度达到了32.3 wt%.在B3LYP理论水平上,氢分子与SiLi_5~+相互作用过程中的平均氢吸附能在1.36～2.62 kcal·mol~(-1)之间,从平均氢吸附能看,此系统满足可逆吸氢反应的热力学要求,可以作为理想储氢材料的候选物.