Sn_(1-x)Sb_xO_2固溶体电极的形成能与电子结构

为研究Sb掺杂对Ti/snO_2电极稳定性与导电性的影响,采用基于密度泛函理论的平面波赝势方法对金红石型SnO_2及不同比例Sb掺杂SnO_2体系进行了第一性原理计算,用广义梯度近似方法优化了Sn_(1-x)Sb_xO_2固溶体电极的晶体结构,计算了掺杂前后体系的电子结构以及不同掺杂比例时的形成能.结果表明:Sb替代Sn后,晶格常数与晶胞体积均增加,但掺杂形成能随掺杂量变化不大,在掺杂量为0.083时掺杂形成能达到最低值5.08 eV,稳定性最好.掺杂Sb后,在费米能级至最低导带处存在Sb 5s电子态分布,产生施主能级;同时Sb掺杂后,在导带底形成的可填充电子数也从未掺杂的4增加到了掺杂后的19,导电性明显增强,且在掺杂量为0.063时导电性最强.本文的计算结果为钛基Sn_(1-x)Sb_xO_2氧化物电极的开发与应用提供了理论依据.     

稀土掺杂PbO2电极的制备及催化性能研究

以SnCl4.5H2O,Sb2O3,La（NO3）3（或Nd（NO3））为前驱体（摩尔比分别为Sn∶Sb∶La（Nd）=100∶6∶（0.5,1,2）,制备稀土（La,Nd）掺杂Sn,Sb溶胶,以钛电极为基体,用溶胶-凝胶法制备稀土（La,Nd）掺杂SnO2中间层,热处理温度为450和500℃,热处理时间共5 h;采用电沉积法制备PbO2表面层,得到改性PbO2阳极,优化了制备改性PbO2电极的稀土掺杂量。以含油污水为目标有机物,借助于CODCr去除情况分析电极的电催化氧化能力;分析了电极结构与电催化特性之间的关系。采用SEM和XRD分析了制备电极的表面形貌、晶体结构并通过电化学工作站对其析氧电位进行了表征分析。结果表明,中间层掺杂La元素的电极,掺杂比为Sn∶Sb∶La=100∶6∶1时电极性能最好;而中间层掺杂Nd元素,掺杂比为Sn∶Sb∶Nd=100∶6∶2时电极的性能最好,此比例时电极对目标有机物CODCr去除率分别为91.90%和90.93%。     

Ti掺杂SnO2 半导体固溶体的第一性原理研究

Ti掺杂SnO2固溶体是钛基氧化物耐酸阳极的重要组成部分. 采用基于密度泛函理论的第一性原理对Sn1-xTixO2(x=0, 1/12, 1/8, 1/6, 1/4, 1/2, 3/4, 5/6)固溶体的电子结构进行计算, 分析了能带结构、 电子态密度和电荷密度以及晶格参数的变化. 结果表明, Ti掺入SnO2晶格后, 其晶格参数随组分增加近似呈直线降低, Ti-O键的共价性强于Sn-O键. 掺杂后带隙仍为直接带隙, 且随着掺杂比例的增加, 带隙逐渐减小. 当掺杂比例x=0.5时, 形成能达到最低值(-6.11 eV), 固溶体最稳定. 本文的计算结果为钛基氧化物电极材料的研究与开发提供了一定的理论依据.     

Ru掺杂LiFePO4电子结构和性能的第一性原理研究

基于第一性原理和超软赝势平面波方法,对Ru掺杂LiFePO_4的原子几何结构和电子结构进行了研究。结果表明Ru掺杂后LiFePO_4晶胞参数a和b显著降低,晶胞参数c略微的增大,掺杂后晶胞体积收缩;当掺杂量为0.01时体系Fermi能最高,能量密度高。掺杂体系在Fermi能级附近态密度电子峰强度增大,态密度峰向低能方向移动,掺杂后能级减小,有利于LiFePO_4导电性能增强。能带计算结果显示,随着掺杂量的增加,体系带隙降低,能带下降,导带底向费米面移动,电子从价带跃迁到导带更加容易。电化学性能测试结果显示,当Ru的掺杂量较小时(0.01),费米面附近能带数增加,有利于电子传递,材料表现出最佳的放电比容量和倍率性。当掺杂量较大时(0.05,0.1),过多Ru将阻碍Li~+扩散通道,不利于电极材料的倍率性能。Ru掺杂能影响LiFePO_4电子结构,改善LiFePO_4性能,掺杂量不宜太大。     

PMC敏化SnO2纳米结构多孔膜电极的光电化学特性

研究了五甲川菁(PMC)敏化SnO2纳米结构电极的光电化学行为.结合循环伏安曲线及五甲川菁的光吸收阈值,初步确定了五甲川菁染料电子基态和激发态能级.结果表明,五甲川菁染料电子激发态能级能与SnO2纳米粒子导带边位置相匹配,因而使用该染料敏化可以显著地提高SnO2纳米结构电极的光电流,使SnO2纳米结构电极吸收波长红移至可见光区和近红外区,光电转换效率(IPCE)得到明显改善,其值最高可达45.7%.     

PMC敏化SnO2纳米结构多孔膜电极的光电化学特性

研究了五甲川菁（PMC）敏化SnO2纳米结构电极的光电化学行为．结合循环伏安曲线及五甲川菁的光吸收阈值,初步确定了五甲川菁染料电子基态和激发态能级．结果表明,五甲川菁染料电子激发态能级能与SnO2纳米粒子导带边位置相匹配,因而使用该染料敏化可以显著地提高SnO2纳米结构电极的光电流,使SnO2纳米结构电极吸收波长红移至可见光区和近红外区,光电转换效率（IPCE）得到明显改善,其值最高可达45．7％．     

钕改性钛基SnO2/Sb电催化电极的制备及表征

为改善钛基SnO2／Sb电极的电催化性能,采用浸渍法制备了Nd改性钛基SnO2／Sb电极。以活性艳红X-3B为目标有机物,考察电极的电催化性能,对制备温度和Nd掺杂量进行了研究,确定了适宜的制备条件为：热处理温度550℃,Nd掺杂量1.0％。采用SEN,EDS,XRD及XPS等分析方法对所制备电极的表面形貌、元素组成及结构进行分析,发现掺杂Nd可使SnO2粒径变小,有利于电极电催化性能的改善,同时Nd元素的引入可使杂质元素sb,Nd在电极表面涂层富集。Nd改性钛基SnO2／Sb电极表面主要是四方相金红石结构的SnO2晶体,掺杂的sb和Nd分别以Sb^5＋和Nd^3＋的形式存在。电极动电位扫描测试结果表明,Nd改性钛基SnO2／Sb电极具有较高的阳极析氧电位,有利于有机物的阳极氧化降解。     

Dy改性SnO2 / Sb电催化电极的制备及表征

为改进钛基SnO2／Sb电极的电催化性能，采用高温热氧化法制备了稀土Dy改性钛基SnO2／Sb电极。以苯酚为目标有机物，考察了所制备电极的电催化活性，并采用SEM、EDS、XRD等分析方法表征了电极的形貌、组成及结构。对制备温度和Dy添加量进行了详细的实验研究，确定了适宜的制备条件为热处理温度650℃、Dy添加量1％左右。研究表明，结晶良好的掺杂SnO2晶粒有助于苯酚的快速彻底分解。Dy掺杂后，半径较大的Dy^3 可能取代半径较小的Sn^4 ，导致SnO2晶胞膨胀。引入Dy可提高SnO2晶粒的形核与长大速率之比，使SnO2的平均粒径变小，有利于电极催化性能的改善。但同时Dy掺杂使杂质原子Sb、Dy在电极表层富集，高含量的Dy会降低电极的性能。     

Sno2+Sb203中间层的制备条件对Ti/SnO2+Sb2O3/PbO2阳极性能的影响

研究了聚合前驱体制备的SnO2+Sb2O3中间层的焙烧温度、锑含量对Ti/SnO2+Sb2O3/PbO2阳极性能的影响. 用XRD、ESEM和探针法对锡锑中进行了表征,应用阳极寿命快速检测法测定了Ti/SnO2+Sb2O3/PbO2电极在1.0 mol/L H2SO4溶液中的寿命,并用极化曲线和电荷容量表征了锡锑中间层对钛基PbO2阳极性能的影响. 实验结果表明,聚合前驱体制备中间层的焙烧温度和锑含量对Ti/SnO2+Sb2O3/PbO2电极的寿命和性能有显著的影响. 在锡锑中间层的制备温度为500 ℃、n(Sn):n(Sb)=9:1时,制得的Ti/SnO2+Sb2O3/PbO2电极用阳极寿命快速检测法测得的电极寿命达30h,具有良好的稳定性.     

过渡金属掺杂SnO2的电子结构与磁性

采用密度泛函理论及赝势平面波方法, 对未掺杂SnO2以及过渡金属V、Cr、Mn掺杂SnO2的超原胞体系进行了几何优化, 计算了晶格常数、电子结构与磁学性质. 结果表明, 6.25%与12.5%两种掺杂浓度时, 体系的电子自旋和磁学性质没有发生很大的变化; 相对于未掺杂SnO2, 过渡金属掺杂后SnO2中O原子有向过渡金属移动的趋势, 并使得O与掺杂金属之间键长变短; 在V和Cr掺杂后, SnO2具有半金属性质, 而Mn掺杂SnO2没有发现上述性质. 6.25%与12.5%的杂质浓度对自旋和磁矩影响不大, 掺杂产生的磁矩主要来自于过渡金属3d电子态, 且磁矩的大小与过渡金属的电子排布有关. V、Cr、Mn掺杂SnO2后的总磁矩分别为0.94μB、2.02μB、3.00μB. 磁矩主要来源于过渡金属3d轨道的自旋极化, 当O原子出现负磁矩的时候, 还有很小一部分磁矩来源于临近过渡金属的Sn原子.     

Probing the electronic structures of ternary perovskite and pyrochlore oxides containing Sn(4+) or Sb(5+)

Experimental and computational studies were performed to understand the electronic structure of ternary perovskites (ASnO(3), A = Ca, Sr, Ba, Cd), pyrochlores (RE(2)Sn(2)O(7), RE = Y, La, Lu; Cd(2)Sb(2)O(7)), and defect pyrochlore oxides (Ag(2)Sb(2)O(6)) containing the main group ions Sn(4+) and Sb(5+). In all compounds, the lowest energy states in the conduction band arise primarily from the antibonding Sn/Sb 5s-O 2p interaction. In the alkaline-earth stannate perovskites (BaSnO(3), SrSnO(3), and CaSnO(3)) the conduction bandwidth decreases strongly in response to the octahedral tilting distortion triggered by the decreasing size of the alkaline-earth cation. This in turn leads to a corresponding increase in the band gap from 3.1 eV in BaSnO(3) to 4.4 eV in CaSnO(3). The band gap of CdSnO(3) is relatively small (3.0 eV) considering the large octahedral tilting distortion. The origin of this apparent anomaly is the mixing between the empty Cd 5s orbitals and the antibonding Sn 5s-O 2p states. This mixing leads to a widening of the conduction band and a corresponding decrease in the band gap. The participation of the normally inert A-site cation in the electronic structure near the Fermi level can be considered an inductive effect, as it utilizes substitution on the A-site to directly modify the electronic structure of the SnO(3)(2)(-) framework. While the pyrochlore structure is more complicated, the energy level and width of the lowest energy conduction band can be analyzed in a manner similar to that utilized on the perovskite structure. The Sn-O-Sn and Sb-O-Sb bonds are highly distorted from linear geometry in pyrochlore, leading to a relatively narrow conduction band and a wide band gap. In Cd(2)Sb(2)O(7) and Ag(2)Sb(2)O(6) the Cd(2+) and Ag(+) ions exhibit a strong inductive effect that widens the conduction band and lowers the band gap significantly, very similar to the effect observed in the perovskite form of CdSnO(3).     

Structure of hydrated tin dioxide doped with Sb(III) ions

The effect of antimony doping of tin dioxide at Sb/Sn = 0.2–2.5 on the physical properties and structure of air-dry samples of hydrous tin dioxide, SnO₂ ? nH₂O (HTD), was studied by IR and Raman spectroscopy, powder X-ray diffraction, impedance measurements, TGA, and electron microscopy. The doped materials retained the structure of undoped HTD materials if the Sb/Sn ratio did not exceed the threshold value of 1.0. When Sb/Sn > 1, crystalline antimony oxide admixture appeared. The data of IR spectroscopy attested to the presence of two types of water in HTD-Sb, namely, physisorbed and chemisorbed water. The major part of water of the former type can be removed by evacuation at room temperature. Chemisorption occurs upon coordination of water molecules by metal ions through the formation of metal–oxygen bonds. Water molecules of the latter type are retained in evacuated samples at room temperature and on heating above the boiling point of liquid water. By impedance spectroscopy, HTD-Sb samples were shown to possess fairly high proton conductivity at high humidity; however, the conductivity decreased by two orders of magnitude after partial removal of water molecules of the former type. This attests to the destruction of the loosely bound hydrogen bond network, across which proton transfer takes place. It was also found that under conditions of constant humidity, the proton conductivity successively decreases with increasing antimony concentration. This is attributable to the fact that Sb(III) ions polarize the local environment to a lesser extent than Sn(IV) ions.     

Structural characterizations and electronic properties of Ti-doped SnO2(110) surface: a first-principles study

The Ti-doped SnO2(110) surface has been investigated by using first-principles method with a slab model. The geometrical optimizations and band-structure calculations have been performed for four possible doping models. Our results indicate that the substitution of Ti for sixfold-coordinated Sn atom at the top layer is most energetically favorable. Compared to the undoped surface, those Sn and O atoms located above Ti atom tend to move toward the bulk side. Besides the surface relaxations, the doping of Ti has significant influences on the electronic structures of SnO2(110) surface, including the value and position of minimum band gap, the components of valence and conduction bands, the distributions of the charge densities, and the work function of the surface. Furthermore, the effects introduced by the substitution of Ti atom observed in the experiments can be well explained when the sixfold-coordinated Sn atom at the first layer is replaced by Ti atom.     

(Sn,Sb)O2-x基纳米结构厚膜材料气敏特性及机理

对采用水热合成技术所形成的纳米(Sn,Sb)O2 x晶粒结构、厚膜材料的气敏特性及其机理进行了研究,并采用XRD、TEM手段对纳米尺度的（Sn、Sb)O2 x晶粒的结构与表面效应及晶粒形态进行了表征.结果表明,当掺杂Sb5＋的浓度（摩尔分数xSb5＋)为（2.9～5.8)×10－6时,（Sn、Sb)O2 x纳米晶粒表面的电子缺陷浓度增大,增强了对气体的吸附能力,从而提高了对可燃性气体的灵敏度.同时可使晶粒保持短柱状的形态特征,对其灵敏度有一定的控制作用.     

Cu^2+离子掺杂SnO2固溶体催化剂的晶格容量效应:NH3选择性还原NOx反应性能提高的本质原因

NOx排放给人类健康和环境带来了严重的危害,目前已发展了多种消除其污染的方法.其中氨选择性催化还原(NH3-SCR)技术是固定源和移动源柴油机排放NOx的有效消除方法之一.非贵金属氧化物催化剂由于廉价、且原料来源丰富,用于NH3-SCR反应在过去几十年一直备受人们关注.由于晶格畸变和不等价取代等原因,与单组分氧化物催化剂相比,替代型金属氧化物固溶体催化剂通常具有更优异的物理化学性能.其中典型的例子是已被广泛用作汽车尾气净化转化器储氧材料的铈锆固溶体.与纯CeO2相比, Zr^4+离子溶入立方萤石CeO2晶格形成固溶体结构后,显著提高了其稳定性和储氧能力.近八年来,我们以四方金红石型SnO2为溶剂,系统地研究了系列金属阳离子在其晶格中的溶解行为,并考察了其催化反应性能.为深入理解固溶体催化剂的结构与反应性能之间的关系,我们首次创建了简单易行的XRD外推法定量金属氧化物固溶体中溶质阳离子的晶格容量.结果表明,其它离子掺杂形成SnO2基固溶体可显著增加其表面缺位氧和Lewis酸性位点的数量,且可使缺位氧在较高温度下保持稳定,显著提高了所得催化剂的反应性能.另外我们还发现,当溶质离子含量为晶格容量时可得到最大量的纯相固溶体,此时催化剂通常具有最优的性能,具有明显的阈值效应.很多研究表明,含CuO的一些催化材料通常对NOx选择还原具有良好的低温活性和选择性,但把Cu^2+离子溶入SnO2晶格构建固溶体催化剂用于NH3-SCR反应迄今未见报道.因此,为获得性能优良的催化剂,本文采用共沉淀法制备了系列不同Cu^2+离子含量的Sn-Cu复合氧化物固溶体催化剂,并采用XRD外推法测定了Cu^2+离子在SnO2中的晶格容量,为0.10 g CuO/gSnO2,相当于Sn/Cu摩尔比为84/16.Raman结果表明, Cu^2+离子含量低于晶格容量时,随其含量增加,表面氧缺位数量增加,且在晶格容量时达到最大.H2-TPR, O2-TPD和NH3-TPD结果表明,随着Cu^2+离子含量增加,催化剂表面活性氧物种和表面酸中心的数量均增加;在Cu^2+离子含量接近晶格容量时,催化剂中形成最大量的纯固溶体相,上述活性中心均可达到最大量.此时,催化剂具有最佳的NH3-SCR反应性能.因此, Cu^2+离子溶入SnO2晶格形成固溶体催化剂,在结构和反应性能上均具有明显的晶格容量阈值效应.通过将Cu^2+离子含量调控在晶格容量,可获得反应性能最好的Sn-Cu复合氧化物固溶体催化剂.     

Importance of cations in the properties of Zintl phases: the electronic structure of and bonding in metallic Na6TlSb41

The novel metallic compound Na(6)TlSb(4) consists of four-membered TlSb(3) rings joined by pairs of Sb atoms into Tl(2)Sb(8) units, the last of which is further interconnected into 1D anionic chains via Tl-Tl bonds. The contrast of its metallic conductivity with that of the 2 - e(-) poorer, electron precise, and semiconducting Zintl phase K(6)Tl(2)Sb(3), which has virtually the same anionic network, has been investigated by ab initio LMTO-DFT methods. Sodium ion participation is found to be appreciable in the (largely) Sb p valence band and especially significant in an additional low-lying conduction band generated by antimony ppi and sodium orbitals. The one pyramidal 3-bonded Sb atom appears to be largely responsible for the interchain conduction process. The substitution of one Tl by Sb, which occurs when the countercation is changed from potassium in K(6)Tl(2)Sb(3) to sodium, yielding only Na(6)TlSb(4), is driven by a distinctly tighter packing, a corresponding increase in the Madelung energy, and binding of the excess pair of electrons in the new conduction band.     

Cr、Sn、Co掺杂对层状二维材料MoSi2N4的电子和光学性能的影响(英文)

基于新合成的二维材料MoSi₂N₄(MSN),我们建立了一系列MSN的掺杂模型进行了第一原理计算。首先,我们计算了本征MSN的电子特性,包括其能带结构和态密度。然后我们研究了Cr、Sn和Co掺杂对MSN的电子和光学性质的影响。结果表明,在3种掺杂体系中,Co掺杂体系表现出最低的形成能,这表明Co掺杂体系是最稳定的。通过带隙计算表明,尽管3种掺杂模型都降低了MSN的固有带隙,但却表现出3种不同的电子特性。态密度图也显示,Cr和Co掺杂体系都在导带底(CBM)和价带顶(VBM)附近产生局部尖峰。此外,光学性质的计算中表明,掺杂后体系的光学性质也得到了改善。     

Magnetic and electronic properties of CaCu3Cr4O12 and CaCu3Cr2Sb2O12 by first-principles density functional calculation

The electronic and magnetic properties of CaCu3Cr4O12 and CaCu3Cr2Sb2O12 are investigated by the use of the full-potential linearized augumented plane wave (FPLAPW) method. The calculated results indicate that CaCu3Cr4O12 is a ferrimagnetic and half-metallic compound, in good agreement with previous theoretical studies. CaCu3Cr2Sb2O12 is a ferrimagnetic semiconductor with a small gap of 0.136 eV. In both compounds, because Cr4+ 3d (d2) and Cr3+ 3d (d3) orbitals are less than half filled, the coupling between Cr-Cu is antiferromagnetic, whereas that between Cu-Cu and Cr-Cr is ferromagnetic. The total net spin moment is 5.0 and 3.0 microB for CaCu3Cr4O12 and CaCu3Cr2Sb2O12, respectively. In CaCu3Cr4O12, the 3d electrons of Cr4+ are delocalized, which strengthens the Cr-Cr ferromagnetic coupling. For CaCu3Cr2Sb2O12, the doping of nonmagnetic ion Sb5+ reduces the Cr-Cr ferromagnetic coupling, and the half-filled Cr3+ t2g (t2g3) makes the chromium 3d electrons localized. In addition, the ordering arrangement of the octahedral chromium and antimony ions also prevents the delocalization of electrons. Hence, CaCu3Cr2Sb2O12 shows insulating behavior, in agreement with the experimental observation.