Au在Zr掺杂的CeO2(110)面吸附的第一性原理研究

采用基于广义梯度近似的投影缀加平面波(projector augmented wave)雁势和具有三维周期性边界条件的超晶胞模型,用第一性原理方法,计算并分析了Au在CeO2(110)和Zr掺杂的CeO2(110) 面的吸附能,吸附结构和电子结构等特征.从而得出Zr掺杂对Au/ CeO2(110)吸附体系的影响.结果表明:Zr的掺杂增大了Au在CeO2(110) 面的吸附能,并改变了最强吸附位置,且导致了吸附体系中衬底结构较大的变化;Zr的掺杂使吸附体系引入了更为复杂的间隙态,使得Zr掺杂的吸附体系有更好的催化活性;Zr的掺杂使吸附原子Au的氧化程度加强,由无掺杂吸附体系中Au得到电子变为Zr掺杂吸附体系中的Au失去电子.以上结果有助于人们更清楚地了解三元催化剂中Zr掺杂的影响以及贵金属Au与CeO2-ZrO2混合氧化物的协同作用机理.     

Au(110)表面结构和氧原子吸附的第一性原理研究

用密度泛函理论(DFT)研究了金属Au(110)表面结构以及氧原子的吸附状态.计算得到Au(110)-(1×2)缺列再构表面原子的弛豫分别是-15.0%(Δd₁₂/d₀)和-1.1%(Δd₂₃/d₀),表面能为52.7 meV/²,功函数Φ=5.00 eV;Au(110)-(1×3)缺列再构表面的Δd_{1 关键词： 缺列再构Au(110)表面 STM图像 氧原子吸附}     

Cu/CeO2(110)界面特性的第一性原理研究

Cu-CeO₂体系因其特殊的催化能力而在固体氧化物燃料电池和水煤气转化反应等多个催化领域有重要应用. 采用基于密度泛函理论的第一性原理方法, 在原子和电子层面上系统地研究了单个Cu原子及Cu小团簇在CeO₂(110)面上的吸附构型, 价键特性和电子结构, 结果表明: 1) 单个Cu原子的最稳定吸附位是两个表面O的桥位; 2) Cu团簇的稳定吸附构型为扭曲的四面体结构; 3) Cu原子及Cu团簇的吸附在CeO₂(110)面的gap区域引入了间隙态, 这些间隙态主要来自于Cu及其近邻的O和表层还原形成的Ce³⁺, 间隙态的出现表明Cu的吸附增强了CeO₂(110)表面的活性; 4) 吸附的单个Cu原子及Cu团簇分别被CeO₂(110)面表层的Ce⁴⁺离子氧化形成了Cu^δ+和Cu₄^δ+, 并伴随着Ce³⁺离子的形成, 这个反应可归结为Cu_x/Ce⁴⁺→Cu_x^δ+/Ce³⁺; 5) Cu团簇的吸附比Cu单原子的吸附引入了更多的Ce³⁺离子, 进而形成了更多的Cu^δ+-Ce³⁺催化活性中心. 结合已报道的Cu/CeO₂(111)界面特性, 更加全面地探明了Cu与CeO₂(111)和(110)两个较稳定低指数表面的协同作用特性, 较为系统地揭示了Cu增强CeO₂催化特性的原因及Cu与CeO₂协同作用的内在机理. 关键词： 2')" href="#">Cu/CeO₂ U')" href="#">DFT+U 吸附 电子结构     

H2 分子在Li3N(110)表面吸附的第一性原理研究

采用第一性原理方法研究了H₂分子在Li₃N(110)晶面的表面吸附. 通过研究H₂/Li₃N(110)体系的吸附位置、吸附能和电子结构发现: H₂分子吸附在N桥位要比吸附在其他位置稳定,此时在Li₃N(110)面形成两个-NH基,其吸附能为1.909 eV,属于强化学吸附;H₂与Li₃N(110)面的相互作用主要是H 1s轨道与N 关键词： 第一性原理 3N(110)')" href="#">Li₃N(110) 2')" href="#">H₂ 吸附和解离     

蓝宝石衬底上Gd2O3掺杂CeO2氧离子导体电解质薄膜的生长及电学性能

采用反应磁控溅射方法,在(0001)蓝宝石单晶衬底上,制备了纳米多晶Gd₂O₃掺杂CeO₂(GDC)氧离子导体电解质薄膜,采用X射线衍射仪(XRD)、原子力显微镜(AFM)对薄膜物相、结构、粗糙度、表面形貌等生长特性进行了表征,利用交流阻抗谱仪测试了GDC薄膜不同温度下的电学性能;实验结果表明,GDC薄膜为面心立方结构,在所研究的衬底温度范围内,均呈强(111)织构生长;薄膜表面形貌随衬底温度发生阶段性变化：衬底温度由室温升高到300℃时, 关键词： 2O₃掺杂CeO₂电解质薄膜')" href="#">Gd₂O₃掺杂CeO₂电解质薄膜 反应磁控溅射 生长特性 电学性能     

N/Fe共掺杂锐钛矿TiO2(101)面协同作用的第一性原理研究

基于周期性密度泛函理论研究了N/Fe共掺杂对锐钛矿TiO₂(101)面的修饰作用. 计算了铁替位单掺杂TiO₂(101)面及晶体内部后, 晶体结构变化及形成能. 通过形成能的比较发现, Fe从晶体表面向体内迁移时受到势垒阻碍作用. 同时, 对不同位置表面N/Fe近邻共掺杂晶体形成能的比较, 得出了表面共掺杂的最稳定结构. 通过对电子结构及态密度的分析发现: 表面共掺杂态中, N/Fe共掺杂可改变TiO₂(101)面的电子结构, 并使TiO₂由半导体性向半金属性转变. 关键词： 2(101)面')" href="#">锐钛矿TiO₂(101)面 N/Fe共掺杂 第一性原理 半金属性     

Ti原子在Al(110)表面吸氢过程中催化作用的第一性原理研究

运用第一性原理方法对H₂分子在Ti掺杂和纯的Al(110)表面的吸附情况进行了研究,发现有Ti原子掺杂时,存在一个H₂分子的吸附路径,即位于Al(110)面顶位Ti原子上方的H₂分子会发生解离,并与Ti原子形成TiH₂分子,然后TiH₂分子向能量更低的空位移动并接近Al(110)表面.态密度与电荷布居分析显示,吸附完成后H原子与表面Al原子存在较强的共价键作用,这为Al-H类物质及Na_{3 关键词： 钛 吸附 解离能 第一性原理}     

纳米CeO2-xNx固溶体的光谱特征对其催化性能影响研究

二氧化铈(CeO₂)具有储量丰富，价格低廉，催化性能优异等特性而得到广泛应用。通过在其晶格中掺杂其他离子制得CeO₂固溶体，可以进一步调控CeO₂的晶格大小，增加晶格缺陷浓度，从而有效提高催化性能。目前研究较多的掺杂离子多为金属阳离子，而对非金属阴离子掺杂的研究尚有待深入探索。本文以CO(NH₂)₂为N源，采用水热法合成不同N掺杂浓度的纳米CeO_2-xN_x固溶体(x=0.00，0.05，0.10，0.15，0.20)，系统对固溶体的微观结构及光谱特征进行表征。X射线衍射(XRD)结果表明，所有掺杂浓度的CeO_2-xN_x固溶体均呈萤石立方单相结构。与纯CeO₂相比，N含量为0.05时样品的晶胞参数显著增大，而随掺杂浓度的进一步增加，晶胞参数又呈现出逐渐减小的趋势。拉曼(Raman)测试表明，N掺杂样品的F_2g振动模式峰向高波数移动，其原因是由于当N3-取代部分O2-后，Ce4+周围出现Ce—N键，Ce—N键长因静电引力变强而缩短，从而引起峰位的移动。通过紫外可见吸收光谱(UV-Vis)分析掺杂所引起样品电子跃迁状态的改变，发现N元素的掺杂使CeO₂在可见光区域具有了吸光性能，CeO_2-xN_x固溶体的能隙明显减小，这是由于N(2p)与O(2p)的电子轨道发生交互作用而形成中间能级，使得电子跃迁所需能量降低，从而引起能隙的红移。荧光光谱(PL)测试表明，发射峰强度随N掺杂浓度的增大而增大，其原因一方面是由于N掺杂会引起晶格缺陷及氧空位比例的提升，发生带间跃迁的几率变大，进而提高发射峰的相对强度；另一方面，N的掺杂在价带O(2p)与导带Ce(4f)间形成中间能带，同样会导致发射峰变强。为表征纳米固溶体的催化特性，分别选取N掺杂量最小的CeO_1.95N_0.05与N掺杂量最高的CeO_1.80N_0.20以及纯CeO₂作为典型催化剂，采用球磨法制备Mg₂Ni/Ni/CeO_2-xN_x复合材料，系统分析了复合材料电极的储氢动力学性能。交流阻抗(EIS)测试发现，催化剂可以有效提高储氢合金的表面电荷转移活性，N掺杂量越高，CeO₂基固溶体的催化活性越强；动电位极化曲线测试表明，掺杂催化剂也能显著提高H原子在合金内部的扩散速率，且CeO_1.95N_0.05较CeO_1.80N_0.20具有更好的催化活性。催化机理主要从催化剂的微观结构及光谱特征进行分析，如前所述，随着N含量的提高，CeO₂固溶体晶格中的氧空位比例增大，晶格畸变程度提高，N的掺杂还使固溶体的电子跃迁能隙降低，从而有利于电子在合金表面的迁移；同时，纳米材料的晶粒尺寸越小，表明晶粒表面缺陷比例越大，说明催化剂的活性增强，因此表现为N掺杂浓度越高，复合材料电极交流阻抗弧半径的越小，即CeO_1.80N_0.20可以更加有效提高复合材料的表面活性；另一方面，若催化剂的晶胞体积增大，可使H原子在穿过材料表面的传输过程中具有更大的空间，由于CeO_1.95N_0.05的晶胞参数大于CeO_1.80N_0.20催化剂，故H原子通过催化剂进入合金内部的传输更加容易。H原子在合金内部的扩散速率与催化剂的晶胞参数或晶胞体积的大小密切相关。     

密度泛函理论研究Run和RunAu(n=1-12)团簇的结构和电子性质

采用密度泛函理论中的广义梯度近似(GGA) 对 Ru_n Au和Ru_n 团簇的几何构型进行优化,并对能量、频率、电子性质和磁性质进行了计算. 结果表明,Ru_n Au团簇的最低能量结构可以通过Au原子代替Ru_n+1团簇中的Ru原子生长而成.除了局域的结构畸变,Ru_n Au和Ru_n+1团簇具有相似的几何结构.二阶能量差分、电离势、亲和势和分裂能表明Ru₅, Ru₈, Ru₅Au, Ru₈Au 是稳定的团簇,Au的掺杂没有改变Ru_n 的相对稳定性.通过电子性质的分析发现,当Au原子掺杂在Ru_n 中,团簇的化学活性增加,且团簇的能隙主要由电子的配对效应决定;对于大多数团簇来说,Au原子掺杂提高了Ru_n Au的磁矩. 关键词： n Au和Ru_n 团簇')" href="#">Ru_n Au和Ru_n 团簇 几何结构 电子性质     

SrTiO3(001)表面上Au和N原子相互作用的第一性原理研究

采用基于密度泛函理论的第一性原理平面波赝势方法研究了SrTiO₃(001)表面上Au和N原子间相互作用的微观机理.通过比较分析N置换表面层O原子前后SrTiO₃(001)表面吸附Au原子体系的相关能量和电子结构,发现SrTiO₃(001)表面吸附Au原子和N替代表面层O原子的置换过程二者之间存在明显的"协同效应",即N原子置换SrTiO₃(001)表面层O原子的过程增强了相应表面吸附Au原子的稳定性,而SrTiO关键词： 表面结构 相互作用 第一性原理     

Pd与CeO2(111)面的相互作用的第一性原理研究

采用基于广义梯度近似的投影缀加平面波(projector augmented wave) 赝势和具有三维周期性边界条件的超晶胞模型，用第一性原理计算方法，计算并分析了Pd在CeO₂(111)面上不同覆盖度时的吸附能，价键结构和局域电子结构. 考虑了单层Pd和1/4单层Pd两种覆盖度吸附的情况. 结果表明：1)在单层吸附时，Pd的最佳吸附位置是O的顶位偏向Ce的桥位；在1/4单层吸附时，Pd最易在O的桥位偏向次层O的顶位吸附.2) 单层覆盖度吸附时，吸附原子Pd之间的作用较强；1/4单 关键词： 三元催化剂 Pd 2')" href="#">CeO₂ 吸附 密度泛函理论     

DFT calculations for Au adsorption onto a reduced TiO2 (110) surface with the coexistence of Cl

Residual chlorines, which originate from HAuCl₄, enhance the aggregation of gold (Au) nanoparticles and clusters, preventing the generation of highly active supported Au catalysts. However, the detailed mechanism of residual-chlorine-promoted aggregation of Au is unknown. Herein to investigate this mechanism, density functional theory (DFT) calculations of Au and Cl adsorption onto a reduced rutile TiO₂ (110) surface were performed using a generalised gradient approximation Perdew, Burke, and Ernzerhof formula (GGA–PBE) functional and plane-wave basis. Although both Au and Cl atoms prefer to mono-absorb onto oxygen defect sites, Cl atoms have a stronger absorption onto a reduced TiO₂ (110) surface, abbreviated as rTiO₂ (110) in the following, than Au atoms. Additionally, co-adsorption of a Cl atom and a Au atom or Au nanorod onto a rTiO₂ surface was investigated; Cl adsorption onto an oxygen defect site weakens the interaction between a Au atom or Au nanorod and rTiO₂ (110) surface. The calculation results suggest that the depletion of interaction between Au and rTiO₂ surface is due to strong interaction between Cl atoms at oxygen defect sites and neighbouring bridging oxygen (O^B) atoms.     

Multienzyme-Mimetic Activity of Gold/Cerium Oxide Nanozyme

Redox-active nanozymes offer low-cost controlled synthesis, high stability, and tunable catalytic properties over natural enzymes, which have attracted wide attention in the field of disease diagnosis and treatment. However, the improvement of catalytic activity remains an important challenge for nanozymes. Herein, the Au/CeO₂ nanozymes is developed to achieve enhanced multiple enzyme-mimetic activity. The Au/CeO₂ nanozymes at 5% doping possess best peroxidase-like activity with threefold higher catalytic rate than CeO₂. For catalase-mimic catalysis, the Au/CeO₂ nanozymes at 5% doping also exhibited a 1.5-fold enhanced reaction rate higher than pure CeO₂. The superoxide dismutase (SOD)-like capacity of Au/CeO₂ nanozymes is proportional to Au content. The Au/CeO₂ nanozymes at 10% doping show optimal SOD-like capacity of 60.2 U mg⁻¹. In vitro experiments validate the regulation ability of intracellular oxidative stress and inflammation. Au/CeO₂ nanozymes can reduce lipopolysaccharide- or H₂O₂-induced oxidative damage by scavenging excess ROS in nerve cell. Therefore, Au/CeO₂ can be used as a promising antioxidant in disease treatment, and the study offers general guidelines for achieving enhanced biocatalytic property through atomic doping.     

Characterization and catalytic performance of pure and Li2O-doped CuO/CeO2 catalysts

Pure and Li₂O-doped CuO/CeO₂ catalysts calcined at 500 °C were prepared by impregnation method. The catalysts are characterized by DTA, TG-DTG, XRD, IR, TEM, nitrogen adsorption at −196 °C and the catalytic decomposition of hydrogen peroxide at 30 °C.The effects of molar ratio, heat treatment time and the doping on the structural, surface and catalytic properties of nanocrystalline Cu/Ce-mixed oxides system have been studied. It was found that the catalytic activity of ceria-supported copper oxide catalysts increased by increasing both the heat treatment time and dopant content. However, the pure Cu/Ce-mixed oxide solids containing 10 wt.% CuO exhibited the best performance. The characterization results indicated that the higher surface area, the formation of solid solution between copper and cerium oxides, and the high dispersion of copper species on the ceria were responsible for the high catalytic activity of the CuO/CeO₂ catalysts.     

First-principles study of electrical structures and optical properties of Ag or Au doped MgF2 crystal

The geometric structure, electronic and optical properties of MgF₂ crystal mixed with Ag, Au are obtained by adopting the first-principles calculation of plane wave ultra-soft pseudo-potential technology based upon the density function theory (DFT). The calculation results show that the doping of Ag and Au diminishes of the MgF₂ system and the occurrence of half-metallic properties with a greater influence of Au than Ag. In addition, the refractive index and absorption coefficient of the MgF₂ system are enhanced because of the doping. The modulation action on the refractive index of MgF₂ indicates potential application of the forbidden bandwidth doping in optical devices.     

Examining the redox and formate mechanisms for water–gas shift reaction on Au/CeO2 using density functional theory

We perform DFT calculations to investigate the redox and formate mechanisms of water–gas-shift (WGS) reaction on Au/CeO₂ catalysts. In the redox mechanism, we analyze all the key elementary steps and find that the OH cleavage is the key step. Three possible pathways of OH cleavage are calculated: (1) OH_ad^″+*^′→H_ad^′+O_ad^″; (2) H_ad^′+OH_ad^″→H₂(g)+O_ad^″+*^′; and (3) OH_ad^″+OH_ad^″→2O_ad^″+H₂(g) (*′: the free adsorption sites on the oxides; ad′: adsorption on the metal; ad″: adsorption on the oxide, respectively). In the formate mechanism, we identify all the possible pathways for the formation and decomposition of surface formates in the WGS reaction. It is found that there is a shortcoming in the redox and formate mechanisms which is related to surface oxygen reproduction. Four possible pathways for producing surface oxygen are studied, and all the barriers of the four pathways are more than 1 eV. Our results suggest that the processes to reproduce surface oxygen in the reaction circle are not kinetically easy.     

基于约束非平衡溶剂化理论的对硝基苯胺π-π*光谱移动 (cited: 1)

采用共沉淀法制备不同组分类水滑石前驱体Co-M-Al和Co-M-Ce-Al (M=Zn, Ni, Cu)复合氧化物催化剂催化分解N₂O. 结果表明,Co-M-Al系列氧化物催化剂的催化活性Co-Ni-Al系列>Co-Zn-Al系列>Co-Cu-Al系列;CeO₂添加使得催化剂催化活性进一步提高,N₂O分解温度T₅₀和T₉₀均下降80 oC;继续负载碱金属K也使氧化物催化剂催化活性提高,N₂O分解温度T₅₀和T₉₀下降约50 oC.     

The surface properties and the activities in catalytic wet air oxidation over CeO2-TiO2 catalysts

No-noble metal CeO₂-TiO₂ catalysts prepared by sol-gel method were developed and examined for catalytic wet air oxidation (CWAO) of acetic acid. The structure of the catalysts was measured by BET, SEM, XRD, XPS and DTA-TG. We investigated the effect of the interactions of Ce and Ti on the structure of CeO₂-TiO₂ catalysts. The mechanisms of the relationships between the different content of Ti and the activity of CeO₂-TiO₂ catalysts were discussed. The results showed that the average crystal size of CeO₂ decreased and the surface areas increased; the low valence of Ce³⁺ increase, and the chemisorbed oxygen slightly decreased with the increase of Ti content on the surface of CeO₂-TiO₂ catalysts. The order of the activity in CWAO of acetic acid followed: Ce/Ti 1/1 > Ce/Ti 3/1 > Ce/Ti 1/3 > Ce/Ti 5/1 > CeO₂ > TiO₂ > no catalyst. In CWAO of acetic acid, the optimal atomic ratio of Ce and Ti was 1, and the highest COD removal was over 64% at 230 °C, 5 MPa and 180 min reaction time over Ce/Ti 1/1 catalyst. The excellent activity and stability of CeO₂-TiO₂ catalysts was observed in our study.     

Zr催化剂对NaAlH4和Na3AlH6可逆储氢性能的影响

采用基于密度泛函理论的平面波赝势方法,分别计算纯净的以及掺杂Zr的NaAlH₄和Na₃AlH₆的晶格结构常数、能量、电子局域函数和电子态密度.结果表明：NaAlH₄和Na₃AlH₆分别是带隙为46和31 eV的绝缘体;NaAlH₄和Na₃AlH₆中Al—H键是共价键,Na—H键是离子键;Zr原子替代Na原子 关键词： 储氢 4')" href="#">NaAlH₄ 3AlH₆')" href="#">Na₃AlH₆ Zr掺杂     

Density functional theory study of NO2-sensing mechanisms of pure and Ti-dopedWO3 （002） surfaces

Density functional theory (DFT) calculations are employed to explore the NO₂-sensing mechanisms of pure and Ti-doped WO₃ (002) surfaces. When Ti is doped into the WO₃ surface, two substitution models are considered: substitution of Ti for W_6c and substitution of Ti for W_5c. The results reveal that substitution of Ti for 5-fold W forms a stable doping structure, and doping induces some new electronic states in the band gap, which may lead to changes in the surface properties. Four top adsorption models of NO₂ on pure and Ti-doped WO₃ (002) surfaces are investigated: adsorptions on 5-fold W (Ti), on 6-fold W, on bridging oxygen, and on plane oxygen. The most stable and likely NO₂ adsorption structures are both N-end oriented to the surface bridge oxygen O_1c site. By comparing the adsorption energy and the electronic population, it is found that Ti doping can enhance the adsorption of NO₂, which theoretically proves the experimental observation that Ti doping can greatly increase the WO₃ gas sensor sensitivity to NO₂ gas.