Au_(38)团簇上小分子H_2O和O_2共同吸附的第一性原理研究

利用密度泛函理论(DFT)计算的方法,对O_2,H_2O单独吸附和共吸附在Au_(38)团簇上的吸附性质进行了结构,能量和电子分析.计算结果表明,O_2倾向于吸附在edge位,H_2O则倾向于吸附在top位.Au(100)表面较之Au(111)表面更有利于O_2,H_2O的吸附,这与实验结果相符合.H_2O和O_2共吸附研究表明,H_2O的存在促进了O_2的吸附.Mulliken和分态密度(PDOS)分析得出:在共吸附中,H_2O将部分电子转移给了O_2,促进了O_2的活化与解离,并生成了类似H_2O_2的中间态,从而为催化氧化反应提供了O活性物种.     

O2在Si掺杂石墨烯上吸附与活化

采用包含色散力校正的密度泛函理论方法(DFT-D)研究了O2在Si掺杂石墨烯(Si-Gra)上吸附与活化. 研究结果表明: 1) 与纯净石墨烯相比, Si掺杂极大的增强了石墨烯对O2的吸附能力. O2的最稳定吸附构型是以Side-on 模式吸附在掺杂的Si的顶位, 形成O-Si-O三元环. 次稳定吸附构型是与Si及近邻的一个C形成O-Si-C-O四元环结构. 两个吸附构型对应的吸附能分别为-2.40和-1.93 eV; 2) O2有两种分解路径: 直接分解路径(势垒为0.53 eV)和整体扩散后的分解路径(势垒为0.81 eV); 3) 分解之后的两个O原子分别吸附在Si的顶位和相邻碳环的两个碳原子的桥位; 4) 电子结构分析表明吸附的O2从Si-Gra获得较多电荷, 从而被活化. 总之, Si-Gra具有较强的催化氧气还原能力, 是一种潜在的良好的非金属氧还原催化剂.     

O_2在Si掺杂石墨烯上吸附与活化

采用包含色散力校正的密度泛函理论方法(DFT-D)研究了O2在Si掺杂石墨烯(Si-Gra)上吸附与活化.研究结果表明:1)与纯净石墨烯相比,Si掺杂极大的增强了石墨烯对O2的吸附能力.O2的最稳定吸附构型是以Side-on模式吸附在掺杂的Si的顶位,形成O-Si-O三元环.次稳定吸附构型是与Si及近邻的一个C形成O-Si-C-O四元环结构.两个吸附构型对应的吸附能分别为-2.40和-1.93eV;2)O2有两种分解路径:直接分解路径(势垒为0.53eV)和整体扩散后的分解路径(势垒为0.81eV);3)分解之后的两个O原子分别吸附在Si的顶位和相邻碳环的两个碳原子的桥位;4)电子结构分析表明吸附的O2从Si-Gra获得较多电荷,从而被活化.总之,Si-Gra具有较强的催化氧气还原能力,是一种潜在的良好的非金属氧还原催化剂.     

SO2在CaCO3颗粒表面转化的DRIFTS研究

碳酸钙 (CaCO3 )是大气中矿物颗粒物的重要组分 ,其非均相大气化学行为很不清楚。利用原位漫反射红外傅里叶变换光谱 (DiffuseReflectanceInfraredFourierTransformSpectroscopy ,DRIFTS)研究了二氧化硫(SO2 )在CaCO3 颗粒物表面的转化情况。通过比较不同条件下 ,亚硫酸盐和硫酸盐的原位光谱 ,探讨了SO2在CaCO3 表面氧化中臭氧 (O3 )所起的作用。结果表明 ,利用DRIFTS原位分析反应器研究CaCO3 表面硫酸盐的生成是可行的。在存在O3 条件下 ,SO2 在CaCO3 表面能够被氧化成硫酸盐 ,反应分为吸附和氧化两个步骤进行。     

氧化石墨烯负载的Pt单原子催化硼胺烷水解机理的理论研究（英文）

本文研究了氧化石墨烯负载Pt单原子(Pt_1/Gr-O)催化硼胺烷(NH_3BH_3)全水解反应机理,即一分子的NH_3BH_3生成三分子的氢气(H_2)的过程,在水解路径中,首先吸附的硼胺烷连续断裂两个B-H键生成第一分子的H_2.接着,一个H_2O分子与*BHNH_3基团(*表示吸附态)反应生成*BH(H_2O)NH_3,其中伸长的O-H键断裂后形成*BH(OH)NH_3.然后,第二个H_2O与*BH(OH)NH_3反应生成*BH(OH)(H_2O)NH_3,在指向Pt_1/Gr-O表面的O-H断裂后,生成BH(OH)_2NH_3并脱附到水溶液中,两个水分子脱氢产生的两个H原子脱附生成第二个H_2分子,且Pt_1/Gr-O催化剂恢复.脱附后的BH(OH)_2NH_3在水溶液中水解生成第三个H_2分子.纵观整个水解反应,H_2O分子和*BHNH_3基团的结合是反应速控步,其反应能垒是16.1 kcal/mol.因此,Pt_1/Gr-O有希望成为室温催化NH_3BH_3全水解催化剂.     

FeO+催化N2O与CO反应的密度泛函理论研究

本文采用密度泛函理论DFT-B3LYP方法6-311+G(2d) 的基组, 计算研究了气相中六重态和四重态FeO+离子催化N2O和CO生成N2和 CO2反应的微观机理, 通过计算两种重态金属离子亲氧性（OA）, 从热力学方面说明了主题反应的可行性。分析反应过程的热力学性质和动力学因素得到FeO+与N2O复合生成反应复合物, 之后继续与CO复合成中间体是能量有利反应路径,所得结果与实验观测相符.     

原位DRIFTS研究CH4部分氧化和CO2重整的耦合

8%Ru-5?/γ-Al2O3催化剂对于甲烷的低温活化具有较好的催化活性,在500℃下甲烷、二氧化碳和氧气的耦合反应中,吸热反应二氧化碳重整和放热反应甲烷部分氧化进行耦合强化,使得耦合反应中的甲烷转化率为38.8%。用原位漫反射傅里叶红外光谱法对钌系催化剂耦合甲烷部分氧化和二氧化碳重整反应体系机理进行研究。CO在8%Ru-5?/γ-Al2O3上吸附,表明CO在催化剂表面上波数为2 167 cm-1(2 118 cm-1)和2031 cm-1(2 034 cm-1)处形成孪生态Ru(CO)2和Ce(CO)2吸附物种,而且高温下CO吸附物种很容易从催化剂表面脱附出来。原位漫反射红外实验结果表明甲烷部分氧化反应时催化剂表面上有吸附物种碳酸根、甲酰基(甲酸盐)和一氧化碳的形成,其中表面的甲酰基和甲酸盐物种是甲烷部分氧化反应的主要活性中间物,这些中间活性中间体由甲烷吸附态CHx和催化剂表面的氧吸附态结合而形成的,随后这种中间物种再分解为CO产物;甲烷和二氧化碳重整反应时没有新的吸附物种产生,由此提出重整反应的机理是吸附态的甲烷和二氧化碳在催化剂活性中心上进行活化解离而生成合成气;甲烷、二氧化碳和氧气耦合反应过程中出现新的羟基物种(桥式羟基Ru-(OH)2),耦合反应机理复杂可能是由部分氧化和重整两类反应机理的复合,其中桥式羟基Ru-(OH)2参与了反应的进行。     

CuO-CeO2-MnOx/γ-Al2O3催化剂选择性催化脱除NO机理研究

利用溶胶凝胶法制备CuO-CeO2-MnOx/γ-Al2O3催化剂颗粒,在固定床上测试其催化脱硝活性.CuO-CeO2-MnOx/γ-Al2O3催化剂在200～450℃范围内脱硝效率保持在70%以上.利用程序升温方法研究了催化剂对NH3的氧化性能,活性组分负载量增多,加强了催化剂对NH3氧化性能.红外表征显示NH3被吸附在催化剂的L酸位和B酸位.NO以多种硝酸盐物种在催化剂表面吸附.吸附态NH3参与SCR反应,但吸附态NO物种仅部分参加SCR反应.     

红外光谱研究大气痕量气体在α-Al_2O_3表面上的协同反应

利用傅里叶变换显微红外光谱仪(micro-FTIR)研究SO2/O3,SO2/NO2在α-Al2O3颗粒物上的协同反应。结果表明,O3和NO2都可以氧化SO2在α-Al2O3矿尘上反应形成硫酸盐。比较生成的硫酸盐峰面积随反应时间的变化可以发现,O3/SO2在颗粒物表面的反应速率较NO2/SO2快。     

Au10催化CO氧化反应机理的密度泛函理论研究

采用密度泛函理论方法研究了Au10团簇催化CO氧化反应的详细机理. 对CO、O2、O、CO2四种主要吸附物及CO+O2、CO2+O、CO+O和CO+O+O四种共吸附物的吸附行为进行计算, 得到最佳活性吸附位. 模拟反应分别按照Langmuir-Hinshelwood(LH)机理和Eley-Rideal(ER)机理进行, 其中LH机理包括L1、L2两条路径, ER机理包括E1、E2两条路径. 通过对各路径活化能比较得到: 首先CO+O2→CO2+O反应按照LH机理进行的可能性较大, 并且相比较L1、L2两条路径, 由于反应按照L1路径进行时只需克服33.9和56.4 kJ•mol-1的能垒, 所以反应更易按照L1路径进行, 最佳反应路径为O2(gas)+CO(gas)→O2(ads)+CO(gas)→O2(ads)+CO(ads)→OCOO(ads)→O(ads)+ CO2(ads); 然后CO+O→CO2反应分别克服6.9和4.3 kJ•mol-1能垒, 放热352.1 kJ•mol-1, 说明低温下吸附态的O原子很容易与CO反应生成第二个CO2分子.     

CH3OH在Ga-Rich GaAs(001)-(4×2)表面上的吸附与解离: 团簇模型的密度泛函计算

采用简单团簇模型结合密度泛函理论研究了CH3OH在Ga-Rich GaAs(001)-(4×2)表面上的吸附与解离过程. 计算结果表明, CH3OH在Ga-Rich GaAs(001)-(4×2)表面上首先会形成两种化学吸附状态, 然后CH3OH经解离生成CH3O自由基和H原子吸附在表面不同位置上. 通过比较各个吸附解离路径, 发现解离后的H原子相对更容易吸附在位于表面第二层紧邻的As原子上.     

WO_3(001)表面活性氧物种的理论研究

采用第一性原理结合周期性平板模型的方法,对O_2在完整和缺陷WO_3(001)表面的吸附行为进行了研究.结果表明:WO_3(001)完整表面上吸附态的O_2不易成为表面氧化反应的活性氧物种,当吸附质与表面作用时,将优先与表面晶格氧(O_t)成键,进而形成表面缺陷态,体系呈现金属性,电导率增大.比较O_2在缺陷表面上各吸附构型的吸附能发现,O_2的吸附倾向于发生在缺陷位置(W_v)上,且表现为氧气分子中的两个氧原子均与缺陷位W_v作用,形成新的活性氧物种(O_2~-);吸附后表面被氧化,电导率降低.     

乙烯渣油沥青基活性炭纤维和粘胶基活性炭纤维的表面性质与脱硫活性

研究了在Ｏ２和Ｈ２Ｏ存在下,乙烯渣油肝基活性炭纤维（ＥＴＰ ＡＣＦ）和粘胶基活性炭纤维（Ｃｅｌｌｕｌｏｓｅ ＡＣＦ）的脱硫活性,结果表明,在比表面积相近的情况下,ＥＴＰ ＡＣＦ的脱硫活性明显低于Ｃｅｌｌｕｌｏｓｅ ＡＣＦ,官可归因于后者具有较强的吸附和催化氧化ＳＯ２能力及较大的吸水量,尤其是具有较强的催化氧化Ｓ２的能力,这些能力又珉春表面含有含氮官能团以及某些含氧官能团有关,因此ＡＣＦ的表面官能团     

Photoelectron diffraction study of a catalytically active overlayer: C2H2 on Pd{111}

A quantitative structure determination of a newly discovered (2×2) adsorption phase of acetylene chemisorbed on Pd{111} has been performed by scanned-energy mode photoelectron diffraction: this phase corresponds to the threshold coverage for the catalytic conversion of acetylene to benzene. The carbon atoms in the C₂H₂ molecule are located almost over bridge sites with a C–C bond length of 1.34+0.10 Å, the centre of the molecule being positioned almost over a hollow site. Of the two hollow sites the hcp site (directly above a second layer Pd atom) is favoured, particularly by a subset of the data most sensitive to this aspect of the structure, but the full analysis indicates that the fcc site (above a third layer Pd atom) cannot formally be excluded. The adsorption site adopted by acetylene in the higher coverage phase on Pd{111} is essentially identical. This is the dominant structure in the coverage regime which is catalytically active for the conversion of acetylene to benzene. The implications of these findings for acetylene coupling reactions over Pd{111} are discussed.     

Electronic and magnetic properties of copper-family-element atom adsorbed graphene nanoribbons with zigzag edges

We have investigated the electronic and magnetic properties of copper-family-element (CFE) atom adsorbed graphene nanoribbons (GNRs) with zigzag edges using first-principles calculations based on density functional theory. We found that CFE atoms energetically prefer to be adsorbed at the edges of nanoribbons. Charges are transferred between the CFE atom and carbon atoms at the edge, which reduce the local magnetic moment of carbon atoms in the vicinity of adsorption site and change the electronic structure of GNRs. As a result, Cu adsorbed zigzag GNR is a semiconductor with energy band gap of 0.88 eV in beta-spin and energy gap of 0.22 eV in alpha-spin, while Ag adsorbed zigzag GNR and Au adsorbed zigzag GNR are both half-metallic with the energy gaps of 0.68 eV and 0.63 eV in beta-spin, respectively. These results show that CFE atom adsorbed zigzag GNRs can be applied in nanoelectronics and spintronics.     

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。     

Effect of surface deactivation on molecular chemisorption: Co on αFe(100) surfaces

Clean and partially deactivated αFe(100) surfaces show variable chemical reactivity towards carbon monoxide and unsaturated hydrocarbon molecules depending on preparation. Bonding of chemisorbed CO to clean Fe occurs according to the Blyholder model. UV-photoelectron spectroscopy (UPS) indicates a severe stretching of the C-O bond at low temperatures (98°K – 223°K) and complete dissociation at higher temperatures (≈ 300°K). Electron bonding interactions can be quenched to varying degrees by prechemisorption of C, O, P, or S. UPS spectra for CO chemisorption on Fe (100) + S indicate an unstretched molecule and provide a clear resolution of the 1π and 5σ levels due to reduced forward- and back-bonding interactions. These observations are directly related to the mechanism of sulfur poisoning in Fischer-Tropsch catalysis of higher hydrocarbons. The general utility of deactivation techniques for interpretation of surface-molecule interactions is discussed.     

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.     

A density functional theory study on the adsorption of CO and O₂ on Cu-terminated Cu₂O（111） surface

The adsorptions of CO and O2 molecules individually on the stoichiometric Cu-terminated Cu2O(111) surface are investigated by first-principles calculations on the basis of the density functional theory.The calculated results indicate that the CO molecule preferably coordinates to the Cu2 site through its C atom with an adsorption energy of -1.69 eV,whereas the O2 molecule is most stably adsorbed in a tilt type with one O atom coordinating to the Cu2 site and the other O atom coordinating to the Cu1 site,and has an adsorption energy of -1.97 eV.From the analysis of density of states,it is observed that Cu 3d transfers electrons to 2π orbital of the CO molecule and the highest occupied 5σ orbital of the CO molecule transfers electrons to the substrate.The sharp band of Cu 4s is delocalized when compared to that before the CO molecule adsorption,and overlaps substantially with bands of the adsorbed CO molecule.There is a broadening of the 2π orbital of the O2 molecule because of its overlapping with the Cu 3d orbital,indicating that strong 3d-2π interactions are involved in the chemisorption of the O2 molecule on the surface.     

Molecular orbital study of the chemisorption of carbon monoxide on a tungsten (100) surface

The adsorption energies of carbon monoxide chemisorbed at various sites on a tungsten (100) surface have been calculated by extended Hückel molecular orbital theory (EHMO). The concept of a “surface molecule” in which CO is bonded to an array of tungsten atoms W_n has been employed. Dissociative adsorption in which C occupies a four-fold, five-coordination site and O occupies either a four- or two-fold site has been found to be the most stable form for CO on a W surface. Stable one-fold and two-fold sites of molecularly adsorbed CO have also been found in which the CO group is normal to the surface plane and the C atom is nearest the surface. Adsorption energies and molecular orbitals for the stable molecularly and dissociatively adsobred CO sites are compared with the experimental data on various types of adsorbed CO, i.e., virgin-, α-, and β-CO. Models are suggested for each of these adsorption types. The strongest bonding interactions occur between the CO 5σ orbital and the totally symmetric 5d and 6s orbitals of the W_n cluster. Possible mechanisms for conversion of molecularly adsorbed CO to dissociatively adsorbed CO are proposed and the corresponding activation energies are estimated.