TiO2气相光催化氧化降解三氯乙烯的产物分布及失活机理研究

用ＧＣ／ＭＳ、ＴＰＤ和ＸＰＳ方法,研究了三氯乙烯的气相光催化降解反应,检测到新的中间体乙二酰氯（ＣＩＣＯＣＯＣＩ）。对产物分布的分析表明,水蒸汽的存在能显著抑制含氯副产物的生成,改变反应产物的分布。使用过的催化剂的ＸＰＳ谱图显示,催化剂表面存在含氯副产物,反应副产物在催化剂表面的积累是导致催化剂失活的主要原因。     

双金属氰化物配合物(DMC)催化剂的制备及表征

分别以乙二醇二甲醚,二乙二醇二乙和１,４－二氧六环为有机配体,制备了一系列双钓饵鹅的催化剂;用Ｘ射线衍射（ＸＲＤ）和Ｘ射线光电子能谱（ＸＰＳ）技术,研究了催化剂的晶相结构和表面状态。结果表明,钻以原料Ｚｎ３〖Ｃｏ（ＣＮ６）【２．ｘｈ２Ｏ中的物种形式存在,在催化剂的制备过程中没有氧化还原反应发生,有机 本只与锌离子配位,这 与位作用破坏了Ｚｎ（２〗Ｃｏ（ＣＮ）６〖２．１２Ｈ２的晶体结构,催化剂的表面     

稀土对磷钒催化剂性能的影响

用Ｘ射线粉末衍射，Ｘ光电子能谱和氨－程序升温脱附等方法研究了添加稀土元素后磷钒催化剂的晶相组成及表面性质。将催化剂应用于正丁烷选择氧化制备顺酐，用固定床反应器对催化剂活性进行了评价。     

银-磷催化剂催化乙二醇制乙二醛及其表面性质

用银－磷催化剂研究了原料气线速、空速、氧醇摩尔比、反应温度、乙二醇重量浓度对催化氧化乙二醇制乙二醛的反应活性的影响．结果表明，在相近的反应条件下，银－磷催化剂能使副产物ＣＯ２的产率从电解银的３０％降到１３．３％，而使乙二醛收率从５４％增至８１％．Ｘ射线光电子能谱表明，在银表面上形成了稳定的表面磷化合物并占据了一部分深度氧化的活性位，因而提高了反应的选择性．     

金属蒸气法制备聚合物固载双金属催化剂———Pd-Cu催化剂的价态,分散度与活性

利用金属蒸气法制备了三种不同金属重量比的树脂固载及活性炭负载Ｐｄ Ｃｕ双金属催化剂．透射电镜（ＴＥＭ）和Ｘ 射线衍射（ＸＲＤ）测定结果表明催化剂中Ｐｄ Ｃｕ已形成合金．合金粒度极小，平均直径小于５ｎｍ．树脂固载催化剂金属粒度远小于活性炭负载催化剂的金属粒度．Ｘ 射线光电子能谱（ＸＰＳ）结果表明Ｐｄ和Ｃｕ均以零价态存在．在４ 甲基 ３ 戊烯 ２ 酮加氢反应中，树脂固载催化剂的活性和选择性均高于相应的活性炭负载催化剂     

甲酸和乙酸在二氧化锆表面化学吸附的光电子能谱研究

利用Ｘ射线光电子能谱（ＸＰＳ）和紫外光电子能谱（ＵＰＳ）等表面分析方法，表征了甲酸和乙酸在ＺｒＯ２表面 的反应和吸附态。室温下，甲酸在ＺｒＯ２表面以ＨＣＯＯ－（ａ）的形态被吸附，部分ＨＣＯＯ－（ａ）进一步分解产生Ｏ~(２－)（ａ）， ＨＣＯ（ａ）和ＣＨ_ｘ（ａ），加热有利于表面甲酸根的分解。乙酸在ＺｒＯ２表面的反应与甲酸相似。甲酸和乙酸在ＺｒＯ２表面 的吸附实质就是表面酸碱中和反应。     

硅烷偶联剂改性的二氧化钛光催化降解气相苯

 用硅烷偶联剂KH-570对二氧化钛光催化剂进行了改性,制备了一种新型光催化剂. 以苯作为 模拟气体,在静态反应装置中考察了该催化剂的光催化性能. 结果表明,KH-570能显著提高 二氧化钛对气相苯的光催化降解性能,其转化率是纯二氧化钛的2.5倍. 采用红外光谱和X射线光电子能谱对催化剂进行了表征.     

金属蒸气法制备聚合物固载双金属催化剂——Pd—Cu催化剂的价态,分散度…

利用金属蒸气法制备了三种不同金属重量比的树脂固载及活性炭负载Ｐｄ－Ｃｕ双金属催化剂。透射电镜（ＴＥＭ）和Ｘ－射线衍射（ＸＲＤ）测定结果表明催化剂中Ｐｄ－Ｃｕ已形成合金。合金粒度极小，平均直径小于５ｍｍ。树脂固载催化剂金属粒度远小于活性炭负载催化剂的金属粒度。Ｘ－射线光电子能谱（ＸＰＳ）结果表明Ｐｄ和Ｃｕ均以零价态存在。在４－甲基－３－戊烯－２－酮加氢反应中，树脂固载催化剂的活性和选择性均高于相应的     

稀土钼钒磷杂多酸半菁盐的合成,表征和催化性能

用降解法首次制得Ｄａｗｓｏｎ结构的稀土钼钒磷酸钾。通过它们与溴化（Ｅ）－１－丁基－４－［２－（４－二甲氨基苯）乙烯基］吡啶反应，制备了种未见文献报道的具有下列组成的新型稀土杂多配合物的有机衍生物，研究了其红外、紫外，可见光谱、Ｘ射线光电子能谱、Ｘ射线粉末衍射及热重－差热谱，以镧配合物为催化剂，对乙酸与正丁醇、异戊醇的酯化反应进行了初步研究。     

CO2加氢合成甲醇的超细Cu-ZnO-ZrO2催化剂的表征

采用原位顺磁共振（ＥＰＲ）、原位Ｘ射线光电子能谱（ＸＰＳ）和程序升温还原（ＴＰＲ）等手段,对ＣＯ２加氢合成甲醇用的不同粒度的超细Ｃｕ－ＺｎＯ－ＺｒＯ２催化剂各组分的相互作用进行了研究。结果表明,ＺｒＯ２的加入改变了催化剂的表面结构和配位状态,增加了活性组分的分散度,提高了催化剂的稳定性。实验还发现,催化剂的粒度对各组分的相互作用有着重大的影响,催化剂的粒度较小时,Ｃｕ＾２＋主要以团簇的形式存在,易     

Oxygen, carbon, and sulfur segregation in annealed and unannealed zerovalent iron substrates

Finely ground and pretreated iron substrates known as "zerovalent iron" or "Fe0" are used as reductants in the environmental remediation of halogenated hydrocarbons, and the composition of their surfaces significantly affects their reactivity. Samples of unannealed and annealed (heat-treated under H2/N2) zerovalent iron were analyzed using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Surface concentration of the iron and of the impurities observed by XPS and AES, carbon, chlorine, sulfur, and oxygen, were measured before and after soaking in trichloroethylene (TCE) and in water saturated with TCE (H2O/TCE) to simulate chlorocarbon remediation conditions. Samples pretreated by annealing at high temperature under H2 contained less iron carbide. The carbide contaminant was evident in both iron and carbon XPS spectra, with binding energies of 709.0 and 283.3 eV for the Fe 2p3/2 and C 1s, respectively. The annealed Fe0 surface also contained more sulfur. The carbide concentration was essentially unchanged by TCE and H2O/TCE exposure, whereas the sulfur decreased in proportion to chlorine adsorption following the dechlorination reaction. While oxygen concentration is initially lower on the annealed substrate surface, it rapidly increased during the model TCE remediative treatment process and thus does not represent a significant effect of the annealing process on surface reactivity.     

Density functional theory study of the oxidation of ammonia on the IrO2(110) surface

In this study, we employed density functional theory (DFT) to investigate the oxidation of ammonia (NH(3)) on the IrO(2)(110) surface. We characterized the possible reaction pathways for the dehydrogenation of NH(x) species (x = 1-3) and for the formation of the oxidation products N(2), N(2)O, NO, NO(2), and H(2)O. The presence of oxygen atoms on coordinatively unsaturated sites (O(cus)) of the oxygen-rich IrO(2)(110) surface promotes the oxidation of NH(3) on the surface. In contrast, NH(3) molecules prefer undergoing desorption over oxidation on the stoichiometric IrO(2)(110) surface. Moreover, the O(cus) atoms are also the major oxidants leading to the formation of oxidation products; none of the oxidations mediated by the bridge oxygen atoms were favorable reactions. The energy barrier for formation of H(2)O as a gaseous oxidation product on the IrO(2)(110) surface is high (from 1.83 to 2.29 eV), potentially leading to the formation of nitrogen-atom-containing products at high temperature. In addition, the selectivity toward the nitrogen-atom-containing products is dominated by the coverage of O(cus) atoms on the surface; for example, a higher coverage of O(cus) atoms results in greater production of nitrogen oxides (NO, NO(2)).     

高导电性和催化活性的Janus-TiNbCO2析氢反应催化材料

探寻具有高导电性和高催化活性的析氢反应（HER）催化材料一直是可持续能源发展研究中的热点。Ti₂C具有表面活性位点多和优良的力学稳定性、导电性等,已成为潜在的制氢催化剂。然而,终端O修饰Ti₂C表面,会降低该材料的导电性,进而限制了电子在价带与导带间的输运。本研究通过Nb掺杂,构建双电层Janus-TiNbCO₂,并借助VASP软件研究了Janus-TiNbCO₂的能带结构、HER性能和HER反应路径过渡态。结果表明,Janus-TiNb-CO₂为导体材料,其在应力、氧空位缺陷和H*覆盖度的影响下,均表现出极优异的催化活性,计算获得的最优ΔG_H*值为0.02 eV。H*在Janus-TiNbCO₂上可能以Heyrovsky路径进行反应,该路径的迁移能势垒为0.23 eV。Janus-TiNbCO₂是一种具有HER应用前景的催化材料。     

Cr掺杂ZnO(10(¯1)0)表面的原子结构和电子性质研究

多相催化中ZnO基催化剂广泛应用于甲醇合成、水汽变换和合成气转化等诸多领域.近期发展的ZnCrOx-分子筛双功能催化剂(OX-ZEO)打破了传统合成气转化的ASF分布,能够高选择性地实现CO加氢转化为低碳烯烃.其中CO在ZnCrOx表面活化被认为是OX-ZEO催化的关键基元过程,但是ZnCrOx表面的活性位组成和结构目...     

X-ray photoelectron spectroscopy-based valence band spectra of passive films on titanium

Titanium (Ti) is always covered by thin passive films. Thus, valence band (VB) spectra, obtained using X-ray photoelectron spectroscopy (XPS), are superpositions of the VB spectra of passive films and that of the metallic Ti substrate. In this study, to obtain the VB spectra only of passive films, angular resolution (for eliminating the substrate Ti contribution) and argon ion sputtering (for removing passive films) were used along with XPS. The passive film on Ti was determined to consist of a very thin TiO₂layer with small amounts of Ti₂O₃, TiO, hydroxyl groups, and water with a thickness of 5.9 nm. The VB spectra of Ti were deconvoluted into four peak components: a peak at ~1 eV, attributed to the Ti metal substrate; a broad peak in the 3–10 eV range, mainly attributed to O 2p (~6 eV) and O 2p-Ti 3d hybridized states (~8 eV), owing to the π (non-bonding) and σ (bonding) orbitals in the passive oxide film; and a peak at ~13 eV, attributed to the 3σ orbital of O 2p as OH⁻or H₂O. The VB region spectrum between approximately 3 and 14 eV from Ti is originating from the passive film on Ti. In particular, characterization of VB spectrum obtained with a takeoff angle of less than 24° is effective to obtain VB spectrum only from the passive film on Ti. The property as n-type semiconductor of the passive film on Ti is probably higher than that of rutile TiO₂ceramics.     

Interaction of oxygen with TiN(001): N<-->O exchange and oxidation process

This work presents a detailed experimental and theoretical study of the oxidation of TiN(001) using a combination of synchrotron-based photoemission and density functional theory (DFT). Experimentally, the adsorption of O2 on TiN(001) was investigated at temperatures between 250 and 450 K. At the lowest temperature, there was chemisorption of oxygen (O(2,gas)-->2O(ads)) without significant surface oxidation. In contrast, at 450 K the amount of O2 adsorbed increased continuously, there was no evidence for an oxygen saturation coverage, a clear signal in the Ti 2p core level spectra denoted the presence of TiOx species, and desorption of both N2 and NO was detected. The DFT calculations show that the adsorption/dissociation of O2 is highly exothermic on a TiN(001) substrate and is carried out mainly by the Ti centers. A high oxygen coverage (larger than 0.5 ML) may induce some structural reconstructions of the surface. The exchange of a surface N atom by an O adatom is a highly endothermic process (DeltaE=2.84 eV). However, the overall oxidation of the surface layer is thermodynamically favored due to the energy released by the dissociative adsorption of O2 and the formation of N2 or NO. Both experimental and theoretical results lead to conclude that a TiN+mO2 -->TiOx + NO reaction is an important exit channel for nitrogen in the oxidation process.     

Site-dependent electron-stimulated reactions in water films on TiO2(110)

Electron-stimulated reactions in thin [<3 ML (monolayer)] water films adsorbed on TiO(2)(110) are investigated. Irradiation with 100 eV electrons results in electron-stimulated dissociation and electron-stimulated desorption (ESD) of adsorbed water molecules. The molecular water ESD yield increases linearly with water coverage theta for 0< or =theta< or =1 ML and 11 ML, the water ESD yield per additional water molecule adsorbed (i.e., the slope of the ESD yield versus coverage) is 3.5 times larger than for theta<1 ML. In contrast, the number of water molecules dissociated per incident electron increases linearly for theta< or =2 ML without changing slope at theta=1 ML. The total electron-stimulated sputtering rate, as measured by postirradiation temperature programmed desorption of the remaining water, is larger for theta>1 ML due to the increased water ESD for those coverages. The water ESD yields versus electron energy (for 5-50 eV) are qualitatively similar for 1, 2, and 40 ML water films. In each case, the observed ESD threshold is at approximately 10 eV and the yield increases monotonically with increasing electron energy. The results indicate that excitations in the adsorbed water layer are primarily responsible for the ESD in thin water films on TiO(2)(110). Experiments on "isotopically layered" films with D(2)O adsorbed on the Ti(4+) sites (D(2)O(Ti)) and H(2)O adsorbed on the bridging oxygen atoms (H(2)O(BBO)) demonstrate that increasing the water coverage above 1 ML rapidly suppresses the electron-stimulated desorption of D(2)O(Ti) and D atoms, despite the fact that the total water ESD and atomic hydrogen ESD yields increase with increasing coverage. The coverage dependence of the electron-stimulated reactions is probably related to the different bonding geometries for H(2)O(Ti) and H(2)O(BBO) and its influence on the desorption probability of the reaction products.     

Computational study of ethanol adsorption and reaction over rutile TiO(2) (110) surfaces

Studies of the modes of adsorption and the associated changes in electronic structures of renewable organic compounds are needed in order to understand the fundamentals behind surface reactions of catalysts for future energies. Using planewave density functional theory (DFT) calculations, the adsorption of ethanol on perfect and O-defected TiO(2) rutile (110) surfaces was examined. On both surfaces the dissociative adsorption mode on five-fold coordinated Ti cations (Ti(4+)(5c)) was found to be more favourable than the molecular adsorption mode. On the stoichiometric surface E(ads) was found to be equal to 0.85 eV for the ethoxide mode and equal to 0.76 eV for the molecular mode. These energies slightly increased when adsorption occurred on the Ti(4+)(5c) closest to the O-defected site. However, both considerably increased when adsorption occurred at the removed bridging surface O; interacting with Ti(3+) cations. In this case the dissociative adsorption becomes strongly favoured (E(ads) = 1.28 eV for molecular adsorption and 2.27 eV for dissociative adsorption). Geometry and electronic structures of adsorbed ethanol were analysed in detail on the stoichiometric surface. Ethanol does not undergo major changes in its structure upon adsorption with its C-O bond rotating nearly freely on the surface. Bonding to surface Ti atoms is a σ type transfer from the O2p of the ethanol-ethoxide species. Both ethanol and ethoxide present potential hole traps on O lone pairs. Charge density and work function analyses also suggest charge transfer from the adsorbate to the surface, in which the dissociative adsorptions show a larger charge transfer than the molecular adsorption mode.     

N doping of TiO2(110): photoemission and density-functional studies

The electronic properties of N-doped rutile TiO2(110) have been investigated using synchrotron-based photoemission and density-functional calculations. The doping via N2+ ion bombardment leads to the implantation of N atoms (approximately 5% saturation concentration) that coexist with O vacancies. Ti 2p core level spectra show the formation of Ti3+ and a second partially reduced Ti species with oxidation states between +4 and +3. The valence region of the TiO(2-x)N(y)(110) systems exhibits a broad peak for Ti3+ near the Fermi level and N-induced features above the O 2p valence band that shift the edge up by approximately 0.5 eV. The magnitude of this shift is consistent with the "redshift" observed in the ultraviolet spectrum of N-doped TiO2. The experimental and theoretical results show the existence of attractive interactions between the dopant and O vacancies. First, the presence of N embedded in the surface layer reduces the formation energy of O vacancies. Second, the existence of O vacancies stabilizes the N impurities with respect to N2(g) formation. When oxygen vacancies and N impurities are together there is an electron transfer from the higher energy 3d band of Ti3+ to the lower energy 2p band of the N(2-) impurities.