The adsorption of water on clean and oxygen covered Cu(110)

The water adsorption on clean and oxygen precovered Cu(110) surfaces is studied by means of UPS, LEED, work function measurements and ELS. At 90 K on the clean surface molecular water adsorption is indicated by UPS. The H₂O molecules are bonded at the oxygen end and the H-O-H angle is increased as compared with the free molecule. In the temperature range between 90 and 300 K distorted H₂O molecules and adsorbed hydroxyl species (OH) are detected, which are desorbed at room temperature. On an oxygen covered surface hydroxyl groups are formed by dissociation of adsorbed water molecules at a lower temperature than on the clean surface. Multilayers of condensed water are found below 140 K in both cases.     

An XPS study of the water adsorption on Cu(110)

The adsorption of H₂O on clean and oxygen precovered Cu(110) is studied at temperatures between 90 and 300 K by XPS. On the oxygen precovered surface three O(1s) emission lines are detected at lower temperature. They originate from adsorbed atomic oxygen, from OH groups, and from H₂O molecules. For an oxygen coverage of half a monolayer, XPS indicates that during H₂O decomposition the preadsorbed oxygen does not directly participate in the OH formation. After water adsorption on the clean surface three O(1s) emission lines are found, which are due to H₂O molecules, “disturbed” H₂O molecules, and OH groups. The XPS results are directly correlated with information about the adsorbates obtained by UPS. Coverages are determined from the XPS spectra for the detected species.     

A computer study of the absorption spectra of the water-carbon monoxide disperse system

The IR absorption, emission, and reflectance spectra of (CO) _i (H₂O)₂₀, 1 ≤ i ≤ 10, clusters were calculated using the molecular dynamics model. After the adsorption of CO molecules by clusters, IR radiation absorption and reflection by the system composed of them weakened, whereas thermal radiation power increased. We tracked changes in spectral characteristics as the number of molecules in clusters increased. Growing water clusters decreased absorption and gradually increased IR emission power. The growth of a water cluster with the addition of CO molecules to it as a rule caused the opposite effect. On the whole, clusterization and the entrapment of CO molecules by clusters had an antigreenhouse effect.     

The interaction of H2O molecules with iron films studied with MIES,UPS and XPS

X-Ray Photoelectron Spectroscopy (XPS), Metastable Induced Electron Spectroscopy (MIES) and Ultraviolet Photoelectron Spectroscopy (UPS) were applied to study the interaction of H₂O molecules with iron films.During the interaction with H₂O molecules under ultrahigh vacuum conditions, an oxide film is formed on the iron surface. UPS and XPS still show metallic contributions, even for a surface which is exposed to about 10³ L. The oxide film thickness amounts to about 1.8 nm. No hydroxide formation is observed at all, neither in UPS nor in MIES. Further impinging H₂O molecules do not interact with the surface, because the oxide film inhibits the dissociation of impinging molecules.H₂O exposure beyond 10⁹ L does not lead to a significant increase of the oxide layer, which saturates at a thickness of 1.8 nm. In particular, no surface hydroxide is observed at this exposure. Neither XPS UPS nor MIES reveal any indication for this.     

The adsorption of methanol on Pt(111), an IR reflection and UV photoemission study

IR reflection (absorption) spectroscopy (IRS) under grazing incidence and UV photoemission (UPS) with He I and He II radiation were used to study the adsorption of CD₃OD and CH₃OH, respectively, on Pt(111) at temperatures between 90 and 350 K. At 90 K a first chemisorbed layer of methanol consists of molecules being strongly chemisorbed at their oxygen end. On top of this first layer two other phases of methanol are detected. For both the second and third phase the IR spectra indicate hydrogen bonding between the molecules. From UPS a stronger contribution to chemical bonding at the oxygen end of the molecules is derived for the second phase. On top of the second phase amorphous multilayers condense which exhibit a phase transition into the crystalline α-ice modification of methanol upon annealing to 125 K. Thermal desorption proceeds via loss of the α-ice multilayers (135 K), desorption of the second (“amorphous”) methanol phase to a final dissociation of molecules in the first layer into CO and H. About 3% of a monolayer of CO remains on the surface at temperatures above 230 K. No stable intermediate in the decomposition of methanol into CO is detected.     

A photoelectron spectroscopic investigation of the interaction between H2O and oxygen on Ag(110)

The adsorption and reaction of H₂O with adsorbed oxygen atoms on Ag(110) was examined by UPS. In agreement with previous EELS results, H₂O formed multilayers of ice upon adsorption at 140 K. The ice layers could be easily distinguished from monolayer coverages of chemisorbed H₂O (present above 160 K) by UPS. The ice layers produced (1) strong attenuation of the emission from the Ag d-bands, (2) a nearly 2 eV shift of H₂O valence levels to higher binding energy and (3) strong attenuation of emission from the H₂O 3a₁ orbital. H₂O was observed to react stoichiometrically with O(a) above 250 K to produce a pure layer of adsorbed hydroxyl species. The UPS spectra for these species exhibited features at ?5.8 and ?8.7 eV, as well as strong features above the d-bands. These spectra were compared with those for OH(a) on other surfaces, and the difficulties of identifying OH by UPS due to contamination by excess H₂O are discussed.     

Adsorption behavior of H2O on clean and oxygen precovered Ni(s)(111)

Photoelectron spectroscopy (UPS), thermal desorption spectroscopy (TDS), isotope exchange experiments, work function change (δφ) and LEED were used to study the adsorption and dissociation behavior of H₂O on a clean and oxygen precovered stepped Ni(s)[12(111) × (111)] surface. On the clean Ni(111) terraces fractional monolayers of H₂O are adsorbed weakly in a single adsorption state with a desorption peak temperature of 180 K, just above that of the ice multilayer desorption peak (T_m = 155 K). In the angular resolved UPS spectra three H₂O induced emission maxima at 6.2, 8.5 and 12.3 eV below E_F were found for θ ≈ 0.5. Angular and polarization dependent UPS measurements show that the C_2v symmetry of the H₂O gas-phase molecule is not conserved for H₂O(ad) on Ni(s)(111). Although the Δφ suggest a bonding of H₂O to Ni via the negative end of the H₂O dipole, the O atom, no hints for a preferred orientation of the H₂O molecular axes were found in the UPS, neither for the existence of water dimers nor for a long range ordered H₂O bilayer. These results give evidence that the molecular H₂O axis is more or less inclined with respect to the surface normal with an azimuthally random distribution. H₂O adsorption at step sites of the Ni(s)(111) surface leads in TDS to a desorption maximum at T_m = 225 K; the binding energy of H₂O to Ni is enhanced by about 30% compared to H₂O adsorbed on the terraces. Oxygen precoverage causes a significant increase of the H₂O desorption energy from the Ni(111) terraces by about 50%, suggesting a strong interaction between H₂O and O(ad). Work function measurements for H₂O+O demonstrate an increase of the effective H₂O dipole moment which suggests a reorientation of the H₂O dipole in the presence of O(ad), from inclined to a more perpendicular position. Although TDS and Δφ suggest a significant lateral interaction between H₂O+O(ad), no changes in the molecular binding energies in UPS and no “isotope exchange” between ¹⁸O(ad) and H₂¹⁶O(ad) could be observed. Also, dissociation of H₂O could neither be detected on the oxygen precovered Ni(s)(111) nor on the clean terraces.     

BaxOy小团簇修饰Ru(0001)表面的结构稳定性和氮分子吸附性质

为了说明钡助剂的存在形式, 本文采用第一性原理方法研究了Ba_xO_y小团簇修饰Ru(0001)表面的结构稳定性和氮分子吸附性质. 基于总能的热力学分析发现, 在实验条件下(500 K, P_H2O/P_H2<10^-3), Ba₂O团簇比BaO₂, BaO, Ba和O等团簇(原子)更加稳定. 这证实含有金属性钡原子的团簇也是氧化钡助剂可能的工作状态. 表面电荷差分密度说明Ba₂O团簇的氧和钡原子与衬底的作用不同. 不过Ba₂O团簇氧和钡原子附近的氮分子吸附行为相似, Ba₂O团簇增强了氮分子和衬底的相互作用. Ba₂O团簇氧和钡原子附近的氮分子吸附能分别为0.78 和0.88 eV, 均大于清洁表面的0.67 eV. 氮分子间距和氮分子的拉伸振动频率都表明Ba₂O团簇在一定程度上活化了吸附氮分子. Ba₂O团簇氧和钡原子附近的N–N键长分别为0.117和0.116 nm, 大于清洁表面的0.114 nm. 氧和钡原子附近氮分子的拉伸振动频率分别为 1888 和1985 cm^-1, 小于清洁表面的2193 cm^-1. 电荷差分密度的计算结果说明, 削弱作用主要来自于Ba₂O团簇中钡离子和氮分子间的静电作用. 两者间的静电作用增加了氮分子π 反键轨道的占据数, 促进了氮分子极化, 从而削弱氮分子键.     

Comprehensive facilitating of water oxidation reaction by ultrasonic attenuation of hydrogen-bonded structure of water

The balance between water-metal interactions and water-water hydrogen bonding (HBs) controls the process of water adsorption on metallic surfaces. In other hand, the yield of oxygen evolution reaction (OER) is dependent on the binding energy of H₂O at electrode surface. Therefore, on a specific metal substrate, attenuation of HBs may be a promising route for improving OER. In this study, the computational and experimental evidences indicate that the performance of ultrasonically irradiated deionized water (USI-DW), participated in water oxidation reaction (WOR), is different from its in the intact bulk water. To date, establishing of new electrocatalysts with lower overpotentials (η) and higher current densities (J) in OER have been mostly considered based on metals and oxide materials. Here, we ultrasonically agitated the water clusters formed by strong HBs, and as a sustainable improvement route explored its particular effects on the efficiency of OER. The molecular modeling (MM) of the (H₂O)_n clusters (n = 1–100 molecules), the corresponding IR spectra, the molecular orbitals energy levels and the adsorption of free and cluster confined H₂O molecules on the Pt surface were studied by the appropriate quantum mechanical (QM) methods. The result of deconvolution of FTIR spectra recorded for USI-DW in the –OH stretching region (∼2600–3900 cm⁻¹) properly confirmed the expected increase of the single water molecules. The reduction in overpotentials was 82 ± 8 mV and 158 ± 12 mV, to reach the J of 1 mA cm⁻¹ at the typical pHs 12.2 and 13.1, respectively.     

Adsorption of oxygen on clean gaas surfaces investigated by ultraviolet photoemission

The adsorption of oxygen at exposures of up to 10⁵ L on differently oriented, ion-bombarded and annealed GaAs surfaces was investigated by UPS. Coverages θ_As for the clean surfaces and oxygen coverages for the oxygen exposed surfaces were estimated by additional SXPS measurements. It was concluded that at small exposures molecular and atomic adsorption are comparable in quantity and that atomic adsorption (oxidation) becomes maximum at θ_As, ≈ 0.2 for (111)Ga and (001) surfaces. Bonding of oxygen molecules should involve Ga sites. Specific bonding of oxygen atoms (O-Ga or O-As) was not indicated by the two stable UPS peaks as they occurred for arsenic coverages from 0 to 0.5 and did not shift their energy positions. They simply indicate the two states of the adsorbate atoms, single and double bonds, to substrate atoms. For the surfaces prepared here, monolayer coverage by oxygen was obtained at about 10¹⁰L. Likewise adsorption of H₂O was investigated.     

UPS and XPS studies of the chemisorption of O2, H2 AND H2O on reduced and stoichiometric SrTiO3(111) surfaces; The effects of illumination

About one monolayer of Ti³⁺ species is detectable at the surface of reduced SrTiO₃(111) single crystals by XPS and UPS. O₂, H₂ and H₂O have been adsorbed in the dark and the decrease on the concentration of the Ti³⁺ species has been monitored as a function of the gas exposures. Subsequent band gap illumination partially restores the Ti³⁺ initial concentration in the cases of O₂ and H₂ exposures but not in the case of H₂O. The Ti³⁺ photogeneration on the oxygen covered surface is associated with oxygen photodesorption as indicated by XPS and UPS. UPS measurements give evidence for surface hydroxylation resulting from water and hydrogen adsorption. The activity of the stoichiometric SrTiO₃(111) crystal face for O₂ and H₂ adsorption is very low when compared with the reduced SrTiO₃ samples.     

Investigation of structural evolution of hydrogen-bond networks of water clusters at 1 and 300 K

Computer simulation of water clusters (H₂O) _n , Na⁺(H₂O) _n and K⁺(H₂O) _n (n ?? 8) at temperatures of 1 and 300 K was carried out using the Monte Carlo method. All the types of the hydrogen-bond network structures at equilibrium configurations of the water clusters and, among them, the most probable ones at temperatures of 1 and 300 K, were detected. The analysis of the most probable types of hydrogen-bond networks at equilibrium configurations of water clusters revealed that clusters with n water molecules inherit the configuration of clusters with n ? 1 water molecules with an accuracy of one hydrogen bond.     

水蒸气对二氧化硅膜的影响：吸附性能与渗流效应

研究了在50和90 oC时水蒸气对孔径约为4 ?的二氧化硅膜的吸附性能和渗流效应影响,采用椭圆偏振光谱分析水蒸气的吸附性能,以及测定氦气-H₂O二元混合气体的透过性能. 研究表明水蒸气在二氧化硅膜上的吸附行为符合一阶Langmuir等温线,同时,在H₂O分子存在的条件下,氦气的透过率会急剧下降. 通常,在极小孔内气体分子的传输被认为是不连续的,而是在势能下从一个占有位置跳跃到另外一个空位上. 当在二氧化硅表面的H₂O分子覆盖率上升时,氦气的透过率急剧下降可能与渗流效应有关,其中吸附在二氧化硅表面的H₂O分子阻碍了氦气分子的跳跃.     

H2O interaction with clean and oxygen precovered Ni(110)

The interaction of water vapour with clean as well as with oxygen precovered Ni(110) surfaces was studied at 150 and 273 K, using UPS, ΔΦ, TDS, and ELS. The He(I) (He(II)) excited UPS indicate a molecular adsorption of H₂O on Ni(110) at 150 K, showing three water-induced peaks at 6.5, 9.5 and 12.2 eV below E_F (6.8, 9.4 and 12.7 eV below E_F). The dramatic decrease of the Ni d-band intensity at higher exposures, as well as the course of the work function change, demonstrates the formation of H₂O multilayers (ice). The observed energy shift of all water-induced UPS peaks relative to the Fermi level (ΔE_max = 1.5 eVat 200 L) with increasing coverage is related to extra-atomic relaxation effects. The activation energies of desorption were estimated as 14.9 and 17.3 kcal/mole. From the ELS measurements we conclude a great sensitivity of H₂O for electron beam induced dissociation. At 273 K water adsorbs on Ni(110) only in the presence of oxygen, with two peaks at 5.7 and 9.3 eV below E_F (He(II)), being interpreted as due to hydroxyl species (OH)^δ? on the surface. A kinetic model for the H₂O adsorption on oxygen precovered Ni(110) surfaces is proposed, and verified by a simple Monte Carlo calculation leading to the same dependence of the maximum amount of adsorbed H₂O on the oxygen precoverage as revealed by work function measurements. On heating, some of the (OH)^δ? recombines and desorbs as H₂O at ? 320 K, leaving behind an oxygen covered Ni surface.     

Isotope effect and cluster size dependence for water and hydrated hydrogen halide clusters: multi-component molecular orbital approach

In order to explore the proton/deuteron (H/D) isotope effect on the structures, wavefunctions, and size dependence of water clusters, both electronic and nuclear wavefunctions are determined simultaneously. The optimized centres and the exponents for the nuclear orbitals indicate the Ubbelohde effect, i.e. the deuteron has weaker hydrogen bonding than the proton. Calculations are made also of hydrogen halide water clusters, Such as HF(H₂O)_n, HB_r(H₂O)_n, (n = 0–4), and their deuterated species. Only the hydrogen transferred ring structure is optimized for the protonic HBr (H₂O)₃ cluster, while both the hydrogen transferred and the non-transferred structures are obtained for the deuterated DBr (H₂O)₃ cluster under the one-particle multi-component treatment. The proton in the HF molecule is localized more than those in the HCl and HBr molecules, and no hydrogen transferred structures are obtained for HF water clusters.     

Adsorption of N2O on Ru(001)

The adsorption of N₂O on Ru(001) at ~ 100K has been studied using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and thermal desorption spectroscopy (TDS). At low exposures, N₂O partly dissociates leaving atomic oxygen on the surface and desorbing N₂. With increasing N₂O exposures, molecular adsorption becomes dominant. He II UPS of the gas phase, solid and monolayer adsorbed molecular N₂O are compared. To within experimental error, the peak spacings in all three are the same. The distributions of intensities in the gas and solid phase spectra are the same. In the monolayer spectra, the 7~σ (terminal nitrogen lone pair) orbital intensity is decreased significantly indicating that it is more strongly coupled to the surface than the other valence orbitals. No molecular N₂O remains after heating to above 180 K and no detectable amount of dissociated nitrogen appears. Molecularly adsorbed N₂O is easily dissociated by an electron beam to give N₂(g), NO(g) and O(a).     

Adsorption of small molecules on transition metal doped rhodium clusters Rh3X (X = 3d, 4d atom): a first-principles investigation

The adsorption behaviours of seven molecules (CO, CO₂, N₂, NO, O₂, N₂O and NO₂) on Rh₃X (X?=Sc-Zn, Y-Cd) clusters are systematically investigated by density-functional calculations. Rh₃X clusters exhibit physical adsorption when interacting with CO₂, CO, N₂ and NO. The adsorption energies (E_ads) can be ranked as follows: NO?>?CO?>?CO_2?≥?N₂. Compared with pure Rh₄ cluster, the adsorption capacity changes with the doping element. Chemical adsorption can be obtained for Rh₃X when adsorbing O₂, N₂O and NO₂. E_ads shows an order of E_ads(O₂)?>?E_ads(NO₂)?>?E_ads(N₂O). When O₂ is adsorbed, energy barrier with doping Tc or Cr atom is substantially reduced, which indicates that chemical reactivity of O₂ on Rh₄ can be significantly enhanced. The doped rhodium clusters can be viewed as good candidates in the discrimination between different gas molecules.     

Site-specific interaction of H2O with ZnO single-crystal surfaces studied by thermal desorption and UV photoelectron spectroscopy

The adsorption and condensation of H₂O(D₂O) on ZnO(101&#x0304;0), (0001)Zn and (0001&#x0304;)O surfaces was investigated by means of thermal desorption (TDS) and UV photoelectron spectroscopy (UPS). The clean ZnO single-crystal surfaces were prepared by Ar-ion sputtering and annealing and characterised by Auger electron spectroscopy, LEED, UPS and work-function measurements. On all three surfaces six different adsorption states were found. In the monolayer regime there is a stronger bonding to Zn sites (desorption temperature 340 K) than to O sites (190 K), The bonding to the Zn sites seems to be accompanied by some clustering. Before the chemisorption layer is completed a first ice state is found whose desorption temperature shifts from 162 to 168 K with increasing exposures. At higher exposures the multilayer ice state is found at 152 K. On the (0001&#x0304;)O face defect-induced features were identified. The water lone-pair orbital 1b₁, whose energy falls between the O p and the Zn 3d emission of the substrate and which is known to show bonding shifts, was analysed using angle-resolved UPS. In the monolayer, the main chemisorption states are found at E_B^V(1b₁) = ?9.6 eV for the (0001)Zn face and at ? 10.6 eV for the (0001&#x0304;)O face and are compared with the multilayer ice emission at 1&#x0304;1.1 eV. The difference in binding energies shows the same trend as the TDS data. For the (101&#x0304;0) face the 1b₁ emission is very broad, indicating some overlap between different states.     

States of water molecule adsorbed on Si(111) surface

Calculated electronic energy structure of an overlayer of water molecules chemisorbed on Si(111), with a molecular plane perpendicular to the surface, reveals that 3a₁ molecular state is removed upon adsorption, and the resulting state densities cannot be reconciled with the UPS spectrum. These results, and state densities obtained from different atomic configurations are interpreted to rule out the molecular adsorption on Si(111) surface at room temperature.     

(TiO2)n(n=3—6)团簇吸附水分子的理论研究

给出了优化小分子在团簇表面吸附结构的遗传算法.结合经验势函数,搜寻了水分子在(TiO₂)_n(n=3—6)团簇上可能的吸附方式;利用B3LYP/6-31G^**方法对各种吸附结构进行了优化.结果表明水分子主要通过O原子以非解离方式吸附到团簇中配位数较低或位置比较凸出的Ti原子上.分子轨道分析表明,水分子与团簇之间的成键主要来自吸附位Ti原子3s3p轨道的贡献,水分子的轨道保持了气相水分子中的基本特征,但离域化程度增大 关键词： 2团簇')" href="#">TiO₂团簇 2O吸附')" href="#">H₂O吸附 遗传算法 DFT