氢原子在Ru(0001)和Ru(100)面上吸附扩散势能面的结构

本文构造了H—Ru相互作用的五参数Morse势,用经典的对势方法研究了氢原子在Ru(0001)和RU(1010)面上的吸附和扩散,得到了氢原子在两个表面上的吸附位、吸附几何、结合能及本征振动等数据与实验结果符合得很好;同时研究了两个体系的吸附扩散势能面结构.     

氢原子在Ru(0001)表面的化学吸附

用密度泛函理论研究了氢原子的污染对于Ru(0001)表面结构的影响. 通过PAW(projector-augmented wave)总能计算研究了p(1×1)、p(1×2)、(3^(1/2)×3^(1/2))R30°和p(2×2)等几种氢原子覆盖度下的吸附结构, 以及在上述结构下Ru(0001)面fcc(面心立方)格点和hcp(六方密堆)格点的氢原子吸附. 所得结果表明, 在p(1×1)-H、p(1×2)-H、(3^(1/2)×3^(1/2))R30°-H和p(2×2)-H几种H原子覆盖度下, 以p(1×1)-H结构单个氢原子吸附能为最大. 在p(1×1)-H吸附结构下,由于氢原子吸附导致的Ru(0001) 表面第一层Ru 原子收缩的理论计算数值分别为-1.11%(hcp 吸附)和-1.55%(fcc 吸附), 因此实际上最有可能的情况是两种吸附方式都有一定的几率. 而实验中观察到的“清洁”Ru(0001)表面实际上是有少量氢原子污染的表面. 不同覆盖度和氢分压下氢原子吸附的污染对Ru(0001)表面结构有极大的影响,其表面的各种特性都会随覆盖度的不同而产生相应的变化.     

氢原子在Ni(100), Ni(111)和Ni(110)面上吸附扩散势能面的结构

本文构造了氢-镍相互作用的5参数Morse势, 用经典的对势方法研究氢原子在Ni(100), Ni(111)和Ni(110)面上的吸附和扩散, 得到氢原子在三个表面上的吸附位、吸附几何、结合能及本征振动等数据, 和实验结果符合得很好。同时, 系统地研究了三个体系的吸附扩散势能面结构。     

氢原子在Ni(111)次表面和Ni(211)、(533)台阶面上的吸附与振动

应用原子与表面簇合物相互作用的五参数Morse势(5-MP)方法对氢原子在Ni(111)表面和次表面以及Ni(211), (533)台阶面进行了系统研究, 得到了氢原子在上述各面的吸附位、吸附几何、结合能和本征振动频率. 计算结果表明, 在Ni(111)面上, 氢原子优先吸附在三重位, 随着覆盖度的增加会吸附在次表面八面体位和四面体位. Ni(211), (533)的最优先吸附位都是四重位, 当氢原子的覆盖度增大时占据(111)平台的三重吸附位. 靠近台阶面的吸附位受台阶和平台高度的影响很大. 此外, 我们计算了氢原子在各表面的不同吸附位的扩散势垒, 获得氢原子在各表面的最低能量扩散通道.     

氢原子在镍台阶面上吸附、振动和表面扩散行为的理论研究

本文用对势方法研究了氢原子在Ni(510)台阶面上的吸附和振动, 计算结果与实验符合得很好。并考察了氢原子在Ni(997)台阶面上的吸附和扩散, 结果表明,台阶对下台面上扩散的氢原子开成捕获势阱, 对上台面扩散的氢原子形成反射势,这也很好地支持了实验结果。     

原子氧在Ru低指数面及(1120), (1121)台阶面上的吸附

利用原子与表面簇合物相互作用的5参数Morse势方法(简称5-MP)系统地研究了O-Ru低指数面及Ru(1120), (1121)台阶面体系, 获得了吸附几何、结合能、振动频率等临界点特性, 所得相关数据与实验结果非常吻合. 并且通过理论计算及原子吸附态振动指纹的遗传、遗变特性预言了氧原子在Ru(1121)台阶面的吸附. 本文认为氧原子在HCP晶格的金属表面上的吸附倾向于三重位.     

原子H在Cu(100)(111)(110)上的吸附扩散研究

采用5-MP势方法,对原子氢在金属Cu的3个低指数面上的吸附特性,如吸附几何、吸附能、振动频率等以及吸附扩散势能面结构进行了比较系统的研究,计算结果显示低温低覆盖条件下,氢原子在Cu(110)表面上只存在赝式三重位和长桥位吸附态,没有短桥位吸附态,并且获得了实验和理论的支持.     

H原子在Ru(111)台阶面上的吸附位和吸附态

利用原子和表面簇合物相互作用的五参数 Morse势方法 (简称 5 -MP)研究了 H-Ru( 1 1 2 1 )台阶面吸附体系 ,并利用推广的 LEPS方法研究了 2 H-Ru( 1 1 2 1 )体系 ,探讨了表面吸附态之间的相互作用 .研究结果表明 ,H原子在开放的 Ru( 1 1 2 1 )台阶面表面上的晶胞存在 4种不等价的表面三重吸附态 .还存在两类与表面有直接扩散通道的内层吸附态 .理论分析表明 ,TDS实验出现的 α态是与内层吸附态有强相互作用的强排斥表面吸附态 ,β态为弱排斥表面吸附态 ,而 γ态为与内层吸附态无相互作用的表面吸附态 .实验上将 α态归属为四重吸附态的推测没有获得理论结果的支持 .     

氢原子在Pd(997)台阶面上的吸附和扩散

用对势方法研究了氢原子在Pd（997）台阶面上的吸附和扩散．计算结果表明，氢原子在台阶下形成最稳定的吸附态，并分析了其新的振动模式．理论分析表明，台阶对下台面上扩散的氢原子形成捕获势，对上台面扩散的氢原子形成反射势，很好地支持了实验结果．     

H原子在Ru(1121)台阶面上的吸附位和吸附态

利用原子和表面簇合物相互作用的五参数Morse势方法(简称5-MP)研究了H-Ru(1121)台阶面吸附体系,并利用推广的LEPS方法研究了2H-Ru(1121)体系,探讨了表面吸附态之间的相互作用.研究结果表明,H原子在开放的Ru(1121)台阶面表面上的晶胞存在4种不等价的表面三重吸附态.还存在两类与表面有直接扩散通道的内层吸附态.理论分析表明,TDS实验出现的α态是与内层吸附态有强相互作用的强排斥表面吸附态,β态为弱排斥表面吸附态,而γ态为与内层吸附态无相互作用的表面吸附态.实验上将α态归属为四重吸附态的推测没有获得理论结果的支持.     

Hydration processes of electrolyte anions and cations on pt(111), Ir(111), Ru(001) and Au(111) surfaces: coadsorption of water molecules with electrolyte ions

Water adsorption on Pt( 111) and Ru(001) treated with oxygen, hydrogen chloride and sodium atom at 20 K has been studied by Fourier transform infrared spectroscopy, scanning tunneling microscopy and surface X-ray diffraction. Water molecules chemisorb predominantly on the sites of the electronegative additives, forming hydrogen bonds. Three types of hydration water molecules coordinate to an adsorbed Na atom through an oxygen lone pair. In contrast, water molecules adsorb on electrode surfaces in a simple way in solution. In 1 mM CuSO4 + 0.5 M H2SO4 solution on an Au(111) electrode surface, water molecules coadsorb not only with sulfuric acid anions through hydrogen bonding but also with copper, over wide potential ranges. In the first stage of underpotential deposition (UPD), each anion is accommodated by six copper hexagon (honeycomb) atoms on which water molecules dominate. At any UPD stage water molecules interact with both the copper atom and sulfuric acid anions on the Au(111) surface. Water molecules also coadsorb with CO molecules on the surface of 2 x 2-2CO-Ru(001). All of the hydration water molecules chemisorb weakly on the surfaces. There appears to be a correlation between the orientation of hydrogen bonding water molecules and the electrode potential.     

Adsorption of bisulfate on the Ru(0001) single crystal electrode surface

Adsorption of anions from sulfuric acid solutions has been studied on Ru(0001) single crystal and polycrystalline surfaces by electrochemical techniques and in-situ Fourier transform infrared spectroscopy. Infrared spectroscopy shows that bisulfate is the anion adsorbed on the Ru(0001) surface. The bisulfate adsorption is detected at the H₂ evolution potential and extends into the potential region where the Ru surface is oxidized. A method for extracting unipolar bands from bipolar bands has been presented. The tuning rate of adsorbed bisulfate in the double layer potential region of Ru(0001) was found to be significantly smaller than those observed for other platinum metals. This has been ascribed to a small change in bisulfate coverage on Ru(0001) in this potential range. Bisulfate vibration frequencies are higher on this surface than at any face-centered cubic metal with the (111) orientation. Oxidation of the Ru(0001) surface is limited to one electron per Ru atom, distinctly different from the high degree of oxidation seen in polycrystalline surfaces. For oxidized polycrystalline Ru, only solution phase sulfates and bisulfates are observed in the IR spectra.     

The structure, growth and reactivity of electrodeposited Ru/Au(111) surfaces

In order to elucidate electronic effects on the oxidation of CO on small Ru clusters, we investigated this reaction on well defined Ru/Au(111) model systems via parallel in-situ STM studies of the structure and electrochemical deposition of Ru on Au(111) in H₂SO₄ solution and cyclic voltammetry of CO monolayer oxidation on these surfaces. The Ru deposit consists of nanoscale islands, which coalesce with increasing coverage. The Ru saturation coverage depends on the deposition potential, resulting in Ru submonolayer (>0.1 V), (defective) monolayer (≥−0.1 V), and multilayer films (<−0.1 V). At potentials >0.6 V irreversible formation of Ru oxide/hydroxide species is observed, which can be partly reduced in the range 0.4 to 0.0 V. CO stripping commences at ≈0.1 V and occurs over a broad potential range. From the stripping charge a local CO coverage on the Ru monolayer islands of 0.7 ML was estimated. The observed influence of the morphology of the Ru deposit on the CO stripping voltammetry is explained by (local) variations in the CO adsorption energy due to electronic modifications of the Ru film.     

Interaction of CO and deuterium with bimetallic, monolayer Pt-island/film covered Ru(0001) surfaces

The adsorption properties of structurally well defined bimetallic Pt/Ru(0001) surfaces, consisting of a Ru(0001) substrate partly or fully covered by monolayer Pt islands or a monolayer Pt film, were studied by temperature programmed desorption (TPD) using CO and deuterium as probe molecules. Additionally, the adsorption of CO was investigated by infrared reflection absorption spectroscopy (IRAS). The presence of the pseudomorphic platinum islands or monolayer film leads to considerable modifications of the adsorption properties for both adsorbates, both on the Pt covered and, to a smaller extent, on the bare Ru part of the surfaces. In addition to distinct weakly bound adspecies, which are adsorbed on the monolayer Pt islands, we find unique contributions from island edge desorption, from spill-over processes during the desorption run, and a general down-shift of the peak related to desorption from Pt-free Ru(0001) areas with increasing Pt coverage. These effects, which we consider as characteristic for adsorption on bimetallic surfaces with large contiguous areas of the respective types, are discussed in detail.     

CO在Cs/Ru(1010)表面上吸附的ARUPS研究

CO adsorption on Ru(100) and Cs/Ru(10O) surfaces has been investigated using ARUPS, at low temperature 150K. The 5σ+1π and 4σ levels of CO molecule were　found in angle-rcsolved UP spectra showing that CO is in molecular adsorption states on clean and Cs precovercd Ru(1010). The dependence of CO 4σ intensity on incident angle suggests that adsorbed CO stands upright on clean Ru(1010) surface; But adsorbed CO, with a short-range interaction with Cs atom [15], does not stand upright and tilts in <1210> azimuth on a Cs-precovered Ru(1010) surface.     

Adsorption Site and State of Nitrogen Atom on Ru（0001）, （1010） Low-index and （1120）, （1121） Stepped Surfaces

The adsorptions of nitrogen atoms on Ru(0001), (1010) low index surfaces and (1120), (1121) stepped surfaces were investigated by the five-parameter Morse potential(5-MP) method in details. Calculated results demonstrate that N atoms show a tendency to be adsorbed at threefold sites. No subsurface state was found for N atoms on Ru(1010) surface. There exist 6 stable adsorption sites for N atoms on Ru(1121) stepped surface which can be classified into 3 types: the on-surface adsorption state, the facet adsor...     

Ni(115)台阶面对氢表面微观动力学行为的影响

用５参数Ｍｏｒｓｅ势模拟氢－镍表面体系相互作用势，考察了氢原子在Ｎｉ（１１５）台面上吸附扩散行为。同时构造了氢分子与Ｎｉ（１００）和Ｎｉ（１１５）台阶面 相互作用推广的ＬＥＰＳ势面面，考察了氢分子解离化学吸附的微观动力学性质。