氧分子在Pt低指数面上的吸附和解离

应用原子和表面簇合物相互作用的5参数Morse势方法(简称5-MP)构造推广的LEPS势对O₂-Pt分子体系进行了系统的研究, 获得了O₂分子在Pt的2个低指数面(111)和(110)重构面上的吸附几何、结合能和振动频率等临界点性质; 计算结果显示O₂在Pt(111)面上难解离, 且存在超氧化吸附态, 同时, 应用表面分子解离限和晶面解离距的概念分析了(111)面上的解离机理; 并根据分子指纹性质, 将O₂在Pt(110)缺行重构面上出现的振动频率860, 930, 1250 cm^－1进行了合理的指派.     

氧原子和羟基在Ni低指数表面的吸附动力学研究

应用5-参数Morse势方法模拟了O－Ni表面相互作用势,考察了氧原子在镍三个低指数表面的吸附特性.同时构造了羟基与Ni（100）、Ni（110）和Ni（111）表面相互作用的推广LEPS势,获得了羟基在表面的吸附位、吸附几何、结合能及本征振动等数据.理论结果表明,羟基垂直吸附于镍表面的高对称位是稳定的,垂直吸附于Ni（100）表面4-重洞位的吸附能为96.98 kJ•mol－1,垂直吸附于Ni（111）表面3-重洞位的吸附能为96.00 kJ•mol－1,在Ni（110）表面存在两种吸附态：垂直吸附于长桥位的吸附能为99.38 kJ•mol－1,倾斜14°吸附于赝势三重位吸附能为96.98 kJ•mol－1.理论结果与实验结果符合得较好.     

红外光谱研究Pt-Re/Al2O3重整催化剂的表面结构

CO和NO吸附或两者竞争吸附在Pt／Al2O3，Re／Al2O3和Pt－Re／Al2O3催化剂上的红外光谱可以给出Pt和Re的表面结构信息．本文研究的催化剂为低金属载量的Pt／Al2O3，Re／Al2O3和工业型Pt－Re／Al2O3，其中Pt含量0．22％，Re含量0．43％（质量分数）．实验结果表明，用NO与CO双分子竞争吸附的红外光谱实验方法可分别表征还原态Pt－Re／Al2O3重整催化剂上Pt表面和Re表面，并视需要可对Pt表面和Re表面进行半定量分析．在还原态工业型Pt－Re／Al2O3重整催化剂表面上，没有明显迹象表明有Pt－Re合金形成．     

H原子在W低指数面上的吸附位和吸附态

应用原子和表面簇合物相互作用的5参数Morse 势及由5参数Morse势组装推广的LEPS方法对H-W低指数表面吸附体系进行了研究, 并获得了全部临界点特性. 计算结果表明, 低覆盖度下, H原子优先吸附在W(100)面的内层吸附位二层桥位B', 获得156 meV的垂直振动频率, 随着覆盖度的增加, H原子稳定吸附在表层的五重洞位(二层顶位)、桥位及顶位. 内层吸附位的优先吸附, 对与其邻近的表面吸附位的临界点性质有一定影响. 在W(110)面上只存在三重洞位的稳定吸附态, 垂直振动频率为151 meV. 在W(111)面上存在三种稳定吸附态, 子表面吸附位H₁, 桥位B'和顶位T, 分别获得104, 200, 259 meV的垂直振动频率. 在低覆盖度下, H原子优先吸附在子表面吸附位H₁.     

CO在Pt低指数面上吸附行为的理论研究

用密度泛函理论(DFT)中的广义梯度近似(GGA)方法对CO-Pt低指数面吸附体系进行了结构优化, 并对吸附体系的吸附热、C—O键和C—Pt键的键长、布居数分析、电子态密度进行了研究. 计算结果表明, 在0.25 ML(monolayer)的覆盖率下, CO最容易在Pt(100)晶面的桥位、Pt(110)晶面的短桥位、Pt(111)晶面的hcp三重位吸附, 吸附热分别达到了2.11、2.37、1.96 eV; CO在吸附成键过程中伴有电子在CO分子和Pt之间的转移. 吸附后, C—O键被削弱, 键长变长, 金属内部的作用亦被削弱, 其表层Pt 原子的布居数明显降低; 态密度分析表明, CO在吸附过程中, 其4σ、1π、5σ、2π轨道均参与成键.     

CO在某些过渡金属表面吸附活化的DFT研究

采用DFT方法对CO在M(100)(M= Cu、Ag、Au、Pd、Pt)表面上的吸附行为进行了系统的比较性研究.结果表明,CO分子在这些过渡金属单晶表面上发生的是非解离性吸附,吸附后C－O键长都变长了,均不同程度地削弱了C－O键,继而活化了CO分子；从表面结合能、重叠集居数、轨道电子数变化等方面分析了成键强弱顺序,发现CO的吸附强度随Pd(100)、Pt (100)、Cu (100)、Ag(100)、Au(100)顺序依次减弱,并且将CO与过渡金属间的结合能(BE)、过渡金属的d电子转移数分别与水煤气变换反应活性数据进行了关联,在定性上比较好地解释了金属铜的催化活性优于其它金属的原因.     

一氧化碳分子在Pt/t-ZrO2(101)表面的吸附性质

运用广义梯度密度泛函理论(GGA-PW91)结合周期平板模型方法,研究了CO分子在完整与Pt负载的四方ZrO2(101)表面的吸附行为.结果表明:表面第二层第二氧位和表面第二桥位分别为CO分子和Pt原子在完整ZrO2(101)表面的稳定吸附位,且覆盖度为0.25ML(monolayer)时均为稳定吸附构型,吸附能分别为56.2和352.7kJ·mol-1.CO分子在负载表面的稳定吸附模式为C-end吸附,吸附能为323.8kJ·mol-1.考察了CO分子在负载表面吸附前后的振动频率、态密度和轨道电荷布居分析,并与CO分子和Pt原子在ZrO2表面的结果进行比较.结果表明,C端吸附CO分子键长为0.1161nm,与自由的和吸附在ZrO2表面后的CO相应值(0.1141和0.1136nm)相比伸长.吸附后C―O键伸缩振动频率为2018cm-1,与自由CO分子相比发生红移;吸附后CO带部分正电荷,电子转移以Pt5dCO2π的π反馈机理占主导地位.     

N2在W(001)表面上吸附模式的研究

1976年McCreery等提出了双原子分子—固体表面吸附势的研究方法,这是一种改进的LEPS法.本文用该方法研究了N_2在W(001)表面上的吸附模式.该法建议用下式来表示双原子—固体表面的相互作用势:     

CN在 Pt(100)表面吸附的密度泛函研究

采用密度泛函方法,以原子簇Pt14为模拟表面,对CN自由基分子在Pt(100)表面上不同吸附位的吸附情况进行了研究.结果表明,CN分子吸附在Pt(100)面上时,通过原子C垂直吸附在表面顶位是其最佳吸附方式,CN键振动频率明显发生蓝移,与实验事实相吻合;而在桥位及四方穴位吸附时CN键振动频率均发生红移.吸附前后,CN分子的σ、π电子与底物间的电荷转移的差异决定了CN键振动频率的不同变化.     

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 .     

Adsorption of carbon monoxide on Pd low‐index surfaces and (110) reconstructed surface

Adsorption and diffusion of carbon monoxide on Pd low‐index surfaces and missing‐row Pd (110) reconstructed surface have been investigated by the extended London–Eyring–Polyani–Sato (LEPS) method constructed by means of a five‐parameter Morse potential. All critical characteristics, such as adsorption site, adsorption geometry, binding energy, CO vibrational frequency have been obtained and compared with the experimental and theoretical data. On these surfaces, the stable adsorption sites of CO are changed with increasing CO coverage. On the missing‐row Pd (110) reconstructed surface, there are five stable adsorption sites: H₁, H₂ (H₁ and H₂ are threefold hollow sites on (111) subsurface), B (bridge site on the second layer), SB (short‐bridge site), and T (top site). Copyright © 2010 John Wiley & Sons, Ltd.     

DFT investigation of CO adsorption on Pt(211) and Pt(311) surfaces from low to high coverage

Adsorption of CO on Pt(211) and Pt(311) surfaces has been investigated by the density functional theory (DFT) method (periodic DMol3) with full geometry optimization. Adsorption energies, structures, and C-O stretching vibrational frequencies are studied by considering multiple possible adsorption sites and comparing them with the experimental data. The calculated C-O stretching frequencies agree well with the experimental ones, and precise determination of adsorption sites can be carried out. For Pt(211), CO adsorbs at the atop site on the step edge at low coverage, but CO adsorbs at the atop and bridge sites simultaneously on both the step edge and the terrace with further increasing CO coverage. The present results interpret the reflection adsorption infrared (RAIR) spectra of Brown and co-workers very well from low to high coverage. For Pt(311), CO adsorbs also at the atop site on the step edge at low coverage. The lifting of reconstruction by CO adsorption occurs also for Pt(311), whereas the energy gain for lifting the reconstruction of the Pt(311) surface is smaller than that for Pt(110). The largest difference between the stepped Pt(211)/Pt(311) and Pt(110) surfaces is the occupation on the edge sites at higher coverage. For the stepped surfaces, the bridge site begins to be occupied at higher coverage, whereas the atop site is always occupied for the Pt(110) surface.     

Studies of CO adsorption on Pt(100), Pt(410), and Pt(110) surfaces using density functional theory

Adsorption of CO on Pt(100), Pt(410), and Pt(110) surfaces has been investigated by density functional theory (DFT) method (periodic DMol(3)) with full geometry optimization and without symmetry restriction. Adsorption energies, structures, and vibrational frequencies of CO on these surfaces are studied by considering multiple possible adsorption sites and comparing them with the experimental data. The same site preference as inferred experiments is obtained for all the surfaces. For Pt(100), CO adsorbs at the bridge site at low coverage, but the atop site becomes most favorable for the c(2 x 2) structure at 1/2 monolayer. For Pt(410) (stepped surface with (100) terrace and (110) step), CO adsorbs preferentially at the atop site on the step edge at 1/4 monolayer, but CO populates also at other atop and bridge sites on the (100) terrace at 1/2 monolayer. The multiple possible adsorption sites probably correspond to the multiple states in the temperature-programmed desorption spectra for CO desorption. For Pt(110), CO adsorbs preferentially at the atop site on the edge for both the reconstructed (1 x 2) and the un-reconstructed (1 x 1) surfaces. When adjacent sites along the edge row begin to be occupied, the CO molecules tilt alternately by ca. 20 degrees from the surface normal in opposite directions for both the (1 x 2) and (1 x 1) surfaces.     

The adsorption and dissociation of O2 on Cu low-index surfaces

The extended LEPS of O(2)-Cu single crystal plane systems is constructed by means of 5-MP (the 5-parameter Morse potential). Both the adsorption and dissociation of O(2) on Cu low-index surfaces are investigated with extended LEPS in detail. All critical characteristics of the system that we obtain, such as adsorption geometry, binding energy, eigenvalues for vibration, etc., are in good agreement with the experimental results. Our calculated results suggest there are many differences between O(2)-Cu (110) and O(2)-Pd (110) systems. On a Cu (110) surface, O(2) adsorbs in a tilted configuration and there are two lowest energy dissociation channels along the [001] and [10] directions, respectively. We speculate that the adsorption geometry of O(2) on the metal surfaces relates to the lattice constant of metal. Meanwhile, We use the concepts of the molecular dissociation limit and the surface dissociation distance to analyze again the dissociation mechanism of the O(2) on the low-index surfaces.     

Electrochemical behaviour of oxocarbons on single crystal platinum electrodes: Part V. Tetrahydroxy-p-benzoquinone in 0.5 M sulphuric acid medium

The electrochemical behaviour of tetrahydroxy-p-benzoquinone (THQ) on Pt(111), Pt(100) and Pt(110) surfaces has been studied in sulphuric acid solutions by cyclic voltammetry. The experimental results show that THQ is the oxocarbon having a lesser tendency to form CO-like species after adsorption on platinum surfaces. THQ is directly adsorbed on Pt(111) and Pt(100), although it is not stable and undergoes a slow reaction to CO adspecies on Pt(100) surfaces. Clear evidence of CO adspecies has been found only on Pt(100) electrodes.     

The adsorption and co-adsorption of oxygen and carbon monoxide on Pt3Ni(111): a vibrational study

High-resolution electron energy loss spectroscopy has been used to investigate the adsorption and co-adsorption of oxygen and CO on the Pt(3)Ni(111) surface. For the sake of comparison, similar measurements have also been performed on the Pt(111) surface. We find that CO adsorbs at the same manner on both surfaces. By contrast, significant differences between the two surfaces exist concerning the adsorption of O and the co-adsorption of O with CO.     

Studies of surface processes of electrocatalytic reduction of CO_2 on Pt(210), Pt(310) and Pt(510)

Surface processes of CO2 reduction on Pt(210), Pt(310), and Pt(510) electrodes were studied by cyclic voltammetry. Different surface structures of these platinum single crystal electrodes were obtained by various treatment conditions. The experimental results illustrated that the electrocatalytic activity of Pt single crystal electrodes towards CO2 reduction is decreased in an order of Pt(210)>Pt(310)>Pt(510), i.e., with the decrease of (110) step density on well-defined surfaces. When the surfaces were reconstructed due to oxygen adsorption, the catalytic activity of all the three electrodes has been enhanced to a cer- tain extent. Although the activity order remains unchanged, the electrocatalytic activity has been en- hanced more significantly as the density of (110) step sites is more intensive on the Pt single crystal surface. It has revealed that the more open the surface structure is, the more active the Pt single crystal electrode will be, and the easier for the electrode to be transformed into a surface structure that exhib- its higher activity under external inductions. However, the relatively ordered surfaces of Pt single crystal electrode are comparatively stable under the same external inductions. The present study has gained knowledge on the interaction between CO2 and Pt single crystal electrode surfaces at a micro- scopic level, and thrown new insight into understanding the surface processes of electrocatalytic re- duction of CO2.     

Rh和Pt超薄层电极上的CO吸附行为(英文)

利用沉积在粗糙金电极上的过渡金属超薄层电极技术 ,我们获得了氢及一氧化碳在Rh和Pt表面上吸附的拉曼信号 ,并对两者之间的相互作用进行了分析 ..我们还进行了二氧化碳在这两种金属表面的还原行为的初步研究 ,以及对不同方式获得的一氧化碳吸附拉曼信号的特点进行了分析 .     

氧在C－Ni（100）表面反应动力学的研究──Ⅱ．动力学计算结果

根据Ｏ２＋Ｃ－Ｎｉ（１００）表面反应的推广ＬＥＰＳ势能面，并用ＱＣＴ方法研究了该体系的反应动力学行为．结果给出了分子化学吸附和解离原子化学吸附及ＣＯ脱附反应的分子动态特征，以及态－态过程的吸附几率．考察了各种能量形式对吸附、脱附几率的影响和各类吸附、脱附几率的变化规律．