铂单晶电极表面不可逆反应动力学──Ⅱ铂单晶(100)晶面电极上甲酸氧化反应动力学参数解析

运用程序电位阶跃方法，避免甲酸解离吸附的干扰，成功地研究了Pt（100）单晶电极上甲酸经活性中间体直接氧化至CO2的反应动力学．提出对电化学暂态实验数据进行积分变换求解动力学参数的方法，编制了相关的计算机软件，首次获得甲酸在Pt（100）单晶电极上直接氧化的反应动力学参数。结果给出在0．02V至0．15V电位区间，速率常数kf的对数随电极电位线性增长，kf从9．51×10－4上升到1．38×10－2cm·s－1．获得传递系数β＝0．309，5×10－3mol·L－1HCOOH＋0．5mol·L－1H2SO4溶液中甲酸的扩散系数D＝1．80×10－5cm2．s－1．     

Pt（111）电极上O2与OHad的吸脱附及氧还原反应动力学

研究了Pt（111）电极在0．1mol／LHClO4溶液中O2吸附与OHad脱附及氧还原反应的动力学．研究发现OHad的可逆吸脱附速率很快;在氧还原的动力学或动力学与传质混合控制区,恒电位下氧还原的电流随反应时间缓慢衰减,在转速较大,扫速较慢的情形下正向扫描过程中氧还原的电流总是明显低于逆向扫描的电流;Pt／0．1mol／LHClO4从无O2切换到O2饱和时,其开路电位迅速从0．9V增加到1．0V．结果表明,Pt（111）电极上O2解离生成OHad速率很快,ORR过程中OHad会在表面缓慢积累,氧还原反应的动力学主要由反应 OHad＋H^＋＋e→←H2O的平衡热力学决定．     

锑(III)在铂电极上的欠电位沉积行为

由于经欠电位沉积（UPD）形成的吸附金属原子居可以改变电极表面的结构和组成，从而达到增强电祝活性的目的，因此欠电位沉积在电化学领域中颇受重视．对于梯（Ⅲ）的欠电位沉积行为，自1953年Mills和Wills发现锑（Ⅲ）可在AS电极上形成单电子层[1]以后，Schimide等人和Motoo等人分别研究证实梯（Ⅲ）可在Au电极上[2]和Pt电极上[3]发生火电位沉积，并且Motoo等人使用梯（V）化合物测定了每个吸附梯原子占据的铂原子数[4]．本文试图用电位扫描法、微分电容法、电位阶跃法等实验方法对锑（Ⅲ）在柏电极上的大电位沉积并为进行系统的研究…     

硫酸溶液中Pt(111)电极面上存在SO2-4的XPS证据

Pt（111）电极在硫酸溶液中的循环伏安图已被多个研究小组所得到[1-3]．对图上出现的高于正常氢吸脱附电位出现的两个电流峰（Clavilier等[1]首次发现并称之为异常峰）的解释至今没有得到一致意见．分歧焦点是异常峰的出现是由于强键合吸附氢还是吸附其它阴离子所致·本文用XPS和LEED研究异常峰电位处浮出的Pt（111）电极表面，发现尖锐异常峰的出现是由于表面上吸附了离子．1实验文献＊中详细说明了实验所用装置．主要部份是把装有XPS、LEED、MS、Ar“枪的超高真空腔门HV）与测量循环伏安图的腔（EC）联在一起·UHV中基压强为4x…     

Pt和Sb、S吸附原子修饰的Pt电极上正丙醇氧化的CV和EQCM研究

运用电化学循环伏安法和石英晶体微天平研究了正丙醇在Pt电极和以Sb、S吸附原子修饰的Pt（Pt/Sbad和Pt/Sad）电极上的吸附和氧化过程.从电极表面质量变化角度指出正丙醇的氧化与电极表面氧物种有着极其密切的关系.Pt电极表面Sb吸附原子能在较低的电位下吸附氧，可显著提高正丙醇电催化氧化活性，与在Pt电极上相比较,正丙醇氧化的峰电位负移了0.29 V,峰电流增加了近2倍.相反,Pt电极表面S吸附原子的氧化会消耗表面氧物种，饱和吸附S原子的Pt电极上正丙醇的电氧化受到抑制.本文从表面质量变化提供了吸附原子电催化作用的新数据.     

Pt电极表面共吸附层NO和CO氧化还原的CV及原位FTIR研究

应用电化学循环伏安方法（CV）和原位傅里叶变换红外反射光谱（in situ FTIRS）研究了酸性溶液中Pt多晶电极表面NO和CO的共吸附行为及吸附态CO对吸附物种NO氧化还原反应的影响．研究结果表明,0．20V（VS．SCE）时,CO和NO能同时稳定吸附在Pt电极表面,CO以线性吸附态（CO L）存在,NO以桥式吸附态（NOB）和线性吸附态（NO L）共存．CO L 的共存使得NO的还原电流峰电位负移约0．024V,并且促使不易被氧化的NO B在0．93V处被氧化．原位FTIRS研究进一步表明,NO可以置换预吸附在电极表面的CO,NO和CO在Pt多晶电极表面的吸附是一个竞争吸附的过程．在0．45V-1．2V电位区间,NO和CO都能转化为环境友好产物,分别为NO3-和CO2．且Pt电极表面共吸附物种CO的量直接影响NO B的氧化产物NO3-的生成量．     

[Pt]—Ni（Ⅱ）电极的研究

我们首次发现Pt浸于镍、钴或铁盐溶液中,只有镍可形成[Pt]-Ni(Ⅱ)电极。在NaOH电解液中,此电极有明显的氧化还原峰,表现出Ni电极的特征。本文研究[Pt]-Ni(Ⅱ)电极的电化学性能、电极制备的影响因素。 1 实验部分 研究电极:Pt为基底,用5~#金相砂纸磨光,在王水中浸渍,二次蒸馏水冲洗(也可再进     

Pt(100)/离子液体OMIPF6界面结构的STM研究

本文运用电化学扫描隧道显微术研究了离子液体OMIPF₆中Pt（100）表面结构在电化学双层区随电极电位的变化. OMI⁺阳离子在Pt（100）表面形成有序吸附结构,并且在约1.2 V宽的电位区间内稳定地存在Pt（100）表面。在电位负于-0.6 V时,有序吸附结构会发生向无序吸附结构的转变. 在电位正于+0.6 V时,较强的静电排斥力才能克服OMIPF₆与Pt（100）表面之间的化学作用,从而导致OMI+阳离子的脱附. 研究表明,OMI+阳离子具有的较长烷基侧链与Pt金属产生的较强化学相互作用是影响该Pt（100）/ OMIPF6界面结构的重要因素.     

金属Pt表面水蒸汽分子吸附的量子力学计算

基于电子与振动近似方法和密度泛函B3LYP理论, 氧和氢原子选择6-311G**基函数, Pt选择赝势基组LanL2DZ, 优化得到Pt-OH₂结构和微观性质, 稳态结构Pt-H₂O分子中, Pt与H₂O不在同一平面, Pt倾向于与O原子结合. 计算了100～898.15 K温度下, 水蒸汽分子在Pt表面吸附反应的热力学函数值和平衡压力, 拟合得到ΔS⁰,ΔH⁰, ΔG⁰, ln p与温度的函数关系. 室温以上ΔG⁰＞0 kJ•mol^－1, 水蒸汽分子在Pt表面不能稳定吸附; 200 K以下, ΔG⁰＜0 kJ•mol^－1, 能够稳定吸附. 计算了不同温度下水蒸汽分子在Pt表面发生解离反应的ΔG⁰和平衡压力, 室温以上ΔG⁰＞0 kJ•mol^－1. 100～898.15 K温度下, 水蒸汽分子在Pt表面不容易发生解离, 实际反应过程中以完整分子形式参与反应.     

铂配合物cis-[Pt(NH_3)_2(4-mepy)Cl]NO_3与甲基-谷胱甘肽作用的NMR研究

使用质子核磁共振方法测定了新的抗癌活性配合物cis－[Pt（NH3）2（4－mepy）Cl]＋与甲基-谷胱甘肽（GS－Me）的反应及其动力学．结果表明Pt与GS－Me间形成1：1加合物．为了解结合部位，对Pt－GS－Me配合物进行pH滴定，由GS－Me的质子核磁共振谱对pH的依赖关系判断Gs－Me只通过S原子与Pt配位，而氨基和羧基不参与配位反应．由配体吡啶环质子核磁共振随时间的变化，提出了两步反应机制：首先GS－Me通过S原子与Pt配位，然后由于S配位的高度反位效应使反应的NH3活动化．通过1HNMR方法测定了第一步反应的速率常数k＝0．017L·mol－1·s－1（pH3．1）和k＝0．013L·mol－1·s－1（pH7．2）．     

In situ FTIRS studies of kinetics of HCOOH oxidation on Pt(110) electrode modified with antimony adatoms

The electrochemical behavior of irreversibly adsorbed antimony on a Pt(110) electrode (Pt(110)/Sb) with various coverages was studied using cyclic voltammetry. The kinetics of HCOOH oxidation via reactive intermediates on Pt(110)/Sb were investigated quantitatively by employing the potential step technique and in situ FTIR spectroscopy. The results demonstrated that Sb adatoms were stable on Pt(110) when the electrode potential was below 0.45 V (SCE). It has been revealed that the dissociative adsorption of formic acid can be inhibited by the presence of Sb_ad on the Pt(110) surface. The electrocatalytic effects of Sb_ad towards HCOOH oxidation consist in a negative shift of the oxidation potential (about 350 mV) and the enhancement of the oxidation current. Based on the data processing method of integration transform developed in our previous papers, the kinetics of HCOOH oxidation on Pt(110)/Sb electrodes of different θ_Sb have been investigated quantitatively, and both the rate constant k_f and the transfer coefficient β were determined and reported.     

Structure sensitivity of methanol electrooxidation pathways on platinum: an on-line electrochemical mass spectrometry study

By monitoring the mass fractions of CO(2) (m/z 44) and methylformate (m/z 60, formed from CH(3)OH + HCOOH) with on-line electrochemical mass spectrometry (OLEMS), the selectivity and structure sensitivity of the methanol oxidation pathways were investigated on the basal planes--Pt(111), Pt(110), and Pt(100)--and the stepped Pt electrodes--Pt(554) and Pt(553)--in sulfuric and perchloric acid electrolytes. The maximum reactivity of the MeOH oxidation reaction on Pt(111), Pt(110), and Pt(100) increases in the order Pt(111) < Pt(110) < Pt(100). Mass spectrometry results indicate that the direct oxidation pathway through soluble intermediates plays a pronounced role on Pt(110) and Pt(111), while, on Pt(100), the indirect pathway through adsorbed carbon monoxide is predominant. In 0.5 M H(2)SO(4), introducing steps in the (111) plane increases the total reaction rate, while the relative importance of the direct pathway decreases considerably. In 0.5 M HClO(4), however, introducing steps increases both the total reaction rate and the selectivity toward the direct oxidation pathway. Anion (sulfate) adsorption on (111) leads to a more prominent role of the direct pathway, but, on all the other surfaces, (bi)sulfate seems to block the formation of soluble intermediates. For both electrolytes, increasing the step density results in more methylformate being formed relative to the amount of CO(2) detected, indicating that the [110] steps themselves catalyze the direct oxidation pathway. A detailed reaction scheme for the methanol oxidation mechanism is suggested based on the literature and the results obtained here.     

Sb在Pt(100),Pt(110),Pt(111)及Pt(320)上不可逆吸附的电化学特性

研究了Sb在Pt(1 0 0 ) ,Pt(1 1 0 ) ,Pt(1 1 1 )和Pt(32 0 )单晶面上不可逆吸附的电化学特性 .发现当扫描电位的上限Eu≤ 0 .45V时 ,Sbad可以稳定地吸附在Pt(1 0 0 ) ,Pt(1 1 0 )和Pt(1 1 1 )表面 ,而Sbad在Pt(32 0 )表面稳定的电位较低 ,为Eu≤ 0 .40V .从饱和吸附Sb的铂单晶电极出发 ,通过改变电位扫描上限Eu 和电位扫描圈数可以获得不同Sb覆盖度 (θSb)的电极 .根据Sb和H在铂单晶电极表面共吸附的定量数据 ,对Sb在不同铂单晶面上饱和吸附的模型进行了初步探讨 .     

Effect of mass transfer process on hydrogen adsorption on polycrystalline platinum electrode in sulfuric acid solution

The hydrogen adsorption on polycrystalline platinum electrode experimentally as well as on single crystal Pt(110), Pt(100) and Pt(111) electrode theoretically were studied. The study of forced convection on the electrode surface promotes the HUPD research from static process to a convective mode and provides a new strategy to investigate the hydrogen adsorption in solution.     

Reaction mechanism of methanol decomposition on Pt‐based model catalysts: A theoretical study

The decomposition mechanisms of methanol on five different Pt surfaces, the flat surface of Pt(111), Pt‐defect, Pt‐step, Pt(110)(1 × 1), and Pt(110)(2 × 1), have been studied with the DFT‐GGA method using the repeated slab model. The adsorption energies under the most stable configuration of the possible species and the activation energy barriers of the possible elementary reactions involved are obtained in this work. Through systematic calculations for the reaction mechanism of methanol decomposition on these surfaces, we found that such a reaction shows the same reaction mechanism on these Pt‐based model catalysts, that is, the final products are all H (H_ads) and CO (CO_ads) via O? H bond breaking in methanol and C? H bond scission in methoxy. These results are in general agreement with the previous experimental observations. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010.     

Structure-relationships in electrocatalysis: oxygen reduction and hydrogen oxidation reactions on Pt(111) and Pt(100) in solutions containing chloride ions

Kinetics of the oxygen reduction reaction (orr) and the hydrogen evolution–oxidation reactions (her/hor) were studied on the Pt(111) and Pt(100) surfaces in 0.05 M H₂SO₄ containing Cl⁻. The orr is strongly inhibited on the (100) surface modified by adsorbed Cl⁻ (Cl_ad), and it occurs as a 3.5e⁻ reduction via solution phase peroxide formation. In the hydrogen adsorption (H_upd) potential region, the orr is even more inhibited, and corresponds only to a 2 e⁻ reduction at the negative potential limit where the electrode is covered by one monolayer of H_upd and some (unknown) amount of Cl_ad. On the Pt(111)---Cl_ad surface, the orr is inhibited relatively little (in addition to that caused by strong bisulfate anion adsorption on this surface), and the reaction pathway is the same as in Cl⁻ free solution. The kinetics of the hor on Pt(111) are the same in pure solution and in a solution containing Cl⁻, since Cl_ad does not affect platinum sites required for the breaking of the H---H bond. A relatively large inhibition of the hor is observed on the (100) surface, implying that strongly adsorbed Cl_ad is present on the surface even near 0 V.     

微型氧弹热量计和C60及C70的燃烧焓

富勒烯是新发现的一类碳的稳定单质，其分子骨架中含有多个五员环及非平面球壳状大力键.与全为六员环的平面大r键的石墨结构相比，这些张力提高了分子能量.通过富勒烯的生成焰的测定，对了解这些分子的稳定性和反应性，它们的生成机理，以及研究分子的结构与能量的规律是很有意     

Adsorbed intermediates of formaldehyde oxidation and their role in the reaction mechanism

Formaldehyde oxidation was studied on the basal planes of platinum single crystals. Electrochemical and IR spectroscopy data give new information on the mechanism of oxidation. Formaldehyde oxidation at platinum electrodes is a surface-sensitive reaction. From the three basal planes of Pt(hkl), Pt(111) is the most active one. The less active surfaces Pt(100) and Pt(110) are blocked by adsorbed carbon monoxide at the initial stages of the reaction as the formaldehyde is admitted in the solution with the electrode polarized at 0.05 V. Besides CO(ad), other adsorbed species are formed. From these, methylene glycolate, H2COO(ad), is the intermediate of the fast oxidation pathways forming CO2 and HCOOH as soluble products. According to IR data the yields of soluble products at Pt(111) were calculated at 0.6 V, giving 63% for HCOOH and 37% for CO2. At 0.05 V the Pt(111) surface becomes slowly blocked by CO(ad), as observed when the electrode was left in contact with the formaldehyde solution over a period of several minutes. The same blockage occurs during a cyclic voltammogram, which causes a lowering of activity during the second potential scan. A general scheme of the reaction is proposed.     

HNCO热解为CO2和HNCNH的反应机理理论研究

利用从头算ＲＨＦ／３－２１Ｇ方法研究了ＨＮＣＯ二聚后生成ＨＮＣＮＨ和ＣＯ２的反应机理。计算表明,该反应是分步反应,由反应物经第一过渡态生成四元环中间体,再经过第二过渡态分解为产物,与实验得到的结论一致。反应的第一步是速度控制步骤,计算得到的活化位垒为１７２．５５ｋＪ·ｍｏｌ＾－１,与实验上测得的１７６．４０±１６．３０ｋＪ·ｍｏｌ＾－１相吻合。反应的第二位垒为８３．６８ｋＪ·ｍｏｌ＾－１,在实验条     

等电子-等自旋与非等旋反应的G2(MP2)和G2研究

我们在前文［1－2］中分别用MP2－4／6－31G**／／MP2／6－31G**及MP4／6－311G（2df，Zpd）／／MP2／6－31G**研究了一些双原子氢化物、卤化物、硫化物和氧化物的化学反应的烂变·这些化学反应按如下类型分为四组，即（1）反应物与生成物之间为等电子一等自旋关系，（2）价层等电一等旅，（3）等施和（4）非等旅·结果表明，MP4／6－3fiG（2才，ZPd）对于（1），（2）和（3）类反应，基本上与实验误差小于士15kJ·mo－‘而对非等旋反应仍有较大误差；MPZ－4／6－31G””只对（1）类反应较好．由于PoPle等人近几年来创立的Gaussi…