Pt(111)单晶电极上乙二醇解离吸附反应动力学

运用电化学循环伏安和程序电位阶跃方法研究了乙二醇在Pt(111)单晶电极上的解离吸附过程.动力学研究的定量结果指出,乙二醇解离吸附反应的平均速率随电极电位变化呈火山型分布,其最大值在0.10 V(vs SCE)附近.测得在含2×10－3 mol•L－1乙二醇的溶液中,最大初始解离速率vi为4.35×10－12 mol•cm-－2•s－1.     

铂电极上锑吸附原子对1,2-丙二醇电催化氧化性能的影响

运用电化学循环伏安(CV)和电化学原位石英晶体微天平(EQCM)研究了Pt电极表面不可逆吸附Sb原子的电化学特性以及Pt电极上Sb吸附原子对0.1mol·L-1H2SO4溶液中1,2 丙二醇电催化氧化性能的影响.研究发现,当扫描电位的上限Eu≤0.50V(SCE)时,Sb可以稳定地吸附在Pt电极表面,饱和覆盖度为0.34;通过控制电位扫描上限和扫描圈数剥离部份Sb可方便地得到Sbad的不同覆盖度;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1,2 丙二醇电催化氧化活性.与Pt电极相比较,Sb饱和吸附原子修饰的Pt电极使1,2 丙二醇氧化的峰电流增加了近2倍.作者还从表面质量变化提供了吸附原子电催化作用的新数据.     

碱性介质中甘氨酸在Pt电极上解离吸附和氧化反应的原位红外反射光谱研究

运用原位红外反射光谱研究了碱性介质中甘氨酸在Pt电极上的解离吸附和氧化反应行为,并利用纳米Pt膜电极的异常红外效应鉴定反应过程中生成的表面吸附物种.结果表明:甘氨酸在Pt电极上极易发生解离,生成强吸附于电极表面上的氰基负离子,该吸附物种在低于0V电位下能稳定存在,并抑制甘氨酸的进一步反应.当电位高于0.2V时,氰基负离子被氧化为氰酸根离子进入溶液,使甘氨酸发生氧化反应,生成氰酸盐和碳酸盐等产物.     

二十四面体Pt纳米晶电极上甲酸解离吸附反应动力学研究

研究了甲酸在二十四面体Pt纳米晶（THHPtNCs）电极表面解离吸附反应过程.电化学原位红外反射光谱结果显示,甲酸在低电位（-0.20V（SCE））即可在THHPtNCs电极上氧化到CO2,同时发生分子内化学键断裂生成吸附态CO物种.运用程序电位阶跃暂态方法定量研究甲酸解离吸附反应动力学,测得5×10^-3mol·L^-1 HCOOH＋0.1mol·L^-1 H2SO4溶液中甲酸在THHPtNCs电极上解离吸附的最大平均速率υamax为13.19×10^-10mol·cm^-2·s^-1,是商品Pt/C催化剂电极上υamax的1.5倍.研究结果揭示了THHPtNCs的反应活性显著高于Pt/C催化剂.     

酸性和碱性介质中甘氨酸解离吸附和氧化的EQCM研究

用电化学石英晶体微天平(EQCM)研究酸性和碱性介质中甘氨酸在Pt电极上的吸附和氧化过程.结果表明,甘氨酸的解离吸附和氧化行为与溶液的酸碱性密切相关.酸性溶液中甘氨酸吸附较弱,碱性溶液中则产生强吸附物,且当电位低于0V(vs.SCE)时可吸附于Pt电极表面.此外,碱性溶液中甘氨酸还表现出较高的电氧化活性.通过EQCM定量检测上述过程中Pt电极表面的质量变化,测定了不同电位区间(氢区、双电层区和氧区)每传递一个电子所对应的电极表面吸附物种的平均摩尔质量.     

丙三醇在Pt电极上吸附和氧化过程的原位FTIR反射光谱研究

运用电化学循环伏安(CV)和原位FTIR反射光谱方法,研究了丙三醇在Pt电极上的氧化过程。结果指出,丙三醇的氧化是一个复杂的表面过程,其间包括脱水、吸附、解离等步骤.根据CV和红外实验数据,本文提出了Pt电极上丙三醇解离吸附的表面反应机理和不同电位下丙三醇氧化的分子过程。     

中性介质中L-丝氨酸在Pt电极上解离吸附和氧化的原位FTIR研究

运用电化学循环伏安(CV)和原位红外反射光谱(in situ FTIRS)研究了中性介质中L-丝氨酸在Pt电极上的解离吸附和氧化过程. 结果表明, 在中性溶液中, 以两性离子形式存在的丝氨酸可以在很低的电位下(-0.6 V, vs. SCE)在Pt电极表面发生解离吸附, 生成强吸物种一氧化碳(COL)、(COB)和氰负离子(CN-). 研究结果还表明, 当电位低于0.7 V(vs. SCE)时, CN-能稳定存在于电极表面, 抑制丝氨酸的进一步反应. 在更高电位时则主要为丝氨酸分子的氧化过程.     

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 .     

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.     

甘氨酸修饰的Pt(111)电极上的氧还原

利用单晶旋转圆盘电极技术（Hanging Meniscus Rotating Disk Electrode,　HMRD）在硫酸和高氯酸溶液中分别研究了甘氨酸修饰的Pt(111)电极表面氧分子的电催化还原反应. 实验发现：在硫酸溶液中,经甘氨酸修饰的Pt(111)电极表面的氧还原活性明显提高,其中氧还原的半波电位与Pt(111)电极的相比正移约0.1 V,而在高氯酸溶液中,甘氨酸修饰的Pt(111)电极的活性几乎没有发生变化. 该实验结果表明：甘氨酸修饰的Pt(111)电极一方面抑制了SO₄^2-在电极表面的吸附,另一方面又能在电极表面提供相邻的空位供氧分子吸附. 通过与文献中报道的CN^-修饰的Pt(111)电极上的氧还原结果的对比,可以推测甘氨酸修饰的Pt(111)电极表面氧还原活性提高是由于甘氨酸在Pt(111)表面可能先被氧化成CN^-后吸附在电极表面,进而促进了氧分子的电催化还原反应.     

甲酸解离吸附的动力学和时间分辨FTIR特征

 运用电化学暂态（电位阶跃）方法和时间分辨FTIR反射光谱研究甲酸在Pt电极上的解离吸附过程，揭示了这一表面分子过程的反应速率在－0．25至0．25VvsSCE区间呈火山形变化的规律，还测得在含10－3mol•L－1HCOOH的溶液中最大的初始解离速率（－0．06V时）为9.33×10－11mol•cm－2•s－1.     

Electrocatalytic properties of Pt(111), Pt(332), Pt(331) and Pt(110) single crystal electrodes towards ethylene glycol oxidation in sulphuric acid solutions

In the present paper four platinum single crystal electrodes, two basal planes of Pt(111) and Pt(110) and two stepped surfaces of Pt(332) and Pt(331), were prepared and used in the study of electro-oxidation of ethylene glycol (EG). All of these Pt single crystal electrodes belong to the [1 0] zone of crystallography, and exhibit on their surface (111) symmetry sites or certain combinations of terraces of (111) symmetry with steps of (111) symmetry type. It has been found that as a result of a favourable steric matching of surface sites the Pt(110) electrode manifested a higher activity both for EG dissociative adsorption and oxidation than that of the Pt(111) electrode. The stepped surfaces of Pt(332) and Pt(331) operated with certain combinations of characteristics of Pt(111) and Pt(110). The best electrocatalytic properties have been obtained with a Pt(331) electrode, and this is attributed both to the configuration of the atomic arrangement and to the stability of this surface.In summary, the above results show that the performance of a given Pt single crystal electrode in EG oxidation at a potential below 1.0 V may be evaluated by three factors.

1. (1) The ability to resist self-poisoning (AB) which describes the difficulty of EG dissociative adsorption on the electrode surface.

2. (2) The activity for EG oxidation (AC). In considering that the threshold potential for EG oxidation on all electrodes is at 0.3 V and that the self-poisoning is encountered in PGPS, the activity for EG oxidation may be reasonably characterized by the intensity of the peak current acquired in NGPS near 0.6 V, which corresponds to the maximum current of EG oxidation on an activated (non-poisoned) surface of the electrode.

3. (3) The stability of activity during potential cycling (SA) between 0.05 and 1.0 V, which describes the resistance to the decrease of intensity of the EG oxidation current during voltammetric cycling.

For the two basal planes studied, the AB and SA of Pt(111) are higher than those of Pt(110), but its AC is much lower than that of Pt(110). These differences are clearly related to the surface atomic arrangement of the two electrodes. As has been discussed above, the surface of Pt(111) is atomically smooth and stable during voltammetric cycling. The surface of Pt(110) presents, however, atomic steps and is reconstructed under experimental conditions, i.e. certain steric configurations are encountered on the Pt(110) surface. The high AC and the low AB may be assigned to a favourite stereographic matching during EG adsorption and oxidation on Pt(110).The two electrodes with stepped surfaces, Pt(332) and Pt(331), contain different densities of (110) sites, which are formed on the border between terrace and step, as shown in Fig. 8. The AB of these two electrodes has been observed at a moderate range between that of Pt(111) and the AB of Pt(110). With a majority of (111) sites on its surface, the electrode of Pt(332) operates at a relatively higher AC than Pt(111) does, and its SA is not as good as that of Pt(111) but is much better than the SA of a Pt(110) electrode. In all cases the highest AC and SA are obtained with a Pt(331) electrode. It may be seen from the profile of a (331) plane (shown by the cross-section of A-A in Fig. 8) that all atoms on the top of the surface participated in forming (110) sites, and the atom on the step has two functions — one is to form a (110) site with an atom located in the terrace of second layer and the other is to form a (111) site in the terrace of the same layer. It has been mentioned in the above discussions that the Pt(110) electrode keeps a higher AC due to favourite stereographic matching in EG adsorption and oxidation, but its SA is the worst, due to the instability of the surface. The highest AC and SA obtained with Pt(331) may be ascribed not only to the high density of (110) sites existing on the surface, but also to the stabilization of these (110) sites, and moreover, the synergy generated by the atomic arrangement of the Pt(331) surface may also contribute to the performance of the Pt(331) electrode.     

乙二醇在铂电极上吸附和氧化过程的现场FTIR反射光谱研究(Ⅰ)──酸性介质

运用循环伏安法和现场FTIR反射光谱研究了酸性介质中乙二醇在铂电极上的吸附和氧化行为,指出乙二醇电催化氧化是通过解离吸附产物和反应中间体双途径机理进行的。经FTIR反射光谱检测,解离吸附产物为CO,反应中间体主要有CH₂OH─COOH和HOOC─COOH等。本文还在分子水平上解释了铂电极上乙二醇吸附和氧化循环伏安特征的内在原因。     

甲酸在Pt(100)单晶电极表面解离吸附过程的动力学

有机小分子在电催化剂表面的解离吸附,是燃料电池阳极氧化过程中发生自毒化现象的主要原因.事实上这类解离吸附是一种表面分子过程,包括有机分子在电极表面吸附,分子内断键,生成新的吸附分子或基因等步骤.Sun等研究了甲醇等在一系列铂单晶电极上的解离吸附,发现这类过程极强地依赖于电极表面原子排列结构.虽然已有大量文献报导了运用原位红外光谱检测各类有机小分子解离吸附物种,但迄今仍未见到动力学方面的研究结果.显然,对这种在电化学条件下表面分子反应过程的动力学研究,必将进一步揭     

镍和铂单晶(111)面上氢解离的比较研究

镍和铂单晶（１１１）面上氢解离的比较研究周鲁，孙本繁，吕日昌，唐向阳，滕礼坚（中国科学院大连化学物理研究所分子反应动力学国家重点实验室，大连１１６０２３）关键词镍晶面，铂晶面，氢解离吸附，位能面，分子催化过渡金属镍和铂是催化加氢、脱氢以及临氢重整的重...     

Kinetics of dissociative adsorption of formic acid on electrodes of tetrahexahedral platinum nanocrystals

In the present paper we study the kinetics of dissociative adsorption of formic acid on the electrode of tetrahexahedral platinum nanocrystals (THH Pt NCs). In situ FTIR spectroscopic results demonstrate that HCOOH can be oxidized to CO2 at a low potential (-0.2 V(SCE)) on the THH Pt NCs electrode, and the chemical bonds inside formic acid molecule are broken to form adsorbed COL species. The kinetics of the dissociative adsorption of HCOOH was quantitatively investigated by employing programmed potential s...