In situ scanning FTIR microscopy and IR imaging of Pt electrode surface towards CO adsorption

In situ scanning FTIR microscopy was built up for the first time in the present work, which consists of an FTIR apparatus, an IR microscope, an X-Y mapping stage, and the specially designed electrochemical IR cell and computer software. It has been demonstrated that this new space-resolvdin situ IR technique can be used to study vibration properties of micro-area, and to perform IR imaging of electrode surface. The chemical image obtained using this technique for CO adsorption on Pt electrode illustrated, at a space-resolution of 10^-2 cm, the inhomogeneity and the distribu-tion of reactivity of micro-area of electrode surface. Project supported by the National Natural Science Foundation of China (Grant No. 29525307).     

电化学原位步进扫描时间分辨显微镜FTIR反射光谱

结合步进扫描傅立叶变换红外光谱仪和红外显微镜，建立了电化学原位步进扫描时间分辨显微镜FTIR反射光谱.采用微电极和利用纳米结构表面的异常红外效应，显著提高表面吸附物种的红外检测灵敏度和红外电极表面对极化电位的响应速度，使广泛应用的外反射型薄层红外电解池的时间常数(τ=R1Cd)从使用常规盘电极的约40 ms降低到0.65 ms.研究了酸性介质中CO在Pt电极上的吸附过程，谱图的时间分辨率达50 μs.     

低碳醇氧化电极表面pH值的测量及应用

研究了Ir/IrO₂微平面电极在低碳醇氧化电极表面的pH-E_ocp（pH-开路电位)关系,测量了几种低碳醇在电化学氧化过程中距离电极表面50 μm以内的不同距离处的pH值,对不同低碳醇电化学氧化产生的酸强度进行了比较与分析;Ir/IrO₂微平面电极的pH-E_ocp关系曲线与“醇-羧酸”体系种类有关;乙二醇在电化学氧化过程中产生的pH值最低,甲醇次之,乙醇产生的pH值最高,在500 nm处的稳态pH值分别为0.191、1.13和2.99。通过向电解液中加入NaF,考察了生成的H⁺和F^-结合对金属钛选择性微区刻蚀作用,在乙二醇为前驱体的体系中微孔刻蚀加工速率约为30 nm/min。     

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.     

Formate,an active intermediate for direct oxidation of methanol on pt electrode

The electro-oxidation of methanol on a Pt thin film electrode in acidic solution has been investigated by in situ surface-enhanced IR absorption spectroscopy. A new IR peak is observed at around 1320 cm-1 when the electrode potential is more positive than 0.5 V, where the bulk oxidation of MeOH occurs. This peak has been assigned to the symmetric stretching of formate species adsorbed on the Pt electrode surface. It is the first observation of formate adsorption during the electro-oxidation of methanol on a Pt surface. A near proportional relationship between the intensity of the IR band of the formate species and MeOH electro-oxidation current is observed. A new reaction scheme via non-CO pathway with formate as the active intermediate is proposed for the methanol electro-oxidation process.     

Nanocomposite with Polypyrrole Encapsulated within SBA‐15 Mesoporous Silica: Preparation and Its Electrochemical Application

The nanocomposite with polypyrrole (PPy) confined in ordered mesoporous silica SBA‐15 channels was synthesized by in situ electropolymerization. X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, N₂ adsorption/desorption, and FT‐IR studies indicated that the nanocomposite has the well‐ordered hexagonal structures and PPy was in situ polymerized into the channels instead of the outer surface of SBA‐15. Furthermore, the PPy/SBA‐15 nanocomposite was used as an electrode modifier. We found that the nanocomposite‐modified electrode exhibited good electrocatalytic activities for hydroquinone oxidation where PPy chains could facilitate the electron transfer between molecular sieves and electrode surface. Three dihydroxybenzene isomers (hydroquinone, catechol and resorcinol) have been successfully detected at PPy/SBA‐15 modified electrode by preconcentration of the analyte.     

Piezoelectric transmission spectroelectrochemistry with a normal piezoelectric quartz crystal as an optically-transparent electrode

Piezoelectric transmission spectroelectrochemistry (PTSEC), i.e., the combination of electrochemistry and spectroelectrochemistry (SEC) with electrochemical quartz crystal microbalance (EQCM) technique is reported by using a normal piezoelectric quartz crystal (PQC) as an optically-transparent electrode (OTE). A theoretical relationship between the PQC response and the spectroelectrochemical response is derived and used to estimate the apparent molar absorptivity of the absorbing species deposited on the OTE on the PQC surface. The complex of copper with aspartic acid is used to test this new PQC-SEC technique. Results show that the combination of three such diverse techniques provides a very useful methodology for studying electrode processes and electrode surface characteristics in situ.     

Nanostructured gold colloid electrode based on in situ functionalized self-assembled monolayers on gold electrode

A novel method for fabricating nanostructured gold colloid electrode based on in situ functionalization of self-assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) on gold electrode is proposed. The in situ functionalization of 4-ATP SAMs yields a redox active monolayer of 4′-mercapto-N-phenylquinone diimine (NPQD). When the amino-rich surface is exposed to gold colloid, the citrate-stabilized gold nanoparticles (GNPs) can be anchored onto the surface of the in situ functionalized electrode by the electrostatic interactions and a new nanostructured gold colloid surface was obtained. The mixed monolayers of in situ functionalized product, NPQD, and 1,4-benzenedimethanethiol (BDMT) can provide a more compact and order platform to fabricate GNPs on the electrode surface. The film formed by this technique has the advantages of high organization and uniformity, which could provide a desirable microenvironment to assemble GNPs and facilitate the concentration of the analyte from the bulk solution to the electrode surface. The nanostructured gold colloid electrode has favorable effect on the electrochemical oxidation of naphthol isomers.     

Infrared Spectroscopy During Electrocatalytic Turnover Reveals the Ni‐L Active Site State During H2 Oxidation by a NiFe Hydrogenase

A novel in situ IR spectroscopic approach is demonstrated for the characterization of hydrogenase during catalytic turnover. E. coli hydrogenase 1 (Hyd‐1) is adsorbed on a high surface‐area carbon electrode and subjected to the same electrochemical control and efficient supply of substrate as in protein film electrochemistry during spectral acquisition. The spectra reveal that the active site state known as Ni‐L, observed in other NiFe hydrogenases only under illumination or at cryogenic temperatures, can be generated reversibly in the dark at ambient temperature under both turnover and non‐turnover conditions. The observation that Ni‐L is present at all potentials during turnover under H₂ suggests that the final steps in the catalytic cycle of H₂ oxidation by Hyd‐1 involve sequential proton and electron transfer via Ni‐L. A broadly applicable IR spectroscopic technique is presented for addressing electrode‐adsorbed redox enzymes under fast catalytic turnover.     

Quantitative SNIFTIRS studies of (bi)sulfate adsorption at the Pt(111) electrode surface

Subtractively normalized interfacial Fourier transform infrared reflection spectroscopy (SNIFTIRS) was applied to study (bi)sulfate adsorption on a Pt(111) surface in solutions of variable pH while maintaining a constant total bisulfate/sulfate ((bi)sulfate) concentration without the addition of an inert supporting electrolyte. The spectra were recorded for both the p- and s-polarizations of the IR radiation in order to differentiate between the IR bands of the (bi)sulfate species adsorbed on the electrode surface from those species located in the thin layer of electrolyte. The spectra recorded with p-polarized light consist of the IR bands from both the species adsorbed at the electrode surface and those present in the thin layer of electrolyte between the electrode surface and ZnSe window whereas the s-polarized spectra contain only the IR bands from the species located in the thin layer of electrolyte. A new procedure was developed to calculate the angle of incidence and thickness of the electrolyte between the Pt(111) electrode surface and the ZnSe IR transparent window. By combining these values with the knowledge of the optical constants for Pt, H(2)O and ZnSe, the mean square electric field strength (MSEFS) at the Pt(111) electrode surface and for thin layer of solution were accurately calculated. The spectra recorded using s-polarization were multiplied by the ratio of the average MSEFS for p- and s-polarizations and subtracted from the spectra recorded using p-polarization in order to remove the IR bands that arise from the species present within the thin layer cavity. In this manner, the resulting IR spectra contain only the IR bands for the anions adsorbed on the Pt(111) electrode surface. The spectra of adsorbed anions show little change with respect to the pH ranging from 1 to 5.6. This behavior indicates that the same species is predominantly adsorbed on the metal surface for this broad range of pH values and the results suggest that sulfate is the most likely candidate for this adsorbate.     

The mechanism of the dissolution,spray and deposition technique--a novel infrared sampling method

The dissolution, spray and deposition (DSD) technique, a novel infrared (IR) sampling technique, gives very sharp spectra for amino acids and peptides. The mechanism of this unique technique has been established by scanning electron microscopy (SEM) studies and found to be due to the formation of several layers of fairly large KBr crystals in situ on an IR transparent window. The zwitterions of the amino acids and dipeptides are adsorbed on the surface of these large KBr crystals, which ensures the isolation of monomers of the amino acid or dipeptide zwitterions in the KBr matrix, thereby leading to sharp and well-resolved IR spectra. This methodology provides a powerful IR sampling technique, akin to matrix isolation, with the added advantage of being extremely cost effective as it does not require low-temperatures or a sophisticated experimental set up.     

Current pulse measurement of capacitance during molten salt electrochemical experiments

In earlier work in our laboratories, a current pulse method was developed that allows in situ (dynamic) measurements of electrode capacitance. The present work describes the successful application of the technique to the study of electrode properties in molten salt electrolytes. As expected, the electrode capacitance increases as the electrode surface area exposed to a molten salt bath increases. Furthermore, creep of the bath along the surface of a conductive ceramic anode and subsequent ingress into the anode pores is observed as an increase in capacitance. The pulse technique also gives an indication of phase changes that occur during the reduction of a solid titanium dioxide cathode and a highly sensitive measure of the temperature at which initial freezing of the calcium chloride electrolyte begins. These observations provide useful in situ information about changes in electrode properties in molten salt electrolytes that are difficult to obtain from other techniques. For consideration in the Special Edition: Oldham Festchrift Dedicated to our dear friend Keith B. Oldham on the occasion of his 80th birthday.     

团聚铂纳米粒子电极在甲醇氧化中的电催化特性

用H2还原法并以Nafion作为稳定剂合成团聚的Pt纳米粒子，附载于玻碳表面制备电催化剂.透射电子显微镜（TEM）和扫描电子显微镜（SEM）表征结果指出,团聚Pt纳米粒子的平均尺寸约为400 nm.运用电化学循环伏安法(CV)和原位傅立叶变换红外反射光谱（in situ FTIRS）研究甲醇的氧化过程，发现团聚Pt纳米粒子电极具有较高的电催化活性.原位FTIRS研究结果检测到甲醇在所制备的电催化剂上氧化的中间体为线型吸附态CO物种，其红外吸收给出异常红外效应的光谱特征.     

In situ STM studies of electrochemical growth of nanostructured Ni films and their anomalous IR properties

We have extended the study of anomalous IR properties, which were initially discovered on nanostructured films of platinum group metals and alloys, to nanostructured films of nickel, a member of the iron group triad, and broadened the fundamental knowledge on this subject. Nanostructured thin films of nickel supported on glassy carbon [nm-Ni/GC(n)] were prepared by electrochemical deposition under cyclic voltammetric conditions, and the thickness of films was altered systematically by varying the number (n) of potential cycling within a defined potential range for electrodeposition. Electrochemical in situ scanning tunneling microscopy (STM) was employed to monitor the electrochemical growth of nanostructured Ni films. These in situ STM images illustrated that, along the increase of the film thickness, Ni films have undergone a transformation from layer structure to island structure and finally to lumpish arris structure. Investigations by in situ FTIR spectroscopy employing adsorbed CO as the probe revealed that these nanostructures of Ni films yield abnormal IR features, Fano-like IR features, and normal IR features, respectively. The IR bands of CO adsorbed on Ni thin films of a layer structure were inverted in their direction and enhanced in their intensity up to 15.5 times on an nm-Ni/GC(4) electrode. The Fano-like IR features, which are defined as a bipolar band with its negative-going peak on the low wavenumber side and its positive-going peak on the high wavenumber side, are observed for the first time on Ni thin films of an island nanostructure, i.e., at the nm-Ni/GC(16) electrode. IR features changed to normal absorption in CO adsorbed on the nm-Ni/GC(25) electrode, i.e., that with lumpish arris nanostructured Ni film of a larger thickness.     

普鲁士蓝膜修饰铂电极的现场拉曼光谱电化学表征(英文)

采用现场拉曼光谱电化学技术表征了普鲁士蓝膜修饰铂电极的循环伏安过程 .结果显示 ,随着修饰膜的微观结构由普鲁士蓝向普鲁士白或相反过程转化 ,表征两种不同结构的拉曼特征振动谱峰及其强度变化呈现出明显的可逆特征 .     

A butadiyne-linked diruthenium molecular wire self-assembled on a gold electrode surface

A 1,3-butadiyne-linked diruthenium complex 4 is successfully brought onto the gold surface in a lying flat mode to form self-assembled monolayers (SAMs) showing reversible multiple redox behaviors on the electrode surface. The diruthenium species with different oxidation states, particularly the Ru(2)(III,III) state which is unstable and impossible to isolate from the solution, can be detected by in situ IR spectroscopy.     

Electrochemiluminescent Nucleic Acid Hybridization Assay

Electrochemiluminescence (ECL) is a technique by which a chemiluminescent reaction is generated from reagents produced in the vicinity of an electrode surface when a potential is applied. ECL methods have more significiant advantages over more convential chemiluininescent techniques. In particular, the necessary reactants are produced in situ at a given electrode, enabling the reaction to be controlled through small changes in the applied potential. Furthermore, since light emission is located only in the immediate vicinity of the electrode surface, light colletion is not only efficient but facile.     

超薄层红外光透电解池的设计和应用

采用真空镀膜技术制得了超薄型红外光透极电极，设计了适用于水溶液体系和多种固体电极体系的红外光透薄层电解池，通过亚铁氰化钾水溶液／金电极体系和亚硫酰氯／碳电极体系的现场红外光谱电化学测试证明：该电解池具有结构简单，光谱响应灵敏，适用范围较宽等优点。     

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.     

原位红外光谱法研究对氯苯酚在Pt电极上的电氧化行为

采用原位红外光谱法研究了碱性条件下对氯苯酚(PCP)在Pt电极上电化学氧化的脱氯反应机理. 研究结果表明Pt电极对PCP有良好的电化学反应活性, 其氧化过程首先是对氯苯酚负离子氧化生成对氯苯氧自由基, 该自由基可与对氯苯酚负离子作用生成芳香醚低聚物; 随着电位升高, 对氯苯酚负离子经电化学氧化生成了苯二酚盐(还可能存在其氧化产物不饱和羧酸盐); 当电位继续升高, 苯二酚盐进一步氧化形成苯醌; 最后, 在Pt表面生成小分子羧酸盐, 同时生成了最终产物CO2. 但由于芳香醚低聚物等不溶性聚合物膜的形成并吸附在Pt电极表面, 可造成Pt电极毒化, 使得Pt电极在使用过程中逐渐失去活性.