钙钛矿型氧化物负载纳米金属催化剂结构的动态调变及其催化氧化CO反应性能

研究了钛酸钡和钛酸钙担载的Ag和Pt纳米催化剂的表面结构随氧化-还原处理过程的动态变化及其对CO完全氧化反应性能的影响.发现氧化物担载的Ag催化剂在氧化处理后其催化活性较还原处理的高; X射线衍射(XRD)和X射线光电子能谱(XPS)表征结果表明,氧化处理能够提高载体表面Ag颗粒的分散度,而还原处理导致Ag颗粒的聚集,从而降低了催化氧化CO反应的活性.氧化-还原处理改变了担载Ag纳米粒子的尺寸并影响其CO氧化反应活性.与此相反,氧化物担载的Pt催化剂在还原处理后所表现出的CO氧化反应活性较氧化处理的高; 对比研究发现,氧化和还原处理后Pt纳米粒子的尺寸基本相同,但是氧化处理的样品中Pt表面物种以氧化态为主,而还原处理后Pt表面物种主要为金属态.Pt纳米粒子表面化学状态随氧化-还原处理的调变是导致表面催化活性差异的主要原因.     

Aucore Ptshell纳米粒子对甲醇氧化的电催化性能研究

应用两步化学还原法制备不同厚度的AucorePtshell纳米粒子,经紫外可见光谱(UV-V is)、透射电子显微镜(TEM)表征.该金纳米颗粒经化学还原包裹铂后平均粒径明显增大,调节金与铂的含量可获得不同包裹厚度的AucorePtshell纳米粒子.循环伏安法研究表明,粒径为70~80 nm的AucorePtshell纳米粒子对甲醇的氧化具有较好的电催化活性,并且其电催化性能随着电位循环扫描次数的增加而增强.     

金催化作用的结构敏感性

金催化是纳米催化的代表性体系,金催化作用表现出复杂的结构敏感性。这篇综述总结了金催化作用研究的文献结果和我们利用从单晶到纳米晶的模型催化剂研究金催化作用的进展。展示了NO分解,CO氧化,丙烯在氢气和氧气气氛中环氧化等反应中金催化作用的结构敏感性和金催化剂的活性结构,讨论了金纳米粒子几何结构和电子结构、金纳米粒子–氧化物载体相互作用对金催化作用的影响和金表面低温高催化活性的来源,并展望了金催化作用结构敏感性的未来研究方向。     

金催化作用的结构敏感性（英文）

金催化是纳米催化的代表性体系,金催化作用表现出复杂的结构敏感性。这篇综述总结了金催化作用研究的文献结果和我们利用从单晶到纳米晶的模型催化剂研究金催化作用的进展。展示了NO分解,CO氧化,丙烯在氢气和氧气气氛中环氧化等反应中金催化作用的结构敏感性和金催化剂的活性结构,讨论了金纳米粒子几何结构和电子结构、金纳米粒子–氧化物载体相互作用对金催化作用的影响和金表面低温高催化活性的来源,并展望了金催化作用结构敏感性的未来研究方向。     

立方体形Au_(core)-Pd_(shell)-Pt_(cluster)纳米材料对甲酸电催化的研究

应用晶种生长法制得金纳米立方体,Aucore-Pdshell和Aucore-Pdshell-Ptcluster电催化剂,通过改变溶液的H2PdCl4和H2PtCl6的用量以控制Pdshell的厚度和Ptcluster的覆盖度.采用扫描电镜(SEM)、透射电镜(TEM)观察了金纳米立方体的表面结构.利用循环伏安法(CV)研究了不同Pd层厚度的立方体形Aucore-Pdshell纳米粒子和不同Pt岛覆盖度的立方体形Aucore-Pdshell-Ptcluster纳米粒子对甲酸氧化的电催化性能.结果表明,与立方体形Aucore-Pdshell纳米粒子相比,"核-壳-岛"结构的立方体形Aucore-Pdshell-Ptcluster纳米粒子对甲酸的电氧化具有更高活性.当Pd壳层厚度为3层,Pt岛覆盖度为0.5时,电催化活性最高.     

PdCu合金纳米晶体的制备和电催化活性研究

改变表面活性剂1-十八烯（ODE）和油胺（OLA）或油酸（OA）的配比,以1,2-二羟基十六烷二醇作还原剂同时还原乙酰丙酮铜Cu(acac)2和乙酰丙酮钯Pd(acac)2一步法制备了单分散的球形和米花形的PdCu纳米粒子.透射电子显微镜和XRD等结构表征表明,两种形状的PdCu纳米粒子均为（111）面占优的合金纳米晶体,其平均粒径分别为12.7 ± 0.18 和 20.4 ± 0.31 nm.电化学循环伏安法（CV）测定了两种PdCu合金纳米粒子对甲酸氧化的电催化活性.结果表明,在球形PdCu纳米粒子上得到的甲酸氧化峰电流密度约为米花状纳米粒子（PdCu-B）上的5.6倍.同时,前者显示出了更好的抗CO毒化能力.计时电流测量也表明,球状PdCu纳米粒子比米花状纳米粒子有更好的电催化稳定性能.     

甲醇在铂修饰的氧化钛电极上电催化氧化行为的研究

运用电化学方法评价了电化学阴极还原-阳极氧化两步法制得的以钛为基体的铂修饰的钛氧化物(Pt-TiO_x/Ti)电极对甲醇电催化氧化的性能,结果表明,制得的修饰电极对甲醇氧化呈现了很高的电催化活性和好的稳定性.通过X光电子能谱(XPS)、扫描隧道显微镜(STM)和现场傅立叶变换红外(FTIR)反射光谱等技术,发现修饰电极对甲醇氧化具有高的电催化性能,可归属于纳米级Pt粒子在TiO_x中的高度分散及由于Pt和TiO_x的相互作用,使电极表面对甲醇氧化中间产物CO的吸附量大大降低.     

单分散PtNi纳米粒子特殊的红外光学性能(英文)

采用电位置换反应以及化学还原法制备了单分散PtNi纳米粒子,循环伏安结果显示该纳米粒子在0.1mol·L-1硫酸介质中对CO的氧化表现出比本体Pt电极更好的电催化活性.以CO为探针分子,采用电化学原位红外光谱研究了PtNi纳米粒子上的特殊红外光学性能.结果表明,PtNi纳米粒子无论是在玻碳电极还是在金电极上,均表现出对称的双极谱峰,同时给出很强的增强效应.论文研究结果有助于进一步了解低维纳米材料特殊红外性能的本质.     

AucorePtshell础纳米粒子对甲醇氧化的电催化性能研究

应用两步化学还原法制备不同厚度的AucorePtshell纳米粒子，经紫外可见光谱（UV-Vis）、透射电子显微镜（TEM）表征．该金纳米颗粒经化学还原包裹铂后平均粒径明显增大，调节金与铂的含量可获得不同包裹厚度的AucorePtshell纳米粒子．循环伏安法研究表明，粒径为70-80nm的AucorePtshell纳米粒子对甲醇的氧化具有较好的电催化活性，并且其电催化性能随着电位循环扫描次数的增加而增强．     

Au-Pd/石墨烯和Au-Pd/碳纳米管催化电化学氧化甲酸（英文）

利用化学还原法合成了石墨烯和碳纳米管负载的Au-Pd纳米粒子.石墨烯负载的Au-Pd纳米粒子(AuPd/G)的粒径远小于碳纳米管负载的Au-Pd纳米粒子(Au-Pd/CNTs)的粒径,且Au-Pd纳米粒子在复合材料上分布均匀.与碳纳米管负载的Au-Pd纳米粒子催化剂相比,石墨烯负载的Au-Pd催化剂对甲酸的催化显示出更好的电催化活性,结果表明作为Au-Pd纳米粒子的基底,石墨烯可以明显提高Au-Pd纳米粒子的电催化活性.在0.1mol/L H_2SO_4中,该纳米修饰电极对甲酸有良好的电催化作用,甲酸在电极上的氧化动力学过程为扩散控制过程.     

Self-assembly of mixed Pt and Au nanoparticles on PDDA-functionalized graphene as effective electrocatalysts for formic acid oxidation of fuel cells

Pt and Au nanoparticles with controlled Pt?:?Au molar ratios and PtAu nanoparticle loadings were successfully self-assembled onto poly(diallyldimethylammonium chloride) (PDDA)-functionalized graphene (PDDA-G) as highly effective electrocatalysts for formic acid oxidation in direct formic acid fuel cells (DFAFCs). The simultaneously assembled Pt and Au nanoparticles on PDDA-G showed superb electrocatalytic activity for HCOOH oxidation, and the current density associated with the preferred dehydrogenation pathway for the direct formation of CO(2) through HCOOH oxidation on a Pt(1)Au(8)/PDDA-G (i.e., a Pt?:?Au ratio of 1?:?8) is 32 times higher than on monometallic Pt/PDDA-G. The main function of the Au in the mixed Pt and Au nanoparticles on PDDA-G is to facilitate the first electron transfer from HCOOH to HCOO(ads) and the effective spillover of HCOO(ads) from Au to Pt nanoparticles, where HCOO(ads) is further oxidized to CO(2). The Pt?:?Au molar ratio and PtAu nanoparticle loading on PDDA-G supports are the two critical factors to achieve excellent electrocatalytic activity of PtAu/PDDA-G catalysts for the HCOOH oxidation reactions.     

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.     

Electrochemical Sensor for Oxidation of NO Based on Au-Pt Nanoparticles Self-assembly Film

Au-Pt bimetallic nanoparticles film used as an efficient electrochemical sensor was prepared by self-assembled Au-Pt bimetallic nanoparticles on a glassy carbon (GC) substrate using thioglycolic acid as a linker. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) showed that the Au-Pt nanoparticles self-assembly film was dense and uniform. Electrochemical experiments revealed that Au-Pt bimetallic nanoparticles film/GC electrode showed high electrocatalytic activity to the oxidation of nitric oxide.     

Effect of the iridium oxide thin film on the electrochemical activity of platinum nanoparticles

The influence of the iridium oxide thin film on the electrocatalytic properties of platinum nanoparticles was investigated using the electro-oxidation of methanol and CO as a probe. The presence of the IrO(2) thin film leads to the homogeneous dispersion of Pt nanoparticles. For comparison, polycrystalline platinum and Pt nanoparticles dispersed on a Ti substrate in the absence of an IrO(2) layer (Ti/Pt) were also investigated in this study. Inverted and enhanced CO bipolar peaks were observed using an in situ electrochemical Fourier transform infrared technique during the methanol oxidation on the Pt nanoparticles dispersed on a Ti substrate. Electrochemical impedance studies showed that the charge transfer resistance was significantly lower for the Ti/IrO(2)/Pt electrode compared with that of the massive Pt and Ti/Pt nanoparticles. The presence of the IrO(2) thin film not only greatly increases the active surface area but also promotes CO oxidation at a much lower electrode potential, thus, significantly enhancing the electrocatalytic activity of Pt nanoparticles toward methanol electro-oxidation.     

An Electrochemical Sensor Based on Gold Nanoparticles Incorporated in Mesoporous MFI Zeolite for Determination of Purine Bases in DNA

An electrochemical sensor was developed based on gold nanoparticles incorporated in mesoporous MFI zeolite for the determination of purine bases. Au nanoparticles (AuNPs) were incorporated into the mesoporous MFI zeolite (AuNPs/m‐MFI) by post‐grafting reaction. The composite materials were characterized by transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS) and electrochemical methods. Au nanoparticles with a size of 5‐20 nm are uniformly dispersed in the pores of mesoporous MFI zeolite. And the morphology of MFI zeolite can be perfectly kept after pore expansion and Au nanoparticles incorporation. The electrocatalytic oxidation of purine bases (guanine and adenine in DNA) is investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The surface‐confined Au nanoparticles provide the good catalytic activity for oxidation of purine bases. The simultaneous detection of guanine and adenine can be achieved at AuNPs/m‐MFI composites modified glassy carbon electrode (GCE). The electrochemical sensor based on AuNPs/m‐MFI exhibits wide linear range of 0.5–500 μM and 0.8–500 μM with detection limit of 0.25 and 0.29 μM for guanine and adenine, respectively. Moreover, the electrochemical sensor is applied to evaluation of guanine and adenine in herring sperm DNA samples with satisfactory results.     

The electrooxidation of small organic molecules on platinum nanoparticles supported on gold: influence of platinum deposition procedure

The electrocatalytic properties of small platinum nanoparticles were investigated for the oxidation of CO, methanol, and formic acid using voltammetry, chronoamperometry, and surface-enhanced Raman spectroscopy. The particles were generated by galvanostatic deposition of platinum on a polished gold surface from an H₂PtCl₆ containing electrolyte and ranged between 10 and 20 nm in diameter for low platinum surface concentrations, 10 and 120 nm for medium concentrations, and full Pt monolayers for high concentrations. CO stripping and bulk CO oxidation experiments on the particles up to 120 nm in diameter displayed pronounced structural effects. The CO oxidation current-time transients show a current decay for low platinum coverages and a current maximum for medium and high coverages. These results were also observed in the literature for particles of 2- to 5-nm size and agglomerates of these particles. The similarities between the literature and our results, despite large differences in particle size and morphology, suggest that particle structure and morphology are also very important catalytic parameters. Surface-enhanced Raman spectroscopy data obtained for the oxidation of CO on the Pt-modified Au electrodes corroborate this conclusion. A difference in the ratio between CO adsorbed in linear- and bridge-bonded positions on the Pt nanoparticles of different sizes demonstrates the influence of the surface morphology. The oxidation activity of methanol was found to decrease with the particle size, while the formic acid oxidation rate increases. Again, a structural effect is observed for particles of up to ca. 120 nm in diameter, which is much larger than the particles for which a particle size effect was reported in the literature. The particle shape effect for the methanol oxidation reaction can be explained by a reduction in available “ensemble sites” and a reduction in the mobility of CO formed by decomposition of methanol. As formic acid does not require Pt ensemble sites, decreasing the particle size, and thus, the relative number of defects, increases the reaction rate. Dedicated to Prof. Dr. Teresa Iwasita on the occasion of her 65th birthday in recognition of her numerous contributions to interfacial electrochemistry.     

基于Pt/Au双金属修饰针灸针的非酶葡萄糖传感器

通过在不锈钢针灸针（AN）表面依次电沉积金（Au）纳米颗粒和铂（Pt）纳米颗粒,基于它们在AN表面的协同作用,实现了一种用于非酶葡萄糖检测的电化学生物传感器。首先,通过扫描电子显微镜对其功能界面（Pt/Au/AN）进行表征,结果显示类似卷心菜的纳米材料均匀致密地分布在AN表面。然后,通过循环伏安法和电化学阻抗法对Pt/Au/AN电极的电化学特性进行了研究。结果表明,与Au/AN或Pt/AN电极相比,Pt/Au/AN电极对葡萄糖氧化表现出优越的电催化活性。这表明双金属Pt/Au的接触界面是葡萄糖氧化的重要电催化位点。在pH7.4的模拟生理介质中,制得传感器的线性范围为0.1~35 mmol·L^-1,检测限为0.0763 mmol·L^-1,对葡萄糖的检测表现出较高的灵敏度和良好的抗干扰性能、稳定性。此外,该传感器已成功用于人体血清葡萄糖的检测。     

Electro-oxidation of formic acid catalyzed by FePt nanoparticles

The electrocatalytic oxidation of formic acid at a gold electrode functionalized with FePt nanoparticles was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a mixed solution of 0.1 M HCOOH and 0.1 M HClO4. The FePt bimetallic nanoparticles, with a mean diameter of 3 nm, were prepared by a chemical reduction method. The Au/FePt nanostructured electrode was prepared firstly by the deposition of FePt nanoparticles onto a clean Au electrode surface, followed by ultraviolet ozone treatment to remove the organic coating. In CV measurements, two well-defined anodic peaks were observed at +0.20 and +0.51 V (vs. a Ag/AgCl quasi-reference). The anodic peak at +0.20 V was attributed to the oxidation of HCOOH to CO2 on surface unblocked by CO, whereas the peak at +0.51 V was ascribed to the oxidation of surface-adsorbed CO (an intermediate product of HCOOH oxidation) and further oxidation of bulk HCOOH. From the onset potential and current density of the electro-oxidation of HCOOH, FePt nanoparticles exhibit excellent electrocatalytic activities as compared to Pt and other metal alloys. EIS measurements were carried out to further examine the reaction kinetics involved in the HCOOH electro-oxidation. The EIS responses were found to be strongly dependent on electrode potentials. At potentials more positive than -0.25 V (vs. Ag/AgCl), pseudo-inductive behavior was typically observed. At potentials between +0.3 and +0.5 V, the impedance response was found to reverse from the first quadrant to the second quadrant; such negative Faradaic impedance was indicative of the presence of an inductive component due to the oxidation of surface-adsorbed CO. The impedance responses returned to normal behavior at more positive potentials (+0.6 to +0.9 V). The mechanistic variation was attributed to the formation of different intermediates (CO or oxygen containing species) on the electrode surface in different potential regions. Two equivalent circuits were proposed to model these impedance behaviors.     

Butylphenyl-functionalized Pt nanoparticles as CO-resistant electrocatalysts for formic acid oxidation

Butylphenyl-functionalized Pt nanoparticles (Pt-BP) with an average core diameter of 2.93 ± 0.49 nm were synthesized by the co-reduction of butylphenyl diazonium salt and H(2)PtCl(4). Cyclic voltammetric studies of the Pt-BP nanoparticles showed a much less pronounced hysteresis between the oxidation currents of formic acid in the forward and reverse scans, as compared to that on naked Pt surfaces. Electrochemical in situ FTIR studies confirmed that no adsorbed CO, a poisoning intermediate, was generated on the Pt-BP nanoparticle surface. These results suggest that functionalization of the Pt nanoparticles by butylphenyl fragments effectively blocked the CO poisoning pathway, most probably through third-body effects, and hence led to an apparent improvement of the electrocatalytic activity in formic acid oxidation.     

纳米金催化一氧化碳氧化反应的理论研究

近年来,纳米金催化剂独特的催化性质,特别是其优异的低温催化氧化活性,引起了人们极大的研究热情.除低温选择氧化外,在精细化学品合成、大气污染物消除、氢能的转换和利用等领域也开发出了一系列有广泛应用前景的金催化反应.此外,体相金的化学惰性和纳米金的超高活性之间差异的“鸿沟”也引起了理论工作者浓厚兴趣,试图从原理上理解体相金和纳米金活性差异的根源. CO催化氧化是最具有代表性的研究金催化活性的化学反应,本文主要综述了近十多年来金催化 CO氧化反应理论计算方面的研究工作.一般认为, CO在纳米金表面的吸附是 CO氧化反应的初始步骤.密度泛函理论研究表明, CO在金表面的吸附强度主要与被吸附金原子的配位数有关：金配位数越低, CO的吸附能越强,部分研究结果表明两者之间存在近似的线性关系.我们研究发现, CO吸附强度也与被吸附金周围配位金原子的相对位置有关,其中位于正下方的配位金原子加强 CO吸附,而位于侧位的配位金原子则弱化 CO吸附,这显然削弱了 CO吸附与金配位数线性关系的可靠性.理论研究表明,在纯金表
　　面上 O2吸附强度一般很弱,只有在一些特殊结构的金团簇上才有较强的吸附,但在 Au/TiO2界面及 CeO2表面上 O2吸附较强.金表面原子氧的吸附和金的表面结构有关.我们发现,原子氧倾向于在金的表面形成一种线性的 O–Au–O结构以增加其稳定性.当金表面的氧覆盖度增大时,会形成一种金氧化物薄膜结构,其结构依赖于氧的化学势和金的表面结构.纳米金催化 CO氧化反应机理可能因体系、载体等的差异而不同.大部分理论计算结果表明,在纯金表面上 O2很难直接解离形成原子氧,因此反应机理可能是吸附的 CO先与 O2反应形成了一种 CO–O2中间体,然后解离形成 CO2.在 Au/TiO2和 Au/CeO2催化剂上 CO催化氧化机理争议很大,均有计算结果支持 LH机理和 M–vK机理.另外,根据实验上观察到了负载型纳米金能直接活化分子氧的结果,理论上也提出了分子氧先解离为原子氧再与 CO反应的氧解离机理.针对如何解离分子氧问题,人们分别提出了低配位金模型、正方形金结构模型、Ti5c模型及 Au/Ti5c模型等.我们也提出了一种独特的双直线 O–Au–O模型来理解 Au/TiO2或 Au/CeO2界面解离活化分子氧.理论计算结果表明,低配位的金,金和载体之间的电荷转移,以及金所表现出的强相对论效应对于纳米金的活性影响很大.需要特别指出的是,金的强相对论效应有助于理解金表面的 CO吸附与金配位的关系、金表面原子氧的吸附特性、金氧化物薄膜的结构和分子氧的活化等过程.我们认为,金的强相对论作用导致了体相金的化学惰性以及纳米金的活性,因此相对论效应的深入研究将有助于理解金催化 CO氧化反应机理,从而有助于深层次理解纳米金催化活性来源.