乙醇在Pt/nanoTiO2-CNT复合催化剂上的电催化氧化

通过前驱体Ti(OEt)4直接水解和电化学扫描电沉积法制备在Ti基体上的纳米TiO2-碳纳米管复合膜载Pt(Pt/nanoTiO2-CNT)复合催化剂. 透射电镜 (TEM) 和X射线衍射 (XRD) 结果表明, 锐钛矿型纳米TiO2粒子和Pt纳米粒子(粒径均为5~10 nm)均匀地分散在碳纳米管表面. 通过循环伏安和计时电流法研究表明, Pt/nanoTiO2-CNT 复合催化剂(Pt载量为0.32 mg•cm−2) 具有高达51.8 m2•g−1的电化学活性比表面积, 常温常压下对乙醇的电化学氧化具有高催化活性和稳定性, 乙醇氧化峰电位分别为0.59、0.96和0.24 V, 氧化峰电流密度分别达到−115、−113和−75 mA•cm−2. 复合催化剂对乙醇电氧化的高催化活性可归因于nanoTiO2、CNT和Pt纳米粒子的协同催化作用.     

PVP封端剂对Pd纳米晶电催化氧化甲醇和乙醇性能的影响

Direct alcohol fuel cells (DAFCs) have attracted considerable research interest because of their potential application as alternative power sources for automotive systems and portable electronics. Pd-based catalysts represent one of the most popular catalysts for DAFCs due to their excellent electrocatalytic activities in alkaline electrolytes. Thus, it is of great importance to understand the structure-activity relationship of Pd electrocatalysts for alcohol electrocatalysis. Recently, size- and shape- controlled Pd nanocrystals have been successfully synthesized and subsequently used to study the size and shape effects of Pd electrocatalysts on alcohol electrocatalysis, in which the Pd (100) facet exhibited higher electrocatalytic oxidation activity for small alcohol molecules than the Pd (111) and (110) facets. Although it is well known that capping ligands, which are widely used in wet chemistry for the size- and shape-controlled synthesis of metal nanocrystals, likely chemisorb onto the surfaces of the resulting metal nanocrystals and influence their surface structure and surface-mediated properties, such as catalysis, this issue was not considered in previous studies of Pd nanocrystal electrocatalysts for electrocatalytic oxidation of small alcohol molecules. In this study, we prepared polyvinylpyrrolidone (PVP)-capped Pd nanocrystals with different morphologies and sizes and comparatively studied their electrocatalytic activities for methanol and ethanol oxidation in alkaline solutions. The chemisorbed PVP molecules transferred charge to the Pd nanocrystals, and the finer Pd nanocrystals had a higher coverage of chemisorbed PVP, and thus exposed fewer accessible surface sites, experienced more extensive PVP-to-Pd charge transfer, and were more negatively charged. The intrinsic electrocatalytic activity, represented by the electrochemical surface area (ECSA)-normalized electrocatalytic activity, of Pd nanocubes with exposed (100) facets increases with the particle size, indicating that the more negatively-charged Pd surface is less electrocatalytically active. The Pd nanocubes with average sizes between 12 and 19 nm are intrinsically more electrocatalytically active than commercial Pd black electrocatalysts, while the activity of Pd nanocubes with an averages size of 8 nm is less. This suggests that the enhancement effect of the exposed (100) facets surpasses the deteriorative effect of the negatively charged Pd surface for the Pd nanocubes with average sizes between 12 and 19 nm, whereas the deteriorative effect of the negatively charged Pd surface surpasses the enhancement effect of the exposed (100) facets for the Pd nanocubes with average sizes of 8 nm due to the extensive PVP-to-Pd charge transfer. Moreover, the Pd nanocubes with average sizes of 8 nm exhibit similar intrinsic electrocatalytic activity to the Pd nanooctahedra with (111) facets exposed and average sizes of 7 nm, indicating that the electronic structure of Pd electrocatalysts plays a more important role in influencing the electrocatalytic activity than the exposed facet. Since the chemisorbed PVP molecules block the surface sites on Pd nanocrystals that are accessible to the reactants, all Pd nanocrystals exhibit lower mass-normalized electrocatalytic activity than the Pd black electrocatalysts, and the mass-normalized electrocatalytic activity increases with the ECSA. These results clearly demonstrate that the size- and shape-dependent electrocatalytic activity of Pd nanocrystals capped with PVP for methanol and ethanol oxidation should be attributed to both the exposed facets of the Pd nanocrystals and the size-dependent electronic structures of the Pd nanocrystals resulting from the size-dependent PVP coverage and PVP-to-Pd charge transfer. Therefore, capping ligands on capped metal nanocrystals inevitably influence their surface structures and surface-mediated properties, which must be considered for a comprehensive understanding of the structure-activity relationship of capped metal nanocrystals.     

双极纳米电极阵列实现单个铂纳米颗粒上氢气析出反应的电致化学发光成像

本文制备了嵌于多孔阳极氧化铝（AAO）膜中直径为200 nm,间距为450 nm的高密度（5.7 × 10⁸ cm^-2）的金纳米电极阵列,纳米电极分布规则,尺寸高度均一。我们将该金纳米电极阵列作为双极电极阵列,可将电极一侧的电化学法拉第信号在另一侧电极上转化成电致化学发光（ECL）信号,从而实现对单个铂纳米颗粒上氢气析出反应（HER）进行亚微米空间分辨率的电化学成像。本文介绍的方法为高空间分辨率成像电催化材料、能源材料以及细胞过程的局部电化学活性提供了一个良好的平台。     

Exploring the Strain Effect in Single Particle Electrochemistry using Pd Nanocrystals

Tuning the surface strain of heterogeneous catalysts is recognized as a powerful strategy for tailoring their catalytic activity. However, a clear understanding of the strain effect in electrocatalysis at single-particle resolution is still lacking. Here, we explore the electrochemical hydrogen evolution reaction (HER) of single Pd octahedra and icosahedra with the same surface bounded {111} crystal facet and similar sizes using scanning electrochemical cell microscopy (SECCM). It is revealed that tensilely strained Pd icosahedra display significantly superior HER electrocatalytic activity. The estimated turnover frequency at −0.87 V vs RHE on Pd icosahedra is about two times higher than that on Pd octahedra. Our single-particle electrochemistry study using SECCM at Pd nanocrystals unambiguously highlights the importance of tensile strain on electrocatalytic activity and may offer new strategy for understanding the fundamental relationship between surface strain and reactivity.     

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.     

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．     

Tracking the Electrocatalytic Activity of a Single Palladium Nanoparticle for the Hydrogen Evolution Reaction

The nanoparticle-based electrocatalysts’ performance is directly related to their working conditions. In general, a number of nanoparticles are uncontrollably fixed on a millimetre-sized electrode for electrochemical measurements. However, it is hard to reveal the maximum electrocatalytic activity owing to the aggregation and detachment of nanoparticles on the electrode surface. To solve this problem, here, we take the hydrogen evolution reaction (HER) catalyzed by palladium nanoparticles (Pd NPs) as a model system to track the electrocatalytic activity of single Pd NPs by stochastic collision electrochemistry and ensemble electrochemistry, respectively. Compared with the nanoparticle fixed working condition, Pd NPs in the nanoparticle diffused working condition results in a 2–5 orders magnitude enhancement of electrocatalytic activity for HER at various bias potential. Stochastic collision electrochemistry with high temporal resolution gives further insights into the accurate study of NPs’ electrocatalytic performance, enabling to dramatically enhance electrocatalytic efficiency.     

Size-dependent electrocatalytic activity of gold nanoparticles on HOPG and highly boron-doped diamond surfaces

Gold nanoparticles were prepared by electrochemical deposition on highly oriented pyrolytic graphite (HOPG) and boron-doped, epitaxial 100-oriented diamond layers. Using a potentiostatic double pulse technique, the average particle size was varied in the range from 5 nm to 30 nm in the case of HOPG as a support and between < 1 nm and 15 nm on diamond surfaces, while keeping the particle density constant. The distribution of particle sizes was very narrow, with standard deviations of around 20% on HOPG and around 30% on diamond. The electrocatalytic activity towards hydrogen evolution and oxygen reduction of these carbon supported gold nanoparticles in dependence of the particle sizes was investigated using cyclic voltammetry. For oxygen reduction the current density normalized to the gold surface (specific current density) increased for decreasing particle size. In contrast, the specific current density of hydrogen evolution showed no dependence on particle size. For both reactions, no effect of the different carbon supports on electrocatalytic activity was observed.     

维生素E绿色还原法制备银纳米粒子的研究

采用一种绿色还原法制备银纳米粒子,以维生素E为还原剂,淀粉为稳定剂,在液相中还原硫酸银,通过改变溶液的pH值和反应时间,得到不同粒径的黄色银纳米粒子,并分别采用透射电镜、红外光谱、紫外-可见吸收光谱、扫描电镜和电化学方法对银纳米粒子进行表征。结果表明:维生素E在溶液中被氧化生成苯醌,反应得到的银纳米粒子为球形,粒径为8~25 nm;在较强碱性条件下,得到的银纳米粒子尺寸较小,分布较均匀,其平均粒径约为10 nm;不同条件下生成的银溶胶分别在417、411、409、408 nm处出现紫外吸收峰,这些吸收峰均为银纳米粒子的表面共振吸收;生成的银纳米粒子具有很好的电化学性质,并对L-半胱氨酸的电化学反应显示了良好的催化活性。     

壳层厚度可调控的Ag@Pd@Pt纳米粒子的合成和甲酸电催化研究

在本课题组研究55 nm Au@Pd@Pt对甲酸电催化效果基础上,我们采用Ag取代Au制备55 nm Ag@Pd@Pt纳米粒子以降低催化剂的成本,并对甲酸的电催化行为进行研究. 研究表明：少量Pt的存在可大幅度提高催化剂的活性,当Pt的覆盖度为0.5 单原子层（ML）时,起始氧化电位最为靠前,氧化峰电流最大,这与Au@Pd@Pt纳米粒子对甲酸电催化行为类似. 与Au@Pd@Pt纳米粒子相比,其最佳起始氧化电位偏正0.05 V,但电催化活性并没有明显的降低. 通过改变催化剂比表面积研究甲酸的电催化行为,发现将9 nm Ag纳米粒子作为内核的9 nm Ag@Pd@Pt负载在活性炭中,在保持催化活性不变的情况下,碳载的催化剂价格可比55 nm Au@Pd@Pt纳米粒子降低220倍左右.     

Oxygen Evolution Reaction on Nanoporous Gold Modified with Ir and Pt: Synergistic Electrocatalysis between Structure and Composition

Active oxygen evolution reaction electrocatalysts for water splitting have received great attention because of their importance in the utilization of renewable energy sources. Here, the electrochemical oxygen evolution reaction activities of a nanoporous gold (NPG)‐based electrode in acidic media are investigated. The dependence of the oxygen evolution reaction activity on the NPG surface area shows that the large electrochemical surface areas of the NPG are effectively utilized to enhance electrocatalytic activity. The NPG surfaces are modified with Pt using atomic layer electrodeposition methods, and the resulting NPG@Pt exhibited enhanced electrocatalytic activities compared to those of the NPG and flat Pt electrodes. Ir‐modified NPG (NPG@Ir) electrodes are prepared by spontaneous exchange of Ir on NPG surfaces and exhibit enhanced electrocatalytic activity compared to that of flat Ir surfaces. The modification of NPG@Pt with Ir results in NPG@Pt/Ir electrodes, and their electrocatalytic activities exceed those of NPG@Ir. The enhanced oxygen evolution reaction activity on NPG@Pt/Ir over that on NPG@Ir surfaces is examined by X‐ray photoelectron spectroscopy. The oxygen evolution reaction activity on NPG@Pt/Ir surfaces demonstrates synergistic electrocatalysis between the nanoporous surface structure and active electrocatalytic components.     

Pt/十六烷基三甲基溴化铵纳米聚集体修饰玻碳电极促进析氢(英文)

A novel, cost‐effective, and simple electrocatalyst based on a Pt‐modified glassy carbon electrode (GCE), using cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, is reported. Am‐phiphilic CTAB molecules were adsorbed on GCE by immersion in a CTAB solution. The positively charged hydrophilic layer, which consisted of small aggregates of average size less than 100 nm, was used for accumulation and complexation of [PtCl6]2? anions by immersing the electrode in K2PtCl6 solution. The modified electrode was characterized using scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, impedance spectroscopy, and electrochemical methods. The electrocatalytic activity of the Pt particles in the hydrogen evolution reaction (HER) was investigat‐ed. The results show that the CTAB surfactant enhances the electrocatalytic activity of the Pt parti‐cles in the HER in acidic solution.     

Pt/C催化剂对乙醇电氧化的粒径效应

利用有机溶胶方法, 通过控制溶剂挥发温度制备了具有不同粒径大小的Pt/C催化剂. 制得的Pt/C催化剂中, Pt粒子具有非常优异的均一性和良好的分散度. 电化学研究表明, 对于乙醇的电催化氧化, Pt/C催化剂存在着明显的粒径效应. 当Pt粒子粒径为3.2 nm时, Pt/C催化剂对乙醇的电催化氧化的质量比活性最佳. X射线光电子能谱(XPS)的研究显示, Pt/C催化剂对乙醇氧化的粒径效应与其零价Pt含量以及Pt粒子的比表面积密切相关.     

Plasmon-Enhanced Electrochemiluminescence at the Single-Nanoparticle Level

Plasmon-enhanced electrochemiluminescence (ECL) at the single-nanoparticle (NP) level was investigated by ECL microscopy. The Au NPs were assembled into an ordered array, providing a high-throughput platform that can easily locate each NP in sequential characterizations. A strong dependence of ECL intensity on Au NP configurations was observed. We demonstrate for the first time that at the single-particle level, the ECL of Ru(bpy)₃²⁺-TPrA was majorly quenched by small Au NPs (<40 nm), while enhanced by large Au ones (>80 nm) due to the localized surface plasmon resonance (LSPR). Notably, the ECL intensity was further increased by the coupling effect of neighboring Au NPs. Finite Difference Time Domain (FDTD) simulations conformed well with the experimental results. This plasmon enhanced ECL microscopy for arrayed single NPs provides a reliable tool for screening electrocatalytic activity at a single particle.     

碳纳米管结构对碳纳米管载Pt催化剂电催化性能的影响

在制备单、双壁及不同管径的多壁碳纳米管(CNTs)的基础上, 用液相还原法把Pt沉积到单、双壁和管径不同的多壁CNTs上. 发现制得的CNTs载Pt(Pt/CNTs)催化剂对甲醇氧化的电催化活性随CNTs管径减小而增加. 这归结于管径小的CNTs的比表面积较大, 含氧基团多, 有利于提高Pt粒子分散度, 加上管径小的单壁CNTs具有更高的导电性, 这些因素都有利于提高Pt/CNTs催化剂对甲醇氧化的电催化活性.     

A strategy for the high dispersion of PtRu nanoparticles onto carbon nanotubes and their electrocatalytic oxidation of methanol

Carbon nanotubes (CNTs) were non-covalently functionalized by 1-pyrenecarboxaldehyde (PCA) via π-π stacking interactions. PCA not only acts as the reductant for the deposition of PtRu nanoparticles, but the oxidation product of PCA can also effectively anchor and stabilize the in-situ-produced PtRu?NPs on the surface of CNTs. Transmission electron microscopy demonstrates that PtRu?NPs are uniformly dispersed on the surface of CNTs with small particles sizes of about 1.7 nm. The obtained PtRu-NP/CNT composites have higher electrochemical surface areas, electrocatalytic activities, and better stability towards methanol oxidation compared to PtRu?NPs supported on pristine CNTs.     

反应pH值对微波法合成的Mo修饰的Pt/C催化剂结构和乙醇电氧化催化性能的影响

通过调节微波反应溶液的pH值合成了一系列Mo修饰的Pt/C催化剂并用于乙醇的电氧化催化反应.利用X射线衍射(XRD)、透射电子显微镜(TEM)及X射线光电子能谱(XPS)对催化剂的晶型结构、微观形貌、粒径尺寸和表面电子结构进行了表征,并采用循环伏安法(CV)、计时电流法(CA)和电化学阻抗谱(EIS)对催化剂的乙醇电氧化催化性能进行了测试.结果表明,碱性环境有利于催化剂组分在碳载体上的均匀分布,pH值为14时制得的催化剂组分颗粒尺寸最小,且分布最均匀.该催化剂不仅表现出了最大的有效电化学比表面积和最高的乙醇电氧化催化活性,而且具有最稳定的乙醇氧化催化性能.     

丙醇和丁醇异构体在钯镍电极上的电催化氧化

β环糊精(β-CD)具有特殊的空腔结构,将β-CD修饰的多壁碳纳米管(MWCNT)涂在钛基底上,采用电沉积的方法在修饰的钛基底上沉积纳米PdNi催化剂。SEM结果表明,PdNi纳米颗粒在β-CD/MWCNT修饰的钛片上有较好的分散度,粒径为90~130 nm。在碱性溶液中,测试了PdNi-β-CD/MWCNT/Ti电极分别对丙醇和丁醇不同异构体氧化的电催化活性;通过计算与-OH相连的碳原子上的Muliken净电荷,分析不同异构体的氧化机理。结果表明,不同异构体的氧化活性不同,PdNi-β-CD/MWCNT/Ti电极对正丙醇和正丁醇的氧化活性明显高于其异构体,-OH所在碳原子上的Muliken 净电荷越小,醇类分子越容易被氧化。     

Synthesis of flower-like gold nanoparticles and their electrocatalytic activity towards the oxidation of methanol and the reduction of oxygen

This article describes the synthesis of branched flower-like gold (Au) nanocrystals and their electrocatalytic activity toward the oxidation of methanol and the reduction of oxygen. Gold nanoflowers (GNFs) were obtained by a one-pot synthesis using N-2-hydroxyethylpiperazine-N-2-ethanesulphonic acid (HEPES) as a reducing/stabilizing agent. The GNFs have been characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and electrochemical measurements. The UV-visible spectra show two bands corresponding to the transverse and longitudinal surface plasmon (SP) absorption at 532 and 720 nm, respectively, for the colloidal GNFs. The GNFs were self-assembled on a sol-gel-derived silicate network, which was preassembled on a polycrystalline Au electrode and used for electrocatalytic applications. The GNFs retain their morphology on the silicate network; the UV-visible diffuse reflectance spectra (DRS) of GNFs on the silicate network show longitudinal and transverse bands as in the case of colloidal GNFs. The GNFs show excellent electrocatalytic activity toward the oxidation of methanol and the reduction of oxygen. Oxidation of methanol in alkaline solution was observed at approximately 0.245 V, which is much less positive than that on an unmodified polycrystalline gold electrode. Reduction of oxygen to H2O2 and the further reduction of H2O2 to water in neutral pH were observed at less negative potentials on the GNFs electrode. The electrocatalytic activity of GNFs is significantly higher than that of the spherically shaped citrate-stabilized Au nanoparticles (SGNs).     

Controllable Electrodeposition of Platinum Nanoparticles on Graphene Nanosheet for Methanol Oxidation Reaction

A simple and cost-effective electrochemical method synthesized platinum nanoparticles on graphene nanosheet (PtNPs@GNS) is reported, and the Pt loading of the PtNPs@GNS can be controlled by electrodeposition. The structure and element analysis of the PtNPs@GNS have been investigated by scanning electron microscopy (SEM), Raman spectrum, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The electrochemical measurement including electrochemical active surface area, current density, mass activity, oxidation peak potential,shows the PtNPs@GNS have more performance electrocatalytic properties for methanol oxidation reaction (MOR) compared to Vulcan XC-72 carbon (XC-72) supported PtNPs electrocatalysts. Probably, the cause which may be attributes to no aggregation of PtNPs and the well-dispersion on surface of GNS, so PtNPs@GNS show large electrochemically active surface area, highly electrocatalytic activity and stability in direct methanol fuel cells.