The synthesis and structural characterization of a charge transfer complex of iodine and indole trimer

Indole electrooxidation using iodine as supporting electrolyte yields sheaves of very thin black needles identified as a charge transfer complex of iodine and an indole trimer. X-ray diffraction studies on this material allows us univocally to propose a reliable crystal model in which a disorder involving both I₃⁻ residues and organic molecules is evidenced. The structure consists of stacked molecules of indole trimers (cations) and columns of iodines (anions).     

Investigation of methanol electrooxidation on Au/C catalyst in alkaline medium

Gold nanoparticles supported on activated carbon (Au/C) are prepared by rapid reduction with KBH₄, after was partially deposited on the surface of the activated carbon by the reaction of and ammonia. Through the characterization of the transmission electron microscope and X-ray powder diffraction, the mean diameter of the Au nanoparticles (AuNPs) decreases with the increase of the Au loading. The energy dispersive X-ray spectroscopy analysis is carried out for measuring the Au loadings of the Au/C catalysts. The results exhibit the Au/C catalyst with 20 wt% Au has the highest loading efficiency (94.5%). The origin of the catalytic activity of Au/C catalysts for the methanol electrooxidation (MEO) is investigated by the cyclic voltammetry, which indicates that the current densities normalized by the actual Au loading for the MEO increase with a decrease in the mean diameter of AuNPs by a factor of 2.42–3.17. Based on this result, the active sites (corners, edges and step sites) for the MEO are proposed.     

电氧化合成Co3+及其在对甲砜基苯甲酸制备中的应用

本文对Co3+的电氧化合成以及用作氧化对甲砜基甲苯合成对甲砜基苯甲酸进行了系统研究。研究表明，选用阳极二氧化铅、阴极铅为电极板，陶瓷膜作为阳离子交换膜，电解液浓度为C(Co2+)=0.5mol/L、C(硫酸)=4.0mol/L、C(硫酸铵)=0.15mol/L，电极间距d=2cm、电流密度J=350A/m2、电解温度t=10℃，电解液Co2+转化率可达80%，电解氧化电流效率67.5%。在进行对甲砜基甲苯的氧化时，控制电解液浓度为C(Co3+)=0.4mol/L、C(硫酸)=4.0mol/L、C(硫酸铵)=0.15mol/L，Co3+与对甲砜基甲苯的摩尔比n（Co3+）：n（对甲砜基甲苯）=6:1，反应温度30℃，反应时间30min，对甲砜基苯甲酸的收率可达97.8%，精制后纯度在98.5%以上。     

Electrochemical polymerization of benzene in the presence of Ag+, Pb2+ and Cu+ ions

Poly(p-phenylene) (PPP) films were synthesized by using benzene and fluorosulphonic acid (FSO₃H) as a strong acid containing Ag⁺, Pb²⁺ and Cu⁺ ions in methylene chloride (CH₂Cl₂) solution. Addition of Ag⁺ or Pb²⁺ ions into the polymerization medium improved the PPP films formation, but Cu⁺ ion did not have an effect on polymerization. PPP films were characterized by cyclic voltammetry, IR and TGA. Dry conductivities were measured by using four probe technique. Received: 18 September 2000 / Reviewed and accepted: 20 September 2000     

On the kinetics and mechanism of simultaneous CO and NO oxidations on polyoriented and Pt nanoparticles

Simultaneous carbon and nitrogen monoxide oxidations were studied on different platinum surfaces to envisage the kinetics and mechanism of oxidations in acid media. Nanosized platinum specimens were prepared by an electrochemical method without chemical capping agents and platinum ion precursors. Crystalline oriented particles were obtained from a platinum surface by applying symmetric or asymmetric potential programs in concentrated sulfuric acid followed by cathodizations at very large negative potentials.Nitrogen monoxide arising from nitrite solutions showed synergetic oxidation profiles when first scanning the potential towards cathodic values in solutions containing carbon monoxide. Nitrite oxidative desorption to nitrate arose as a mass controlled process, whereas carbon monoxide oxidation to carbon dioxide occurred firstly from its adsorbate and then associated with carbon monoxide bulk solution.Tafel lines were derived including the potential dependence of surface coverages by oxygen containing adsorbates together with those by carbon and nitrogen monoxides. No changes for nitrogen oxide oxidation Tafel slopes were detected either in the presence or the absence of carbon monoxide (ca. 0.120 Vdec⁻¹) above 1 V, whereas carbon monoxide oxidation varies the slope from 0.040 to ca. 0.060 Vdec⁻¹ when nitrogen monoxide adsorbates were formed.     

One-step fabrication of ordered Pt-Cu alloy nanotube arrays for ethanol electrooxidation

Novel one dimensional (1D) nanostructured metallic electrodes have received much attention in the area of the fuel cell because of their extremely high surface-to-volume ratios and excellent activities. Here, we report the one-step fabrication of Pt-Cu alloy nanotube arrays. As determined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, ordered Pt-Cu alloy nanotubes have been successfully fabricated utilizing a nanochannel alumina template. The electrocatalytic activities of the Pt-Cu alloy nanotubes for the oxidation of ethanol in acidic medium were investigated by cyclic voltammetry. The results show that the Pt-Cu alloy nanotubes can be used as effective electrocatalysts for ethanol oxidation in direct alcohol fuel cells.     

A novel graphite modified paper based cobalt-cobalt oxalate-nickel electrode for the electrooxidation of hydrogen peroxide

The use of fossil energy has caused a serious burden on the environment, so it is urgent to find new and developable energy sources. H₂O₂ as a new type of clean fuel for fuel cell has received widespread attention. In this paper, a novel graphite modified paper based cobalt-cobalt oxalate-nickel (FG@Co–CoC₂O₄–Ni) electrode is fabricated by the simple “pencil depicting-electrodeposition-oxalic acid etching-electrodeposition” process for the electrooxidation of H₂O₂ in alkaline environment. The as-prepared FG@Co–CoC₂O₄–Ni electrode owns a novel and special three-dimensional (3D) porous structure, which can greatly increase the diffusion of reactants (NaOH and H₂O₂) during the electrochemical reaction process and lead a high catalytic activity for the electrooxidation of H₂O₂. More importantly, three main nanomaterial (Co, CoC₂O₄ and Ni) and some new generated substances during the CV test in NaOH solution (e.g. Ni(OH)₂, NiOOH, Co(OH)₂, CoOOH, Co₃O₄ and Co₂O₃ etc.) are on the surface of paper, which will enhance the electrocatalytic activity of the FG@Co–CoC₂O₄–Ni electrode to a great extent due to their synergistic effect. When the reaction solution contains 1.0 mol dm^?3 NaOH and 0.2 mol dm^?3 H₂O₂, the FG@Co–CoC₂O₄–Ni electrode exhibits a much higher oxidation current density (270.6 mA cm^?2) than the FG, FG@Co, FG@Ni, FG@Co–Ni and FG@Co–CoC₂O₄ electrodes. Besides, the whole preparation process for the FG@Co–CoC₂O₄–Ni electrode doesn't use any organic binder, ensuring the electrode owns good conductivity and stability for the electrochemical reaction. At last, the electrocatalytic mechanism for the electrooxidation of H₂O₂ is discussed. The Ni compounds and Co compounds are believed as the main catalytic substances, and the metallic Co core provides a fast route for the transfer of electrons. The super catalytic activity makes the prepared electrode in this study to be a promising material for the electrooxidation of H₂O₂ and the novel design idea gives some guidance for the fabrication of electrode materials in the field of fuel cell.     

Layered Au-Pd-Au nanorod catalysts: Pd-layer thickness effects on catalyst performance

Au/Pd/Au and Au/Pd layered nanorods (NR) with different Pd thickness, down to 15 nm, are electrodeposited in Si-supported porous anodized aluminum thin film templates. These structures are, in contrast to Au-Pd core-shells, mechanically relaxed, so that chemical and electronic interaction effects between Au and Pd are expected to predominate in controlling their performance in the electrooxidation of formic acid. The XRD results are conclusive about the formation of pure metal layers, but a corrugated Au/Pd interface is revealed by scanning electron microscopy. The CV behavior of the different structures shows that the PdO reduction peak is shifted towards more noble values as the Pd thickness decreases. Regarding the electrocatalytic oxidation behavior there is a substantial increase in performance with decreasing Pd-layer thickness. It is further shown that the Au/Pd/Au nanostructures perform better than the Au/Pd bilayer structure for the same Pd layer thickness. Also the long term behavior is improved. Both CV and electrocatalytic behaviors are discussed in terms of interfacial intermixing between Pd and Au at the nanoscale and a higher interface contribution for thinner Pd layers.     

Carbon-ceramic supported bimetallic Pt-Ni nanoparticles as an electrocatalyst for oxidation of formic acid

The Pt-Ni nanoparticles supported on carbon-ceramic electrode (CCE) are prepared by an electrodeposited process. The obtained catalyst is characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and cyclic voltammetry. The results show that the Pt-Ni nanoparticles (Flower like), which are uniformly dispersed on carbon-ceramic, are 20-50 nm in diameters. The Pt-Ni/CCE catalyst, which has excellent electrocatalytic activity for formic acid (FA) electrooxidation than a comparative Pt/CCE catalyst, shows great potential as less expensive electrocatalyst for FA electrooxidation. On the other hand, the Pt-Ni/CCE catalyst has satisfactory stability and reproducibility when stored in ambient conditions or continues cycling. These results indicate that the system studied in the present work is the most promising system for use in direct formic acid fuel cells.     

Carbon-supported PtAu alloy nanoparticle catalysts for enhanced electrocatalytic oxidation of formic acid

The understanding of the electrocatalytic activity of bimetallic nanoparticle catalysts requires the ability to precisely control the composition and phase properties. In this report, we describe a new strategy in the preparation of a series of carbon supported platinum-gold bimetallic nanoparticles with various bimetallic compositions which were loaded onto a carbon black support and subjected subsequently by thermal treatment (Pt_100−mAu_m/C). The Pt_100−mAu_m/C catalysts are characterized by X-ray diffraction (XRD), transmission electron spectroscopy (TEM), and induced coupled plasma-atomic emission spectroscopy (ICP-AES). The XRD pattern for the bimetallic nanoparticles shows single-phase alloy character. This ability enabled us to establish the correlation between the bimetallic composition and the electrocatalytic activity for formic acid (FA) electrooxidation. The electrocatalytic activities of the catalysts toward FA oxidation reaction are shown to strongly depend on the bimetallic PtAu composition. Within a wide range of bimetallic composition, the Pt₅₀Au₅₀/C catalyst shows the highest electrocatalytic activity for the FA oxidation, with a mass activity eight times higher than that of Pt/C. The high performance of the PtAu/C catalyst can be ascribed to the increased selectivity toward the FA dehydrogenation at the decreased availability of adjacent Pt atoms.