On-line mass spectrometry system for measurements at single-crystal electrodes in hanging meniscus configuration

We present the construction and some first applications of an On-line electrochemical mass spectrometry system for detecting volatile products formed during electrochemical reactions at a single-crystal electrode in hanging meniscus configuration. The system is based on a small inlet tip made of porous Teflon and a Peek holder, which is brought in close proximity (ca. 10–20 μm) to the electrode surface. The tip is connected to the mass spectrometer by glass and metal tubing. Because of the small amount of gas entering the mass spectrometer, no differential pumping is needed during the measurement. The tip construction and preparation introduced here leads to reproducible voltammetry with very good cleanliness characteristics. The presence of the tip has no significant influence on the blank voltammetry of a Pt(111) in sulfuric acid, and on voltammetric responses for CO adlayer oxidation, methanol oxidation, and hydroxylamine electrochemistry on Pt(111). The formation of gaseous products in these reactions can be followed accurately and is in good agreement with earlier results obtained by other mass spectrometric or spectroscopic techniques. The time response and tailing of the setup is on the order of seconds and mainly determined by the distance between the tip and the electrode.     

Application of electrode materials and catalysts in electrocatalytic treatment of dye wastewater

The dye industry produces a large amount of hazardous wastewater every day worldwide, which brings potential threaten to the global environment. As an excellent method for removal of water chroma and chemical oxygen demand, electrocatalytic methods are currently widely used in the treatment of dye wastewater. The selection and preparation of electrode materials and electrocatalysts play an important role on the electrocatalytic treatment. The aim of this paper is to introduce the most excellent high-efficiency electrode materials and electrocatalysts in the field of dye wastewater treatment. Many electrode materials such as metal electrode materials, boron-doped diamond anode materials and three-dimensional electrode are introduced in detail. Besides, the mechanism of electrocatalytic oxidation is summarized. The composite treatment of active electrode and electrocatalyst are extensively examined. Finally, the progress of photo-assisted electrocatalytic methods of dye wastewater and the catalysts are described.     

Electrodeposition of catalytically active nickel for the oxygen evolution reaction — effects of anionic composition

Nickel electrodes were prepared by electrodeposition in electrolytes of various anionic compositions. The deposition conditions and bath types were evaluated with special emphasis on the electrocatalytic properties for the oxygen evolution reaction (OER). Electrochemical characterizations in a 5 mol/L KOH solution at 25°C showed that the electrode deposited from the chloride bath, having a low Tafel slope of 50 mV/dec and an overpotential of 396 mV at 100 mA/cm², is the most catalytically active among electrodes prepared in electrolytes of various anionic compositions. The electrode activity for the OER is related to the real surface areas, which depend on the anion compositions in the deposition bath and the deposition conditions.     

Preparation of methanol oxidation electrocatalysts: ruthenium deposition on carbon-supported platinum nanoparticles

Methanol oxidation electrocatalysts were prepared from Ru electrochemical or spontaneous deposition on commercial-grade carbon-supported Pt nanoparticles (Pt-Vulcan XC72, E-TEK). The resulting Ru coverage was estimated by cyclic voltammetry in supporting electrolyte. The maximum electrocatalytic activity for methanol oxidation at room temperature was observed at lower Ru coverage for spontaneous deposition than for electrodeposition; _Ru 10% vs 20%, respectively. On the other hand, higher current densities for methanol oxidation were obtained in the case of electrodeposited Ru. These two results were related to the presence of non-reducible ruthenium oxides in the spontaneous deposit. The present work provides evidence that (i) efficient DMFC electrocatalysts can be achieved by Ru deposition on Pt nanoparticles, and (ii) formation of a PtRu alloy is not a required condition for effective methanol electrooxidation.     

MnO超微粒子的制备及其对PEMFC电催化性能的研究

用微乳液法合成了 Mn O超微粒子 ,探讨了影响萃取率及粒度的因素 ,得到了最佳反应条件 ,并用透射电子显微镜 (TEM)、X射线衍射仪 (XRD)及红外光谱 (FTIR)进行了表征。得到了粒径为 5 nm左右的 Mn O超微粒子 ,并在质子交换膜燃料电池 (PEMFC)的铂电极中加入 5 nm的Mn O超微粒子作为催化剂 ,改变了电池的放电机理 ,提高了输出电压。为 PEMFC的商品化进行了有价值的探索。     

Electro-oxidation of hydrazine on electrodes modified with vitamin B12

In this paper we report a kinetic study of the electro-oxidation of hydrazine catalyzed by vitamin B₁₂ pre-adsorbed on an ordinary pyrolytic graphite electrode. Kinetic parameters were determined by linear sweep voltammetry and rotating-disk electrode polarization curves. The order of the reaction is 1 in OH⁻ ions and Tafel plots give slopes of 80 mV/decade. A possible redox-catalysis mechanistic scheme is proposed.     

The significance of defect chemistry for the rate of gas–solid reactions: three examples

Three examples are revisited in which the reaction rate could be reliably correlated with point defect chemistry highlighting the role of point defects as acid–base active centers. In the case of dehydrohalogenation of tertiary butyl chloride, AgCl becomes increasingly active as heterogeneous catalyst, if AgCl is homogeneously or heterogeneously doped. By such a procedure the silver vacancy concentration is adequately increased. The oxygen incorporation into SrTiO₃ offers an example in which the surface mechanism in terms of adsorbed species, oxygen vacancies and electronic centers has been elucidated. Appropriate surface coatings give rise to significant catalytic effects. Increasing iron (acceptor) doping not only changes the point defect chemistry but also the nature of the rate determining step. Lastly, the electrocatalytic function of Sr-doped LaMnO₃ is considered as regards oxygen reduction reaction and O²⁻ incorporation into Y-doped ZrO₂ in the context of solid oxide fuel cells. Again the defect chemistry is of prime importance for the reaction rate.     

Ti基RuO2-CeO2-SnO2涂层阳极的电催化性能

利用热分解法制备了不同CeO2含量的Ti基RuO2-CeO2-SnO2涂层阳极, 通过循环伏安曲线和电化学阻抗谱测试了所制备的涂层阳极的电催化性能, 并用扫描电镜对涂层阳极的表面形貌进行了观察. 结果表明 制备温度对涂层阳极的性能有很大影响, 在涂层阳极中引入CeO2可以增加RuO2-CeO2- SnO2涂层的有效活性表面积, 从而提高涂层阳极的电催化活性, 且CeO2含量的最佳摩尔分数为0.4.     

Anionic Regulated NiFe (Oxy)Sulfide Electrocatalysts for Water Oxidation

The construction of active sites with intrinsic oxygen evolution reaction (OER) is of great significance to overcome the limited efficiency of abundant sustainable energy devices such as fuel cells, rechargeable metal–air batteries, and in water splitting. Anionic regulation of electrocatalysts by modulating the electronic structure of active sites significantly promotes OER performance. To prove the concept, NiFeS electrocatalysts are fabricated with gradual variation of atomic ratio of S:O. With the rise of S content, the overpotential for water oxidation exhibits a volcano plot under anionic regulation. The optimized NiFeS‐2 electrocatalyst under anionic regulation possesses the lowest OER overpotential of 286 mV at 10 mA cm^?2 and the fastest kinetics being 56.3 mV dec^?1 to date. The anionic regulation methodology not only serves as an effective strategy to construct superb OER electrocatalysts, but also enlightens a new point of view for the in‐depth understanding of electrocatalysis at the electronic and atomic level.     

Design of Ultrathin Pt‐Based Multimetallic Nanostructures for Efficient Oxygen Reduction Electrocatalysis

Nanocatalysts with high platinum (Pt) utilization efficiency are attracting extensive attention for oxygen reduction reactions (ORR) conducted at the cathode of fuel cells. Ultrathin Pt‐based multimetallic nanostructures show obvious advantages in accelerating the sluggish cathodic ORR due to their ultrahigh Pt utilization efficiency. A focus on recent important developments is provided in using wet chemistry techniques for making/tuning the multimetallic nanostructures with high Pt utilization efficiency for boosting ORR activity and durability. First, new synthetic methods for multimetallic core/shell nanoparticles with ultrathin shell sizes for achieving highly efficient ORR catalysts are reviewed. To obtain better ORR activity and stability, multimetallic nanowires or nanosheets with well‐defined structure and surface are further highlighted. Furthermore, ultrathin Pt‐based multimetallic nanoframes that feature 3D molecularly accessible surfaces for achieving more efficient ORR catalysis are discussed. Finally, the remaining challenges and outlooks for the future will be provided for this promising research field.