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High performance Pt nanoparticles prepared by new surfactants for C1 to C3 alcohol oxidation reactions

In this study, platinum nanoparticles have been prepared using PtCl4 as a starting material and 1-hexylamine, N-methylhexylamine, N,N-dimethylhexylamine, 1-heptylamine, N-methylheptylamine, and N,N-dimethylheptylamine as surfactants. All these surfactants were used in this synthesis, for the first time, to explore the effect of primary, secondary, and tertiary amine and chain length on the size and catalytic activity toward C1–C3 alcohol electro-oxidation. The electrochemical performance of all catalysts was determined using cyclic voltammetry and chronoamperometry. These techniques indicate that the highest electrocatalytic performance was generally observed when electrochemical surface area (ECSA), percent platinum utility, roughness factor, and the number of CH3 groups attached to the nitrogen atom is higher and the chain length shorter (C6H13). In addition, other important properties such as the crystal structure of platinum, size, and distribution of the platinum nanoparticles on the carbon support, and Pt(0) to Pt(IV) ratio, were determined using X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy. It was found that increasing ECSA, Pt(0)/Pt(IV) ratio, % Pt utility, and roughness factor improves the C1–C3 alcohol oxidation catalytic performance.

Characterisation of carbon-supported Pt–Sn bimetallic catalysts for the electrochemical oxidation of methanol

Carbon-supported platinum oxide–tin oxide samples have been studied as electrocatalysts for methanol oxidation. The Teflon-bonded electrodes are found to be poor electrocatalysts. X-Ray photoelectron and Mossbauer spectroscopy, together with electron microscopy, have been used to determine the nature of the bimetallic crystallites. Differences in the activity of various Pt–Sn-containing electrodes for methanol oxidation are discussed.

Effects of sodium hypochlorite on gutta-percha and Resilon cones: An atomic force microscopy and scanning electron microscopy study

The aim of this study was to evaluate the effects of 6% sodium hypochlorite (NaOCl) on gutta-percha (GP) and Resilon cones. Six standardized GP and Resilon cones were selected and cut 3mm from their tip. One GP and 1 Resilon cone were used as control samples. Cones were immersed in 6% NaOCl for 1, 5, 10, 20, and 30 minutes, thoroughly rinsed with nanopure water, and dried with filter paper. Then, surface topography was analyzed by atomic force microscopy and scanning electron microscopy coupled to an energy-dispersive x-ray (EDX) spectrometer. According to the root mean square and depth analysis values obtained from atomic force microscopic evalution, there were no significant differences found among the GP groups. However significant differences were found among Resilon cones (P ≤ .05). SEM images and EDX graphics showed that there were no prominent differences between GP and Resilon groups. These results showed that 6% NaOCl solution can be used in the disinfection of GP and Resilon cones. No alterations were observed on the GP cones, but it can change the surface of Resilon cones.

Carbon Supported Pt+Os Catalysts for Methanol Oxidation

11% Pt/C, 10% Pt + 1%Os/C, 9% Pt + 2%Os/C, 8% Pt + 3%Os/C, 7% Pt + 4%Os/C, 6% Pt + 5%Os/C and 5%Pt + 6% Os/C catalysts have been prepared for methanol oxidation reaction. Transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and cyclic voltammetry have been used to understand the nature of the species present in these catalysts. 7% Pt + 4% Os/C was the most active catalyst, while 8% Pt + 3% Os/C was the least active one. It is found that the metal particle size and distribution on the carbon support, the surface composition and the oxidation states of the metal particles, the metal-metal and metal support interactions are important parameters to define the activity of the catalyst.

Effect of a thermal treatment on the activity of carbon-supported Pt, Pt+W and Pt+Mo electrocatalysts for methanol oxidation reactions

Abstract Previous studies on carbon supported Pt, Pt+W and Pt+Mo indicated that Pt+Mo was the most active electrocatalyst at low potentials and that Pt+W has similar properties as pure Pt in methanol oxidation. Those samples were thermally treated at 900 °C in a hydrogen gas atmosphere for 6 hours to observe the effect on metal particle sizes and on their distribution on carbon support. It was found that thermally treated Pt+Mo/XC-72 remains the most active catalyst at all potentials compared to the other heated samples. The heat treatment caused the sintering of small particles leading to a decrease in activity of the catalysts except Pt+Mo/XC-72. The heat treated samples were characterised by voltammetry, X-ray diffraction, transmission electron microscopy and energy dispersive X-ray analysis techniques. The methanol oxidation reaction was followed by in-situ FTIR spectroscopy to identify products and adsorbed species on the surface of electrode.

Spectroscopic, Magnetic and Crystal Structure Analysis of Diammine-bis(2,6-dibromo-4-chlorophenolato-O)copper(II)

The [Cu(C6H2Br2ClO)2(NH3)2] complex was synthesized and characterized by XRD, UV/vis, FTIR, DSC, elemental analysis and magnetic susceptibility measurements. The structural analysis of the title complex indicated that it is a monomeric centrosymmetric compound which crystallizes in the monoclinic system, P21/c, and has a trans-planar CuO2N2 coordination [Cu-O 1.940(5) and Cu-N 1.978(7) Å ]. In the coordination sphere of the Cu atom, there are long range interactions with Br2 and the centrosymetrically related Br2i (i: −x,−y,−z) atoms [Cu-Br2: 3.079(2) Å ], resulting in a tetragonally elongated octahedral structure for the CuO2N2Br2 coordination. The molecules form one-dimensional chains along the x-axis of the unit cell held together by intermolecular hydrogen bonds.