Thapanee Sarakonsri

Electrochemical Deposition of Platinum and Palladium on Gold Nanoparticles Loaded Carbon Nanotube Support for Oxidation Reactions in Fuel Cell

Pt and Pd sequentially electrodeposited Au nanoparticles loaded carbon nanotube (Au-CNT) was prepared for the electrocatalytic study of methanol, ethanol, and formic acid oxidations. All electrochemical measurements were carried out in a three-electrode cell. A platinum wire and Ag/AgCl were used as auxiliary and reference electrodes, respectively. Suspension of the Au-CNT, phosphate buffer, isopropanol, and Nafion was mixed and dropped on glassy carbon as a working electrode. By sequential deposition method, PdPtPt/Au-CNT, PtPdPd/Au-CNT, and PtPdPt/Au-CNT catalysts were prepared. Cyclic voltammograms (CVs) of those catalysts in 1 M H2SO4 solution showed hydrogen adsorption and hydrogen desorption reactions. CV responses for those three catalysts in methanol, ethanol, and formic acid electrooxidations studied in 2 M CH3OH, CH3CH2OH, and HCOOH in 1 M H2SO4 show characteristic oxidation peaks. The oxidation peaks at anodic scan contribute to those organic substance oxidations while the peaks at cathodic scan are related with the reoxidation of the adsorbed carbonaceous species. Comparing all those three catalysts, it can be found that the PdPtPt/Au-CNT catalyst is good at methanol oxidation; the PtPdPt/Au-CNT effectively enhances ethanol oxidation while the PtPdPd/Au-CNT exceptionally catalyzes formic acid oxidation. Therefore, a different stoichiometry affects the electrochemical active surface area of the catalysts to achieve the catalytic oxidation reactions.

PREPARATION OF CdIn2Se4n-TYPE SEMICONDUCTOR USED AS THERMOELECTRIC MATERIAL BY SOL–GEL METHOD

The objective of this research was to study the effect of various parameters such as temperature and pH to the formation of cadmium indium selenide (CdIn2Se4) thin films, which were fabricated by sol–gel dip-coating method. This n-type semiconductor compound is suitable for application as thermoelectric materials. Cadmium, indium, selenium precursors were separately dissolved by solvents: ethanol, hydrochloric acid, and acetic acid to form metal alkoxides. The precursor solutions were then mixed together in N2 atmosphere. These metal alkoxides were hydrolyzed by adding water and then polycondensed by adding ethylene glycol to become gels. These gels were adjusted to various acid-base values by adding diethylnolamine. Glass substrates were dipped into the gels to form thin films. These thin films were annealed at various temperatures in N2 atmosphere and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and fourier transfrom infrared spectroscopy (FTIR) techniques. The results indicated that CdIn2Se4 compound occurred by the reaction at room temperature with pH 4 and annealed at 450°C in N2 atmosphere.

Microwave-assisted Pt–Co–Cr/C ternary compound preparation applied as a cathode catalyst for PEMFC

The present study describes the preparation of catalyst nanocomposites comprised of 20 wt.% Pt–Co–Cr (2:1:1) particles attached on the surface of carbon Vulcan XC-72R by microwave radiation; cases of carbon being chemically treated and untreated are considered. Ethylene glycol was used as the solvent and electron source for the microwave-assisted reduction reaction, whereas H2PtCl6xH2O, Co(NO3)36H2 O and Cr(NO3)39H2 O were used as metal precursors. The C powder surface was chemically modified by stirring the C in 8N H2 O2 for 48 h. For the nanocomposite in which C was not treated, EDS analysis showed a content of 4.9 wt.% Pt and 1.2 wt.% Cr with only a trace amount of Co. Higher Pt and Cr contents were observed in the catalyst sample prepared from treated carbon (5.6% Pt and 2.2% Cr), but no Co was detected. Chromium appeared as Cr3 O4 in both samples confirmed by the XAS spectrum. The obtained phase was therefore Pt–Cr3 O4 /C for both samples. The TEM results indicated that the average particle size of Pt–Cr3O4 was 2.22 ±0.41 nm on treated C and 1.93 ±0.34 nm on untreated C. By the CV technique, it was observed that the catalytic activity of the treated carbon Pt–Cr3O4 catalyst was not only higher than that of the untreated carbon Pt– Cr3 O4 catalyst, but also higher than that of the standard platinum catalyst.

Preparation and Applications of Precious Metals Adsorbed Activated Carbon Cloth

Precious metal nanoparticles (e.g. Au, Pd and Pt) on activated carbon cloths (ACCs) were simply prepared by impregnation of metal salts dissolving in ethanol solution. Pretreatment of the ACCs was firstly performed in hydrochloric acid solution and nitric acid as oxidizing agent was employed in order to introduce oxygen complex on the ACCs fiber surfaces. Uniformly dispersed metal nanoparticles with diameter of 5-20 nm on the ACC surfaces were simply achieved without using reducing agents. Morphology and composition of the metal adsorbed ACCs were examined by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), respectively. Electrolytic activity of metal/ACCs was investigated by using cyclic voltammetry (CV) to demonstrate the electron-transfer properties. Results demonstrate that metals adsorbed ACCs were easily prepared with simple procedures which will be more convenient for preparations and applications.

Electron Microscopy Investigation of FeNi/NrGO Nanocomposite Catalysts for Fuel Cells Application

High efficiency but low cost FeNi nanoparticles supported on NG (nitrogen-doped graphene) catalysts for ORR (oxygen reduction reaction) were prepared by electrodeposition method. NG was obtained via thermal annealing of ball milled graphene with melamine. XRD (X-ray diffraction), Raman, and XPS (X-ray photoelectron spectroscopy) analyses showed multiple layers with a low degree of disorder and characteristic of pyridinic-N were a major feature. The deposition of FeNi was carried out potentiostatically with voltage of -7.0 and -6.0 V for 100 s at room temperature. Different concentration of FeCl2·4H2O and NiCl2·6H2 O in ethylene glycol solution was varied. XRD patterns confirmed FeNi alloy formation and SEM (scanning electron microscopes) images reviewed that 0.025 M FeNi solution achieved spherically dispersed FeNi nanoparticles with diameters of 50-100 nm cover on NG particles and some parts appear as corals shape dendrite cluster. Only spherical particles were observed in other conditions. Average sizes of particle vary without trend. CV analysis shows that catalysts prepared with 0.50 M and at -7.0 V which has the smallest particle sizes, gave higher performance over others and commercial Pt/C catalysts. Therefore, this catalyst is expected to have good performance in ORR.

Analytical Electron Microscopy Study of SiSn/(Reduced Graphene Oxide) Nanocomposite Powder Applicable to Li-Ion Battery Anodes

Materials such as Si and Sn have much higher theoretical capacities as electrodes than a commercial graphite material and therefore are expected to be more opted for high performance Li ion batteries [1,2]. However, the major problem to use these metal substances is a huge volume change that causes cracking and climbing on the electrode surface. Carbon could be used as a supporting material to buffer the problematic volume change. There is a new type of carbon sheet, reduced graphene oxide (rGO) that is graphene produced by reducing graphene oxide [3]. In this study, we synthesized SiSn/rGO nanocomposite powder using a solution route method and examined its structure by means of analytical electron microscopy. The electrochemical characterization of the SiSn/rGO nanocomposite was also examined.

Electrical and Mechanical Properties of Surface Functionalized Carbon Nanotubes Incorporated Graphite-Phenolic Composite Bipolar Plate for PEMFC

This research aims to study the effect of the functionalization of the multiwall carbon nanotubes (MWCNTs) on the mechanical property improvement of phenolic composites for bipolar plate applications in proton exchange membrane fuel cells (PEMFC). The MWCNTs were oxidized by strong acid and silanized by silane coupling agent in order to enhance the interfacial adhesion between the MWCNTs and matrix and were used as reinforcement in the phenolic composites. The silanized MWCNTs was found to improve the mechanical properties of the composites; however, they caused the decrease of electrical conductivity due to the wrapping of the MWCNTs with non-conductive silane molecules. Nevertheless, the conductivity of more than 100 S/cm is maintained to meet the DOE requirement of materials for use as bipolar plates.

Structural investigation of SiSn/(reduced graphene oxide) nanocomposite powder for Li-ion battery anode applications

We synthesized SiSn/(reduced graphene oxide (rGO)) nanocomposite powder for a Li-ion battery material and characterized the structure by transmission electron microscopy (TEM) and analytical scanning transmission electron microscopy (STEM). Graphene oxide was prepared by Hummers method. The graphene oxide powder processed by heat treatment was added together with Si powder into a solution of SnCl2 ⋅ 2(H2O) dissolved in N2 bubbled ethylene glycol, and the solution was reacted with NaBH4. The product had a nominal atomic ratio of Si: Sn: C = 14: 3.5: 100. High-resolution TEM/STEM analysis revealed that the powder consisted of crystalline particles of Sn, Si, and SiO as well as thin reduced graphene oxide (rGO) lamellae of amorphous-like graphite with distorted lattices that were often found in areas as local as a few nm2. The aggregated Si and SiO particles grew up to several hundred nm across. Sn particles grew as large as a few tens of nm while those as small as a few nm were scattered on the (0001) rGO s...

Synthesis of CdIn2Se4 and Cu0.5Ag1.5InSe3 Compounds via Chemical and Solid-State Methods

CdIn2Se4 and Cu0.5Ag1.5InSe3 are high-performance thermoelectric materials. In this study, both CdIn2Se4 and Cu0.5Ag1.5InSe3 powders were synthesized using a microwave and solution method followed by annealing in nitrogen atmosphere. CdIn2Se4 was synthesized by two routes. First, CdSe was prepared using a microwave method. Second, In metal was prepared using a solution method. The prepared metals were annealed in nitrogen atmosphere. From the x-ray diffraction (XRD) results, CdIn2Se4 was observed as the main phase with CdSe and In2O3 as contaminant phases. The synthesis of Cu0.5Ag1.5InSe3 was also divided into two steps. First, CuAg and Se were prepared using a microwave method. Second, In metal was prepared using a solution method. The prepared metals were annealed in nitrogen atmosphere. From the XRD results, Cu0.5Ag1.5InSe3 was observed as the main phase with Cu0.5−xAg1.5−yInx+ySe and Se as contaminant phases.