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Research of Dimethyl Ether Electrooxidation Mechanism on Platinum Single Crystals and Highly Active Catalysts

Author: LuLeiLei
Tutor: YinGePing
School: Harbin Institute of Technology
Course: Chemical Engineering and Technology
Keywords: Dimethyl ether Electro-oxidation Fuel cell Platinum single crystal Nanocrystalline
CLC: TM911.4
Type: PhD thesis
Year: 2009
Downloads: 131
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Abstract


Dimethyl ether (Dimethyl ether, DME) is a novel direct oxidation fuel cell fuel, having a low toxicity, and the permeability is small, the number of reaction electrons more advantages, and DME can achieve large-scale, multi-channel prepared is a rich source of new methanol alternative fuels. But lower electro-oxidation activity of dimethyl ether on platinum-based catalysts, especially dimethyl ether electrocatalytic oxidation mechanism remains unclear, hindering direct DME fuel battery (Direct dimethyl ether, fuel can cell DDFC) anode catalyst Research Progress. The purpose of this paper is the use of a platinum single crystal electrode surface atomic structure determination, combined situ electrochemical infrared spectroscopy studies of dimethyl ether in the electro-catalytic oxidation mechanism of the platinum electrode surface, and then guide the design and development of DDFC anode catalyst. Using cyclic voltammetry and chronoamperometry to study the relationship between the electrochemical behavior of the DME with the platinum electrode surface structure. The results show that the DME electro-oxidation on platinum single crystal electrodes on the surface of the electrode structure is very sensitive to the low activity of the Pt (111) and Pt (110) crystal surface, and Pt (100) crystal surface activity is very high. On this basis, using the high-index planes as the working electrode, and found the DME electro-oxidation activity decreased gradually decreasing (100) the platform width, DME only in the long-range order (100) platforms are easily oxidized. Infrared spectroscopy combined with electrochemical scene parsing DME decomposition products on Pt (111) and Pt (100) electrode, found DME at low potentials by dehydrogenation dissociative adsorption occurs, and subsequently converted to the more stable linear adsorption and bridge adsorbed CO (COL (COB), and further at a high potential is oxidized to the final product CO2. electrode Pt (111) and Pt (100) representative examine the supporting electrolyte, the potential control method and DME body the impact of the concentration on the electro-oxidation process in the Pt (111) electrode surface, hydrogen and anion adsorption from the adsorption of dimethyl ether solution was strongly inhibited. through potential step scanning experiments study found, in 0.5 mol ยท L- 1 H2SO4, DME on Pt (111) electrode solution from the adsorption reaction occurs mainly in the 0.2 to 0.5 V, the initial reaction rate at 0.35 V found by calculating the the DME dissociation adsorption stable intermediate CO coverage degrees in between 0.3 ~ 0.5 V is about 0.37., DME on Pt (111) electrode does not occur by direct oxidation reaction compared with Pt (111) electrode, the anions on the activity of the electro-oxidation of DME on Pt (100) less affected, DME electro-oxidation on Pt (100) surface follow dual path mechanism through a comparative study with methanol and cyanide in the Pt (111) electrode modified on DME can speculate, DME low potential of dissociative adsorption process requires three immediately the platinum active site can achieve, and in the high potential range DME via CO bond cleavage to oxidation, the reaction occurs selectively on the long-range order of the Pt (100) surface. spontaneous deposition method on platinum single crystal electrodes deposited metal Ru, the Ru add DME catalytic activity of platinum electrode and the electrode surface structure Ru modification improved the oxidation of Pt (100) DME electric catalytic activity, inhibit the catalytic activity of the Pt (110) and Pt (111) in DME using 30 mass% of Pt / C, and the ratio of different metal PtRu / C and PtIr / C catalyst is prepared by impregnation-reduction, using cyclic voltammetry to study the catalytic activity of the DME. study found that with the increase of the content of Ru or Ir, DME decreased activity, which is due to the addition of Ru / Ir reduce the proportion of 3 closely connected to the platinum atom, thus suppression the DME solution from adsorption reaction using colloidal synthesis of platinum nanocrystals of different shapes, and examined the catalytic activity and stability of the platinum nanocrystals of DME. in K2PtCl6 and K2PtCl4 precursor, sodium polyacrylate (NaPA) protective agent, the former body aging 3 d, respectively, using Pt: NaPA for 1:5 and 1:1 ratio, you can get the cube-shaped platinum nanocrystals, the TEM characterization and cyclic voltammetry curves confirmed this nanocrystalline having the structural characteristics of the crystal plane of {100} to study the catalytic activity of the different shapes of the platinum nano-crystal of DME, and found that the cube-shaped platinum Nanocrystals were higher activity of the DME to K2PtCl4 precursor obtained cube-shaped Nanocrystalline The highest activity is 2.9 times the commercial platinum black catalyst with Pt (100), and its CV curve on some of the typical characteristics of the electrode. findings cube platinum nanocrystals in the air for 90 d, the surface structure is essentially unchanged. can be found through the cube platinum nanocrystals electrochemical step, the shape of the platinum nanocrystals in 1.1V potential range can be basically stable, the potential rises to 1.2V nanocrystals in a relatively short period of stability, but for a long time a high oxidation potential will cause the surface of the long-range order of the (100) crystal plane is disturbed for some stepped also reduced, the catalytic activity of the DME.

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CLC: > Industrial Technology > Electrotechnical > Independent power supply technology (direct power) > Chemical power sources,batteries, fuel cells > Fuel cell
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