ABSTRACTS: January 2002
Journal Archive
ABSTRACTS: January 2002
Abstracts: of Current Literature on the Platinum Metals and their Alloys
PROPERTIES
Novel Carbon Supported Material: Highly Dispersed Platinum Particles on Carbon Nanospheres
p. serp, r. feurer. y. kihn, p. kalck, j. l. faria and j. l. figueiredo, J. Mater. Chem., 2001, 11, (8), 1980-1981
Highly dispersed Pt nanoparticles (3–6 nm) were deposited by low temperature CVD of PtMe2(η4-C8H12)] in a fluidised bed reactor on C. nanospheres of low surface area. Nitric acid oxidative treatment was used to increase the concentration of grafting sites on the C. The precursor was sublimed at 343 K and decomposed at 383 K in the presence of small amounts of H2 added to the He carrier gas at 1316 Pa. This new Pt material may have catalytic and electrochemical applications.
Synthesis of Palladium Nanoparticles in Water-in-Oil Microemulsions
c-c wang, d.-h. chen and t.-c. huang, Colloids Surf. A: Physicochem. Eng. Aspects, 2001, 189, (1-3), 145-154
Pd nanoparticles can be synthesised by the reduction of Pd(NH3)4Cl2 with hydrazine in cationic H2O-in-oil microemulsions of H2O/cetyl-trimefhyl-ammonium bromide, n -butanol/isooctane at 25°C. The Pd nanoparticles are crystalline with a f.c.c. structure. Their magnetic susceptibility was significantly higher than that of bulk Pd.
An Investigation of the Partial Phase Diagrams of Ag-Pd-Gd-20Ru and Ag-Pd-Gd-50Ru Quaternary Systems
k zhang, y. xu and q. li, Precious Met. (Chin.), 2001, 22, (4), 1–6
The phase diagrams of the Ag-Pd-Ru-rich side (Gd < 25 at.%) in the Ag-Pd-Ru-Gd quaternary system were studied by XRD, SEM and optical microscopy. Isothermal sections at 7000C of Ag-Pd-Gd-20Ru and Ag-Pd-Gd-50Ru were determined. Both sections contained three two-phase regions: Pd(Ag) + (Ru), (Ru) + Ag51Gd14 and (Rn) + Pd3Gd; three three-phase regions: Pd(Ag) + Pd3Gd + (Ru), Pd(Ag) + Ag51Gd14 + (Ru) and Pd3Gd + Ag51Gd14 + (Ru); and one four-phase region: Pd(Ag) + Pd3Gd + Ag51Gd14 + (Ru).
Ternary Al-Pd-Co Monoclinic Phases
s. mi, m. yurechko, j. wu and b. grushko, J. Alloys Compd., 2001, 329, (1-2), L1-L4
The ternary Al-Pd-Co V-phase and U-phase were investigated using powder X-ray and electron diffraction. The V-phase has a primitive structure with a = 1.0068(2) nm, b = 0.3755(1) nm, C. = 0.6512(4) nm and β = 102.38(6)° for Al70.0Pd9.2Co20.8. The U-phase has a C-centred monoclinic strucrure with a = 1.9024(4) nm, b = 2.9000(4) nm, C. = 1.3140(4) nm and β = 117.26(3)° for Al69.1Pd16.5Co14.4.
Microstructure Characterization of Ceramic Composites Formed by Controlled Melt Oxidation of Al-Mg-Pd Alloys
m. pinkas, n. frage, e. manor and a. venkert, J. Mater. Sci., 2001, 36, (14), 3525-3529
Ceramic matrix composites were formed by controlled melt oxidation of Al98-xMgxPdx (x = 0.5, 1.5 and 3 at.%) alloys. The Pd addition was found to increase the growth rate, the metal volume fraction, the diameter of the metal channels and promote the formation of a uniform microstructure.
Transition from Nucleation Controlled to Growth Controlled Crystallization in Pd43Ni10Cu27P20 Melts
j. schroers, y.wu, r busch and w. l.johnson, Acta Mater., 2001, 49, (14), 2773-2781
Crystallisation of undercooled Pd43Ni10Cu27TP20 melts was studied under isothermal conditions in a differential scanning calorimeter. The results are summarised in a time-temperature-transformation (TTT) diagram which shows two time scales. One is the time to reach 1% of crystallised volume fraction and reflects the typical ‘nose’ shape of the TTT diagram. The other is the width of the crystallisation event itself, which increases with decreasing temperature from 90 s at 793 K to 10, 200 s at 623 K.
CHEMICAL COMPOUNDS
Linkage of Heteronuclear Rhodium-Platinum Clusters
i. o. koshevoy, s. p. tunik, s. jÄÄskelÄinen, m. haukka and t. a. pakkanen, J. Chem. Soc., Dalton Trans., 2001, (20), 2965-2967
[PtCl(dppm)]2 and [Pt2(CO)3(dppm)2] react with [Rh6(CO)15]2- and [Rh6(CO)15(NCMe)], to give as the main products, [Rh8Pt2(CO)21(dppm)2] (1) and [Rh6Pt4(CO)16(dppm)3] (2), respectively. The mixed metal Rh2Pt2 cluster in (1) and the tetranuclear Pt4 cluster in (2) are bonded to the Rh6 metal core via Rh-Rh and Pt-Rh bonds.
Pincer-Like Amido Complexes of Platinum, Palladium, and Nickel
j. c. peters, s. b. harkins, s. d. brown and m. w. day, Inorg. Chem., 2001, 40, (20), 5083-5091
Bis(8-quinoliyl)amine (1) (BQAH), (2-pyridin-2-yl-ethyl)-(8-quinoUnyl)amine (2), o -dimethylarnino-phenyl(8-quinollnyl)amine (3) and 3, 5-dimethyl-phenyl(8-quinollnyl)amine (4) were prepared from aryl halide and amine precursors by Pd-catalysed coupling reactions. From (1), (BQA)PtCl (BQA)PdCl and (BQA)NiCl were then prepared. While reaction of (2) gave a product mixture, (3) and (4) reacted with (COD)PtCl2 to afford coordinated cyclic dienes.
New Linked Macrocyclic Systems. Interaction of Palladium(ll) and Platinum(ll) with Tri-Linked N2S2-Donor Macrocycles and Their Single-Ring Analogues
i. m. atkinson, j. d. chartres, a. m. groth, l. f. lindoy, m. p. lowe, g. v. meehan, b. w. skelton and a. h. white, J. Chem. Soc., Oalton Trans., 2001, (19), 2801-2806
[M3L](PF6)6 (1) (M = Pt, Pd; L = ligand incorporating three linked, 16-membered, N2S2-donor macrocycles having a l, 3, 5-‘tribenzyl’ or a phloroglucinol core), together with their single-ring analogues were synthesised. Electrospray MS of (1) gives a series of multiply charged ions resulting from the loss of hexafluorophosphate counter ions and hydrogens: [M — n PF6]n+ and [M — n PF6 — m H](n - m )+.
A New Molecular metal Based on Pd(dmit)2: Synthesis, Structure and Electrical Properties of (C7H13NH)[Pd(dmit)2]2 (dmit2- = 2-thioxo-1, 3-dithiole-4, 5-dithiolate)
t. naito, t. inabe, h. kobayashi and a. kobayashi, J. Mater. Chem., 2001, 11, (9), 2199-2204
Air-oxidation of an acetone-acetic acid solution of (C7H13NH)2[Pd(dmit)2] gave black shiny platelets of (C7H13NH)[Pd(dmit)2]2 (1). (1) has a criss-cross columnar structure. Although (C7H13NH)+ is orientationally disordered on a 2-fold axis, (1) exhibited metallic conductivity down to ~ 40 K. The room temperature conductivity is ~ 22 S cm-1 and the resistivity decreased with decreasing temperature.
PHOTOCONVERSION
Luminescence and Photocatalytic Properties of a Platinum(ll)-Quaterpyridine Complex Incorporated in Nafion Membrane
x.-h. li l.-z. wu, l.-p. zhang, c.-h. tung and c.-m. che, Chem. Commun., 2001, (21), 2280-2281
Non-emissive [Pt(2,2' :6',2" :6" 2"'-quateryridine)]-(CF3SO3)2 (1) incorporated in Nafion membrane exhibits strong photoluminescence at room temperature. The rigid matrix of Nafion stabilises (1) towards photochemical decomposition even in the presence of O2. This system can be used as a sensitiser to generate singlet O to oxidise alkenes.
Photoreaction of Platinum(ll) β-Diketonate Complexes with Olefins
f. wang, x. wu, a. a. pinkerton, p. kumaradhas and d. c. neckers, Inorg. Chem., 2001, 40, (23), 6O0O-60O3
Pt(hfac)2 (hfac = 1, 1, 1, 5, 5, 5-hexafluoro-2, 4-pen-tanedionato) reacted with C2H4 when irradiated at 350 nm to give Pt(hfac)2(η2-C2H4). When Pt(hfac)2 and C2H4 were irradiated at 300 nm, a second product, thatwas non-isolable, was detected by 1H and 19F NMR. Pt(hfac)2(η2-C2H4) is not stable at shorter wavelengths. The photoproducts of Pt(hfac)2 with C3H6 and 0f Pt(tfac)2 (tfac = l, l, l-trifluoro-2, 4-pentanedionato) with C2H4 were detected by 1H NMR.
Photoenhanced Reduction of CO2 by H2 over Rh/TiO2 Characterization of Supported Rh Species by Means of Infrared and X-Ray Absorption Spectroscopy
y. kohno, t. yamamoto, t. tanaka and t. funabiki, J. MoL Catal. A: Chem., 2001, 175, (1-2), 173-178
IR study of the photoenhanced reduction ofCO2 by H2 in the presence of Rh/TiO2 (1) showed adsorbed CO arose even on strongly reduced (1). IR and X-ray absorption studies showed a decrease in the Rh particle size with prolonged photoreaction and decreased electron transfer from (1) to adsorbates.
Surfactant Chain Length Effects on the Light Emission of Tris(2, 2' -bipyridyl)ruthenium(ll)/ Tripropylamine Electrogenerated Chemiluminescence
b. factor, b. muegge, s. workman, e. bolton, j. bos and m. m. richter, Anal Chem., 2001, 73, (19), 4621-4624
The anodic oxidation of Ru(bpy)32+ produces electrochemiluminescence (ECL) in the presence of tri-n-propylamine (TPrA) in aqueous nonionic surfactant solution. Increases in ECL efficiency (≥ 5 fold) and TPrA oxidation current (≥ 2 fold) were observed. Slight decrease in ECL intensity was observed with increase of surfactant chain length.
ELECTRODEPOSITION AND SURFACE COATINGS
Electrochemical Deposition of Fine Pt Particles on n-Si Electrodes for Efficient Photoelectrochemical Solar Cells
s. yae, m. kttagaki, t. hagihara, y. mtloshi, h. matsuda, b. a. parktnson and y. nakato, Electrobim. Acta, 2001, 47, (1-2), 345-352
Electrochemical deposition of fine Pt particles on n -Si electrodes (1) from an aqueous H2PtC6 solution was carried out by the single- (SPS) and double-potential step of DPS from methods. The distribution density of the Pt particles was 108 cm-2 for SPS but increased from 10 to 1010 cm-2 by a shift of the pulse potential at the initial step of DPS from -1.0 to -4.0 V vs. SCE. Photoelectrochemical sokr Cells with (1) generated open-circuit photovoltages of 0.51-0.61 V, which is higher than those for n -Si electrodes coated with continuous Pt layers (~ 0.2-0.3 V).
Highly (111)-0riented and Conformal Iridium Films by Liquid Source Metalorganic Chemical Vapor Deposition
j. goswami, c.-g. wang, p. majhi, y.-w. slun and s. k. dey, J. Mater. Res., 2001, 16, (8), 2192-2195
The title Ir films were deposited by a liquid source MOCVD process. The O2-assisted pyrolysis of CH3CpfrCOD yielded Ir films at substrate temperatures, Tsub, of 300-700°C. With increasing Tsub, the (111) orientation increased, and at Tsub = 700°C, the I111/I2oo ratios were as high as 186 and 277 for amorphous SIO2 and native SIO2 surfaces, respectively.
APPARATUS AND TECHNIQUE
Continuous Detection of Volatile Aromatic, Unsaturated or Halogenated Hydrocarbons in Air by Adsorption on Pt-Electrodes and Subsequent Oxidative Desorption
s. ernst, r. herber, e. slavcheva, i. vogel and h. baltrvschat, Electroanalysis, 2001, 13, (14), 1191-1197
Benzene, its derivatives and simple halogenated hydrocarbons can be detected by means of their adsorption at a Pt sensor electrode. The charge is automatically determined during a subsequent sweep to potentials above 1 V (RHE). It is corrected for O2 adsorption and serves as a measure for the substance concentration. A special potential program repeatedly strips the adsorbate from the surface.
Solid Polyelectrolyte (SPE) Membranes Containing a Textured Platinum Catalyst
d. g. bessarabov and w. c. michaels, J. Membrane Sci., 2001, 194, (1), 135-140
Perfluorinated cation-exchange flat-sheet membranes were treated with CH3(CH2)15N(CH3)3Br surfactant The electroless chemical deposition of a Pt catalyst on the modified membranes was achieved by means of the Takenaka-Torikai method. The Pt particles were small in size and pyramidally textured.
Stationary-State Oxidized Platinum Microsensor for Selective and On-Line Monitoring of Nitric Oxide in Biological Preparations
a. cserey and m. gratzl, Anal. Chem., 2001, 73, (16), 3965-3974
A simple electrochemical NO sensor uses a glass sealed Pt microdisk electrode coated with cellulose acetate to reduce both surface fouling by proteins and its response to potential interferences. The electrode utilises NO oxidation with differential pulse amperometry. The oxidation of NO by O2 was found to be second order in [NO] with a rate constant of (8 ± 0.4) × 106 M-2 s-1. Chemical generation of NO by ascorbic acid provides accurate means of calibration and a way for in vivo stimulations.
A Reagentless Glucose Biosensor Based on Glucose Oxidase Entrapped into Osmium-Complex Modified Polypyrrole Films
s. reiter, k. habermÜller and w. schuhmann, Sens. ActuatorsB, Chem., 2001, 79, (2-3), 150-156
The title sensor is formed by entrapment ofglucose oxidase within an electrochemically generated copolymer of an Os-complex substituted pyrrole derivative and pyrrole (1). By employing glassy C. as electrode material, the electron transfer pathway from the enzyme via the polymer-bound (1) to the electrode could be proven even in the presence of traces of O2. Enhancement of the glucose-dependent current was achieved by increasing the hydrophilicity of the polymer film and introduction of carboxylic acid side chains at the polypyrrole backbone.
HETEROGENEOUS CATALYSIS
Kinetics of the CO + O2 Reaction over Three-Way Pt-Rh Catalysts
p. granger, j.j. lecomte, l. leclercq and g. leclercq, Appl. Catal. A: Gen., 2001, 218, (1-2), 257-267
The kinetics of the reaction between CO and O2 over Pt-Rh/Al2O3 was studied using a differential fixed bed flow reactor under reducing conditions (CO:O2 > 5). Temperature, CO and O2 partial pressures were 25-500°C, (5-9) × 10-3 and (0.25-2) × 10-3 atm, respectively. A bimolecular reaction between adsorbed CO and adsorbed O2 molecules is seen as the determining step. CO is adsorbed much more strongly than O2 under the experimental conditions employed.
Effect of the Solvent Used during Preparation on the Properties of Pt/Al2O3 and Pt-Sn/Al2O3 Catalysts
l. s. carvalho, p. reyes, g. pecch1, n. figou, c. l. pleck and m. do carmo rangel, Ind. Eng. Chem. Res., 2001, 40, (23), 5557-5563
The effect of H2O, acetone or EtOH used during Al2O3 impregnation in the preparation of the title catalysts ptoduced catalysts with different properties and performances in n-pentane isomerisation, cyclo-hexane dehydrogenation and n-octane reforming. The catalysts prepared in EtOH had the highest metallic dispersion. Pt/Al203 (acetone) had the highest activity for isomerisation while the activity of Pt-Sn/Al2O3 catalysts was: EtOH > acetone > H2O.
A Novel, Highly Efficient Catalyst for Propane Dehydrogenation
d. akporlaye, s. f. jensen, u. olsbye, f. rohr, e. rohr, m. rytter m. rØnnekleiv and a. i. spjelkavik, ImL Eng. Chem. Res., 2001, 40, (22), 4741-748
Pt,Sn/Mg(Al)O (from calcined hydrotalcite) is a new and highly efficient catalyst for the dehydrogenation of propane. It is superior to conventional Al203-supported systems in terms of lifetime stability, activity and propene selectivity. Impregnation of the calcined hydrotalcite in aqueous solution (or HCl-acidified aqueous solution followed by Cl removal) yields catalyst with better long-term stability than catalyst prepared in EtOH solution.
Selective Transfer Dehydrogenation of Aromatic Alcohols on Supported Palladium
c keresszegi, t. mallat and a. baker, New J. Chem., 2001, 25, (9), 1163-1167
Transfer dehydrogenation of alcohols has been investigated over Pd/support systems using olefins as hydrogen acceptors. Pd/Al2O3 with cyclohexene is the most active and selective system and allows facile and convenient synthesis of aromatic ketones. Hydrogenolysis-type side reactions can be minimised by minute additions of a tertiary amine (selective poisoning of Pd), such as Et3N. The low reactivity of aliphatic and cycloaliphatic alcohols can be utilised for the selective synthesis of aromatic ketones.
Reduction of Nitrogen Oxides over Unsupported Iridium: Effect of Reducing Agent
c wÖgerbauer, m maciejewski and a. baiker, Appl Catal B: Envirvon., 2001, 34, (1), 11-27
Propene, propane, CO and H2 were used as reducing agents in the selective reduction of NOx (NO or NO2) over Ir black, in the presence and absence of O2. Only propene exhibits appreciable activity for the reduction of NO under oxidising conditions. In O2-free atmospheres under large excess of the reducing agent, wifh propene considerable amounts of HCN were formed and with H2 the major product was NH3. The presence of NOx shifts propene oxidation light-off to higher temperatures.
Kinetic Study of CO2 Reforming of Propane over Ru/Al2O3
d. sutton, j.-f. moisan andj. r h. ross, CataL Lett., 2001, 75, (3-4), 175-181
The rate of reaction of C3H8 over Ru/Al2O3 was determined as a function of the partial pressures of the reactants, C3H8 and CO2 at 600 and 650°C. The order of the reaction was 0.3 with respect to CO2, indicating its involvement in the rate determining step of the reaction. The order of reaction was 0 in C3H8. The activation energy of C3H8 was calculated as 86 kJ mol-1. The activation energies for the formation of H2 and CO were calculated as 80 and 66 kJ mol-1, respectively. There was a decrease in the CO:H2 ratio with an increase in temperature.
HOMOGENEOUS CATALYSIS
Palladium(ll)- and Rhodium(lll)-Catalyzed Carbonylation Reaction of Aryltin Compounds
t. ohe, s. motofusa, k ohe and s. uemura, Butt. Chem. Soc. Jpn., 2001, 74, (7), 1343-1348
Aryltin compounds can be employed for carbonylation reactions in the presence of a catalytic amount of Pd(II) salt, with reoxidant, such as CuCl2, in MeCN or AcOH under an atmospheric pressure of CO to give arenecarboxylic acids and diaryl ketones. Rh(III) salts can also be used and reoxidant is sometimes not necessary. More than one of two, three or four aryl groups of the aryltin compounds can be transferred to the products in this catalytic carbonyktion.
Palladium-Catalyzed Cyclization of Allylsilanes with Nucleophilic Displacement of the Silyl Group
i. macsÁri andk.j. szabÓ, Chem. Eur. J., 2001, 7, (19), 4097^106
Allylsilanes with hydroxy or tosylamide groups undergo Pd(II)-catalysed cyclisation to give derivatives of tetrahydrofuran, piperidine and pyrrolidine through an (ƞ3-allyl)Pd (1) intermediate, which is generated by Allylic displacement of the silyl group of the allylsilane precursors. Benzoquinone and Cu(II) chloride can be used for regeneration of the Pd(II) catalyst precursor. The reaction rate for the formation of (1) is highly dependent on the concentration of the chloride ligand and of the solvent.
A New Practical Ketone Synthesis Directly from Carboxylic Acids: First Application oft Coupling Reagents in Palladium Catalysis
l.j. gooben and k. ghosh, Chem. Commun., 2001, (20), 2084-2085
A Pd-catalysed cross-coupling reaction between arylboronic acids and carboxylic acids, activated in situ for the oxidative addition to a tricyclohexylphosphine Pd(O) catalyst by treatment with di(N-succinimidyl) carbonate was demonstrated. A high yielding synthesis of various functionalised arylacetones under mild conditions was achieved. THF was the most effective solvent and an addition of Na2C03 base enhanced the stability of the catalytic system.
Palladium-Catalyzed Arylation of Allylic Alcohols with Aryl Iodides in Water
h. zhao, m.-z. cai,r-h hu and c-s. song, Synth. Commun., 2001, 31, (23), 3665-3669
Pd-catalysed aryktion of Allylic alcohols with aryl iodides occurs in the presence of NaHCO3 and Bu4NCl in H2O with Pd(OAc)2 catalyst. β-Aromatic carbonyl compounds are obtained in good yields. The arylation reaction is highly regioselective with respect to the addition of the aromatic group: only β-substitution is observed. The structural isomer selectivity is also very high: only traces of β-aromatic α,β-unsaturated alcohol compounds are obtained.
Catalytic Dehalogenation of Aryl Halides Mediated by a Palladium/lmidazolium Salt System
m. s. viciu, g. a. grasa and s. p. nolan, Otganometallics, 2001, 20, (16), 3607-3612
The Pd(dba)2/(2,4,6-trimethylphenyl)dihydroimidazolium salt system is effective for the dehalogenation of aryl chlorides, bromides, and polyhalogenated aromatic hydrocarbons. Strong bases with β-hydrogens perform both deprotonation of the imidazolium salt and are H sources for the dehalogenation process. The catalytic system does not require an excess of the Ugand and appears thermally robust. The optimum metal:ligand ratio is 1:1, as 1:2 ratios give very stable and catalytically less active Pd species.
A Silica-Supported, Switchable, and Recyclable Hydroformylation-Hydrogenation Catalyst
a.j. sandee,j. n. h. reek, p. c.j. kamer and p. w. n. m. van leeuwen, l. Am. Chem. Soc., 2001, 123, (35), 8468-476
The immobilised Rh catalyst complex [Rh(A)CO]+ (1) (A = N-(3-trimethoxysUane-n -propyl)-4,5-bis-(diphenylphosphino)phenoxazine) was prepared via bofh the sol-gel process and by covalently anchoring to SiO2. The catalyst—support interactions were fully controlled and easily manipulated by simple changes in the reaction conditions. (1) can be used both as a hydrogenation and a regioselective hydroformylation catalyst. (1) was used for a clean one-pot synthesis of l-nonanol from l-octene via a hydroformylation-hydrogenation cascade reaction and could be quantitatively recovered from the product.
The Activation of O2 at Ruthenium Complexes: Catalytic Chlorination of Unsaturated Organic Substrates within the System O2/HCl/H20
c. limberg and j. h. teles, Adv. Synth. Catal., 2001, 343, (5), 447-449
RuCl3 in concentrated HCl at 145oC can chlorinate aromatic compounds, such as benzene and toluene, catarytically, if O2 is present as the oxidising agent. Similarly, bromination can be achieved in concentrated HBr. When olefins undergo chlorination, two Cl atoms are added to the double bond in an anti fashion, but hydrochlorination products are formed simultaneously. Halogenations proceed via electrophilic routes for the products in both types of reactions for various substrates of the 3-phase system.
Homogeneous Hydrogenation of Arenes Catalyzed by the Bis(dihydrogen) Complex [RuHz(H2)2(PCy3)2]
a. f. borowski, s. sabo-etienne and b. chaudret, J. Mol. Catal. A: Chem., 2001, 174, (1-2), 69-79
Cyclohexane, tetralin and a mixture of tetra- (4H-An) and octa-hydroanthracene (8H-An) were formed by reacting benzene, naphthalene and anthracene, respectively, with H2 under 3 and 20 bar at 8O0C in the presence of [RuH2(H2)2(PCy3)2] (1). However, the increase of H2 pressure lowers the yield of hydrogenation products. (1) may be used directly as a catalyst precursor or may be prepared in situ from RuH{(η3-C6H8)PCy2} {(η2-C6H9)PCy2}] under H2 at room temperature.
FUEL CellS
Methanol Oxidation on a Carbon-Supported Pt Fuel Cell Catalyst - A Kinetic and Mechanistic Study by Differential Electrochemical Mass Spectrometry
z. jusys and r.j. behm, J. Phys. Chem. B, 2001, 105, (44), 10874-10883
MeOH oxidation on a Pt/C fuel Cell catalyst was investigated by online differential electrochemical mass spectrometry (DEMS) at continuous electrolyte flow and defined catalyst utilisation, using a thin film electrode setup and a thin-layer flow-through Cell. MeOH-stripping DEMS experiments, oxidising the adsorbed dehydrogenation products formed on MeOH adsorption at potentials in the H adsorption region, show that its uptake depends on the electrode potential.
The Oxygen Reduction Reaction on a Pt/Carbon Fuel Cell Catalyst in the Presence of Chloride Anions
t.j. schmidt, u. a. paulus, h. a. gastelger and r.j. behm, J. EUctwanal. Chem., 2001, 508, (1-2), 41-7
For the O2 reduction reaction (orr) on a Pt/C fuel Cell catalyst, the activity was shown to decrease in the order: ClO4- > HSO4 > Cl-, which is consistent with the increasing adsorption bond strength of the anions. The orr properties of Pt/Vulcan in the presence of adsorbed Cl- were interpreted as a superposition of the individual orr properties of the Pt(lll)-Cl2d and Pt(lll)-Cl2d Solid ⃒ liquid interface.
ELECTRICAL AND ELECTRONIC ENGINEERING
Recovery Characteristics of Hydrogen-Damaged (Pb, La)(Zr, Ti)O3 Capacitors with Pt and IrO2 Top Electrodes
s.-g. yoon and a. i. kingon, J. Electrochem. Soc., 2001, 148, (7), F137-F139
Pb, La)(Zr, Ti)O3 (PLZT) film capacitors with Pt and IrO2 top electrodes were annealed in H2 and P-E (polarisation-field) hysteresis loops and fatigue properties were examined. The Pt/PLZT/Pt capacitor recovered futty on annealing in O2 at 700°C, but the Ir02/PLZT/Pt capacitor did not fully regain its ferroelectric properties. In 4% H2 at 300°C the IrO2 electrode was reduced to Ir. After a recovery anneal at 700°C in O2 it changed to the Ir02/Ir complex phase.
Influence of Combined Pt and CeO2 Additions on Microstructure and Magnetic Properties in (Nd, Eu, Gd)-Ba-Cu-O
m. muralidhar, m. jirsa, s. nariki and m. murakami, Supercond. Sci. Technol., 2001, 14, (10), 832-838
The effect of the combined addition of Pt and CeO2 on the dispersion of secondary phase Gd2BaCuO2 (Gd-211) particles in melt-processed (Nd0.33Euo.33-Gdo.33)Ba2Cu3Oy (NEG-123) was studied by varying the CeO2 content (0—3%). SEM revealed fhat sub-um-sized Gd-211 particles were distributed uniformly throughout the NEG-123 matrix for < 2 mol% CeO2. The combined addition of Pt and CeO2 is effective in reducing the size of the secondary-phase particles.
Preparation and Properties of dc-splittered IrO2 and Ir Thin Films for Oxygen Barrier Applications in Advanced Memory Technology
c u. pinnow, 1. kasko, c. dehm, b. jobst, m. seibt and u. geyer, ]. Vac. Sci. Technol. B, 2001, 19, (5), 1857-1865
Ir and IrO2 thin films were deposited by DC splittering in pure Ar and Ar/O2, respectively. The stress of the Ir films can be varied from ~ -3.5 GPa for a deposition temperature of 100°C to nearly zero stress if deposited at 500°C. However, IrO2 films exhibited a large compressive stress of ~ -1.5 GPa, which is nearly independent of substrate temperature, but changed with texture and stoichiometry of the films.
Studies of Ruthenium-Doped InP Growth by Low-Pressure Hydride Vapor-Phase Epitaxy
d. sċderstrċm, s. lourdudoss, m. wallnÄs, a. dadgar, o. stenzel, d. bimberg and h. schumann, J. Electrochem. Soc., 2001, 148, (7), G375-G378
Ru-doped InP grown (1) by low-pressure hydride vapour-phase epitaxy using bis(η5-2,4-dimethylpentadienyl)Ru(II) produced Ru concentrations of 2 × 1015 to 2 × 1018 cm-3 by changing the input PH3 and In chloride partial pressures. Resistivities for (1) of > 103 Ω cm were measured under electron injection for Ru concentration of ≥ 2 × 1017 cm-3; under hole injection (1) exhibits a very high resistivity of 1010 Ω cm.
Find an article
