Platinum Metals Rev., 2009, 53, (1), 50
ABSTRACTS: January 2009
CATALYSIS – APPLIED AND PHYSICAL ASPECTS
Toward Less Dependence on Platinum Group Metal Catalysts: The Merits of Utilizing Tin
R. D. ADAMS, D. A. BLOM, B. CAPTAIN, R. RAJA, J. M. THOMAS and E. TRUFAN, Langmuir, 2008, 24, (17), 9223–9226
Minute stoichiometric bimetallic clusters rich in Sn (PtSn2, RhSn2, RuSn2) were shown to be powerful selective hydrogenation catalysts. These “molecular metallic” entities were supported on mesoporous SiO2. High percentages of cyclododecene were obtained at fractional conversions ranging from 0.45–0.70 of the parent 1,5,9-cyclododecatriene at T = 373 K and under solvent-free conditions.
Selective Oxidation of Glucose to Gluconic Acid over Argon Plasma Reduced Pd/Al2O3
X. LIANG, C.-J. LIU and P. KUAI, Green Chem., 2008, 10, (12), 1318–1322
An Ar glow discharge plasma approach was used to reduce PdCl2 supported on γ-Al2O3 at room temperature. The catalyst formed using plasma reduction followed by calcination under Ar at 500°C exhibited a higher activity for selective oxidation of glucose than a H2 thermally reduced catalyst. The plasma reduced catalysts possessed high stability against leaching of active metal into the reaction medium.
Vapor-Phase Selective Hydrogenation of Citral over Pd/Bentonite: Effect of Reduction Method
D. DIVAKAR, D. MANIKANDAN and T. SIVAKUMAR, J. Chem. Technol. Biotechnol., 2008, 83, (11), 1472–1478
Well-dispersed Pd nanoparticles were prepared by a wet impregnation technique over bentonite followed by reduction with H2, NaBH4 or EtOH. Hydrogenation of citral over Pd/bentonite was studied in the vapour phase using a microreactor. Pd/bentonite reduced by EtOH was found to give the highest conversion and Pd/bentonite reduced by NaBH4 was found to give the highest selectivity towards nerol and geraniol. This was attributed to the smallest particle size of Pd in the former catalyst and the presence of B species on the latter catalyst, respectively.
One-Pot Rapid Low-Cost Synthesis of Pd-Fullerite Catalysts
L. C. CHONG, V. STOLOJAN, G. WAGNER, S. R. P. SILVA and R. J. CURRY, J. Mater. Chem., 2008, 18, (40), 4808–4813
Tetrakis(triphenylphosphine)palladium (1) was used as a precursor for the deposition of Pd clusters upon a fullerite during growth using a rapid liquid/liquid interface precipitation. Variation of the ratio of (1) to C60 was used to control the aspect ratio of the nanostructures. The presence of (η2-C60)Pd(PPh3)2 and highly dispersed Pd clusters on the fullerites was established. Pd-fullerite was active as a catalyst for the hydrogenation of 1-ethynyl-1-cyclohexanol under H2.
CATALYSIS – REACTIONS
Rhodium(III) and Iridium(III) Complexes with Quinolyl-Functionalized Cp Ligands: Synthesis and Catalytic Hydrogenation Activity
G. KOHL, H. PRITZKOW and M. ENDERS, Eur. J. Inorg. Chem., 2008, (27), 4230–4235
Bis(ethene) complexes of Rh(I) and Ir(I) with 8-quinolylcyclopentadienyl ligands (CpQ and CpQ*) were oxidised photochemically with Cl-containing solvents or by I2. Upon oxidation, the quinoline ring rotates and the N donor coordinates to the metal centres. Substitution of the halogenido ligands through acetato groups gave highly soluble derivatives, in which the acetate moiety acts as a monodentate or bidentate ligand. The resulting Rh(III) complexes were used for the hydrogenation of 1-hexene. [CpQ*Rh(O2CCH3)]+PF6− gave the highest activity.
Dihydroxylation of Olefins Catalyzed by Polystyrene-sg-imidazolium Resin-Supported Osmium Complex
B.-H. JUN, J.-H. KIM, J. PARK, H. KANG, S.-H LEE and Y.-S. LEE, Synlett, 2008, (15), 2313–2316
OsO4 was immobilised onto poly(1-methylimidazoliummethyl styrene)-surface grafted-PS resin. The formation of the Os complex occurred only on the surface of the polymer support. The catalyst exhibited excellent activity in the dihydroxylation of olefins and could be reused up to three times.
On Board Catalytic NOx Control: Mechanistic Aspects of the Regeneration of Lean NOx Traps with H2
P. FORZATTI, L. LIETTI and I. NOVA, Energy Environ. Sci., 2008, 1, (2), 236–247
Mechanistic aspects of the reduction with H2 of NOx stored on lean NOx trap Pt-Ba/Al2O3 catalysts are reviewed. Under nearly isothermal conditions, the first step is NH3 formation through the reaction of H2 with stored nitrates; in the second step, the NH3 reacts with the nitrates left on the catalysts’ surfaces leading to N2 formation. The first step is much faster than the second. Both steps are catalysed by Pt.
Simultaneous Removal of Soot and NOx over Ir-Based Catalysts in the Presence of Oxygen
R. ZHU, M. GUO and F. OUYANG, Catal. Today, 2008, 139, (1–2), 146–151
The TPR technique was used to study the simultaneous removal of soot and NOx by Ir-based catalysts in the presence of O2. A comparison between Ir/γ-Al2O3 and Pt/γ-Al2O3 demonstrated that the Ir catalyst was more effective. The 1 wt.% Ir/ZSM-5 catalyst exhibited a high level of activity for the simultaneous removal of soot and NOx.
Carbon Supported Pt–Pd Alloy as an Ethanol Tolerant Oxygen Reduction Electrocatalyst for Direct Ethanol Fuel Cells
T. LOPES, E. ANTOLINI and E. R. GONZALEZ, Int. J. Hydrogen Energy, 2008, 33, (20), 5563–5570
Pt-Pd/C (1) with a Pt:Pd atomic ratio 77:23 was prepared by reduction of metal precursors with formic acid. In EtOH-free H2SO4, (1) showed a slightly higher activity towards O2 reduction compared to Pt. In the presence of EtOH a larger increase in overpotential of the ORR on Pt than on Pt-Pd was found, indicating a higher EtOH tolerance of (1).
Electrochemical Characteristics of Pd Anode Catalyst Modified with TiO2 Nanoparticles in Polymer Electrolyte Fuel Cell
E. N. MUHAMAD, T. TAKEGUCHI, G. WANG, Y. ANZAI and W. UEDA, J. Electrochem. Soc., 2009, 156, (1), B32–B37
The modification of a Pd/C catalyst with TiO2 increased the activity for electrochemical oxidation of pure H2, and gave high activity, similar to that of a Pt/C catalyst. The TiO2 increased the dispersion of Pd particles, which resulted in an increase in the active surface area of the catalyst. The effect of TiO2 addition on the performance of a fuel cell with a Pd anode in a 500 ppm CO-contaminated H2 fuel was investigated. The Pd/TiO2/C catalyst had a higher CO tolerance than Pt/C for maintaining high activity for electrochemical oxidation of H2.
METALLURGY AND MATERIALS
Exfoliated Graphene Separated by Platinum Nanoparticles
Y. SI and E. T. SAMULSKI, Chem. Mater., 2008, 20, (21), 6792–6797
A mechanically exfoliated, high-surface area Pt nanoparticle–graphene composite was obtained by drying aqueous dispersions of Pt nanoparticles adhered to graphene. Pt nanoparticles were fixed to graphene by reduction of H2PtCl6 with MeOH in the presence of 3-(N,N-dimethyldodecylammonio) propanesulfonate. The Pt nanoparticles act as spacers.
Microstructural and Magnetic Properties of CoPt Nanowires
H. KHURSHID, Y. H. HUANG, M. J. BONDER and G. C. HADJIPANAYIS, J. Magn. Magn. Mater., 2009, 321, (4), 277–280
CoPt nanowires (1) of high aspect ratio were prepared by electrodeposition into anodised alumina templates using electrolyte at pH 2–6. The as-made (1) exhibit an f.c.c. structure with soft magnetic properties which transform into the f.c.t. L10 phase after thermal treatment. (1) prepared at high pH were f.c.c. nanorods. Thermal annealing led to a preferred (0 0 1) orientation. (1) prepared at lower pH were f.c.c. nanograins. Magnetisation curves for the latter sample were virtually identical in both directions.
Analysis of Deuterium Permeation through Pd81Pt19 Alloy at Stress Conditions
D. DUDEK, Pol. J. Chem., 2008, 82, (10), 1941–1947
The permeation of D2 through a Pd81Pt19 alloy membrane (1) under stress conditions was examined at constant temperature T = 278.2 K and pressures up to 900 hPa(D2). The permeation curves were determined at different initial and boundary conditions. The D2 fluxes were calculated by fitting experimental points with straight lines in the stationary parts of the permeation curves. The D2 permeation through (1) was shown to be changed by stresses created during metal lattice expansion processes.
Synthesis of Nanosized Zn2PtO4
P. KJELLIN and A. E. C. PALMQVIST, J. Mater. Sci., 2008, 43, (22), 7250–7253
A new facile metathetical preparation of nanosized Zn2PtO4 uses PtCl4 mixed with ZnO nanopowder. Relatively low temperature (500°C) and ambient pressure can be employed. The product is washed with HCl in order to remove unreacted ZnO and formed ZnCl2. The small particle size of the Zn2PtO4 makes it suitable for use in catalyst preparation.
Thermochemistry of Pd–In, Pd–Sn and Pd–Zn Alloy Systems
S. AMORE, S. DELSANTE, N. PARODI and G. BORZONE, Thermochim. Acta, 2009, 481, (1–2), 1–6
A high-temperature direct drop calorimeter was used to study the standard enthalpies of formation of solid Pd-M (M = In, Sn and Zn) alloys at 300 K in the M-rich region. The values of ΔHf (kJ mol−1 atoms−1) for the following phases were obtained: PdIn (49 at.% In): −69.0 ± 1.0; Pd2In3 −57.0 ± 1.0; Pd3In7: −43.0 ± 1.0; PdSn2: −50.0 ± 1.0; Pd2Zn9 (77 at.% Zn): −33.7 ± 1.0; Pd2Zn9 (78 at.% Zn): −34.0 ± 1.0; Pd2Zn9 (80 at.% Zn): −35.0 ± 1.0. The obtained results show exothermic values which increase from Pd-Zn to Pd-Sn and Pd-In.
APPARATUS AND TECHNIQUE
A Simple Colorimetric Luminescent Oxygen Sensor Using a Green LED with Pt Octaethylporphyrin in Ethyl Cellulose as the Oxygen-Responsive Element
S. R. RICKETTS and P. DOUGLAS, Sens. Actuators B: Chem., 2008, 135, (1), 46–51
A green LED, in an O2 sensor (1), acts as both a green emission source and an excitation source for a film of O2-sensitive Pt octaethylporphyrin in ethyl cellulose containing TiO2 or ZnO as a scattering agent. (1) has a “traffic light”, red–yellow–green, response to increasing O2 concentration. Singlet O2 stabiliser diazobicyclo[2.2.2]octane increased the stability of (1) significantly. Because of the relatively thick sensor layer used in (1), response times are long, with 90% response times of ∼ 1000 s for N2 to O2 and ∼ 300 s for O2 to N2.
Synthesis of a Platinum(II) Bis(trimethylsilyl)amido Complex: A Better Starting Material for the Cyclometalation of Pincer Ligands
A. ARUNACHALAMPILLAI, M. T. JOHNSON and O. F. WENDT, Organometallics, 2008, 27, (17), 4541–4543
Treatment of [(COD)PtCl2] with LiN(SiMe3)2 in ether at room temperature gave [COD]PtClN(SiMe3)2 (1). The X-ray structure of (1) shows the expected mononuclear pseudo-square-planar Pt in which the chlorine and amido groups are cis to each other. (1) was shown to be a convenient starting material for the preparation of PXP Pt pincer complexes.
An Unprecedented Bonding Mode for Potassium within a PCP-Pincer Palladium Hydride–K-Selectride® Complex
B. J. BORO, E. N. DUESLER, K. I. GOLDBERG and R. A. KEMP, Inorg. Chem. Commun., 2008, 11, (12), 1426–1429
The reaction of (PCP)i-PrPdCl and the reductant K-Selectride® solution (K(sec-Bu3BH) in THF) did not yield a simple (PCP)i-PrPdH species; an adduct (1) that contains bound K(sec-Bu3BH) was obtained. (1) was shown to be a centrosymmetric dimer in the solid state by X-ray crystallography. The tri-coordinate K+ ion bonds only to the terminal Pd hydride and the two bridging B hydrides.
Competitive C–I versus C–CN Reductive Elimination from a RhIII Complex. Selectivity is Controlled by the Solvent
M. FELLER, M. A. IRON, L. J. W. SHIMON, Y. DISKIN-POSNER, G. LEITUS and D. MILSTEIN, J. Am. Chem. Soc., 2008, 130, (44), 14374–14375
The oxidative addition of MeI to [(PNP)Rh(CN)] (1) gave [(PNP)Rh(CN)(CH3)][I] (2). (2) reacts selectively in two pathways. In aprotic solvents C–I reductive elimination of MeI followed by its electrophilic attack on the cyano ligand takes place, giving [(PNP)Rh(CNCH3)][I], while in protic solvents C–C reductive elimination of MeCN takes place forming [(PNP)RhI]. Reaction of (1) with EtI in aprotic solvents gave the corresponding isonitrile complex.
ELECTRICAL AND ELECTRONICS
Thermally-Treated Pt-Coated Silicon AFM Tips for Wear Resistance in Ferroelectric Data Storage
B. BHUSHAN, M. PALACIO and K. J. KWAK, Acta Mater., 2008, 56, (16), 4233–4241
A commercial Pt-coated Si AFM probe was thermally treated in order to form Pt silicide at the near-surface. Nanoindentation, nanoscratch and wear experiments evaluated the mechanical properties and wear performance at high velocities. The thermally treated tip exhibited lower wear than the untreated tip. The enhancement in mechanical properties and wear resistance in the thermally treated film is attributed to silicide formation in the near-surface.
Conjugated Polymers Bearing Iridium Complexes for Triplet Photovoltaic Devices
G. L. SCHULZ and S. HOLDCROFT, Chem. Mater., 2008, 20, (16), 5351–5355
Poly(9,9-dihexylfluorene-co-2-phenylpyridine) (1) and poly(9,9-dioctylfluorene-co-tris(2-phenylpyridine) iridium (III)) (2) were prepared using Suzuki polycondensation. An increase in per cent external quantum efficiency for (2) over (1), from 1.1 to 10.3, is attributed to the formation of the triplet state in (2), and by inference, longer diffusion lengths of the triplet exciton. Introducing the Ir complexes into the polyfluorene-based polymer blended with an electron acceptor enhanced solar cell conversion efficiencies.
On the Photophysical and Electrochemical Studies of Dye-Sensitized Solar Cells with the New Dye CYC-B1
J.-G. CHEN, C.-Y. CHEN, S.-J. WU, J.-Y. LI, C.-G. WU and K.-C. HO, Sol. Energy Mater. Sol. Cells, 2008, 92, (12), 1723–1727
The performance of nanocrystalline TiO2 DSSC fabricated using CYC-B1 (Ru photosensitiser with an alkyl bithiophene group) dye-anchored TiO2 photoelectrode showed an enhancement in cell efficiency when the TiO2 film thickness was increased from 3 µm (eff. = 5.41%) to 6 µm (eff. = 7.19%). The efficiency was maximum at a film thickness of 6 µm, reached its limiting value and remained constant up to 53 µm. Although a similar trend was also observed for N3 dye, the maximum efficiency achieved was only at 27 µm thickness (eff. = 6.75%).
Study of the Surface Morphology of Platinum Thin Films on Powdery Substrates Prepared by the Barrel Sputtering System
A. TAGUCHI, M. INOUE, C. HIROMI, M. TANIZAWA, T. KITAMI and T. ABE, Vacuum, 2008, 83, (3), 575–578
The transition of Pt from a nanoparticle to a film on SiO2 particles was modified by using a sputtering system with a barrel-type powder sample holder. The morphology of Pt changed from highly dispersed nanoparticles to a worm-like structure followed by a continuous Pt film, depending on the amount of Pt modified. TEM showed that the Pt film in the worm-like structure had a uniform thickness of ∼ 2.6 nm.
Study on Corrosion Resistance of Palladium Films on 316L Stainless Steel by Electroplating and Electroless Plating
J. TANG and Y. ZUO, Corros. Sci., 2008, 50, (10), 2873–2878
Pd films with good adhesive strength were deposited on 316L stainless steel. The electroless plated Pd film (1) mainly consisted of Pd, P and N, and the electroplated Pd film (2) was almost pure Pd. Both plated samples showed corrosion resistance in strong corrosive media; (2) was slightly better than (1).