Cermet-type hydrogen separation membrane obtained from fine particles of high temperature proton-conductive oxide and palladium

A mixed ionic and electronic conducting hydrogen separation membrane, which consisted of proton-conductive oxide and metallic palladium, was fabricated. A porous alumina tube was employed as a support, and proton-conductive oxide particles were introduced into a microporous top layer of the support by an impregnation method. Palladium particles were deposited into the same porous layer by chemical vapor deposition. Hydrogen permeated preferentially via the membrane thus obtained with a hydrogen permeance (PH₂) of 1.2 × 10^− 9 mol·m^− 2·s^− 1·Pa^− 1 at 873 K. Selectivity for hydrogen (PH₂/PN₂) increased with the operating temperature due to an increase in proton conductivity of the membrane, and PH₂/PN₂ = 5.7 was attained at 873 K.     

Pd/Ce0.6Zr0.4O2/Al2O3 as advanced materials for three-way catalysts: Part 1. Catalyst characterisation, thermal stability and catalytic activity in the reduction of NO by CO

Pd-loaded Ce_0.6Zr_0.4O₂ solid solutions supported on Al₂O₃ are investigated as catalysts for the reduction of NO by CO. The attention is focused on the role of the Ce_0.6Zr_0.4O₂ and of the Pd dispersion on the catalytic activity. The system shows a very high activity below 500 K, which is almost independent on the Pd dispersion. The high activity is attributed to a promoting effect of the Ce_0.6Zr_0.4O₂ on the NO conversion. Investigation of the influence of high temperature treatments disclosed a thermal stabilisation of both Ce_0.6Zr_0.4O₂ and Al₂O₃ in the Ce_0.6Zr_0.4O₂/Al₂O₃ system.     

Thermal aging of Pd/Pt/Rh automotive catalysts under a cycled oxidizing–reducing environment

Mono- and multi-metallic (bi- and tri-) Pt, Pd and Rh supported on cerium-promoted alumina (La Roche, SAS-1/16) catalysts were tested for activity as TWC, both fresh [G.C. Koltsakis, and A.M. Stamatelos, Progr. Energy Combust. Sci. 23 (1997) 1] and after accelerated aging. Aging consisted of a treatment at 900°C for 5 h during which an oxidizing (2.5% O₂, 10% H₂O, in N₂) and a reducing (5.0% CO, 10% H₂O, in N₂) feedstream were cycled at 0.017 Hz through the catalyst. Activity tests were carried out by increasing temperature from 100 to 600°C at 3°C min⁻¹, while two oxidizing and reducing (±0.5 A/F) feedstreams were alternately (1 Hz) fed through the reactor at 125 000 h⁻¹ (STP). Conversion was continuously analyzed. Light-off temperature, T₅₀, conversion at 500°C (normal running temperature), X₅₀₀, and the stoichiometric window (A/F from 14.13 to 15.13) for stationary feedstreams, were determined.     

Improved performance of Pd electrocatalyst supported on three-dimensional nickel foam for direct ethanol fuel cells

To improve the performance of direct ethanol fuel cells (DEFCs), a three-dimensional (3D), hierarchically structured Pd electrode has been successfully fabricated by directly electrodepositing Pd nanoparticles on the nickel foam (referred as Pd/Nickel foam electrode hereinafter). The electrochemical properties of the as-prepared electrode for ethanol oxidation have been investigated by cyclic voltammetry (CV). The results show that the oxidation peak current density of the Pd/Nickel foam electrode is 107.7 mA cm⁻², above 8 times than that of Pd film electrode at the same Pd loading (0.11 mg cm⁻²), and a 90 mV negative shift of the onset potential is found on the Pd/Nickel foam electrode compared with the Pd film electrode. Furthermore, the peak current density of the 500th cycle remains 98.1% of the maximum value for the Pd/Nickel foam electrode after a 500-cycle test, whereas it is only 14.2% for the Pd film. The improved electrocatalytic activity and excellent stability of the Pd/Nickel foam electrode make it a favorable platform for direct ethanol fuel cell applications.     

Treatment of tissue paper containing radioactive waste and electrochemical recovery of valuables using ionic liquids

Dissolution of tissue paper waste containing valuable contaminants such as uranium and palladium in 1-butyl-3-methylimidazolium chloride (bmimCl) has been studied. Dissolution of 5-7 wt.% tissue paper in bmimCl is complete within 60 min at 373 K and the time required for dissolution increases with increase of loading. It is difficult to dissolve more than 10 wt.% tissue paper in bmimCl and the limiting solubility of tissue paper is 15-17 wt.% at 373 K. Uranium(VI) and Pd(II) in chloride/nitrate form dissolve in bmimCl along with tissue paper. The electrochemical behaviour of uranium(VI) and palladium(II) in the resultant solution in the presence and absence of a co-solvent, DMSO, has been investigated by transient voltammetric techniques at glassy carbon working electrode and the diffusion coefficients have been determined. Electrolysis of a solution of uranium(VI) and palladium(II) loaded tissue paper in bmimCl results in deposition of uranium oxide (UO₂) and metallic palladium, respectively, which were characterized by X-ray diffraction and scanning electron microscopy. The study established the possibility of dissolving tissue paper and other cellulose based materials containing soluble uranium(VI) and Pd(II) compounds in bmimCl, and their recovery from the resultant solution. Cellulose pulp can be regenerated by adding surplus water after the recovery of valuables and the ionic liquid, bmimCl, can be regenerated for further use by vacuum distillation of DMSO and water.     

Palladium selenides as active methanol tolerant cathode materials for direct methanol fuel cell

Palladium selenides, PdSe, Pd₃Se and PdSe₂ have been prepared by the hydrothermal method and investigated for their structural and electrocatalytic properties toward the oxygen reduction reaction (ORR) using SEM/TEM, XRD, cyclic and linear sweep voltammetries. The crystallites of PdSe and PdSe₂ are found to follow tetragonal and orthorhombic crystal structures, respectively. The PdSe electrode in 0.5 M H₂SO₄ exhibits significantly higher electrocatalytic activity than the Pd₃Se or PdSe₂ electrode under similar experimental conditions. Further, a change in the palladium/selenium ratio from unity in the catalyst results in low ORR activity.     

负载型Pd催化剂

介绍了制备负载型钯催化剂的几种方法，以及它在反应中的应用。阐述了几种催化剂载体的优点，最后对这种催化剂的前提提出展望。     

A low-power readout circuit for nanowire based hydrogen sensor

This paper presents a fully integrated lock-in amplifier intended for nanowire gas sensing. The nanowire will change its conductivity according to the concentration of an absorbing gas. To ensure an accurate nanowire impedance measurement, a lock-in technique is implemented to attenuate the low frequency noise and offset by synchronous demodulation or phase-sensitive detection (PSD). The dual-channel lock-in amplifier also provides both resistive and capacitive information of the nanowire in separate channels. Measurement results of test resistors and capacitors show a 2% resolution in the resistance range 10-40 kΩ and a 3% resolution in the capacitance range 0.5-1.8 nF. Moreover, a 28.7-32.1 kΩ impedance variation was measured through the lock-in amplifier for a single palladium nanowire that was exposed to a decreasing hydrogen concentration (10% H₂ in N₂ to air). The chip has been implemented with UMC 0.18 μm CMOS technology and occupies an area of 2 mm². The power consumption of the readout circuit is 2 mW from a 1.8 V supply.     

Catalytic Oxidation of Polyethylene Glycol Dodecyl Ether to Corresponding Carboxylic Acid by Gold, Palladium (Mono and Bimetallic) Nanoparticles Supported on Carbon

Mono and bimetallic catalysts based on Au and Pd nanoparticles were synthesized by sol immobilization method. The catalytic oxidation of polyethylene glycol dodecyl ether was performed using as-synthesized supported catalyst. The use of water as solvent and dioxygen as oxidant makes the reaction interesting from both an economic and environmental point of view. For 100 min, the conversion of polyethylene glycol dodecyl ether using Au–Pd/C bimetallic catalyst was 38%, showing an increase of 9% for Au/C and 15% for Pd/C respectively indicating that a synergetic effect exists between Au and Pd. For the Au–Pd/C catalyst, adding Au after the prior addition and reduction of Pd metal can form the most active catalyst.     

钯(Ⅱ)-对碘偶氮氯膦-吐温-60三元体系分光光度法测微量钯的研究

在钯 (Ⅱ )与对碘偶氮氯膦配合物中加入吐温 6 0 ,形成三元显色体系 ,后者的灵敏度有显著的提高 ,其表观摩尔吸光系数ε63 8=6 0× 10 4L·mol-1·cm-1,钯含量在 0 1～ 1 2mg·L-1范围内符合比耳定律 ;同时方法的选择性亦有所改善 ,可在水相中直接测定微量钯 ,常见阳离子对此反应均无干扰 ,其他贵金属离子也有数倍的允许值 ,在钯催化剂回收液和二次阳极泥的微量钯的测定中 ,获得满意的结果