Amount Of Platinum Group Metals Research Articles

Kinetic and Thermodynamic Studies of Precious Metals Sorption on Impregnated Lewatit VP OC 1026 from Chloride Solutions.

Precious metals are used in many branches of industries. Due to their rarity and diminishing natural resources, more and more new methods are being sought to recover them from secondary sources, which can be electronic waste or spent car exhaust converters. This paper presents the research on the recovery of precious metals from chloride solutions using the Aliquat 336-impregnated Lewatit VP OC 1026 sorbent. The study used a warm impregnation method without toxic solvents, which is beneficial for the environment. The maximal sorption capacities obtained for model solutions in 0.1 M HCl were: 95.6 mg/g for gold, 38.2 mg/g for palladium, and 36.2 mg/g for platinum. There were studied: kinetics and thermodynamics of sorption, as well as amounts of the sorbent, effects of phase contact time and HCl concentration on the sorption of precious metals. Positive values of enthalpy change ΔH° validate that the process is endothermic. The research was also carried out on a real leaching solution obtained by digesting a spent catalytic converter, containing small amounts of platinum group metals. Desorption of precious metal ions was conducted using 1 M thiourea in 1 M hydrochloric acid. The obtained impregnated sorbent proved to be effective for sorption of Au(III), Pd(II), Pt(IV) ions.

Environmental implications of reducing the platinum group metal loading in fuel cells and electrolysers: Anion exchange membrane versus proton exchange membrane cells

Using substantial amounts of platinum group metals (PGM) is one main obstacle to mass-market application of proton exchange membrane (PEM) fuel cells (FC) and electrolysers (EL). Aiming to develop cells with lower PGM contents, low-PGM anion exchange membrane (AEM) cells were developed in an EU-funded project. Environmental impacts are compared to state-of-the-art PEM-FC (two reference years) and PEM-EL applications in a life cycle assessment covering 27 impact categories. While having a lower PGM loading, environmental impacts of the AEM-FC are higher in 26 out of the 27 impact categories than the PEM-FC 2020. Increasing performance and lifetime in sensitivity analyses resulted in more similar environmental performance. The AEM-EL has a lower environmental impact than the PEM-EL in 24 impact categories, including climate change. Considering their low technology readiness level, the findings are promising for the technological roadmap of AEM technology for low-PGM FC and EL.

(Invited) Recycling Considerations for PEM Electrolysis Materials

Hydrogen from water electrolysis has been touted as a green alternative to displace existing hydrogen feedstocks derived from fossil fuels. Proton exchange membrane (PEM)-based electrolyzers are one commercial pathway with the potential to meet the cost, performance, and application requirements. However, to truly represent a sustainable pathway, the production lifecycle needs to be considered, especially related to critical materials such as catalysts and polyfluorinated alkyl substances (PFAS) such as Nafion™ and other polyfluorosulfonic acid (PFSA) membranes. PFAS are beginning to be regulated globally, with a goal of phasing them out where possible. Recycling programs for the polymers used in electrolyzers can assist in keeping them exempt from PFAS regulations, due to the minimized environmental impact and lack of related emissions. In addition, PEM electrolyzers use a significant amount of platinum group metals, including iridium, one of the scarcest naturally occurring elements. Addressing these issues through recycling of key components is an important part of large scale commercialization and deployment.The need for recycling is based on both scarcity and environmental sustainability considerations. Customers are starting to ask more questions about supplier philosophy and documentation of environmental practices. Many manufacturing companies are certified to the ISO9001 quality standard, but many are now looking to be also certified to ISO14001, the environmental standard. ISO14001 represents certification to a group of standards designed to minimize a company’s negative impact on the environment. These standards show a voluntary commitment to environmental regulation and can give companies a competitive advantage when dealing with customers concerned about the environment. While recycling of any particular chemicals is not specifically required by ISO14001, the standards include lifecycle assessments, integration of environmental aspects into product design, reduction of greenhouse gas emissions, and related topics where recycling would have positive impact on the metrics.For platinum group metals, recycling is required to meet the projected capacity demands for electrolyzers before 2050. Many analyses are projecting gigawatt annual capacities for electrolysis within the next 10 years, and in fact several European countries have already made commitments to site part of this capacity. With 7-10 year stack life, recovering stacks to recycle the platinum group metals is important to sustain the existing fielded capacity as more electrolyzers are deployed. Recycling other components such as titanium, stainless steel, and fluoropolymers provides some additional value stream from reclamation as well. For maximum benefit, material collection methods need to be set up within the manufacturing facility, to capture waste materials and scrap, as well as through the field population, so that systems no longer being operated can be reclaimed for materials. This talk will cover some of the business considerations for effective recycling, as well as current practices.

Cl–/ClO– process on SnO2‐based electrodes in low‐concentrated NaCl solutions

AbstractAnode processes on SnO2‐based electrodes in low‐concentrated NaCl solutions have been investigated. The current‐voltage curves for 25 tin oxide anodes doped with various amounts of platinum group metals in 0.5 M NaClO4 and 0.5 M NaClO4 + 0.5 M NaCl have been analyzed. The correlation criterion between the catalytic activity of the coating in relation to the reaction of synthesis of NaClO, NaClO3 from low‐concentrated NaCl solutions, and the oxygen evolution overpotential was found. The formulated criterion is fully met by SnO2‐coatings doped with both palladium (5‐15 at.%) and platinum (5‐10 at.%), which are the optimal electrocatalysts for the synthesis of sodium hypochlorite. In this case, their catalytic activity does not depend on the concentrations of dopant in the range, which allows to obtain anodes with reproducible properties by pyrolysis. The current efficiency of NaClO is 90‐95% and current efficiency of chlorate is less than 1% during the electrolysis of 0.15 M NaCl on Ti/SnO2‐Pt‐Pd anodes at 40‐60 mA/cm2. Palladium exists in the form of PdO phase in the electrocatalytic coating Ti/SnO2‐Pt‐Pd. The surface oxygen concentration in H2Oads and OHads is comparable to the oxygen content of the phase oxides of tin and palladium in the coating containing 19.5 at.% Pd, indicating a high surface content of adsorbed water. Palladium oxides are the main centers of water adsorption, and their presence on the surface of the anodes contributes to the hydroxylation of the surface. Most likely, this property of palladium compounds provides its high electrocatalytic activity in the reaction of formation of hypochlorite, which involves labile oxygen‐containing particles low bonded to the surface.

3D titania nanotube array support for water electrolysis palladium catalysts

A critical step in developing deployable water electrolysis technologies is the reduction in the amount of platinum group metals (PGMs) that are the most active catalysts for hydrogen and oxygen evolution. In this paper, we demonstrate a convenient strategy to reduce the PGM loading in electrolysis by using ultra-low Pd loaded electrocatalysts supported on 3D architectures of titania (TiO2) nanotubes. This manuscript focuses on the following aspects: (1) a comprehensive analysis of the synthesis of the TiO2 support using water-based electrolytes; (2) the deposition of Pd catalyst to the support by either physical vapour deposition or dropcast and (3) functional characterisation of the obtained materials for hydrogen and oxygen evolution in both acidic and alkaline environments. A new strategy is developed to obtain short low aspect ratio 3D titania nanotubes arrays (TNTA) and we demonstrate that an extremely low quantity of Pd (81 µg cm−2) is sufficient to obtain significant activity improvement in an Anion Exchange Membrane (AEM) water electrolyser.

Towards Systematic Understandings and Designs of Electrolyte/Electrode Interfaces By Computational Physics Approaches

Reducing the amount of platinum group metals (PGMs) in catalyst layers is one of major issues in developments of polymer electrolyte fuel cells (PEFCs). Obviously, the mass activity of oxygen reduction reaction (ORR) needs to be enhanced to reduce the PGM-loading. Specific surface area of PGMs also needs to be large enough to decrease the local oxygen transport loss near the catalyst surface [1]. In addition, the catalysts need to be stable enough to ensure long-term operations of PEFCs [2]. To satisfy all these requirements, extensive studies have been carried out on explorations of optimal composition, size and shape of PGM nanoparticles [3] as well as desired controls of catalyst and ionomer distributions [4,5], and remarkable progresses have been achieved in past decades. In those studies, atomistic simulations have made significant contributions on revealing mechanisms underlying experimental observations and designing new materials. Electronic structure calculations adopting density functional theory (DFT), for example, have been utilized as a standard tool to predict the catalytic activity since the first successful reproduction of the volcano plot of ORR [6]. Molecular dynamics (MD) simulations using semi-empirical force fields have been successfully utilized to predict structures and transport properties of ionomer, too [7-9]. In this presentation, we will show results of our applications of DFT and MD simulations to cathode catalysts and ionomer thin films on catalyst surfaces [8,10]. After discussing the power of the conventional methods as well as their limitations, we will discuss recent progresses in state-of-the-art machine-learning methodologies [11-14] as a promising theoretical tool to examine complex finite-temperature properties of electrode/electrolyte interfaces.[1] A. Kongkanand et al. J. Phys. Chem. Lett. 7, 1127 (2016).[2] P. J. Ferreira et al. J. Electrochem. Soc. 152, A2256 (2005).[3] L. Pan et al. Current Opinion in Electrochem., 17, 61 (2019).[4] S. Lister and G. McLean J. Power Sources 130, 61 (2004).[5] S. Ott et al. Nature Mateir. 19, 77 (2019).[6] Nørskov et al. J. Phys. Chem. B 108, 17886 (2004).[7] S. S. Jang et al. J. Phys. Chem. B 108, 3149 (2004).[8] R. Jinnouchi et al. Electrochim. Acta 188, 767 (2016).[9] Y. Kurihara et al. J. Electrochem. Soc. 164, F628 (2017).[10] R. Jinnouchi et al. Phys. Chem. Chem. Phys. 13, 21070 (2011).[11] R. Jinnouchi and R. Asahi J. Phys. Chem. Lett. 8, 4279 (2017).[12] R. Jinnouchi et al. Phys. Rev. Lett. 122, 225701 (2019).[13] R. Jinnouchi et al. Phys. Rev. B 100, 014105 (2019).[14] R. Jinnouchi et al. Phys. Rev. B 101 060201 (2020).

Miniature Fuel cell with Monolithically Fabricated Si Electrode -First prototype with Au-Pd-Pt multilayer catalyst-

Our first fuel cell prototype with a novel Au-Pd-Pt catalyst successfully demonstrated power generation. In order to reduce amount of platinum group metals and obtain high CO tolerance, electrochemical atomic layer depositions of Pd and Pt were applied on the porous Au. 5 ML Pd and sub-ML Pt deposition was attempted and amounts of Pd and Pt were electrochemically estimated to be 125 μg/cm2 and 6 μg/cm2, respectively. No catalyst poisoning to 100 ppm CO was observed during the power generation. Though the peak power was poor around 100 mW/cm2, results were satisfying for the first prototype.

On the Activity of Electrospun Tantalum Doped SnO2 for Durable ultra-Low PGM Fuel Cell Cathodes

Despite the advances in the development of Proton Exchange Membrane Fuel Cells (PEMFCs), some locks still need to be lifted before they are deployed on a large scale: i) Reduce the amount of platinum group metals (PGM) used in the electrodes by increasing the mass activity of the supported catalyst.ii) Improve durability of the electrodes by replace the conventional carbon support In particular, for the cathode side, carbon blacks (e.g. Vulcan XC-72) are conventionally used as a support materials for Pt and Pt-alloy nanoparticles. These materials exhibit high electric conductivity, controlled chemical properties, and high surface area that are of interest in PEMFCs application as electrocatalyst supports. However, carbon blacks are oxidized at the high voltage experienced at the cathode side (e.g. in stop/start conditions) leading to PEMFC major failure due to support corrosion leading to catalyst particles sintering or detachment [1,2]. Alternative supports based on tin oxide have attracted research interest due to their high corrosion resistance and promotion of activity for oxygen reduction reaction (ORR)[3]. The drawback is their low electrical conductivity, that in this work was tackled by doping with tantalum. Ta-doped SnO2 conducting fibers were synthetized by electrospinning followed by calcination [4] (Figure 1). This support was catalyzed with platinum nanoparticles prepared by a microwave-assisted polyol method and characterized for their physico-chemical and electrocatalytic properties towards ORR. In particular, stability to voltage cycling at high potential was evaluated by ex situ electrochemical analysis. A very significant mass activity of 470 A / gPt has been reached with 7.4wt.% of Pt homogenously deposited onto Ta-doped SnO2 nanofibers [5,6]. In addition, improved electrochemical stability was demonstrated with the retention of 70 % of the mass activity up to 10000 cycles from 1 to 1.6 V/RHE. Figure 1: SEM micrograph of 1%at. Ta-doped SnO2 nanofibers. References C. Meier, C. Galeano, I. Katsounaros, A. a. Topalov, A. Kostka, F. Schüth, K. J. J. Mayrhofer, ACS Catal. 2012, 2, 832–843. Yu, H. Li, H. Wang, X.-Z. Yuan, G. Wang, M. Pan, J. Power Sources 2012, 205, 10–23. Savych, S. Subianto, Y. Nabil, S. Cavaliere, D. Jones and J. Rozière, Chem. Chem. Phys. 2015, 17, 16970-16976 . Cavaliere, I. Jiménez-Morales, G. Ercolano, I. Savych, D. Jones and J. Rozière, ChemElectroChem 2015, 2, 1966-1973. Senoo, K. Taniguchi, K. Kakinuma, M. Uchida, H. Uchida, S. Deki, and M. Watanabe, ElectroChem. Commun. 2015, 51, 37–40. Jiménez-Morales, S. Cavaliere, D. Jones, and J. Rozière, Phys. Chem. Chem. Phys. 2018, 20, 8765–8772 . Figure 1

Understanding the features of PGMs in spent ternary automobile catalysts for development of cleaner recovery technology

Abstract With the penetration of automobiles, the number of spent automobile catalysts keeps increasing. The spent catalysts contain a significant amount of platinum group metals (PGMs) as active components. Recycling of precious metals from complex mixtures of auto-catalysts, however, is of great difficulty owing to their heterogeneity and complexity. More importantly, the lack of comprehensive characterization of spent catalysts results in an incomplete understanding of their physicochemical properties. This article analyzed the failure mechanisms and the particular structure between precious metals and aluminosilicate carriers in the spent automotive catalysts. The particle size distribution, compositional distribution, morphology, phase and thermal behavior properties of the spent auto-catalysts were investigated with various techniques, including X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS), laser particle size analyzer, and thermogravimetric differential scanning calorimeter analysis (TG-DSC). With a detailed understanding of the characterization results and thermodynamic analyses, the importance and potential obstacles to enable effective PGMs recovery of corresponding physiochemical features can be identified. On this basis, the pretreatment method of mechanochemical activation associated with the hydrochloric acid leaching system were preliminarily explored. The total leaching rate of PGMs reached 93.42%. The leaching rates of Pt, Rh and Pd were 77.2%, 62.1% and 97.4%, respectively.

A Miniature Fuel Cell with Monolithically Fabricated Si Electrodes: Application of Au-Pd-Pt Multilayer Catalyst

Our first miniature fuel cell prototype with a novel Au-Pd-Pt catalyst successfully demonstrated power generation. In order to reduce amount of platinum group metals and obtain high CO tolerance, electrochemical atomic layer deposition (ALD) of Pd and Pt on porous Au was proposed for the catalyst formation. The electrochemical ALD was realized by surface limited redox replacement (SLRR) process of underpotentially deposited hydrogen (H-UPD-SLRR). The amount of the deposit and catalytic activity of Au-Pd-Pt structures were tested and optimized on Au wire. A performance of a miniature fuel cell prototype with a porous Au layer formed on a Si chip with several Pd monolayers and Pt sub-monolayer coverage was examined. Pd and Pt loadings were estimated to be 101 μg/cm2 and 10 μg/cm2, respectively. Though the peak power was poor around 100 mW/cm2, no performance drop with 100 ppm CO was observed and results were promising as the first prototype.

Pd-H3PW12O40/Zr-MCM-41: An efficient catalyst for the sustainable dehydration of glycerol to acrolein

The gas-phase dehydration of glycerol was investigated over H3PW12O40/MCM-41, H3PW12O40/Zr-MCM-41 and Pd-H3PW12O40/Zr-MCM-41 mesoporous molecular sieves catalysts. MCM-41, Zr-MCM-41 and Pt-H3PW12O40/Zr-MCM-41 were also examined for comparison. The catalysts were characterized by X-ray diffraction, nitrogen adsorption–desorption, NH3-TPD, pyridine-FTIR and thermogravimetric analysis measurements. Compared with MCM-41, Zr-MCM-41 catalyst showed higher acidity and better catalytic performance in glycerol dehydration to acrolein. Compared to Zr-MCM-41, the acidity of H3PW12O40/Zr-MCM-41 catalyst significantly increased and the catalyst showed an enhanced glycerol conversion and acrolein selectivity. In order to improve the stability of H3PW12O40/Zr-MCM-41 catalyst, a small amount of platinum group metals (Pd) was doped. The nitrogen adsorption–desorption results revealed that mesoporous structure of the Pd-H3PW12O40/Zr-MCM-41 catalyst remained almost unchanged, and the specific surface area, pore volume and pore size decreased. In comparison with H3PW12O40/Zr-MCM-41, the total acidity of Pd-H3PW12O40/Zr-MCM-41 catalyst did not show any obvious change, but the number of the Brønsted acid sites increased, the amount of the Lewis acid sites decreased. The Pd-H3PW12O40/Zr-MCM-41 catalyst exhibited significantly higher selectivity for the formation of acrolein, relatively lower coke deposition and excellent catalyst stability. After 50h of reaction, the conversion of glycerol decreased from 100% to 55% over H3PW12O40/Zr-MCM-41 catalyst, while the conversion of glycerol reduced from 97% to 87% over Pd-H3PW12O40/Zr-MCM-41 catalyst. A drastic decrease in conversion after 35h over Pt-H3PW12O40/Zr-MCM-41 catalyst was also observed. Moreover, Pd-H3PW12O40/Zr-MCM-41 catalyst was completely regenerated under the regeneration conditions and exhibited excellent reusability in the dehydration of glycerol to acrolein.

PEM-Type Water Electrolysis/Fuel Cell Reversible Cell with Low PGM Catalyst Loadings

To utilize fluctuating renewable energy stably and effectively, large-scale energy storage systems such as Li-ion, redox-flow and Na-S batteries have been extensively studied. Battery storage system have advantages of high efficiency in energy utilization and rapid response for energy demand, however initial system cost tend to be expensive. Electrochemical hydrogen production and storage is recently attracting attentions as another practical technology because of high energy efficiency of electrochemical water splitting, relatively low technological barrier for large-scale storage, and ease of long-term energy storage and long-range transport without self-discharge. Regenerative fuel cell is an energy storage system using hydrogen as an energy medium. In particular, reversible (unitized) regenerative fuel cells (RFCs) can be functioned both as water electrolyzer and fuel cell in the same electrochemical cell by switching the operation mode, so that much more compact and cheaper system could be realized. In the PEM-type RFC, unsupported platinum/iridium-based catalysts are usually selected in terms of activity and stability for both operation modes. Loading amount of platinum group metals (PGMs) of RFC is relatively high (typically >1 mg cm-2) compared to the fuel cell dedicated system due to stability issue at high potentials during OER. Therefore, reducing PGM loadings without expense of performance and durability is high priority to meet the capital cost of the systems. To reduce the PGM loadings of oxygen electrode of RFC, we examined electro-conductive Magneli phase titanium oxides (in particular Ti4O7) as a catalyst support material [1,2]. High surface area oxide support was prepared by UV laser technique; TiO2 nano particles dispersed in an appropriate solvent (typically acetonitrile) are reduced by pulsed UV laser irradiation [3]. Pt, Ir, and Pt-Ir alloy nano particles were deposited on the oxide support, and their electrocatalytic activities were examined by rotating disk electrode and MEA. Ti4O7-supported Pt catalyst showed 3 times larger electrochemical active area (ECA) than that of commercially available Pt black, and 2.9 and 2.4-fold mass activity was obtained for ORR@0.9V and OER@1.7V, respectively. Initial ORR/OER cycle durability test was conducted for Pt/Ti4O7 catalyst MEA at 80oC between >1.8V for OER and <0.8V for ORR, and almost no performance loss was observed. These results show titanium oxide based materials can be applied as RFC catalyst support, which leads to effective use and lowering PGM loading in the oxygen electrode.

The effect of temperature, cyanide and base metals on the adsorption of Pt, Pd and Au onto activated carbon

Leaching of platinum and palladium with alkaline cyanide solutions has been shown to be feasible for a number of leach modes. The platinum and palladium leaching will typically take place at elevated temperatures, which can range from 55°C on heaps or in tanks to between 120 and 180°C in autoclaves with a better degree of leaching occurring with higher temperatures. Some progress has also been made into the investigation of PGM (platinum group metals; Pt, Pd, Au) adsorption onto activated carbon at room temperature, but as typically higher temperatures (>55°C) are likely for the leaching of Pt and Pd, it is an important factor in the adsorption process of which the effect is still largely unknown. The effects of temperature, free cyanide and base metal (Cu and Ni) concentrations on the adsorption of PGMs from pregnant leach solutions onto granular activated carbon were therefore determined.Common to most diffusion controlled processes, an increase in the adsorption rate of platinum, palladium and gold cyanide with an increase in temperature was observed. Experiments with consecutive contacts of the PGM cyanide solution onto the activated carbon, however, revealed that with an increase in temperature, the amount of PGMs that were adsorbed, decreased with each loading. In the absence of free cyanide and base metals, it was found that after 4 consecutive contacts, 99% of the total amount of Pt and Pd adsorbed at 25°C compared to 85% of the Pt and 83% of the Pd at 50°C. No difference could be seen between the adsorption of gold cyanide at 25 and 50°C after 4 contacts. It has also been established that the detrimental effect of free cyanide on the adsorption of PGMs will increase as the temperature increases. The detrimental effect of the presence of Cu and Ni is evaluated, based upon the amount of the base metals adsorbed at these conditions, which have been found to vary significantly with cyanide and temperature. Generally, Pt and Pd adsorption has been found to be significantly more affected by temperature, cyanide and base metals than the adsorption of gold and needs to be carefully taken into consideration with the design of a PGM adsorption circuit to ensure sufficient Pt and Pd recovery.

Microwave-assisted cloud point extraction of Rh, Pd and Pt with 2-mercaptobenzothiazole as preconcentration procedure prior to ICP-MS analysis of pharmaceutical products

New approaches for acceleration of cloud point extraction of Rh, Pd and Pt by microwave and ultrasound irradiation have been investigated. 2-Mercaptobenzothiazole and Triton X-100 were used as ligand and non-ionic surfactant, respectively. Microwave irradiation substantially increased the procedure efficiency. In contrast no significant effect was observed when a micellar solution was treated with ultrasound energy. The acceleration of complex formation reactions by reducing agents (KI and SnCl2) has also been studied. The use of SnCl2 was a prerequisite for quantitative extraction of Rh. Since the extraction kinetics of platinum depends on its oxidation state and presence of Pd, the addition of SnCl2 equalized the platinum extraction behavior. For the first time the whole cloud point procedure was successively accomplished in a microwave system. 10 min of irradiation were sufficient for gravimetrical phase separation and quantitative extraction of platinum group metals. As a result the procedure time was shortened by a factor of 9 in comparison to conventional hot plate cloud point extraction. The surfactant-rich phase was analyzed after dilution with 1 M HCl by continuous nebulization to ICP-MS. Quantitative recoveries and good plasma tolerance were reported. Detection limits of 1 ng.l−1 (Rh), 5 ng.l−1 (Pd), and 6 ng.l−1 (Pt) were achieved regarding a preconcentration factor of 8. The microwave-assisted cloud point extraction has been successfully applied for simultaneous determination of trace amounts of platinum group metals in pharmaceutical products (Tritace, Vivace, Laprilen and Enalapril).

2003 F.N. Speller Award Lecture:Platinum Group Metal Additions to Titanium: A Highly Effective Strategy for Enhancing Corrosion Resistance

Abstract Although recognized for their exceptional corrosion resistance in a wide range of chemical environments, titanium and its alloys can be susceptible to corrosion in reducing acid media, crevice attack in hot chlorides and other halide solutions, and/or stress corrosion in certain higher-strength alloys. These serious limitations may be practically and cost-effectively overcome to a great extent by the addition of very minor (<0.25 wt%) amounts of platinum group metals (PGMs) to titanium and its alloys; while imparting little or no effect on alloy mechanical/physical properties or metallurgy. Through the catalytic facilitation of cathodic reduction reactions (primarily the hydrogen evolution reaction [HER]) in acidic aqueous media, these PGM alloy additions shift titanium toward noble (positive) potentials where the protective titanium oxide surface film is stable. This radically decreases alloy corrosion rates in dilute inorganic and organic acids with no detrimental influence in oxidizing media o...

Phase Transformation of Ti-Ni Containing Platinum-Group Metals

ABSTRACTSince the maximum shape recovery temperature of the binary Ti-Ni alloys is limited to be around 400K, the increase in martensitic transformation temperature (Ms) of Ti-Ni should be done by alloying for the demand of high temperature applications. Although most of additional elements are known to decrease Ms of Ti-Ni, substitutional elements having large atomic size are expected to increase Ms. In this study, phase constitution, phase transformation temperature, lattice parameter of B2 phase and Vickers hardness were investigated for Ti-Ni alloys containing several platinum-group metals (PGM). The alloy systems investigated were the pseudobinary systems of TiNi-TiRh, TiNi-TiIr and TiNi-TiPt where the PGM atoms substitute for the Ni-sites of TiNi. The phase transformation and phase constitution were assessed by differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). It was found by XRD that TiNi can contain a large amount of the PGMs as Ti(Ni, Rh), Ti(Ni, Ir) and Ti(Ni, Pt). Lattice parameters monotonously increase with increasing amount of PGMs. With increasing Pt content, Ms slightly decreases when less than 10mol%Pt while continuously increases as the rate of 26K/mol%Pt when more than 10mol%Pt. On the other hand, Ms decreases and then disappears with increasing Rh or Ir content. Hardness ranges from HV180 to HV570 and the maximum values in the pseudobinary systems lie around 20–30mol%PGM, suggesting solid solution hardening caused by the substitution of PGMs.

Assessment of Platinum Availability for Advanced Fuel-Cell Vehicles

The supply and demand of platinum-group metals (PGMs) are assessed through 2030. Recent increases in PGM demand and tight supplies from the two main sources have caused platinum and palladium prices to rise substantially. Future PGM demand driven by new technologies could significantly outstrip supplies. Five scenarios are based on different assumptions about demand for platinum in automotive fuel cells, demand for new vehicles in developing countries, the market penetration of vehicles with fuel cells and advanced catalytic converters, and several other factors. The scenarios suggest a midterm boom in the PGM market caused by increasing demand for platinum for fuel-cell vehicles and an increased use of advanced catalytic converters containing high amounts of PGMs, which could squeeze supplies between 2005 and 2020. This period would potentially be followed by a bust in PGM demand by 2030, as recycling exerts an influence on overall demand in developing countries. Demand for PGMs could outstrip supplies regardless of the market penetration rates of fuel-cell vehicles because of the demand for relatively high amounts of PGMs for advanced catalytic converters. Future research should focus on assessing costs associated with increasing PGM production and on PGM market dynamics.

Platinum Metals Catalytic Systems in Nitric Acid Production

The State Institute for the Nitrogen Industry is one of the oldest industrial branches of the research and engineering institutes in Russia and the former U.S.S.R., and in 1991 the Institute celebrated its sixtieth anniversary. This paper gives a brief overview of the main results of work carried out by GIAP alone and in co-operation with other organisations over the past 50 years on the optimisation of the production of non-concentrated nitric acid. In particular developments to reduce the amounts of platinum group metals used in ammonia oxidation and waste gas cleaing, and ways to reduce platinum group metal losses are discussed.

家庭用触媒燃焼器の開発

Recently, the concerns for improved indoor air quality have been increas-ing. For domestic combustors, the emissions of concern are CO, HC, and NOx.Reduction of these gaseous pollutants is feasible by replacing the conventional flame-type combustor with a new combustor design. The catalytic combustor is a particularly attractive technique for simultaneous reduction of CO, HC, and NOx, emissions.To develop a domestic catalytic combustor, platinum group metals supported on a ceramic honeycomb were prepared as a catalyst, and their performances for kerosine combustion were investigated.The main results obtained are as follows.1) The carrier using 33μm diameter of fused silica has a higher thermal shock resistance than that of using 33μm diameter2) The optimum amount of platinum group metals on the carrier was between 1-1.5kg/m3.3) The optimum cell density of the carrier was between 300-400 (1/in2), and optimum depth of the carrier was between 10-20mm.4) The preferable range of excess air ratio was between 1. 3-1.5.5) Concentration of NOx in exhaust gas from the test catalytic combustor was about 0.2ppm when the temperature of the catalyst was 800-900°C.

Some Aspects of Electrocatalysis

To increase our understanding of the electrochemical processes involved during cardiac stimulation by implanted pacemakers, alloys were prepared containing electrocatalytically active platinum group metals and either titanium or tantalum which irreversibly form very inactive oxides. Our work has shown that alloys with as little as 5 per cent platinum group metals exhibit electrochemical characteristics which are more similar to the platinum group metals than to the valve metals. Under some of the conditions certain of these alloys appear to be better electro-catalysts than the platinum group metals. Alloying titanium and tantalum with small amounts of platinum group metals also appears to prevent anodic dissolution of oxide-free titanium and tantalum.