Platinum

Effect of platinum nanoparticle size on catalytic reduction of nitrate in liquid phase was examined under ambient conditions by using hydrogen as a reducing agent. For the size effect study, Pt nanoparticles with sizes of 2, 4 and 8 nm were loaded silica support. TEM images of Pt nanoparticles showed that homogeneous morphologies as well as narrow size distributions were achieved during the preparation. All three catalysts showed high activity and were able to reduce nitrate below the recommended limit of 50 mg/L in drinking water. The highest catalytic activity was seen with 8 nm platinum; however, the product selectivity for N2 was highest with 4 nm platinum. In addition, the possibility of PVP capping agent acting as a promoter in the reaction is highlighted.

The strategic management of resources have recently garnered widespread analytic attention with the prevailing consensus being the "resource curse," and its negative effect on social, economic and political development worldwide. The curse is significantly worse for traditional and indigenous communities where tribal land rests atop valuable subterranean resources without much leverage to negotiate for their use or ownership. Some of the poorest indigenous people live in the most resource-rich regions of the world, a condition that is true in both the developed and developing worlds alike. The Royal Bafokeng Nation of South Africa, however, provides a strong counterpoint. Deemed Africa's richest ethnic group, the nation was able to leverage its political clout to establish a community investment company which administers a lucrative financial portfolio that consists of assets in a diverse range of economic sectors all stemming from platinum resources on Bafokeng tribal land. The case of the Royal Bafokeng Nation provides a stark anomaly to the literature on indigenous access to subterranean resources and begs the question "how do communities navigate leverage with their respective state governments in order to benefit from their subterranean natural resources on their indigenous land?" To examine this question, this paper borrows insights from examples in former Anglophone colonies of settlement for structural context and argues that the Bafokeng's political culture evidenced by its political mobilization, inclinations to litigate and its shrewd politicking provided levers of success in negotiating for communal access to platinum resources.

We analyze the price behavior of the main precious metals-gold, silver, platinum and palladium-before, during and in the aftermath of the 2007-08 financial crisis. Using the mildly explosive/multiple bubble technology developed by Phillips, Shi and Yu (2015, International Economic Review 56(4), 1043-1133), we find significant, short periods of mildly explosive behavior in the spot and futures prices of all four metals. Fewer periods are detected using exchange-rate adjusted prices, and almost none when deflated prices are used. We assess whether these findings are indicative of bubble behavior. Convenience yield is shown to have little efficacy in this regard, while other fundamental proxy variables and position data offer only very limited evidence against prices having been anything other than fundamentals-driven. Possible exceptions are in gold in the run-up to the highpoint of the financial crisis, and in silver and palladium around the launch of specific financial products. Some froth, however, is reported and discussed for each metal.

Cisplatin causes apoptosis of dorsal root ganglia (DRG) neurons. The amount of platinum binding to DNA correlates with cisplatin toxicity in cancer cells 1 . Cisplatin binds neuronal DNA more than a neuron-like dividing cell line (PC12); 10-fold at 24 h and 24-fold greater at 72 h. ...

Soft robots possess many attributes that are difficult, if not impossible, to achieve with conventional robots composed of rigid materials. Yet, despite recent advances, soft robots must still be tethered to hard robotic control systems and power sources. New strategies for creating completely soft robots, including soft analogues of these crucial components, are needed to realize their full potential. Here we report the untethered operation of a robot composed solely of soft materials. The robot is controlled with microfluidic logic that autonomously regulates fluid flow and, hence, catalytic decomposition of an on-board monopropellant fuel supply. Gas generated from the fuel decomposition inflates fluidic networks downstream of the reaction sites, resulting in actuation. The body and microfluidic logic of the robot are fabricated using moulding and soft lithography, respectively, and the pneumatic actuator networks, on-board fuel reservoirs and catalytic reaction chambers needed f...

ABSTRACT:  The objective of this study was to develop a method to measure the oxidation–reduction (redox) potential of hard cheeses such as cheddar and to investigate the impact on this parameter of measurement temperature, and factors associated with electrochemical cell design such as distance between reference and working electrodes and depth into the cheese of the platinum electrodes. For this purpose, a novel, self-sealing, platinum working electrode was constructed which was thin and flexible enough to be inserted directly into the cheese sample. A calomel electrode was used as the reference electrode and the circuit was completed with a 3 M KCl salt bridge. The physical orientation of electrodes, such as distance between reference electrode and working electrode, had a substantial effect on equilibrium time for redox potential measurement. The time required for redox potential to reach equilibrium was 2 d in cheddar cheese and the optimum distance between the platinum and calomel electrodes was 2.5 cm. The fastest equilibration time was obtained when the working electrode was inserted 5 or 6 cm into the cheese. Temperature also had an important effect on redox potential. The shortest time to reach equilibrium of potential was at room temperature (20 °C), but it was not practical to keep cheese at this temperature for a period of 2 d. Therefore, redox measurement at 12 °C was recommended in spite of the longer equilibration time compared with room temperature. The results of this study suggest that the novel platinum working electrode allows reproducible measurement of the oxidation–reduction potential of cheddar cheese.

Platinum-based heterogeneous catalysts are critical to many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the surface active-site atoms are used. Catalysts with single-atom dispersions are thus highly desirable to maximize atom efficiency, but making them is challenging. Here we report the synthesis of a single-atom catalyst that consists of only isolated single Pt atoms anchored to the surfaces of iron oxide nanocrystallites. This single-atom catalyst has extremely high atom efficiency and shows excellent stability and high activity for both CO oxidation and preferential oxidation of CO in H2. Density functional theory calculations show that the high catalytic activity correlates with the partially vacant 5d orbitals of the positively charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidation.

Background: In contrast to the hyper-reactive platinum electrode, iodine-coated platinum electrode shows remarkable inertness toward adsorption and surface processes. For this reason, iodine-coated platinum electrode lends itself to interesting voltammetric applications. Hydrodynamic voltammetric analysis, one of the voltammetric techniques family, has many advantages over stationary voltammetric techniques inter aliathe steady state current and the higher sensitivity. Objective: The present work is aimed at utilization of iodine-coated platinum rotating disk electrode for analysis of iron in spinach.Methods: The developed method is based on a voltammetric sweep at an iodine-coated rotating-disk platinum electrode. The optimized experimental parameters included a potential scan from –0.20 to 0.85 V versus Ag/AgCl/[Cl-] = 1.0 M, 50 mV/s scan rate, and a rotation rate of 1000 rpm. Results: Oxidation of iron at the iodine-coated platinum rotating disk electrode was manifested by a wave...

The objective of this study was to investigate the applicability and performance of the selected ion exchangers with different physicochemical characteristics and functional groups to simultaneously recover three different platinum group elements (PGE), platinum(IV), palladium(II) and rhodium(III), present in a chloride solution produced by the leaching of spent automotive catalysts. The tested ion exchangers included a resin with a quaternary ammonium functional group (Lewatit MonoPlus (M +) MP 600), a resin with a polyamine functional group (Purolite S985) and a resin with a thiouronium functional group (XUS 43600.00). The study also focused on the achievable desorption from the loaded resins using different eluent systems. The leach solution was chlorine-saturated and contained 2.35 mol/L hydrochloric acid, platinum and palladium in concentrations of 0.13 mmol/L, and rhodium 0.03 mmol/L. It was found that XUS 43600.00 showed the best adsorption performance for platinum(IV) and palladium(II) chloride complexes among the investigated resins, but weak affinity for rhodium(III) chloride complexes was observed for all three resins. The adsorption kinetics were found to obey the Ho pseudo-second order expression. For Lewatit MonoPlus (M +) MP 600 and Purolite S985 the adsorption was best described by the Freundlich isotherm, while for XUS 43600.00 the Langmuir isotherm was more apt. Desorption of the PGE was examined using four different elution agents: sodium thiocyanate (2 mol/L), hydrochloric acid (2 mol/L), thiourea (1 mol/L) in hydrochloric acid (2 mol/L), and thiourea (1 mol/L) in sodium hydroxide (2 mol/L). The results showed that platinum and palladium can be fully eluted with the acidic thiourea but desorption of rhodium proved difficult with all the eluents.

Grain boundaries are intrinsic and omnipresent microstructural imperfections in polycrystalline and nanocrystalline materials. They are short-circuit diffusion paths and preferential locations for alloying elements, dopants, and impurities segregation. They also facilitate heterogeneous nucleation and the growth of secondary phases. Therefore, grain boundaries strongly influence many materials' properties and their stabilities during application. Here, we propose an approach to measure diffusion, segregation, and segregation-induced precipitation at grain boundaries at a sub-nanometer scale by combining atom probe tomography and scanning transmission electron microscopy. Nanocrystalline multilayer thin films with columnar grain structure were used as a model system as they offer a large area of random highangle grain boundaries and inherent short diffusion distance. Our results show that the fast diffusion flux proceeds primarily through the core region of the grain boundary, which is around 1 nm. While the spatial range that the segregated solute atoms occupied is larger: below the saturation level, it is 1,2 nm; as the segregation saturates, it is 2-3.4 nm in most grain boundary areas. Above 3.4 nm, secondary phase nuclei seem to form. The observed distributions of the solutes at the matrix grain boundaries evidence that even at a single grain boundary, different regions accommodate different amounts of solute atoms and promote secondary phase nuclei with different compositions, which is caused by its complex threedimensional topology.

A B S T R A C T Platinised titanium mesh is a common electrode material in industrial electrolytic cells and Ce-based redox flow batteries. In this work, the electrodeposition of platinum on a stack of titanium micromeshes is performed from a flowing alkaline solution in a rectangular channel, divided flow cell. The morphology and distribution of the resulting platinum deposits are studied by SEM, EDS mapping and X-ray computed tomography. The active surface area of the electrode was assessed from the charge transfer current for the reduction of Ce(IV) ions and compared to that of planar and expanded metal mesh electrodes. The surface area was estimated by hydrogen electrosorption relative to that at a planar Pt/Ti electrode. As expected from the potential drop within the electrode channel, the individual micromesh near the cell separator showed a higher platinum content. Pt/Ti micromesh offers an extended surface area and enhanced mass transport compared to planar electrodes and conventional expanded metal mesh anodes. The applications for these and alternative electrode structures are discussed.