Exchange Of Cobalt Ions Research Articles

Cobalt phosphide embedded in a 3D carbon frame as a sulfur carrier for high-performance lithium-sulfur batteries

• A porous three-dimensional carbon frame embedded with CoP nanoparticles (CoP@3DC) is synthesized. • CoP has a catalytic effect and can accelerate the conversion of LiPSs to inhibit the shuttle effect. • CoP@3DC/S delivers a superior discharge capacity of 640.6 mAh g −1 after 600 cycles at 1C. Lithium-sulfur (Li-S) batteries deliver a higher energy density than lithium ion batteries and are therefore regarded as next-generation batteries. However, the shuttle effect of soluble lithium polysulfides (LiPSs) and their slow redox kinetics are still the main setbacks for practical application. In this study, a porous three-dimensional carbon frame embedded with CoP nanoparticles (CoP@3DC) was synthesized by pyrolyzing and phosphating an acrylic cation exchange resin previously subjected to cobalt ion exchange. The abundant pores of CoP@3DC inhibit the diffusion of LiPSs, while its conductive three-dimensional carbon skeleton is conducive to the rapid transmission of electrons. In addition, CoP nanoparticles uniformly dispersed in the porous carbon network not only provide numerous chemical adsorption sites for LiPSs, but also accelerate their conversion to Li 2 S. Constant-current charging and discharging tests revealed that the CoP@3DC/S cathode achieves an initial discharge capacity of 1117.37 mAh∙g −1 at 0.5C and maintains a capacity of up to 740.56 mAh∙g −1 after 600 cycles, with a decay rate per cycle of only 0.056 %. Our work provides a facile supporting strategy for transition metal nanoparticles to significantly improve the performance of Li-S batteries.

Effect of Cobalt Ion Exchange and Thermal Pretreatment of Ionomer Thin Films on Conductivity, Water Uptake and Swelling

It is known that Cobalt (Co) can leach out from the Pt-Co alloy catalysts causing degradation of long-term fuel cell performance. Although the fundamental mechanism of performance loss is not fully understood, it has been hypothesized that the Co ion interacts with the nanothin ionomer films in the fuel cell catalyst layer by exchanging with the protons and thereby adversely affecting the performance. However, the effect of Cobalt ion, specifically and the transport properties of nanothin fluorinated ionomers films, in general is not fully known. We have studied the effect of cation(Cobalt) on spin-coated nanothin ionomers on its key properties – (i) proton conduction and water uptake which directly affects the electrochemical performance of fuel cell catalyst layers, and (ii) swelling behavior, which is an indicator of mechanical strength and thereby the durability of the ionomer. Electrochemical impedance spectroscopy (EIS) of films on interdigitated elecrodes for conductivity measurements, quartz crystal microbalance (QCM) for water uptake, and environmental ellipsometry for swelling measurement was employed, Quantification of exchanged Cobalt in nanothin films is non-trivial problem and we have used a set of x-ray techniques (EDX, XPS) for determination of cobalt in the cation exchanged films. In this work conductivity of the different ionomer thin film (~ 30 nm) were tested before and after Cobalt exchange at different temperatures (30-80 °C) and humidity (40-90 % RH) conditions. It was seen that the conductivity of the ionomer thin films decreased after Cobalt exchanged but the proton conduction of some of the non-commercial ionomers is not as strongly affected by Co ion exchange as that of the state-of-the-art Nafion ionomer. We also investigated the effect of ionomer thin film pretreatment on the conductivity of the cobalt exchanged ionomer. It was found that the the samples annealed at 160 °C and then cation exchanged by exposure to cobalt solution showed less reduction in conductivity than unannealed cation exchanged ionomer films. The presentation will share the details of the film preparation and characterization as well as the results for the conductivity, water uptake and swelling of the ionomer films. Figure 1

Kinetics of copper and cobalt ion exchange on inorganic antimony-containing ion exchangers

The exchange capacity, degree of exchange, and separation factors of copper(II) and cobalt(II) ions on the H-form of the inorganic ion exchanger “polysurmin”, a silicon phosphorus antimony ion exchanger, and a composite material based on polysurmin were studied as functions of the ion exchanger contact time in the solution. The results were treated in order to assess the rate-limiting step of the process.

Determination of the maximum retention of cobalt by ion exchange in h-zeolites

This work aimed to determine the maximum content of cobalt that can be incorporated by ion exchange in zeolites H-USY, H-Beta, H-Mordenite, and H-ZSM-5. To reach this goal, batch isotherms at 75ºC were constructed after addition of zeolite samples in flasks filled with cobalt nitrate solution. The equilibrium data were fitted to Langmuir, Freundlich, and Tóth adsorption isotherm models. Langmuir was the best model for zeolites H-Beta, H-Mordenite, and H-ZSM-5, whereas experimental data for H-USY were better fitted to the Freundlich isotherm model. From the isotherms, it was possible to determine the maximum cobalt exchange level (q max) that can be incorporated in each zeolite through ion exchange. In this sense, H-USY presented the highest q max value (2.40 meq/g zeol), while H-ZSM-5 showed the lowest one (0.64 meq/g zeol). These results also show the influence of the zeolite framework related to the channel system, pore opening, presence of cavities and secondary porosity and SiO2/Al2O3 ratio (SAR) on the maximum capacity and behavior of cobalt ion exchange in protonic zeolites.

FTIR of adsorbed species on Co-H-MOR and Co-Na-MOR under CH 4 + NO + O 2 stream: Catalytic activity and selectivity

The selective catalytic reduction (SCR) of NO with CH 4 in the presence of excess O 2 was studied on Co-H-MOR and Co-Na-MOR prepared from H-MOR and Na-MOR, respectively, by cobalt ion-exchange and containing nearly the same Co percentage (66 and 61%) but very different H + and Na + amounts. Catalyst characterization was performed using NO as a probe at room temperature, and by means of in situ FTIR study at the reaction temperature (573–773 K) in the presence of flowing reactant mixtures of various compositions ([CH 4] = 0 or 4000 ppm, [NO] = 0 or 4000 ppm, [O 2] = 0 or 20,000 ppm, balance He). In one selected case, the operando FTIR-GC methodology was used. The activity for SCR was nearly the same on the two catalysts, whereas the selectivity was higher on Co-H-MOR than on Co-Na-MOR. NO adsorption at room temperature did not show major differences in the type of cobalt species present on the two samples, being nearly all cobalt present as isolated Co 2+ with two coordinative vacancies. The in situ FTIR characterization under reaction conditions identifies Co 2+-mononitrosyls. We suggest that this mononitrosyl is a key species for the catalytic activity in the SCR reaction. Conversely, the in situ FTIR study under reaction conditions evidenced major differences between the surface nitrogen-oxo species (NO y , oxidation number of nitrogen >2) formed on the two samples, specifically NO + on Co-H-MOR-66, and Co 2+-monodentate nitrates on Co-Na-MOR-61. We suggest that Co 2+-monodentate nitrate favors the CH 4 combustion, accounting for the finding that the S SCR selectivity of Co-Na-MOR-61 is lower than that of Co-H-MOR-66.

Adsorption of Nitrogen, Oxygen, and Argon in Cobalt(II)-Exchanged Zeolite X

Adsorption of nitrogen, oxygen, and argon on cobalt(II)-exchanged zeolite X at 288.2 and 303.0 K was studied. The nitrogen and oxygen adsorption capacities increase upon cobalt ion exchange up to 71%, beyond which it shows a decreasing trend because of the partial degradation of the zeolite structure during the cation exchange and high-temperature vacuum dehydration processes. The magnitude of the increase in the adsorption capacities for nitrogen is much higher than that of oxygen. The nitrogen/oxygen as well as nitrogen/argon selectivities in the low-pressure region increase with an increase in cobalt exchange. Marginal oxygen selectivity over argon is observed for zeolite samples with higher cobalt exchange. The heats of adsorption values for nitrogen and oxygen increase and that for argon remain unaffected by cobalt exchange in zeolite X. The very high nitrogen adsorption capacity, selectivity, and heat of adsorption in the low-pressure region for cobalt-exchanged zeolite X compared to the parent sodium form of the zeolite show stronger interaction between nitrogen molecules with the extraframework cobalt cations of the zeolite. This stronger interaction has been explained in terms of the pi-complexation between nitrogen molecules and cobalt cations of the zeolites, as confirmed by diffuse reflectance infrared Fourier transform spectroscopy, wherein the N[triple bond]N stretching frequency at 2099 cm(-1) is observed for N2 molecules adsorbed in NaCoX.

63Ni and 57Co Uptake and Selectivity of Tin Antimonates of Different Structure

Tin antimonates of different structure were studied for their uptake of cobalt and nickel in the decontamination of floor drain water and neutral bond water simulates. Selectivity was observed to vary with the structures and degree of crystallinity of the tin antimonates (pyrochlore, rutile, and mixed metal oxides). High selectivity for cobalt of exchangers with pyrochlore structure is attributed to ion exchange of cobalt inside the tunnel structure; nickel uptake evidently took place mostly at the outer surfaces of the materials. Electrostatic forces governed the ion exchange of rutile tin antimonates owing to their particle hydrate structure. With some limitation, the prediction of nickel uptake on tin antimonates from the more abundant cobalt uptake data is considered possible.

Influence of acetate, chloride and nitrate ions on the sorption of cobalt by zeolite ZSM-5

Many factors affect the ion exchange process in zeolites. In this work the influence of different anions such as acetate, chloride and nitrate on the ion exchange of cobalt in zeolite ZSM-5 is discussed. After the ion exchange in the presence of those anions no change was found in the zeolite structure, by X ray diffraction and IR spectroscopy. The retention of cobalt by zeolite ZSM-5 at low concentrations (from 0.001 to 0.3N) was higher when the exchange was done with cobalt nitrate and chloride. This behavior was different in the case of 1N cobalt salts, since the highest sorption uptake was found when working with cobalt acetate and its sorption was directly proportional to its concentration.

Effects of sodium hydroxide treatment on coordination changes of cobalt ions in CoNaY by means of UV/VIS diffuse reflectance spectroscopy

The coordination changes of Co2+ in CoNaY/NaOHs, prepared by cobalt ion-exchange and treatment with NaOH, during dehydration at various temperatures have been investigated by UV/VIS diffuse reflectance spectroscopy. After dehydration of CoNaY/NaOHs at 473 K, the DRS bands show the formation of mixed cobalt oxide species interacted with lattice oxygen. This mixed cobalt oxide species interacted with lattice oxygen decompose during further dehydration at 673 K. The strong intensities of the bands at 660, 575 and 530 nm after dehydration of CoNaY/NaOHs at 873 K indicate that a considerable amount of the cobalt ions remains in the sodalite cage with tetrahedral coordination even after dehydration at 873 K.

Studies of a Hydrous Tin(IV) Oxide Ion Exchanger. VI. Rate of the Isotopic Exchange of Cobalt Ions between the Exchanger in the Cobalt Form and Aqueous Solutions

Abstract The isotopic exchange rate of cobalt ions between a hydrous tin(IV) oxide ion exchanger and aqueous solutions was radiochemically measured in order to obtain fundamental data which could be useful for elucidating the ion-exchange kinetics of the material for the transition metal elements. This rate can be understood by considering that the cobalt in an exchanger exists as three species: (A1) dissociated ions which can diffuse in the exchanger particles; (A2) weakly bound ions to the exchange sites, which are in local equilibrium with A1; and (B) covalently fixed ions to the exchange sites, which are exchanged very slowly with A1. At a small ratio of the amount of B to the total amount of cobalt sorbed on the exchanger, the rate is controlled by the diffusion of A1, with effective diffusion coefficient, \barDeff, a value which depends on the concentration ratio of A2 to A1. When B predominates over A, the concentration ratio of B to A1 greatly affects \barDeff. The values of \barDeff and their activation energy (20 kJ mol−1) were also estimated.

Infrared studies on the acidity of metal impregnated ZSM-5

The Brönsted and Lewis acidity of ZSM-5 supported catalysts containing iron or cobalt is investigated by the characterization of chemisorbed pyridine with infrared spectroscopy. The impregnation of cobalt or iron from aqueous or acetone solutions of metal nitrates causes a redistribution of the relative number of Brönsted and Lewis acid sites in the ZSM-5. This redistribution is postulated to be the result of ion-exchange of cobalt or iron ions for acidic protons within the channels of the ZSM-5. Preparing iron on ZSM-5 by physically mixing Fe 2O 3 with the ZSM-5 causes no acidity redistribution and hence no ion-exchange.

Kinetic studies of ion-exchange of cobalt(II) and nickel(II) on a resin loaded with 5-sulpho-8-quinolinol

The mechanism of ion-exchange of cobalt(II) and nickel(II) on a resin loaded with 5-sulpho-8-quinolinol has been studied, and the chelate-forming reaction in the resin matrix shown to be rate-determining. The observed rate seems to be related to the rate of water-exchange with the metal ion in the aqueous phase, suggesting that complexation in the resin matrix may proceed according to the Eigen mechanism.

The ion-exchange of cobalt(II) in synthetic zeolite linde 4A

The ion-exchange of cobalt(II) in synthetic zeolite linde 4A