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The development of Na-ion full cells (NIFCs) suffers from the issue that the solid electrolyte interphase formation on the carbon anode consumes the limited sodium from cathode and thus incurs the decreased energy density and poor cyclic stability. To address these issues, we herein report that Na2O2 could be used as a sacrificial Na source through spraying its slurry on the surface of cathode, and investigate its stability as well as electrochemical behavior toward NIFCs. The results show that Na2O2 has good chemical and storage stability under a dry atmosphere and has no negative effect on the electrochemical performance of the cathode. Compared with the pristine cathode, the Na2O2-decorated cathode exhibits higher discharge capacity, superior capacity retention, and rate capability in a full cell with a carbon anode. Our cathode Na compensation strategy provides an effective avenue to make up for the irreversible Na+ loss cause by the formation of solid electrolyte interphase on the anode, thereby promoting the electrochemical performance and energy density of NIFCs toward the large-scale application.

Understanding the movement of fluids in the solid Earth system is crucial for answering a wide range of important questions in Earth science. Boron (B) is a perfect tracer for geofluids because of its high solubility and large isotopic fractionation that depends on both temperature and alkalinity. However, the high volatility of boron in acidic solutions at moderate temperatures presents a significant challenge for accurate measurements of the boron concentration and boron isotopic ratios for silicate rock samples. To circumvent this problem, most laboratories use low-temperature dissolution methods that involve concentrated hydrofluoric acid with or without mannitol. However, hydrofluoric acid is highly hazardous and the controlled temperature condition may be difficult to monitor. As a result, relatively few silicate samples have been analyzed for high precision B concentration and isotopic composition measurements, which hinders our understanding of the behavior of B in the solid earth system and the utility of this powerful tracer. Here we report B concentrations and isotopic compositions of the most commonly used geological reference standards dissolved through sodium peroxide sintering and purified using a rapid single-column exchange chromatographic procedure. This streamlined method effectively removes Na and Si from the sample matrix and generates accurate B concentration and isotopic data in as little as a day without the need for expensive lab equipment and reagents. Sintering is already routinely used to dissolve zircon-bearing silicate samples as it ensures complete dissolution. Besides the analysis of boron, other elemental and isotopic analyses can be performed using aliquots of the same dissolution, which greatly speeds up the chemical processing time and reduces uncertainties associated with sample heterogeneity. Using this method, large amounts of material can be processed for ion-exchange chromatography without the need of splitting each sample into separate beakers for dissolution as is often required for the HF + mannitol dissolution method. This new method can rapidly expand the available dataset of the boron concentration and boron isotopes of silicate materials which will certainly advance our understanding of many geologic problems involving fluids.

A novel strategy for selective recovery of chromium from ferronickel slag via microwave assisted sodium peroxide roasting followed by water leaching was proposed in this study. The experimental results showed that 94.21% of chromium was leached with 64.43% of sodium and 6.13% of silicon, while only 0.06 wt% chromium remained in the leaching residue when the mixture of ferronickel slag and sodium peroxide with the mass ratio of 1 was roasted at 600 °C for 20 min before leaching at 50 °C for 1 h with the liquid-to-solid ratio of 10 mL/g. In comparison with conventional roasting, the microwave roasting showed a much higher efficiency for recovering chromium from ferronickel slag with the recovery of chromium increased by 12.92%, resulting from the enhanced conversion of Cr2O3 in the slag to NaCrO2 and from the looser and more porous structure during the roasting process which was beneficial for subsequent water leaching.

Metal-air batteries have attracted extensive research interests due to their high theoretical energy density. However, most of the previous studies were limited by applying pure oxygen in the cathode, sacrificing the gravimetric and volumetric energy density. Here, we develop a real sodium-"air" battery, in which the rechargeability of the battery relies on the reversible reaction of the formation of sodium peroxide dihydrate (Na2O2·2H2O). After an oxygen evolution reaction catalyst is applied, the charge overpotential is largely reduced to achieve a high energy efficiency. The sodium-air batteries deliver high areal capacity of 4.2 mAh·cm-2 and have a decent cycle life of 100 cycles. The oxygen crossover effect is largely suppressed by replacing the oxygen with air, whereas the dense solid electrolyte interphase formed on the sodium anode further prolongs the cycle life.

Microwave technology is being increasingly explored in metallurgical processes. The dielectric properties characterize the action mechanism between electromagnetic energy and minerals. Here, a cavity perturbation method was used to survey the dielectric properties of zinc sulfide concentrate with sodium peroxide additive from 20°C to 600°C at 2.45 GHz. The effects of sodium peroxide additives and temperature on the dielectric properties were investigated. Theoretical analyses showed that the zinc sulfide concentration could be heated quickly when the concentration of sodium peroxide was greater than or equal to 6 wt.%. The heating mechanism is mainly Joule heat loss caused by ionic conduction of sodium peroxide. The heating rate comes from energy conversion and heat conduction at temperatures higher than 400°C. Microwave heating experiments and phase formation verified the correctness of the theoretical analyses. The results provide a better understanding of the microwave roasting mechanism of zinc sulfide concentrate, but also support the use of sodium peroxide as a means to promote thermochemical treatments by microwave irradiation.

The most common method for gold content determination in raw materials is fire assay. An alternative to this method is atomic absorption in a solution obtained by dissolving an initial sample in aqua regia. This study focuses on the sludge of one of the chemical plants, in which the barite concentrate (barium in sulphate form) is fused with calcium chloride at coal presence, and then leached in water. Decomposition of samples in aqua regia followed by atomic absorption analysis, as well as fire assay, showed gold content in the sludge at the level of 1-4 gram per ton. The presence of infusible and chemically resistant compounds in the sludge does not allow to the reliable determination of the gold content. Sintering with sodium peroxide for decomposition of stable compounds at 700 ∘ C, dissolution of sinter in acidic solution, evaporation and fire assay of residue made it possible to establish a reliable concentration of gold in the sludge - 10-20 gram per ton. It was found that a direct determination of gold in acidic sinter leach solution provides inadequate values associated with the influence of the background. Keywords: Gold determination, barium sludge, fire assay, atomic absorption

Recently we have highlighted the importance of hypergolic reactions in carbon materials synthesis. In an effort to expand this topic with additional new paradigms, herein we present novel preparations of carbon nanomaterials, such-like carbon nanosheets and fullerols (hydroxylated fullerenes), through spontaneous ignition of coffee-sodium peroxide (Na2O2) and C60-Na2O2 hypergolic mixtures, respectively. In these cases, coffee and fullerenes played the role of the combustible fuel, whereas sodium peroxide the role of the strong oxidizer (e.g., source of highly concentrated H2O2). The involved reactions are both thermodynamically and kinetically favoured, thus allowing rapid product formation at ambient conditions. In addition, we provide tips on how to exploit the released energy of such highly exothermic reactions in the generation of useful work.

Sodium–oxygen battery cathodes utilise the reversible redox species of oxygen in the presence of sodium ions. However, the oxygen reduction and evolution reaction mechanism is yet to be conclusively determined. In order to examine the part played by surface structure in sodium–oxygen electrochemistry for the development of catalytic materials and structures, a method of preparing clean, well-defined Pt electrode surfaces for adsorption studies in aprotic solvents is described. Using cyclic voltammetry (CV) and in situ electrochemical shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS), the various stages of oxygen reduction as a function of potential have been determined. It is found that on Pt{111} and Pt{110}-(1 × 1) terraces, a long lived surface sodium peroxide species is formed reversibly, whereas on Pt{100} and polycrystalline electrodes, this species is not detected.

It is known that most of the refractory ore are the basis of national economy and widely applied in various fields, however, the complexity of the chemical composition and the diversity of the crystallinity in the mineral phases make the sample pre-treatment of refractory ore still remains a challenge. In this work, the complete decomposition of the refractory ore sample can be achieved just by exposing the solid fusion agent and the refractory ore sample in the microwave irradiation environment for a few minutes, and induced by a drop of water. A digestion time of 15 min for 3.0 g solid fusion agent mixture of sodium peroxide/sodium carbonate (Na2O2/Na2CO3) in a corundum crucible via microwave heating is sufficient to decompose 0.1 g refractory ore sample. An excellent microwave digestion solid agent should meet the following conditions, a good decomposition ability, an outstanding ability of absorbing microwave energy and converting it into heat quickly, a higher melting point than the decomposing temperature of the ore sample. In the research, the induction effect of water plays an important role for the microwave digestion. The energy which is released by the reaction of water and the solid fusion agent (Na2O2) is the key to decompose refractory ore samples with solid fusion agent, which replenished the total energy required for the microwave digestion and made the microwave digestion completed successfully. This microwave digestion technique has good reproducibility and precision, RSD % for Mo, Fe, Ti, Cr and W in the refractory ore samples were all better than 6, except RSD % for Be of about 8 because of the influence of matrix-effect. Meanwhile, the analysis results of the elements in the refractory ore samples provided by the microwave digestion technique were all in good agreement with the analysis results provided by the traditional fusion method except for Cr in the mixture ore samples. In the study, the non-linear dependence of the electromagnetic and thermal properties of the solid fusion agent on temperature under microwave irradiation and the selective heating of microwave are fully applied in this simple microwave technique. Comparing to the traditional fusion decomposition method, this microwave digestion technique is a simple, economical, fast and energy-saving sample pre-treatment technique.

pH is a fundamental parameter in understanding the chemical processes in many fields. Based on the strong oxidative characteristic of the molten lithium carbonate (Li2CO3), an advanced iridium oxide electrode preparation approach is developed by adding sodium peroxide (Na2O2) powder into a Li2CO3 melt in a semi-closed/closed reactor at a high temperature to increase the regional peroxide (O22−) ion concentration in the iridium-melt interface. The iridium oxide film (IROF) of prepared electrodes has a dense and uniform surface with small and cone-shaped particles. Open-circuit tests show that electrodes exhibit a near-Nernstian pH response with good linearity, fast response, high stability (a slight periodic fluctuation of potential change with standard deviation

When sodium (Na)–oxygen (O2) batteries discharge, O2 is reduced on the cathode to form solid sodium oxides deposited on cathode, severely impeding the mass transfer path and causing large voltage polarization, low energy efficiency and poor rate performance. Therefore, a novel cathode is the key to solving the above issues. Here, in-situ growing molybdenum disulfide on carbon cloth (MoS2/CC) as a binder-free cathode is prepared by a simple and facile hydrothermal method. When this cathode is tested in Na–O2 batteries, it presents enhanced oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activity as well as large discharge capacity. What's more, Na–O2 batteries with the MoS2/CC cathode simultaneously produce sodium superoxide (NaO2) and poor crystalline sodium peroxide (Na2O2), which greatly reduces the charge potential.

Stabilizing superoxide (O2−) is one of the key issues of sodium-air batteries because the superoxide-based discharge product (NaO2) is more reversibly oxidized to oxygen when compared with peroxide (O22−) and oxide (O2−). Reversibly outstanding performances of sodium-oxygen batteries have been realized with the superoxide discharge product (NaO2) even if sodium peroxide (Na2O2) have been also known as the discharge products. Here we report that the Lewis basicity of anions of sodium salts as well as solvent molecules, both quantitatively represented by donor numbers (DNs), determines the superoxide stability and resultantly the reversibility of sodium-oxygen batteries. A DN map of superoxide stability was presented as a selection guide of salt/solvent pair. Based on sodium triflate (CF3SO3−)/dimethyl sulfoxide (DMSO) as a high-DN-pair electrolyte system, sodium ion oxygen batteries were constructed. Pre-sodiated antimony (Sb) was used as an anode during discharge instead of sodium metal because DMSO is reacted with the metal. The superoxide stability supported by the high DN anion/solvent pair ($${{\rm{CF}}}_{3}{{\rm{SO}}}_{3}$$ CF 3 SO 3 –/DMSO) allowed more reversible operation of the sodium ion oxygen batteries.

A protocol based on peroxide fusion has been developed for the determination of Au in metallurgical samples and ores covering a wide range of concentrations and diverse mineralogies. The quantity of Na2O2 required was minimised, while maintaining lixiviant efficacy, by the use of mixed NaOH + Na2O2 fluxes. The method was shown to be particularly applicable to the determination of coarsely-particulate gold. Fusion cakes were dissolved in hydrochloric acid and then extracted using methylisobutylketone to provide concentrations appropriate for quantification by graphite furnace atomic absorption spectroscopy and to minimise interferences from dissolved salts. The protocol was tested on a variety of certified reference materials and produced results in excellent agreement (at Au concentrations ranging from 0.05 to 47 μg g− 1) with the traditional lead fire assay method, while avoiding the health and safety issues associated with that technique.

The development of Na–O2 batteries requires understanding the formation of reaction products, as different groups reported compounds such as sodium peroxide, sodium superoxide, and hydrated sodium peroxide as the main discharge products. In this study, we used in operando synchrotron radiation powder X-ray diffraction (SR-PXD) to (i) quantitatively track the formation of NaO2 in Na–O2 cells and (ii) measure how the growth of crystalline NaO2 is influenced by the choice of electrolyte salt. The results reveal that the discharge could be divided into two time regions and that the formation of NaO2 during the major part of the discharge reaction is highly efficient. The findings indicate that the cell with NaOTf salt exhibited higher capacity than the cell with NaPF6 salt, whereas the average domain size of NaO2 particles decreases during the discharge. This fundamental insight brings new information on the working mechanism of Na–O2 batteries.

A novel dietary fiber (MsCDF) based core of maize straw (Core) was prepared by using high boiling solvent of sodium peroxide by high pressure pretreatment (HBSHP). The composition of MsCDF, and several physicochemical properties for MsCDF related to its nutritional quality were investigated. The results revealed that the MsCDF contains high contents total dietary fiber (TDF), soluble dietary fiber (SDF), insoluble dietary fiber (IDF) and two main monosaccharaides, xylose and glucose. Meanwhile, the studies of physicochemical properties of MsCDF indicated that MsCDF performed well water-holding capacity (WHC), oil-holding capacity (OHC), Swelling, solubility (SOL), Glucose dialysis retardation index (GDRI) and adsorption capacity on cholesterol. The results of this study serve as evidence that MsCDF can be used as a functional food additive, Core can be used as a crude material to produce MsCDF and the technology of HBSHP can be used to modify the physico-chemical properties of Core.

Sodium‐based catalysts (such as Na2WO4) were proposed to selectively catalyze OH radical formation from H2O and O2 at high temperatures. This reaction may proceed on molten salt state surfaces owing to the lower melting point of the used Na salts compared to the reaction temperature. This study provides direct evidence of the molten salt state of Na2WO4, which can form OH radicals, using in situ techniques including X‐ray diffraction (XRD), scanning transmission electron microscopy (STEM), laser induced fluorescence (LIF) spectrometry, and ambient‐pressure X‐ray photoelectron spectroscopy (AP‐XPS). As a result, Na2O2 species, which were hypothesized to be responsible for the formation of OH radicals, have been identified on the outer surfaces at temperatures of ≥800 °C, and these species are useful for various gas‐phase hydrocarbon reactions, including the selective transformation of methane to ethane.

It is an unsolved problem how to steer between sodium superoxide and sodium peroxide as discharge products in sodium–oxygen batteries. Sodium peroxide yields a higher theoretical energy density; thus, it is preferred in view of maximized energy density. Three novel approaches to form sodium peroxide are presented: First, cells loaded with sodium superoxide are further discharged in argon, with the aim of reducing sodium superoxide to peroxide. Second, carbon nanotube electrodes preloaded with sodium peroxide are utilized. Third, sodium peroxide is dissolved in the electrolyte to enhance precipitation of solid sodium peroxide. Interestingly, all approaches yield sodium superoxide as a discharge product. Thus, it might not be possible to have high energy density sodium–oxygen batteries with sodium peroxide as the discharge product. However, potential pathways for peroxide formation during discharge have been excluded to help to find the true factors that govern the competition between superoxide and peroxide formation.

The CHROMIC project (effiCient mineral processing and Hydrometallurgical RecOvery of by-product Metals from low-grade metal contaIning seCondary raw materials) aims to recover chromium from steelmaking and ferrochrome slags to regain valuable resources and simultaneously reduce potential environmental impacts. To develop the recovery flowsheets and reliably calculate metal recovery, an accurate assessment of chromium concentration and distribution is essential. Therefore, model streams were thoroughly characterized using a combination of analytical techniques. In all materials, chromium is present in distinct but often small spinel phases, intergrown with other minerals and showing a considerable zonation in Cr content with higher amounts in the cores. The small size of the Cr-rich particles makes recovery by mineral processing challenging. Measured chromium content was found to differ largely based on the chemical dissolution method applied. The analysis of insoluble residues and comparison with a standard reference material evidenced that standard acid dissolution procedures based on HCl/HNO3/HBF4 and HNO3/HF/H2O2 are insufficient to fully dissolve spinel structures, leading to severe underestimations of chromium content. A sodium peroxide treatment is required for a full dissolution of spinels. This is noteworthy, since most of the legislation for the reuse of slags is currently based on acid dissolution methods.

High-pressure phase stabilities up to 600 K and the related properties of Na2O2 under pressures up to 300 GPa were investigated using first-principles calculations and the quasi-harmonic approximation. Two high-pressure phases of Na2O2 that are thermodynamically and dynamically stable were predicted consisting of the Amm2 (distorted P2m) and the P21/c structures, which are stable at low temperature in the pressure range of 0–22 GPa and 22–28 GPa, respectively. However, the P2m and Pbam structures become the most stable instead of the Amm2 and P21/c structures at the elevated temperatures, respectively. Interestingly, the softening of some phonon modes and the decreasing of some elastic stiffnesses in the Amm2 structure were also predicted in the pressure ranges of 2–3 GPa and 9–10 GPa. This leads to the decreasing of phonon free energy and the increasing of the ELF value in the same pressure ranges. The HSE06 band gaps suggest that all phases are insulators, and they increase with increasing pressure. Our findings provide the P–T phase diagram of Na2O2, which may be useful for investigating the thermodynamic properties and experimental verification.

Na–O2 batteries have been attracting attention owing to their intrinsically high theoretical energy density. Several Na–O2 systems can produce various discharge products with different electrochemical performances. For example, sodium superoxide (NaO2) batteries have a low overpotential, and sodium peroxide (Na2O2) batteries have a high capacity. Studies of Na2O2 batteries are relatively scarce, owing to the difficulty of forming pure Na2O2 discharge products. A pure Na2O2 battery system is highly desirable for fully exploring the formation and decomposition of Na2O2 in Na–O2 batteries and evaluating their potential. This model of a Na2O2 battery should also be compatible with in situ characterization. To this end, we constructed a simple rechargeable all-solid-state Na2O2 battery. Using a nanoporous gold film as the cathode and Na–β″-Al2O3 as a solid electrolyte, we assembled a Na–O2 battery that can produce and decompose Na2O2. The all-solid-state Na–O2 battery is a simple model for conducting in situ ambient-pressure x-ray photoelectron spectroscopy (APXPS) investigations. The battery can be cycled at a low overpotential (≈450 mV). Qualitative and quantitative analyses of the APXPS and Raman results demonstrated that Na2O2 was the main discharge product and its transformation occurred during the charge and discharge periods. The operando investigation of this type of all-solid-state Na2O2 battery can help in the comprehensive exploration of the potential of Na–O2 batteries.

23Na MAS NMR spectra of sodium–oxygen (Na–O2) cathodes reveals a combination of degradation species: newly observed sodium fluoride (NaF) and the expected sodium carbonate (Na2CO3), as well as the desired reaction product sodium peroxide (Na2O2). The initial reaction product, sodium superoxide (NaO2), is not present in a measurable quantity in the 23Na NMR spectra of the cycled electrodes. The reactivity of solid NaO2 is probed further, and NaF is found to be formed through a reaction between the electrochemically generated NaO2 and the electrode binder, polyvinylidene fluoride (PVDF). The instability of cell components in the presence of desired electrochemical reaction products is clearly problematic and bears further investigation.

Sodium–oxygen batteries have received much attention recently due to their possible higher energy efficiency and lower cost than lithium–oxygen batteries. Na+ ions are less electrophilic than Li+ ions (softer Lewis bases). Thereby, oxygen reduction in the presence of Na+ ions may undergo a highly reversible one electron process to form sodium superoxide as a main product. However, sodium superoxide may have adverse effects on the stability and cycle life of sodium–oxygen batteries because of its high reactivity towards all kinds of relevant solvents. Therefore, sodium–oxygen batteries, in which the major oxygen reduction products are sodium peroxide moieties, may have an advantage in terms of better stability. This paper reports for the first time on sodium–oxygen batteries in which the cathodes comprise carbon nanotubes (CNTs) decorated with nanoparticles of ruthenium serving as a stationary catalyst. With these cathodes both oxygen reduction and evolution reactions are effectively catalyzed. The main oxygen reduction product on these CNT/Ru containing cathodes was deficient sodium peroxide, analyzed by XRD, XPS and SEM. Sodium–oxygen cells with Ru decorated CNT cathodes exhibited stable cycling performance over 100 cycles, while similar cells having CNT based cathodes showed much lower stability. It was clear that the limiting factor in the sodium–oxygen batteries containing CNT/Ru cathodes was the sodium anodes. Thereby it is believed that the present study is a step forward in the efforts to develop sodium–oxygen batteries.

Red mud, an aluminum industry large-scale waste, was used as a precursor to prepare sodium ferrate(VI) and sodium ferrite following different reaction pathways. Ferrous oxalate extracted from red mud has been used as an intermediate for the preparation of these compounds. The conversion rate to sodium ferrate(VI) from ferrous oxalate was as high as 64% in sodium hydroxide solution with sodium hypochlorite. Furthermore, sodium ferrite was formed after performing the solid–solid reaction at 600 °C using a 1:1 weight ratio of iron oxide (prepared via the ferrous oxalate extraction route from red mud) and sodium peroxide. In contrast, sodium iron silicon oxides were formed when red mud was reacted directly, following similar experimental procedures. These results present an interesting alternative to convert an environmentally unfriendly waste to new value-added products. It is envisaged that sodium ferrate(VI) might be of great interest in terms of wastewater treatment, whereas sodium ferrite and NawFexSiyOz might be of interest in the development of new materials for energy storage.

A novel etching solution using molten potassium hydroxide (KOH) for the identification of dislocation types in a silicon-carbide (SiC) epilayer is identified. Threading screw dislocations (TSDs) and threading edge dislocations (TEDs) are rarely useful for size-based differentiation of etch pits in highly nitrogen (N)-doped SiC through conventional KOH etching. In this study, we report the role of sodium peroxide (Na2O2) and potassium dioxide (KO2) as oxidizing agent additives to the etchant for identifying the dislocation types in highly N-doped 4H-SiC. A Na2O2-KOH phase diagram was calculated to predict the chemical composition of the etchant. Solid-phase Na2O2 remained in the system when added to the etchant at concentrations greater than 13-wt% Na2O2, and it provided excess oxygen to the etchant. We experimentally confirmed that etch pit shapes became more hexagonal and that the etch pit sizes of TSDs and TEDs differed more greatly when more than 20-wt% Na2O2 was added to the etchant. We also found that the size distribution of TEDs was much smaller than that of TSDs after etching using Na2O2-KOH. Dissolved oxygen played an essential role in enhancing the anisotropic etching of highly N-doped SiC and allowed the dislocation types to be identified.

Metal air batteries are considered as promising candidates for room-temperature batteries with high-energy densities. On discharge, atmospheric oxygen is reduced at the positive electrode which, in the ideal case, forms the discharge products in a reversible cell reaction. In Na-O 2 batteries upon discharge either sodium peroxide (Na 2 O 2 ) or sodium superoxide (NaO 2 ) is reported to be formed. So far, the charge carrier transport remains relatively unexplored but is expected to crucially determine the efficiency of such energy storage systems. Na 2 O 2 is predicted to be an electrical insulator wherein the transport presumably is determined by very slow hopping processes. Understanding the basic fundamental properties of the overall charge carrier transport, including also nanostructured forms of Na 2 O 2 , is key to developing high-energy metal oxygen batteries. The present study answers the question how overall, i.e. , total, conductivity changes when going from microcrystalline to nanocrystalline, defect-rich Na 2 O 2 . Nanocrystalline Na 2 O 2 was prepared via a top-down approach, viz by high-energy ball milling. Milling does not only shrink the average crystallite diameter but also introduces a large amount of defects which are anticipated to influence total conductivity. It turned out that even after vigorous mechanical treatment the conductivity of the sample is only increased by ca. one order of magnitude. The activation energy remains almost untouched. Thus, the increase seen might be attributed to an enhanced number of charge carriers. Low-temperature data reveals nearly constant loss relaxation behavior which has frequently explained in terms of strictly localized electrical relaxation processes.

The chemical nature of discharge products in nonaqueous Na–O2 batteries attracts attention due to the differing electrochemical behavior of seemingly similar battery cells forming either sodium peroxide (Na2O2) or sodium superoxide (NaO2). The experimental control parameters for the exclusive formation of one or the other phase during discharge are still unknown. In this paper, the important role of gas phase moisture on the chemical nature of these products is demonstrated by means of operando XRD. Operando XRD is rarely reported for alkali-O2 systems but provides valuable real time information about the solid discharge products, growth/decomposition rates, and side reactions in the cell. In addition, the discharge/charge mechanisms of Na2O2·2H2O are monitored in detail evidencing important differences from the cell reactions forming NaO2 and Li2O2 and refuting previous incorrect conclusions. Moreover, the effect of the applied potential window during cycling is discussed, as it provides valuable informa...

In this work silicon dioxide (SiO2) was synthesized from rice husk as raw material. The sodium peroxide (Na2O2) influence as precursor on the catalytic activity of the final product was investigated. α-cristobalite and tridymite phases of SiO2 were matched by X-Ray Diffraction (XRD) and analyzed by Fourier Transform Infrared (FTIR), Raman Spectroscopy (RS), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The XRD Rietveld Refinement showed few changes as function of sodium peroxide added during the processing. The content of tridymite phase determined in the samples, was diminished from 19.3% to 8.5%. The main α-cristobalite SiO2 phase was identified from XRD, FTIR and RS spectra, while EDS results showed characteristic energy peaks due to the presence of oxygen and silicon, as expected. Particles and cavities in micrometric range were observed at the samples by SEM. However, smooth surfaces were well defined in other samples. The final morphology depending on the amount of sodium peroxide added. The SiO2 produced powder is suitable for the processing of silicon, silicon oxide as well as silicon nitrides thin films.

An efficient process for recycling Eu from BaMgAl11O19: Eu3+ (BAM) waste phosphors has been developed. The treatment of BAM by the sodium peroxide (Na2O2) calcining process followed by acid leaching was investigated. The results demonstrated that the calcination temperature and time more significantly influence the recovery efficiencies of metals than does the mass ratio of Na2O2 to BAM. More than 99% of Eu was recovered under the optimal conditions of 425 °C, mass ratio 1:1 and 30 min duration. The decomposition kinetics of BAM were studied using a series of typical solid-solid reaction kinetic models. The apparent activation energies Ea for the decomposition reactions of Eu, Ba, Al and Mg were calculated as 52.3 kJ/mol, 64.6 kJ/mol, 87.1 kJ/mol and 88.9 kJ/mol, respectively. XRD analysis indicated that the decomposition of BAM involved a multistep reaction. The reaction mechanism was also analyzed at the crystal structure level, which indicated that Ba and Eu atoms in the mirror plane of the unit cell of BAM were replaced by Na from Na2O2 at the beginning, and that BaO2 and Na2MgAl10O17 were produced. Then, Na2MgAl10O17 was decomposed to NaAl7O11 and MgAl2O4, and finally, NaAlO2, MgO, BaCO3 and Eu2O3 were generated at a higher temperature (600 °C). SEM and EDS analysis also demonstrated the proposed substitution and decomposition reactions. This work is expected to open new avenues and provides a theoretical basis for the highly efficient recovery of Eu from waste rare earth phosphors.

Thermal Ionization Mass Spectrometry (TIMS) has been evaluated for the detection of the radioactive isotopes of Sr and Cs. The commercial instrument (i.e., a Thermo Scientific Triton) was investigated for the analysis of isotopic ratios of 89Sr/90Sr and 135Cs/137Cs in the presence of atomic isobars (89Y and 90Zr for 89,90Sr analysis and 135,137Ba for 135,137Cs analysis). The decontamination achievable instrumentally was examined by isotopic ratio measurements of 89Y/88Sr and 90Zr/88Sr for Sr and 135Ba/133Cs and 137Ba/133Cs for Cs. The decontamination found was at or above 2.0E+8 for 90Zr from 88Sr, while the Y demonstrated a temperature dependence as it sublimed from the filament but remained better than ≈ 5E+7. The decontamination of Ba from Cs did not show any temperature dependence and remained above 5E+6 and 8E+6 for 135Ba and 137Ba from 133Cs, respectively. Two standard fusion procedures one with sodium hydroxide (NaOH) plus sodium peroxide (Na2O2) flux, and the second used lithium tetraborate (Li2B4O7) plus lithium metaborate (LiBO2) flux were evaluated for preparation of sample matrices prior to performing chemical separations. Ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) and Sr-spec resin were used to isolate the Cs and Sr, respectively from a prepared background matrix (i.e., Montana Soil). A graded approach, increasing in stable background isotopes, was performed to monitor the chemical and instrumental response. The radioisotopes of Sr and Cs were produced by thermal neutron irradiation of a highly enriched uranium foil. Even though the irradiated sample was not a certified standard it does provide accurate expectation values via the published cumulative fission yield nuclear data in the Evaluated Nuclear Data Files (ENDF) [ 1 ]. The intra-element isotopic ratio results presented in this work for 89Sr/90Sr and 135Cs/137Cs agree with the published data at 1σ. Furthermore, the uncertainty of the isotopic ratio measurements with TIMS was a factor of 5–10 improved compared to these published values.

The sodium oxygen battery is a promising metal-air battery; however, the discharge process is not well understood and the major discharge product is still under debate. The discharge products determined the theoretical specific energy and electrochemical performance of the battery. Now it is demonstrated that NaO2 spontaneously disproportionates to Na2 O2 , no matter whether it is dissolved in solution or stays on the surface. The behaviors of NaO2 in solution and on the surface are different. Solvents play a crucial effect on the disproportionation of dissolved NaO2 species, which is fast in low donor number (DN) solvents such as acetonitrile but sluggish in high DN solvents such as DMSO. In situ XRD results exhibited the different product growing processes in various solvents. Surface NaO2 would slowly disproportionate to Na2 O2 anyway, but this process is relatively slow compared to the time span of discharge process and it does not affect the major product on discharge.

Understanding the oxygen reduction reaction kinetics in the presence of Na ions and the formation mechanism of discharge product(s) is key to enhancing Na-O2 battery performance. Here we show NaO2 as the only discharge product from Na-O2 cells with carbon nanotubes in 1,2-dimethoxyethane from X-ray diffraction and Raman spectroscopy. Sodium peroxide dihydrate was not detected in the discharged electrode with up to 6000 ppm of H2O added to the electrolyte, but it was detected with ambient air exposure. In addition, we show that the sizes and distributions of NaO2 can be highly dependent on the discharge rate, and we discuss the formation mechanisms responsible for this rate dependence. Micron-sized (∼500 nm) and nanometer-scale (∼50 nm) cubes were found on the top and bottom of a carbon nanotube (CNT) carpet electrode and along CNT sidewalls at 10 mA/g, while only micron-scale cubes (∼2 μm) were found on the top and bottom of the CNT carpet at 1000 mA/g, respectively.

The primary discharge product in sodium–air batteries has been reported in some experiments to be sodium peroxide, Na2O2, while in others sodium superoxide, NaO2, is observed. Importantly, cells that discharge to NaO2 exhibit low charging overpotentials, while those that discharge to Na2O2 do not. These differences could arise from a higher conductivity within the superoxide; however, this explanation remains speculative given that charge transport in superoxides is relatively unexplored. Here, density functional and quasi-particle GW methods are used to comparatively assess the conductivities of Na–O2 discharge phases by calculating the concentrations and mobilities of intrinsic charge carriers in Na2O2 and NaO2. Both compounds are predicted to be electrical insulators, with bandgaps in excess of 5 eV. In the case of sodium peroxide, the transport properties are similar to those reported previously for lithium peroxide, suggesting low bulk conductivity. Transport in the superoxide has some features in co...

Metal-air batteries have become promising candidates for modern energy storage due to their high theoretical energy density in comparison to other storage devices. The lower overpotential of Na compared with Li makes Na-air batteries more efficient in terms of battery lifetime. Additionally, the abundance of Na over Li is another advantage for Na batteries compared to Li batteries. Na2O2 is one of the main products of sodium-air battery reactions. The efficiency of air cells is always related to the charge transport mechanisms in the formed product. To unveil these diffusion mechanisms in one of the main products of the cell reaction Na-O2 we systematically investigate the mobility of charge carriers as well as the electronic structural properties of sodium peroxide. The framework of the density functional theory based on hybrid functional approach is used to study the mobility of charge carriers and intrinsic defects in Na2O2. Our calculations reveal that the formation of small electron and hole polarons is preferentially occurring over the delocalized state in the crystal structure of Na2O2. The migration of these small polarons displays activation energies of about 0.92 eV and 0.32 eV for the electron and hole polarons respectively, while the analysis of the charged sodium vacancy mobility reveals an activation energy of about 0.5 eV. These results suggest that the charge transport in sodium peroxide would mainly occur through the diffusion of hole polarons.

The objective of this research is to develop a kinetic model to describe the transesterification of soybean oil with methanol using NaOH-impregnated calcined oyster shell (Na-COS). Batch experiments were performed via a two-factor randomized complete block design using a molar ratio of methanol to oil (MR) of 6, 12, and 18 and catalyst loadings (CL) (mass of catalyst/mass of oil in %) of 2%, 4%, 6%, and 8% to obtain fatty acid methyl ester yields. In addition, the catalyst was studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion spectrometry (TOF-SIMS) to elucidate the role of the catalyst in the transesterification reaction. XRD and XPS analyses suggested that the formation of sodium peroxide (Na2O2) on the surface contributed to catalytic activity. The TOF-SIMS analysis suggested that the transesterification occurred between adsorbed triglyceride and free methanol, similar to the Eley-Rideal mechanism. The transesterification of adsorbed triglyceride to adsorbed diglyceride was found to be the rate-determining step with a rate constant of 0.0059 ± 0.0002 L mol−1 min−1.

A novel method for simultaneous determination of ruthenium and zinc in catalysts for hydrogenation of benzene to cyclohexene was established by inductively coupled plasma optical emission spectrometry after sample digestion by high temperature fusion with Na2O2. Such experiment conditions were investigated as the influence of sample digestion methods, fusion time, fusion temperature, the dosage of Na2O2and interfering ions on the determination. Under the optimized conditions, the limits of detection (LODs) of Ru and Zn for tested solutions were 11 and 13 ng mL-1, respectively. The relative standard deviations (RSDs) for Ru and Zn were 2.01 and 2.35 % (CRu, Zn= 1 mg L-1, n = 7), respectively. The linear ranges of calibration graphs for Ru and Zn were 0.05 ~ 100.00 mg L-1and 0.04 ~ 50.00 mg L-1, respectively. The proposed method was applied to determine catalyst samples with good recoveries and satisfactory results.

The bonding and structures of sodium oxides complexes, Na +/0 ·(O 2 ) n , were studied at various levels of density functional theory (DFT). The neutral sodium complexes have stronger binding energies than those of cationic sodium complexes. The mono-ligated complex exhibited the shortest Na–O distance and the strongest bond dissociation energy in these two sets of complexes. In addition, the neutral and cationic sodium complexes have identical sequential bond dissociation energy trends that are highly dependent on the strength of the electrostatic interaction within the complex.

The corrosion-electrochemical behavior of a nickel electrode is studied in the melt of lithium, sodium, and potassium (40: 30: 30 mol %) carbonates in the temperature range 500-600°C under an oxidizing atmosphere CO2 + 0.5O2 (2: 1), which is partly replaced by gaseous chlorine (30, 50, 70%) in some experiments. In other experiments, up to 5 wt % chloride of sodium peroxide is introduced in a salt melt. A change in the gas-phase composition is shown to affect the mechanism of nickel corrosion. © 2013 Pleiades Publishing, Ltd.

Changes in the diffuse reflectance spectra of titanium-dioxide micropowders (initial, modified by nanoparticles, treated with oxidants such as potassium peroxoborate and sodium peroxide, or ultraviolet irradiated in an oxygen atmosphere) in the range 0.3–2.1 μm after irradiation with ultraviolet light, electrons, or protons are analyzed. The general and distinctive features of changes in the spectra in the visible and near infrared regions are revealed and an explanation of the obtained data is proposed.

International audience; The microstructure and chemical composition of the discharge products generated in sodium-oxygen batteries are analyzed by transmission X-ray microscopy (TXM) revealing a complex architecture. Unexpectedly, sodium peroxide is detected in the cubic-shaped discharge deposits associated with the often reported sodium superoxide. Analyses on the product distribution show a surface layer rich in decomposition products in contact with an O-deficient region enclosing the bulk of these cubes. In addition, we show that oxygen evolution reaction (OER) occurs by a process that involves oxidation and re-dissolution of the bulk fraction, leading to a contraction of the discharge particles and a composition similar to that found in the intermediate phase of the deposits observed at the end of discharge. All these solid compounds are eventually removed at the end of recharge, but formation of these structures evidence possible irreversible pathways that need to be considered for the cycle life improvement.

The Solid Oxide Membrane (SOM) process for magnesium production involves the direct electrolysis of magnesium oxide for energy efficient and low-carbon magnesium production. In the SOM process, magnesium oxide is dissolved in a molten oxy-fluoride flux. An oxygen-ion-conducting SOM tube, made from yttria stabilized zirconia (YSZ), is submerged in the flux. The operating life of the electrolytic cell can be improved by understanding degradation processes in the YSZ, and one way the YSZ degrades is by yttria diffusion out of the YSZ. By adding small amounts of YF3 to the flux, yttria diffusion can be controlled. The diffusion of yttria into the flux was quantified by determining the yttria concentration profile as a function of immersion time in the flux and distance from the flux-YSZ interface. Yttria concentrations were determined using x-ray spectroscopy. The diffusion process was modeled using a numerical approach with an analytic solution to Fick’s second law. These modeling and experimental methods allowed for the determination of the optimum YF3 concentration in the flux to minimize yttria diffusion and improve membrane stability. Furthermore, the effects of common impurities in magnesium ores, such as calcium oxide, silica, and sodium oxide/sodium peroxide, on YSZ stability are being investigated.

The chemistry of the discharge products of metal–oxygen batteries is related to the battery's efficiency but knowledge of their formation mechanism is incomplete. Now, the initial discharge product in sodium–oxygen batteries is shown to be sodium superoxide, which undergoes dissolution and then transforms to sodium peroxide dihydrate.

The superoxide based Na–O2 battery has circumvented the issue of large charge overpotential in Li–O2 batteries; however, the one-electron process leads to limited capacity. Herein, a sodium peroxide based low-overpotential (∼0.5 V) Na–O2 battery with a capacity as high as 7.5 mAh/cm2 is developed with Pd nanoparticles as catalysts on the cathode.

UDC 544.971: 544.03 Using a linear combination of atomic orbitals within the CRYSTAL09 software code, the oscillation frequencies of the atoms of lithium, sodium, and potassium peroxides are calculated. In a quasiharmonic approximation of the Debye model, the thermodynamic potentials, entropy, thermal capacity, and the coefficient of thermal expansion are calculated, and their dependence on pressure and temperature is investigated. Using sodium peroxide as an example, the critical point for the sublimation process is found.

Lauroyl chloride is synthesized by the reaction of phosphorus trichloride and lauroyl acid. It is, in turn, oxidized by a toluene solution of hydrogen peroxide and sodium peroxide to manufacture lauroyl peroxide (LPO). As a retrospective case, a cleaning drum exploded during transfer of the toluene layer including LPO to the filter after separation of the aqueous phase. It is speculated that plant managers did not fully apprehend the hazardous decomposition of LPO, or could not make operators understand it. This study investigated the reaction hazards in the manufacturing process to forestall explosion in the manufacturing of LPO by differential scanning calorimetry (DSC) and TSS model simulations.

In this article, Fe3O4 nanoparticles (2.2 -12.1 nm) were prepared by partial oxidation of Fe2+ ion using sodium peroxide as oxidizing agent in the presence of ammonium hydroxide and ammonium oleate as precipitating reagent and capping agent, respectively. The synthesized products were characterized by XRD, LLS, EDX, TEM, FTIR and chemical analysis. The main effective factors on the formation of smaller average particle size of Fe3O4 nanoparticles were optimized using the L8 Taguchi experimental design. The magnetic behavior of Fe3O4 nanoparticles was determined using vibrating sample magnetometer (VSM) at 300 K.

A method has been developed for the analysis of rare earth elements (REEs) in kimberlite samples using inductively coupled plasma mass spectrometer (ICP-MS). The samples were dissolved using sodium peroxide fusion and after appropriate dilutions the solutions were analyzed using ICP-MS. The paper presents the concentration of rare-earth elements as determined by ICP-MS in eight kimberlite samples from Central India. The method was validated using certified reference materials STSD-1 and STSD-2 from Canadian Certified Reference Material Project. The method detection limit of various REEs varies from 0.12 to 1.54 mg kg−1. The total REE concentrations range from 418 to 726 mg kg−1 and fall within the interval of those reported in the literature for kimberlites. Despite the marked difference in the REE contents, all the analyzed samples show similar REE patterns that resemble those for kimberlites. In order to compare ICP-MS results, the samples were analyzed using instrumental neutron activation analysis which is a reference method for determination of REEs in geological samples.

The effect of temperature, the gas phase composition, and the addition of sodium peroxide on the corrosion behavior of a Kh30N45YuT alloy and 20Kh23N18 steel in a eutectic Li2CO3-K2CO3 melt is studied by measuring the corrosion potential and during steplike anode polarization.