Inductively-coupled Plasma Atomic Emission Research Articles

Seasonal Variation in Fluoride Content in Groundwaters of Langtang Area, Northcentral Nigeria

Abstract Thirty groundwater samples were collected at the peak of the rainy season and analysed for fluoride and other cations and anions in drinking water sources of Langtang area. For comparative purposes, thirty seven groundwater samples were collected in the dry season. The aim of the study was to determine variation in fluoride content with respect to the seasons. Fluoride in water was determined by the Ion Selective Electrode (ISE) and the cations by the Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The anion (sulphate) was determined by Multi – Ion Colorimeter, bicarbonate and chloride by titration method. In addition fluorine content in aquifer materials from a borehole section were determined by Fusion method. The two seasons show variation in content of fluoride in groundwater. Fluoride content in groundwater is higher in the dry season ranging from 0.13 – 10.3 mg/l compared to the 0.06 – 4.60 mg/l values in the rainy season. Content of fluorine (0.01 wt %) in the aquifer materials (sands) is low from depth of 0 to 7.95 m. However, fluorine content increases with depth, from 7.95 to 10.60 m with concentration of 0.04 wt %, 0.05 wt % from 10.60 to 13.25m, and 0.07 wt % from 13.25 to 15.70 m, the content of fluorine however, decreased at depth 15.70 to18.55m with concentration of 0.02 wt % even with fluorite mineral in the aquifer material at this depth. Dilution of fluoride ion as a result of rain input which recharges the aquifer may be the main reason for lower values recorded in the rainy season. Over fifty and sixty percent of waters in both dry and rainy season have fluoride concentration above the WHO upper limit of 1.5 mg/l. Consumption of these elevated values of fluoride in groundwater of the study area, clearly manifests as symptoms of dental fluorosis.

Effect of Calcium Oxide on the Crushing Strength, Reduction, and Smelting Performance of High-Chromium Vanadium–Titanium Magnetite Pellets

The effect of calcium oxide on the crushing strength, reduction, and smelting performance of high-chromium vanadium–titanium magnetite pellets (HCVTMP) was studied in this work. The main characterization methods of an electronic universal testing machine (EUTM), X-ray fluorescent (XRF), inductively-coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), and scanning electron microscope-energy disperse spectroscopy (SEM-EDS) were employed. The crushing strength was affected by the mineral phases generated during oxidative baking and the subsequently-formed pellet microstructures owing to CaO addition. The reduction and smelting properties of HCVTMP with different CaO additives were measured and characterized with different softening-melting-dripping indices. Although HCVTMP showed the highest crushing strength with CaO addition of ca. 2 wt %, more CaO addition may be needed to achieve high permeability of the furnace burdens and a good separation condition of the slag and melted iron. In the formation process of the slag and melted iron, it can be determined that CaO could have a relationship with the transformation behavior of Cr, V, and Ti to some extent, with respect to the predominant chemical composition analysis of ICP-AES and XRF. With the microscopic examination, the restraining formation of Ti(C,N) and the promoting formation of CaTiO3 are in accordance with the improved melting-dripping indices, including the decrease of the maximum external static load and gas permeability, and the increase of the melting-dripping zone and dripping difficulty.

Au-Ni nanoparticles: Phase diagram prediction, synthesis, characterization, and thermal stability

The Au-Ni nanoparticles (NPs) were prepared by oleylamine solvothermal synthesis from metal precursors. The Au-Ni phase diagram prediction respecting the particle size was calculated by the CALPHAD method. The hydrodynamic size of the AuNi NPs in a nonpolar organic solvent was measured by the dynamic light scattering (DLS) method. The average hydrodynamic sizes of the nanoparticle samples were between 18 and 25nm. The metallic composition of the AuNi NP samples was obtained by inductively-coupled plasma atomic emission spectroscopy (ICP-OES). The metallic fraction inside AuNi NPs was varied Au-(30–70)wt%Ni. The steric alkylamine stabilization was observed. The individual AuNi NPs were investigated by transmission electron microscopy (TEM). The dry nanopowder was also studied. The structures of the aggregated samples were investigated by scanning electron microscopy (SEM). The AuNi NPs reveal randomly mixed face-centered cubic (FCC) crystal lattices. The phase transformations were studied under inert gas and air. The samples were studied by differential scanning calorimetry (DSC).

Preparation of Salen–Metal Complexes (Metal = Co or Ni) Intercalated ZnCr-LDHs and Their Photocatalytic Degradation of Rhodamine B

Salen–metal complexes (SalenM) were successfully intercalated into ZnCr layered double hydroxides (LDHs) through coprecipitation method, then a series of novel organic–inorganic hybrid materials were obtained. The structure and properties of the materials were thoroughly characterized by inductively-coupled plasma atomic emission spectrometry (ICP-AES), powder X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), and ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS). Meanwhile, with Rhodamine B (RhB) as a target contaminant, the photocatalytic activities of SalenM-intercalated ZnCr-LDHs were investigated and compared with the traditional LDHs (ZnCr-LDHs, ZnCoCr-LDHs, and ZnNiCr-LDHs). Furthermore, the effect of the intercalation amount of SalenM (M = Co or Ni) on the photocatalytic activity was studied. The results showed that when the molar ratio of SalenM to Cr was 0.75, SalenM-intercalated ZnCr-LDHs exhibited significantly higher photocatalytic activities than the traditional LDHs. The degradation rates of RhB reached about 90%, and all of them had good recycling rates. In addition, the kinetics of photocatalytic process and the mechanism of photocatalysis are discussed.

Layer-by-layer fabrication of polydopamine functionalized carbon nanotubes-ceria-palladium nanohybrids for boosting ethanol electrooxidation

The polydopamine functionalized carbon nanotubes-ceria-palladium nanohybrids (Pd-CeO2−x/PDA-CNTs) is fabricated through layer-by-layer synthetic strategy, aiming to integrate the functions of support (PDA-CNTs), metal oxides (CeO2−x) and Pd nanoparticles (NPs). Various instrumental techniques including transmission electron microscopy (TEM), X-ray diffraction (XRD), inductive coupled plasma atomic emission spectrometer (ICP-AES) and X-ray photoelectron spectroscopy (XPS) not only confirm the formation of nanohybrids but also provide the morphology, structure and composition properties of the as-prepared catalysts. As an anode catalyst towards ethanol electrooxidation reaction (EOR) in direct ethanol fuel cells, the Pd-CeO2−x/PDA-CNTs reveals promoted electrocatalytic performance, accelerated kinetics and enhanced stability. Based on the control experiments and related reports, the synergistic action of PDA, CeO2−x and Pd NPs is the key factor for the superior electrochemical behavior of Pd-CeO2−x/PDA-CNTs, which originates from the integration of various components through layer-by-layer synthetic strategy.

Graphene-Based “Core-Shell” Hierarchical Nanostructured Low-Pt Electrocatalysts for Proton Exchange Membrane Fuel Cells

The operation of proton exchange fuel cells (PEMFCs) is bottlenecked by the sluggishness of the oxygen reduction reaction (ORR) [1]. Accordingly, the development of advanced electrocatalysts (ECs) capable to promote the ORR kinetics is one of the main goals of the research. It is further highlighted that, as of today, the only ORR ECs capable to provide PEMFCs with a performance level compatible with applications require a high loading of strategic elements such as platinum-group metals (PGMs), raising critical issues associated with supply shortages and high costs [1]. This work addresses the above points by the development of innovative ECs characterized by the following features: (i) a low loading of PGMs; (ii) an improved ORR activity in comparison with conventional state-of-the-art ECs [2]; (iii) a “core-shell” morphology. In the proposed ECs the “core” support exhibits a hierarchical structure including the following constituents: (i) graphene flakes, to exploit the benefits associated with the large specific surface area and high electron mobility of graphene [3-6]; (ii) carbon black nanoparticles, to further promote the mass and charge transfer processes of the ECs; and (iii) copper nanoparticles, which are introduced as a sacrificial component modulating the EC morphology and the chemical composition of ORR active sites. The hierarchical “core” support is covered by a carbon nitride “shell”, providing “coordination nests” that embed the ORR active sites [7]. The latter are based on a very low loading of Pt (ca. 3 wt% of the EC) and also include Ni and Cu as “co-catalysts”. The proposed L-PGM ECs are obtained customizing the synthetic protocol devised in our research group [7]. In this work, the final ECs are obtained after a post-synthesis activation process carried out by electrochemical cycling, that plays a crucial role to modulate the physicochemical properties and the morphology. Preliminary results indicate that the proposed approach is promising, as the proposed L-PGM ECs exhibit an improved specific and mass activity in comparison with the state of the art (see Figure). The assay of the metals in the L-PGM ECs is evaluated by inductively-coupled plasma atomic emission spectroscopy (ICP-AES). Vibrational spectroscopies (e.g., confocal micro-Raman) and wide-angle X-ray diffraction (WAXD) are adopted to probe the structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM), both conventional and at high resolution, are used to study the morphology. Cyclic voltammetry with the rotating ring-disk electrode method (CV-TF-RRDE) investigates the electrochemical performance and ORR reaction mechanism. Finally, the fuel cell performance in operating conditions is tested on PEMFC prototypes including the proposed L-PGM ECs at the cathode. Acknowledgements This work was funded by the Strategic Project of the University of Padova “From Materials for Membrane-Electrode Assemblies to Energy Conversion and Storage Devices – MAESTRA”. The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement n°696656. REFERENCES [1] I. Katsounaros, S. Cherevko, A. R. Zeradjanin, K. J. J. Mayrhofer, Angew. Chem. Int. Ed., 53, 102 (2014). [2] J. Zhang, Front. Energy, 5, 137 (2011). [3] S. Sharma, B. G. Pollet, J. Power Sources, 208, 96 (2012). [4] M. Liu, R. Zhang, W. Chen, Chem. Rev., 114, 5117 (2014). [5] A. C. Ferrari, F. Bonaccorso, V. Fal’ko et al., Nanoscale, 7, 4587 (2015). [6] J. H. Chen, C. Jang, S. Xiao, M. Ishigami, M. S. Fuhrer, Nature Nanotech., 3, 206 (2008). [7] V. Di Noto, E. Negro, K. Vezzù, F. Bertasi, G. Nawn, The Electrochemical Society Interface, Summer 2015, 59 (2015). Figure 1

Electrochemical Extraction of Holmium and Thermodynamic Properties of Ho-Bi Alloys in LiCl-KCl Eutectic

The electrochemical reduction of Ho (III) on W electrode and liquid Bi film electrode was investigated in LiCl-KCl eutectic by various electrochemical techniques. The reduction reaction of Ho (III) was found to be diffusion-controlled process with three electrons exchanged, which was considered as quasi-reversible. The diffusion coefficient of Ho (III) was determined by cyclic voltammetry and chronopotentiometry. The results of cyclic voltammetry and square wave voltammetry obtained on Bi film electrode exhibited two new reduction peaks at less negative potential than that on W electrode due to the formation of different Ho-Bi intermetallic compounds. Furthermore, the thermodynamic properties on the formation of Ho-Bi intermetallic compounds were measured using open circuit chronopotentiometry in the temperature range from 773 K to 863 K. The electroextraction of holmium was performed on liquid Bi electrode by potentiostatic and galvanostatic electrolysis. The extractive products were characterized by scanning electron microscopy and energy dispersive spectrometry (SEM-EDS) and X-ray diffraction (XRD). It was showed that Ho-Bi alloys consisted of HoBi and Bi phases. The concentration of Ho (III) was monitored by square wave voltammetry and analyzed by inductive coupled plasma atomic emission spectrometer (ICP-AES). The calibration curve was obtained on linear relationship of peak currents and concentration of Ho (III). Meanwhile, the extraction efficiencies were calculated by ICP-AES and calibration curve, respectively, the highest extraction efficiency could reach 95.9% by potenostatic electrolysis at −1.6 V for 27 h.

On-line prediction of sodium content in vacuum packed dry-cured ham slices by non-invasive near infrared spectroscopy

In the present study, non-invasive near infrared spectroscopy (NIRS) was evaluated as a potential on-line analytical technique to predict the sodium content in dry-cured ham slices. Samples of 310 packages were scanned by applying a remote fibre-optic probe to the surface of the slices, at different temperatures, with no previous manipulation. The sodium content of the meat samples was determined by a reference method based on Inductively Coupled Plasma Atomic Emission Spectrophotometry (ICP-AES) after chemical digestion. Partial least squares (PLS) regression was used as a chemometrics method to perform the calibrations. The models yielded acceptable results with cross validation correlation coefficients (R2CV) determined 86.2–90.2%. The prediction capacity reached in the external validation was 3.63, with a standard prediction error of 0.12% Na. These results show that NIR measurements could be implemented on the packaging line of dry-cured ham slices to provide accurate and relevant information about the sodium content of each packaged products.

Electrochemical behaviour of erbium(III) and its extraction on Cu electrode in LiCl-KCl melts

The electrochemical behaviour of Er(III) was studied on W and Cu electrodes in LiCl-KCl melts by a series of electrochemical techniques. The studies indicated that Er(III) ions were reduced to Er(0) in a one-step diffusion-controlled process exchanging three electrons. The diffusion coefficient of Er(III) was determined and the activation energy for diffusion of Er(III) ions was found to be 35.2 kJ mol−1. The equilibrium potential of the Er(III)/Er(0) redox couple was measured via open circuit chronopotentiometry in the temperature range of 773–923 K, with subsequent calculation of the apparent standard potential, EEr(III)/Er(0)∗0, and the apparent Gibbs free energy of formation for ErCl3, ΔGf∗0(ErCl3). The cyclic voltammogram and square wave voltammogram obtained on Cu electrode, compared with those on W electrode, showed several new pairs of reduction peaks observed at more positive potential, which means that the underpotential deposition of erbium occurs. The thermodynamic properties of the Cu-Er intermetallic compound, Cu5Er, were estimated by open circuit chronopotentiometry. Potentiostatic and galvanostatic electrolysis was performed on Cu electrode to extract erbium. The extraction products, consisting of CuEr, Cu2Er and Cu5Er, were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). Furthermore, the extraction efficiencies were evaluated during potentiostatic electrolysis at different electrolysis times using an inductive coupled plasma atomic emission spectrometer (ICP-AES), which showed that the highest extraction efficiency of Er(III) could reach about 98.92%.

Fe-carbon nitride “Core-shell” electrocatalysts for the oxygen reduction reaction

In this report, the preparation of Fe-carbon nitride (CN)-based electrocatalysts (ECs) with a “core-shell” morphology for the oxygen reduction reaction (ORR) is described. The ECs consist of spherical XC-72R carbon nanoparticles, the “cores”, that are covered by a CN matrix, the “shell”, that embeds Fe species in “coordination nests”. The latter consist of hollow cavities in the CN matrix, whose internal surface is covered by N- and C-ligands able to stabilize alloy nanoparticles or active sites. Two families of CN-based ECs are prepared, which are grouped on the basis of the concentration of N atoms in the CN “shell”. Each group comprises of both a “pristine” and an “activated” EC; the latter is obtained from the “pristine” EC by a suitable series of treatments (A) devised to improve the ORR performance. The chemical composition of the CN-based ECs is determined by Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and microanalysis. The thermal stability under both inert and oxidizing atmospheres is gauged by High-Resolution Thermogravimetric Analysis (HR-TGA). The structure is probed by powder X-ray diffraction, and the morphology is inspected by Scanning Electron Microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM). The surface area of the CN-based ECs is determined by nitrogen physisorption techniques, and the surface composition is probed by X-ray Photoelectron Spectroscopy (XPS). The electrochemical performance and reaction mechanism of the CN-based ECs in the ORR is investigated in both acid and alkaline environments by cyclic voltammetry with the Thin-Film Rotating Ring-Disk Electrode setup (CV-TF-RRDE). The influence of the preparation parameters and of the treatments on the physicochemical properties, the ORR performance, and reaction mechanism is studied in detail. In the alkaline environment the FeFe2-CNl 900/CA“core-shell” EC shows a remarkable ORR onset potential of 0.908V vs. RHE which, with respect to the value of 0.946V vs. RHE of the Pt/C ref., classifies the proposed materials as very promising “Platinum Group Metal-free” ECs for the ORR.

Ni doped ZnS nanoparticles as photocatalyst: Can mixed phase be optimized for better performance?

ZnS nanoparticles with Ni2+ as dopant ions, have been synthesized and characterized by X-ray Diffraction, Inductive Coupled Plasma-Atomic Emission spectroscopy and Transmission Electron Microscopy. UV–vis absorption and photoluminescence spectroscopies were employed to investigate different photo-processes occurring on exposure to UV–vis light. The synthesized NPs were evaluated as photocatalyst for the removal of the color of aqueous solution of rhodamine B (RhB) dye as test solution under 250W High Pressure Mercury Vapor lamp. Mott-Schottky, Cyclic Voltammetery, and hot-probe measurements suggest the change in the ‘type’ of semiconductor from n to p as well as phase change (cubic to wurtzite) take place on increasing the amount of dopant to 10%. The newly appeared phase forms ‘local pockets’ in an overall cubic matrix of ZnS NPs, this way created defects at the local grain boundaries of dissimilar phases. These provide active sites for the adsorption of dye molecules, in turn, improve the efficiency of the material as photocatalyst.

Study of in vitro bioactivity and mechanical properties of diopside nano-bioceramic synthesized by a facile method using eggshell as raw material

In this study, diopside bioceramic was synthesized using a mechanical milling process and subsequent heat treatment. The simplicity of experiments and also the high energy available in ball milling lead to rapid synthesis of the products in comparison with other synthesis methods. Magnesium oxide (MgO), silicon dioxide (SiO2) and eggshell (as the calcium source) powders were weighted in stoichiometric conditions and milled to initial activation of the surface of the powder's mixture. Then a sintering process was conducted to complete formation of diopside nanopowder and also evaluates its thermal stability. The mechanisms occurred during the synthesis of this bioceramic were carefully investigated. X-Ray diffraction analysis (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetry (TG), differential thermal analysis (DTA), and inductive coupled plasma atomic emission spectroscopy (ICP-AES) were used for gathering and analyzing data. The ability and rate of apatite formation on the sample surface were evaluated by Simulated Body Fluid (SBF) test, a method that is well recognized to characterize the in vitro bioactivity of ceramic materials. According to the results obtained, the diopside samples had a significant potential to form apatite layer on their surface during soaking in the SBF solution. Besides, the bonding strength of this bioceramic was about 350±7MPa which was almost more than three times of that reported for hydroxyapatite. An excellent fracture toughness of 4±0.3MPam0.5 was also obtained for this ceramic which was higher than that of previously reported works.

Local and Nonlocal Procurement of Raw Material in Amud Cave, Israel: The Complex Mobility of Late Middle Paleolithic Groups

Studying the distribution of lithic raw materials around prehistoric sites, their procurement, transport, and use, are important for understanding organizational decisions of hunter‐gatherers. Here we examine lithic technological organization in two stratigraphic subunits B4 and B1 (dated ∼ 68 and ∼ 55 ka, respectively) at the Neanderthal site of Amud Cave. The lithic assemblages are made exclusively of flint. An ArcGIS model is used to create a predictive model for daily exploitation territories (DETs) around the site. Using a battery of statistical methods (ANOVA, principal component analysis, and cluster analysis), we link flint visual types with geochemical characteristics (obtained through inductively coupled plasma (ICP) mass spectrometry and ICP atomic emission spectrometry) of both geological and archaeological flints. Results indicate that local materials are abundant in both subunits. Nonlocal raw materials (from areas beyond the modeled DET) amount to 30–40% across all technological categories, suggesting long‐distance transport. The technological patterns of the nonlocal raw material differ between the two subunits. Pending results of additional work, we suggest that nonlocal flint types were likely obtained from distances >60 km. Mobility patterns inferred from this study suggest that Amud Cave was a focal location within its settlement system during both occupation periods, but the manner of site use and mobility patterns changed through time.

Effect of Concentrated Electrolyte on High Voltage Aqueous Sodium-Ion Battery

Introduction Na-ion batteries with aqueous electrolyte have attracted much attention, since it has 3 big advantages about the conductivity, non-flammability and cost. In addition, water is ideal solvent that can dissolve various salts in large amount. However, there is a severe restriction in the selection of the cathode and anode active materials, because of the narrow electrochemical window of water. Most recently, the expansion of the working voltage in aqueous cell have been tried either by judicious choice of active materials [1] and by increasing electrolyte concentration [2], which effectively prevents the electrochemical decomposition of water. Herein, new aqueous sodium-ion battery with inexpensive Na2MnFe(CN)6 (NMHCF) Prussian blue analogues as cathode and NASICON-type NaTi2(PO4)3 (NTP) as anode is introduced. Minor-metal free NMHCF and NTP are very attractive electrode active materials, because they have voltage plateaus near the upper/lower limit of electrochemical window of water. It has been reported that NTP anode can work in aqueous electrolyte reversibly at 2.1 V vs. Na/Na+ [3]. On the other hand, NMHCF has 2 high voltage plateaus at 3.5 V and 3.8 V vs. Na/Na+ and the higher voltage plateau is located above the electrochemical window of water. This is a reason that there are no reports about NMHCF cathode in aqueous electrolyte up to now. Here, to suppress the electrochemical decomposition of water, highly concentrated NaClO4 aqueous electrolyte was tried to realize high voltage aqueous sodium-ion battery with NMHCF cathode and NTP anode. Experimental NaxMn[Fe(CN)6]y·zH2O (NMHCF, 0<x<2, 0<y<1, 0<z) cathode material was obtained by co-precipitating method written in the previous reports [4]. NaTi2(PO4)3 anode material was prepared by conventional solid-state reaction of stoichiometric starting materials. NaxMn[Fe(CN)6]y·zH2O molecular formula was determined by inductive coupled plasma atomic emission spectroscopy (ICP-AES) and thermogravimetric analysis (TGA). Both NMHCF and NTP were mixed with acetylene black (AB) in a weight ratio of active material/AB = 70/25, respectively. In addition, NTP/AB was annealed in Ar atmosphere at 800 °C for 12 h. The cathode and anode pellets were fabricated with 5 wt % of polytetrafluoroethylene binder and punched into disks. And then these pellets were sandwiched by titanium mesh. A three-electrode electrochemical cell (half-cell) and two electrode cell (full-cell) with aqueous electrolyte were used for the galvanostatic charge/discharge test. An Ag-AgCl electrode with saturated KCl and NTP were used as the reference and counter electrodes, respectively. The cathode/anode weight balance for this ion-type cell is 2:3, and the cathode/anode capacity balance is approximately 2:3 (anode capacity excess condition). Here, 1 mol/kg and 17 mol/kg NaClO4 diluted/concentrated aqueous solution were used as aqueous electrolytes. Results and Discussion By the ICP-AES and TGA, the NMHCF cathode molecular formula and theoretical capacity were determined as Na1.27Mn[Fe(CN)6]0.76·1.39H2O and 126 mAh/g, respectively. Figure 1 compares the charge/discharge profiles of NMHCF//NTP full-cell with (a) 1 mol/kg and (b) 17 mol/kg NaClO4 aq. at the rate of 2.0 mA/cm2. In the case of 1 mol/kg electrolyte, the large irreversible capacity corresponding to the O2 gas evolution on cathode was observed on the 1st cycle between 0.5 and 2 V. On the other hand, the full-cell with 17 mol/kg electrolyte showed the reversible behavior in the wider voltage range than the electrochemical window of water. The drastic effect must be due to the suppression of the oxidation by the concentrated aqueous electrolyte. To confirm the Fe2+/Fe3+ and Mn2+/Mn3+ redox reaction of NMHCF cathode in concentrated aqueous electrolyte, X-ray photoelectron spectroscopy and X-ray diffraction were measured during 1st cycle. These results will be discussed on the day.

Hierarchical "Core-Shell" Pt-Ni ORR Electrocatalysts Based on Graphene "Cores" and Carbon Nitride "Shells"

One of the main bottlenecks in the operation of proton-exchange membrane fuel cells (PEMFCs) is the sluggish kinetics of the oxygen reduction reaction (ORR). The latter gives rise to large overpotentials, which degrade significantly the energy conversion efficiency of the device [1]. Our work addresses this issue by the development of innovative ORR electrocatalysts (ECs) characterized by an improved turnover frequency in comparison with state-of-the-art materials [2]. The proposed ECs comprise a hierarchical support “core” based on graphene flakes, which is covered by a carbon nitride (CN) “shell” embedding the ORR active sites. The hierarchical support “core”, which typically comprises both graphene flakes and a carbon black spacer, is devised to facilitate the charge and mass transport phenomena by: (i) reaping the benefits of graphene (e.g., a very high electron mobility, up to 200000 cm2·V-1·sec-1, and specific surface area, up to ca. 2630 m2·g-1); and (ii) fine-tuning the morphology of the final ECs [3-6]. The proposed ECs are obtained by the optimization of the preparation protocol devised in our research group [7]. In particular, the physicochemical properties and the morphology of the final materials are modulated by a post-synthesis activation step carried out by electrochemical de-alloying. The final ECs bear bimetallic ORR active sites comprising Pt as the “active metal” and Ni as the “co-catalyst” [8]. Preliminary results clearly evidence that this approach is capable to yield hierarchical ECs exhibiting a very promising performance in the ORR despite a very low loading of Pt. In detail, the best EC exhibits an ORR onset potential ca. 30 mV higher with respect to that of the Pt/C reference (see Figure). The chemical composition of the ECs is determined by inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis. The structure is elucidated by wide-angle X-ray diffraction (WAXD) and vibrational spectroscopies (e.g., confocal micro-Raman); the morphology is probed by, both conventional and high-resolution, scanning electron microscopy (SEM) and transmission electron microscopy (TEM); the “ex-situ” electrochemical performance and ORR reaction mechanism are gauged by cyclic voltammetry with the rotating ring-disk electrode method (CV-TF-RRDE). Finally, the ECs are implemented at the cathode of single fuel cell prototypes which are tested in operating conditions. REFERENCES [1] I. Katsounaros, S. Cherevko, A. R. Zeradjanin, K. J. J. Mayrhofer, Angew. Chem. Int. Ed., 53, 102 (2014). [2] J. Zhang, Front. Energy, 5, 137 (2011). [3] S. Sharma, B. G. Pollet, J. Power Sources, 208, 96 (2012). [4] M. Liu, R. Zhang, W. Chen, Chem. Rev., 114, 5117 (2014). [5] A. C. Ferrari, F. Bonaccorso, V. Fal’ko et al., Nanoscale, 7, 4587 (2015). [6] J. H. Chen, C. Jang, S. Xiao, M. Ishigami, M. S. Fuhrer, Nature Nanotech., 3, 206 (2008). [7] V. Di Noto, E. Negro, K. Vezzù, F. Bertasi, G. Nawn, L. Toncelli, S. Zeggio, F. Bassetto, Patent application 102015000055603 filed on 28 September 2015. Applicants: Università degli Studi di Padova and Breton S.p.A. (2015). [8] V. Di Noto, E. Negro, K. Vezzù, F. Bertasi, G. Nawn, The Electrochemical Society Interface, Summer 2015, 59 (2015). Figure 1

(Invited) 3D-Catenated EMImCl/(TiCl4)1.4/(δ-MgCl2)x Ionic Liquid Electrolyte for Mg Secondary Batteries

The rapid advance in the fields of portable electronics, load leveling and peak shaving for the power grid and zero-emission automotive applications require the development of new and improved electrical energy storage systems [1,2]. Since the 90’s major improvements have been achieved in magnesium battery technology [3-6]. In comparison to Li, Mg offers the following advantages: (i) a higher volumetric capacity (3832 vs. 2062 mAh·cm-3); (ii) far greater abundance in the Earth’s crust, lowering the costs; (iii) a safer operation and a better compatibility with the environment; and (iv) an acceptable standard reduction potential (-2.36 vs. -3.04 V) [7-9]. The main roadblock for these devices is the development of an efficient and stable electrolyte that is able to reversibly deposit and strip magnesium. Although Grignard and other organo-magnesium compounds exhibit good electrochemical performances [9], they do not exhibit an optimal stability due to their high vapor pressure and flammability. Ionic liquids dissolving a Mg salt with a high crystalline disorder were proposed as promising alternative electrolytes to organo-Mg systems owing to their good electrochemical performance and lack of flammability and thermal stability issues [10]. In the present work a new family of electrolytes is proposed, based on 1-ethyl-3-methylimidazolium chloride (EMImCl), titanium(IV) chloride (TiCl4) and increasing amounts of δ-MgCl2. Specifically, four EMImCl/(TiCl4)1.4/(δ-MgCl2)xelectrolytes, with 0.00 ≤ x ≤ 0.23 are prepared and extensively characterized. The chemical composition was determined by Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The thermal stability was gauged using High-Resolution Thermo Gravimetric Analysis (HR-TGA) and the phase transitions are highlighted with Modulated Differential Scanning Calorimetry (MDSC). Chemical interactions were studied through Fourier-Transform spectroscopy in the medium and far infrared (FT-MIR and FT-FIR) regions and confocal micro-Raman spectroscopy. The electrochemical performance was studied with: (i) Cyclic Voltammetry (CV), to probe Mg deposition and stripping (Fig. 1); (ii) Linear Sweep Voltammetry (LSV), to evaluate the electrochemical stability window; (iii) Chronopotentiometry (CP) experiments coupled with ICP-AES, to confirm and quantify the Mg deposition; and (iv) Broadband Electrical Spectroscopy (BES), to elucidate the long-range charge migration mechanisms of the electrolytes. High level density functional theory (DFT) based electronic structure calculations were undertaken to elucidate structures and vibrational frequency assignments. References 1 M. Armand and J. M. Tarascon Nature 451, 652-657, (2008). 2 B. Dunn, H. Kamath and J. M. Tarascon Science 334, 928-935, (2011). 3 V. Di Noto and M. Fauri, Batterie Primarie (Non Ricaricabili) e Secondarie (Ricaricabili) a Base di Elettroliti Polimerici Basati su Ioni Magnesio, PD99A000179, (1999). 4 V. Di Noto and M. Fauri, Magnesium-based Primary (Non Rechargeable) and Secondary (Rechargeable) Batteries, PCT/EP00/07221, (2000). 5 V. Di Noto, M. Fauri, G. De Luca and M. Vidali, (1998). 6 V. Di Noto, S. Lavina, D. Longo and M. Vidali Electrochim. Acta 43, 1225-1237, (1998). 7 D. Aurbach, G. S. Suresh, E. Levi, A. Mitelman, O. Mizrahi, O. Chusid and M. Brunelli Adv. Mater. 19, 4260-4267, (2007). 8 T. D. Gregory, R. J. Hoffman and R. C. Winterton J. Electrochem. Soc. 137, 775-780, (1990). 9 J. Muldoon, C. B. Bucur, A. G. Oliver, T. Sugimoto, M. Matsui, H. S. Kim, G. D. Allred, J. Zajicek and Y. Kotani Energy and Environmental Science 5, 5941-5950, (2012). 10 F. Bertasi, C. Hettige, F. Sepehr, X. Bogle, G. Pagot, K. Vezzù, E. Negro, S. J. Paddison, S. G. Greenbaum and M. Vittadello ChemSusChem 8, 3069-3076, (2015). Figure 1

Graphene-Supported Au-Ni Carbon Nitride Electrocatalysts for the ORR in Alkaline Environment

This study reports the preparation and characterization of a new family of electrocatalysts (ECs) for the oxygen reduction reaction (ORR) exhibiting a “core-shell” morphology. The “core” consists of graphene sheets, which are covered by a carbon nitride (CN) “shell” embedding Au and Ni active sites. The investigated ECs are labeled AuNi10-CNl 600/Gr and AuNi10-CNl 900/Gr. The chemical composition and thermal stability are studied by inductively-coupled plasma atomic emission spectroscopy (ICP-AES), elemental analysis and by high-resolution thermogravimetric analysis (HR-TGA). The morphology of the ECs is probed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and powder X-ray diffraction (XRD). The ORR performance of the ECs is studied both in acid (0.1 M HClO4) and in alkaline medium (0.1 M KOH) by Cyclic Voltammetry with the Thin-Film Rotating Ring-Disk Electrode (CV-TF-RRDE) method. Both ECs exhibit a promising performance in the ORR in the alkaline medium.

Development of Paper Sludge Ash-Based Geopolymer and Application to Treatment of Hazardous Water Contaminated with Radioisotopes.

Ambient temperature geopolymerization of paper sludge ashes (PS-ashes) discharged from paper mills was studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), induction coupled plasma atomic emission spectrometry (ICP-AES), and X-ray absorption near edge structure (XANES). Two varieties of alkaline liquors were used in the PS-ash based geopolymers, corresponding to aqueous Na-metasilicate and Na-disilicate compositions. PS-ashes were found to be semi-crystalline and to have porous structures that make it possible to absorb much liquor. Flexural strengths of PS-ash-based geopolymers with liquor/filler ratios (L/F) of 1.0–1.5 ranged from 0.82 to 1.51 MPa at 4 weeks age, depending on PS-ashes and liquors used. The reaction process of the constituent minerals of the PS-ash is discussed. Furthermore, we attempted to solidify hazardous water contaminated with radioisotopes. Non-radioactive strontium and cesium nitrates were added as surrogates at a dosage of 1% into the PS-ash-based geopolymers. Generally, high immobilization ratios up to 99.89% and 98.77% were achieved for Sr2+ and Cs+, respectively, depending on the source of PS-ashes, alkaline liquors, and material ages. However, in some cases, poor immobilization ratios were encountered, and we further discussed the causes of the instability of derived geopolymer gels on the basis of XANES spectra.

Crystallographic Analysis of Structural Changes in Lithium Nickel Manganese Cobalt Oxides at Different Stages of Lithiation

Mixed transition metal oxides are among the most promising cathode materials for lithium ion batteries. The high specific capacity, low cost and thermal stability makes Li(Ni1/3Mn1/3Co1/3)O2, so-called NMC, an excellent material for power tool applications. Therefore, main leading battery manufacturer focus on the combination of these three transition metals to combine the strengths of each of them [1]. The development and design of battery materials require deep understanding of the relations between chemistry, structure and its properties. Nowadays, the commercialized NMC can only reach around 60 % of its theoretical capacity when cycled up to 4.2 V. Higher specific capacities might be reached when the upper voltage limit is raised up to 4.5 V [2], but the lifetime of the cathode then decreases drastically. The deintercalation of more than 0.6 moles of lithium in the charge process of the battery leads to irreversible capacity losses. Lithium nickel manganese cobalt oxides with different transition metal ratios were successfully synthesized via coprecipitation route. The cathode materials were characterized physico- and electrochemically and the composition was confirmed via inductive coupled plasma atomic emission spectroscopy (ICP-AES). Structural changes of non-symmetric NMC compounds at different stages of lithiation were recorded using x-ray diffraction. The resulting patterns were analyzed and the structures refined using the Rietveld method implemented in the GSAS (General Structure Analysis System) package [3]. The same procedure of crystallographic characterization of the NMC structure was carried out for different transition metal ratios cycled up to 4.5 V. The results are presented and comparison between symmetric and non-symmetric lithium nickel manganese cobalt oxides will give better insight into structural changes at higher voltages and the relation to their compositions. Acknowledgement This work was financially supported by the Austrian Federal Ministry for Transport, Innovation and Technology (bmvit) and the Austrian Research Promotion Agency (FFG). [1] N. Yabuuchi, T. Ohzuku, Journal of Power Sources 119-121 (2003): 171-174 [2] Q. Yu, Z. Chen, L. Xing, D. Chen, H. Rong, Q. Liu,W. Li, Electrochimica Acta 176 (2015): 919-925 [3] A. C. Larson, R. B. Von Dreele, Los Alamos National Laboratory Report, No. LAUR-86-748, (1987)

Mn(II) Scavenging Electrolyte Additive and Functional Binder

Introduction Mn(II) dissolution from lithium manganese oxide (LiMn2O4) positive electrode and Mn plating on graphite negative electrode are the well-known failure mode in lithium-ion chemistry [1]. The Mn plating degrades the electrochemical performances of graphite electrodes in two ways. One is the self-discharge of graphite, which is accompanied by Mn plating. The other is the degradation of solid electrolyte interphase (SEI), which leads to forthcoming electrolyte decomposition and film deposition. As a result, cell polarization becomes severe due to an increment in film resistance, which eventually leads to a cell failure [2]. To overcome the issues raised by Mn plating on graphite electrodes, several countermeasures have been made. For examples, the scavengers for hydrofluoric acid (HF), which attacks the positive electrodes to leach out Mn ions, have been used as the electrolyte additive. Also Mn(II) scavengers have been developed [3,4]. In this study, 1,4,8,11-tetraazacyclotetradenate (cyclam) and 1,4,7,10-tetraazacyclododecane (cyclen) is tested as a Mn(II) scavenger. Those tetradentate azamacrocyclic compounds are applied as an electrolyte additve or attached on the chains of polyvinylalcohol (PVA) binder. The Mn plating on graphite electrodes seems to be suppressed due to a strong compex formation with Mn(II) ions. Namely, the Mn plating is thermodynamically unfavored due to the complex formation since the reduction potential of Mn(II) moves to the more negative direction than that for the solvent-solvated Mn(II) ions. Moreover, the Mn plating is kinetically hindered due to higher overpotential that is caused by a strong chelate complex formation. Experimental A beaker-type three-electrode cells were fabricated with a graphite electrode (DAG 87 : Super P : PVdF binder = 85:5:10 in wt. ratio), a Li counter electrode and a Li reference electrode. 10 mM of Mn(ClO4)2 was dissolved into an electrolyte solution (1.0 M LiPF6 in EC/DEC, 1/1 = v/v) to simulate the Mn(II)-dissolved electrolyte. To examine the additive effect, 1.0 wt. % of cyclam was added into the Mn(II)-containing electrolyte solution. The cyclen-attached PVA was synthesized by mixing 8 wt. % PVA/water solution and 50 mg of cyclen that carries a carboxylic acid functional group. After casting the mixed solution on Cu foil, esterification was performed at 150 0C for 12 h under vaccum. To examine the Mn(II) scavenging action, the cyclen-attached PVA/Cu foil was immersed in the Mn(II)-containing electrolyte solution for 48 h. Finally, the Mn(II) ions entrapped in the cyclen-attached PVA were leached out by using the mixture of nitric, hydrofluoric and hydrochloric acid. Mn(II) concentration was analyzed by using inductively-coupled plasma atomic emission spectroscopy (ICP-AES). Results and discussion The differential capacity (dQ/dV) plots obtained in the first lithiation period show that the reduction current responsible for Mn plating, which appears in the wide potential range (0.0 ~ 0.8 V vs. Li/Li+) in the Mn(II)-containing electrolyte, disappears when cyclam is added (Fig. 1a). Clearly, cyclam plays the Mn(II) scavenging role. The Mn(II) concentration entrapped in the cyclen-attached PVA is compared with that entrapped in the pure PVA. The comparison shown Fig. 1b ascertains the strong compex formation betweeen Mn(II) ions and cyclen being attached in PVA. The cyclen-attached PVA can be used as a binder for graphite electrode fabrication, which has Mn(II) scavanging function.