Ionics

The preparation and capacitance performances of Mn (OH)2@ secondary porous Ni nano-architecture foam (Mn (OH)2@SPNiNF) hybrids are systematically studied. The SPNiNF structure is simply obtained via a NiC2O4·2H2O in situ growing process on Ni foam surface, combined with a thermally treated process under Ar gas. Then, a layer of Mn (OH)2 film was electrodeposited onto the above SPNiNF sheet by applying a galvanostatical technique. It is shown that the SPNiNF sheet is composed of interconnected nanoparticles with a diameter range of 100–200 nm. The fabricated Mn (OH)2@SPNiNF electrode exhibited a high specific capacitance of 532.7 F g−1 and an areal capacitance of 906 m F cm−2 at a current density of 0.5 A g−1. The Mn (OH)2@SPNiNF electrode also exhibited a low ions diffusion resistance and a good cycling performance along with 85.7% specific capacitance retained after 5000 cycles. An asymmetric Mn (OH)2@SPNiNF //AC super capacitor exhibited an energy density of 69.1 Wh kg−1 at a power density of 0.6 kW kg−1. These results demonstrated that the Mn (OH)2@SPNiNF was a promising electrode material for supercapacitors.

Surfaces and interfaces play a dominant role in the performance of devices like fuel cells and membranes based on ionic materials. The LEIS technique offers a unique possibility to determine the composition of the outermost atomic layer, which is often quite different from that of deeper layers. For instance impurities that are present in minute concentrations −1 ppb or even less- in the bulk may segregate to the surface and there become the dominant species. By carefully sputtering away the top layers also a compositional depth profile can be made of the first 10 to 20 layers. The basic principles of the LEIS technique will be explained, answering questions like: why is it so extremely surface sensitive; what does the instrumentation look like; what can you learn from the results. Its applicability to ionic materials will be demonstrated with results from measurements on various substrates used in fuel cells. The oxygen exchange across the surface of Sm0.8Sr0.2CoO3 can be studied, because it is possible to differentiate between the18O and16O isotopes. One can determine which elements are on top in La0.8Sr0.2Ga0.8Mg0.2O3±δ. The top layer of Ce0.8Gd0.2O1.9 proves to be enriched in Gd oxide. The Y segregation in isotopically enriched YSZ is being studied.

This study examined the effect of mixed alkaline earth modifier fluoride on AC conductivity and dielectric properties in xBaF2–(50–x)CaF2–50B2O3 (x = 5–35 mol%) glass system. The impedance data showed a single-depressed semicircle with decreasing bulk resistance (Rb) with temperature. The change of $${\sigma }_{AC}$$ implied a non-linear relationship with BaF2, which induced a blocking effect on the mobility of the charge carriers at x ≤ 20 mol%, indicating the Mixed Alkaline Earth Effect (MAEE). The abrupt increase at x = 25 mol% was associated with the expansion of the glass network due to the formation of Non-Bridging Oxygen (NBO). All glass samples followed the Overlapping Large-Polaron Tunneling (OLPT) model for the conduction mechanism. The change in ε′ more prominent in low-frequency regions, signifying that polarization was contributed mainly by the space charge polarization. Electrical modulus analysis revealed non-Debye type relaxation, indicating temperature- and composition-dependent dynamic ion processes.

A new electrode composed of sepiolite clay (SC) carbon paste (CP) was developed and used for the adsorptive stripping differential pulse voltammetric quantification of ascorbic acid (AA). The effects of pH, the ratios of the electrode ingredients, accumulation potential, and accumulation time were investigated. The SC/CP electrode (SC/CPE) was found to have a good linear working range (1.4 × 10−8–9.0 × 10−7 mol L−1) and the detection limit of 4.2 × 10−9 mol L−1. The sensitivity is fairly good with LOQ of 0.014 μmol L−1 and LOD of 0.0042 μmol L−1. The selectivity in the presence of some common species, i.e., Na+, Cl−, Ca2+, Mg2+, NO3 − , citric acid, and glucose, at concentrations well above those encountered in body fluids was found to be satisfactory. The SC/CPE system has a lifetime not shorter than a month and proved to be practical for the analysis of not only pharmaceutical formulations but also natural products such as vitamin C-rich fruit Rosa canina and mineral waters.

This work presents a Zn/graphite dual-ion battery using natural graphite as the cathode and metallic zinc as the anode, with ionic liquid-based electrolyte. Upon charge, the Zn2+ cations deposit on the zinc anode, and the trifluoromethanesulfonate (TfO−) anions simultaneously intercalate into the graphite cathode; upon discharge, both the ions are released back into the electrolyte. The 0.2 M Zn(TfO)2/EMImTfO ionic liquid-based electrolyte exhibits a high electrochemical window of 2.8 V (vs. Zn2+/Zn) as well as a high conductivity of 7.3 ms cm−1. The deposition/stripping of zinc on a copper working electrode is systematically studied, which reveals that Zn2+ cations are mobile in the ionic liquid electrolyte, and zinc can be deposited and stripped in this electrolyte. The insertion/extraction of TfO− into/from graphite is also investigated, demonstrating a reversible process. At a current of 0.2 mA cm−2 and within the voltage of 0.8–2.8 V, the Zn/graphite dual-ion cells exhibit a high sloping discharge plateau within 1.8–2.4 V (corresponding to a medium voltage of about 2.0 V), a discharge capacity of 33.7 mAh g−1, and an energy density of 65.1 Wh kg−1; cells deliver a cyclability of 93.5% Coulombic efficiency for 100 cycles. The SEM image reveals that the zinc deposits are compact and dense, and uniformly distribute on anodes with an average grain size of about 200 nm, without the formation of dendrites. The use of high-safety electrolyte and low-cost electrode materials may enable this cell configuration to be a promising candidate for future energy storage systems.

An attempt has been made to synthesize a polymer electrolyte based on biopolymer pectin with ammonium thiocyanate (NH4SCN) salt by solution casting technique. Amorphous/crystalline nature of the polymer electrolyte has been studied by X-ray diffraction technique. The complexation between polymer and salt has been confirmed by Fourier transform infrared spectroscopy. A shift in glass transition temperature of the pectin: NH4SCN electrolytes have been observed from the differential scanning calorimetry thermograms. Ionic conductivity of the electrolytes was measured through impedance spectroscopic technique. The frequency and temperature dependence of ionic conductivity has been studied. The highest conductivity of 1.5 × 10−3 S cm−1 was observed for 40 mol% pectin: 60 mol% NH4SCN sample. Transference number measurement was carried out to confirm the nature of the charge transport species in the polymer electrolyte. Electrochemical stability of the highest conducting sample was studied by linear sweep voltammetry (LSV). The value is found to be 3.69 V. Using highest proton-conducting membrane, a proton battery has been constructed.