Comparison of electrochemical performance of as-cast Pb-1 wt.% Sn and Pb-1 wt.% Sb alloys for lead-acid battery components

A comparative experimental study of the electrochemical features of as-cast Pb-1 wt.% Sn and Pb-1 wt.% Sb alloys is carried out with a view to applications in the manufacture of lead-acid battery components. The as-cast samples are obtained using a water-cooled unidirectional solidification system. Pb-Sn and Pb-Sb alloy samples having similar coarse cell arrays are subjected to corrosion tests in order to assess the effect of Sn or Sb segregation in the cell boundary on the electrochemical performance. Electrochemical impedance spectroscopy (EIS) diagrams, potentiodynamic polarization curves and an equivalent circuit analysis are used to evaluate the electrochemical parameters in a 0.5 M H₂SO₄ solution at 25 °C. Both the experimental and simulated EIS parameters evidence different kinetics of corrosion. The Pb-1 wt.% Sn alloy is found to have a current density which is of about three times lower than that of the Pb-1 wt.% Sb alloy which indicates that dilute Pb-Sn alloys have higher potential for application as positive grid material in maintenance-free Pb-acid batteries.     

Electrochemical investigation of the anodic corrosion of Pb–Ca–Sn–Li grid alloy in H2SO4 solution

The steady-state and anodic corrosion of Pb–0.17 wt.% Ca–0.88 wt.% Sn, and Pb–0.17 wt.% Ca–0.88 wt.% Sn–0.06 wt.% Li alloys in 4.5 M H₂SO₄ at 25 °C were studied using cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. The experimental results show that the lithium added to Pb–Ca–Sn alloy increases corrosion resistance in equilibrium potential and inhibits the growth of the anodic corrosion layer.     

Microstructure and electrochemical corrosion behavior of a Pb-1 wt%Sn alloy for lead-acid battery components

The aim of this study was to evaluate the effect of solidification cooling rates on the as-cast microstructural morphologies of a Pb-1 wt%Sn alloy, and to correlate the resulting microstructure with the corresponding electrochemical corrosion resistance in a 0.5 M H₂SO₄ solution at 25 °C. Cylindrical low-carbon steel and insulating molds were employed permitting the two extremes of a significant range of solidification cooling rates to be experimentally examined. Electrochemical impedance spectroscopy (EIS) diagrams, potentiodynamic polarization curves and an equivalent circuit analysis were used to evaluate the electrochemical corrosion response of Pb-1 wt%Sn alloy samples. It was found that lower cooling rates are associated with coarse cellular arrays which result in better corrosion resistance than fine cells which are related to high cooling rates. The experimental results have shown that that the pre-programming of microstructure cell size of Pb-Sn alloys can be used as an alternative way to produce as-cast components of lead-acid batteries with higher corrosion resistance.     

Effects of cell size and macrosegregation on the corrosion behavior of a dilute Pb–Sb alloy

The aim of this study was to examine the effect of cooling rate on the cellular growth of a Pb–0.85 wt%Sb alloy and to evaluate the influences of cell size and of the corresponding macrosegregation profile on the resultant corrosion behavior. In order to obtain the as-cast samples a water-cooled unidirectional solidification system was used. Such experimental set-up has permitted the development of a clear cellular structural array even for relative high cooling rates and has allowed a wide range of solidification conditions to be analyzed. Macrostructural and microstructural aspects along the casting were characterized by optical microscopy and scanning electron microscope (SEM) techniques. The electrochemical impedance spectroscopy technique and potentiodynamic curves (Tafel extrapolation) were used to analyze the corrosion resistance of samples collected along the casting length and immersed in a 0.5 M H₂SO₄ solution at 25 °C. It was found that the corrosion rate decreases with increasing cell spacing and that the pre-programming of microstructure cell size can be used as an alternative way to produce as-cast components of Pb–Sb alloys, such as battery grids, with better corrosion resistance.     

Corrosion of Pb–Ca–Sn alloy during potential step cycles

Potential step was applied to Pb–Ca–Sn alloy electrode at various potential and time regimes. No severe corrosion was observed during potential step cycle with cathodic potential under −140 mV or over −40 mV versus Pb/PbSO₄ (3.39 M H₂SO₄), or at constant potential without stepping. On the other hand, the Pb–Ca–Sn alloy was severely corroded during potential step with cathodic potential from −120 mV to −60 mV and with anodic potential of +40 mV or more positive. The corrosion could not be decreased with periodical rest at 0 mV, while it could be decreased with periodical reduction at high polarization of, e.g. −160 mV. It was found out that the severe corrosion occurs when the oxidation of Pb to PbSO₄ and partial reduction of passive film of PbSO₄ take turns many times.     

Structure and hydrogen storage properties of Mg2Cu1−xNix (x = 0–1) alloys

The effect of Ni-substitution on the structure and hydrogen storage properties of Mg₂Cu_1−xNi_x (x = 0, 0.2, 0.4, 0.6, 0.8, 1) alloys prepared by a method combining electric resistance melting with isothermal evaporation casting process (IECP) has been studied. The X-ray single-crystal diffraction analysis results showed that the cell volume decreases with increasing Ni concentration, and crystal structure transforms Mg₂Cu with face-centered orthorhombic into Ni-containing alloys with hexagonal structure. The Ni-substitution effects on the hydriding reaction indicated that absorption kinetics and hydrogen storage capacity increase in proportion to the concentration of the substitutional Ni. The activated Mg₂Cu and Mg₂Ni alloys absorbed 2.54 and 3.58 wt% H, respectively, at 573 K under 50 bar H₂. After a combined high temperature and pressure activation cycle, the charged samples were composed of MgH₂, MgCu₂ and Mg₂NiH₄ while the discharged samples contained ternary alloys of Mg–Cu–Ni system with the helpful effect of rising the desorption plateau pressures compared with binary Mg–Cu and Mg–Ni alloys. With increasing nickel content, the effect of Ni is actually effective in MgH₂ and Mg₂NiH₄ destabilization, leading to a decrease of the desorption temperature of these two phases.     

Electrochemical characteristics of an La0.6Sr0.4Co0.2Fe0.8O3–La0.8Sr0.2MnO3 multi-layer composite cathode for intermediate-temperature solid oxide fuel cells

An La_0.6Sr_0.4Co_0.2Fe_0.8O₃–La_0.8Sr_0.2MnO₃ (LSCF–LSM) multi-layer composite cathode for solid oxide fuel cells (SOFCs) was prepared on an yttria-stabilized zirconia (YSZ) electrolyte by the screen-printing technique. Its cathodic polarization curves and electrochemical impedance spectra were measured and the results were compared with those for a conventional LSM/LSM–YSZ cathode. While the LSCF–LSM multi-layer composite cathode exhibited a cathodic overpotential lower than 0.13 V at 750 °C at a current density of 0.4 A cm⁻², the overpotential for the conventional LSM–YSZ cathode was about 0.2 V. The electrochemical impedance spectra revealed a better electrochemical performance of the LSCF–LSM multi-layer composite cathode than that of the conventional LSM/LSM–YSZ cathode; e.g., the polarization resistance value of the multi-layer composite cathode was 0.25 Ω cm² at 800 °C, nearly 40% lower than that of LSM/LSM–YSZ at the same temperature. In addition, an encouraging output power from an YSZ-supported cell using an LSCF–LSM multi-layer composite cathode was obtained.     

Enhanced corrosion resistance of Ni/Sn nano-electrodeposited metal foam for flow field application in simulated PEMFC cathode environment

Metal foam, with large specific surface area, suffers serious corrosion problems, as flow field in proton exchange membrane fuel cell (PEMFC). Ni/Sn nanoparticles are deposited onto the surface at galvanostatic and gradient current, respectively. The morphology of coated foams is examined by scanning electron microscopy (SEM), coupled with x-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The effect of deposited current on its corrosion resistance in simulated PEMFC cathode environment is evaluated by Tafel polarization test, constant potential test and electrochemical impedance spectra. The results show that the coating effectively improved the stability of metal foam in acid environment. A uniform and dense protective film is formed by Ni/Sn electrodeposition at a gradient current density from 0 to 40 mA cm^?2. Its corrosion current at 25, 50 and 80 °C, accounts around 38.0%, 47.3% and 46.7%, respectively, of the value of uncoated metal foam. The most positive corrosion current is obtained, ?0.12 mA, which is explained to higher coating resistance (R_coat). No obvious pitting is depicted in the surface morphology after 8 h, which further proves its high corrosion resistance.     

LSCF–SDC core–shell high-performance durable composite cathode

Core–shell type La_0.6Sr_0.4Co_0.2Fe_0.8O_3−d (LSCF)–Sm_0.2Ce_0.8O_2−d (SDC) powders are synthesized to achieve a high-performance durable cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). The SDC core size is controlled so that all core particles are surrounded by the LSCF particles with no unattached spots. Such a core–shell composite cathode develops an ideal microstructure with improved phase contiguity, homogeneity, and maximized triple-phase boundary density. The cathode that involves an SDC core of 500 nm exhibits the lowest interfacial polarization resistance (0.265 Ω cm² at 650 °C), as well as long-term stability during both thermo-cyclic and electrochemically accelerated tests.     

Characterization of Pr1−xSrxCo0.8Fe0.2O3−δ (0.2 ≤ x ≤ 0.6) cathode materials for intermediate-temperature solid oxide fuel cells

Cathode materials consisting of Pr_1−xSr_xCo_0.8Fe_0.2O_3−δ (x = 0.2–0.6) were prepared by the sol–gel process for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The samples had an orthorhombic perovskite structure. The electrical conductivities were all higher than 279 S cm⁻¹. The highest conductivity, 1040 S cm⁻¹, was found at 300 °C for the composition x = 0.4. Symmetrical cathodes made of Pr_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ (PSCF)–Ce_0.85Gd_0.15O_1.925 (50:50 by weight) composite powders were screen-printed on GDC electrolyte pellets. The area specific resistance value for the PSCF–GDC cathode was as low as 0.046 Ω cm² at 800 °C. The maximum power densities of a cell using the PSCF–GDC cathode were 520 mW cm⁻², 435 mW cm⁻² and 303 mW cm⁻² at 800 °C, 750 °C and 700 °C, respectively.     

Mg@C60 nano-lamellae and its 12.50 wt% hydrogen storage capacity

The design and synthesis of new hydrogen storage materials with high capacity are the prerequisite for extensive hydrogen energy application which can be achieved by multi-site hydrogen storage. Herein, a Mg@C₆₀ nano-lamellae structure with multiple hydrogen storage sites has been prepared through a simple ball-milling process in which Mg nanoparticles (∼5 nm) are homogeneously dispersed on C₆₀ nano-lamellae. The as-obtained C₆₀/Mg nano-lamellae displays an excess hydrogen uptake of 12.50 wt% at 45 bar, which is far higher than the theoretical value (7.60 wt%) of metal Mg and the US Department of Energy (DOE) target (5.50 wt%, 2020 year), also the experimental values reported by now. The enhanced hydrogen storage mainly comes from several storage sites: MgH₂, H_x–C₆₀ (CH chemical bonding), H₂@C₆₀ (the endohedral H₂ in C₆₀). Interestingly, the hybridization of Mg and C₆₀ not only facilitate the dissociation of H₂ molecules to form CH bonding with C₆₀, but also promote the deformation of C₆₀ and access H₂ molecules into the cavity of C₆₀. This work provides new insight into the underlying chemistry behind the high hydrogen storage capacities of a new class of hydrogen storage materials, fullerene/alkaline-earth metals nanocomposites.     

Photovoltaic activity in a ZnTe/PEO–chitosan blend electrolyte junction

A ZnTe/polymer junction has been fabricated and the photovoltaic properties studied. The polymer is a blend of 50 wt% chitosan and 50 wt% polyethylene oxide (PEO). The polymer blend was complexed with ammonium iodide (NH₄I) and some iodine crystals were added to the polymer–NH₄I solution to provide the I⁻/I³⁻ redox couple. The ionic conductivity of the polymer electrolyte is 4.32×10⁻⁶ S cm⁻¹ at room temperature. ZnTe was electrodeposited on ITO conducting glass. The polymer film was sandwiched between the ZnTe semiconductor and an ITO glass to form a ZnTe/polymer electrolyte/ITO photovoltaic cell. The open circuit voltage (V_oc) of the fabricated cells ranges between 300 and 400 mV and the short circuit current between 2 and 5 μA.     

Hydrogen storage properties of Mg-10 wt% Ni alloy co-catalysed with niobium and multi-walled carbon nanotubes

Mg-10 wt% Ni alloys containing up to 1 wt% Nb were fabricated by a casting technique, followed by ball-milling with 5 wt% multi-walled carbon nanotubes. Further mechanical alloying with 1.5, 3, and 5 at % Nb was applied to a cast Mg-10 wt% Ni-370 ppm Nb alloy to investigate the catalytic role of Nb in hydrogen dissociation. The microstructure and distribution of Nb and Mg₂Ni in the alloys were characterised by SEM. The absorption and desorption kinetics of the samples were measured by Sieverts’ apparatus at various temperatures. The results show that addition of Nb during casting accelerates the hydrogen diffusion compared to the cast binary Mg-10 wt% Ni alloy. Moreover, ball-milling of the alloy with metallic niobium leads to the formation of BCC phase of Mg-Nb solid solution, which significantly improves the hydrogenation properties of the alloy. DSC results show that mechanical alloying of Mg-10 wt%Ni-370 ppm Nb with Nb in excess of 1.5 wt% decreases the desorption temperature by approximately 100 °C compared to the ball-milled cast alloy.     

Plasma-assisted CO2 reforming of methane over Ni-based catalysts: Promoting role of Ag and Sn secondary metals

Carbon dioxide (CO₂) and methane (CH₄) are the primary greenhouse gases (GHGs) that drive global climate change. CO₂ reforming of CH₄ or dry reforming of CH₄ (DRM) is used for the simultaneous conversion of CO₂ and CH₄ into syngas and higher hydrocarbons. In this study, DRM was investigated using Ag–Ni/Al₂O₃ packing and Sn–Ni/Al₂O₃ packing in a parallel plate dielectric barrier discharge (DBD) reactor. The performance of the DBD reactor was significantly enhanced when applying Ag–Ni/Al₂O₃ and Sn–Ni/Al₂O₃ due to the relatively high electrical conductivity of Ag and Sn as well as their anti-coke performances. Using Ag–Ni/Al₂O₃ consisting of 1.5 wt% Ag and 5 wt% Ni/Al₂O₃ as the catalyst in the DBD reactor, 19% CH₄ conversion, 21% CO₂ conversion, 60% H₂ selectivity, 81% CO selectivity, energy efficiency of 7.9% and 0.74% (by mole) coke formation were achieved. In addition, using Sn–Ni/Al₂O₃, consisting of 0.5 wt% Sn and 5 wt% Ni/Al₂O₃, 15% CH₄ conversion, 19% CO₂ conversion, 64% H₂ selectivity, 70% CO selectivity, energy efficiency of 6.0%, and 2.1% (by mole) coke formation were achieved. Sn enhanced the reactant conversions and energy efficiency, and resulted in a reduction in coke formation; these results are comparable to that achieved when using the noble metal Ag. The decrease in the formation of coke could be correlated to the increase in the CO selectivity of the catalyst. Good dispersion of the secondary metals on Ni was found to be an important factor for the observed increases in the catalyst surface area and catalytic activities. Furthermore, the stability of the catalytic reactions was investigated for 1800 min over the 0.5 wt% Ag-5 wt% Ni/Al₂O₃ and 0.5 wt% Sn-5 wt% Ni/Al₂O₃ catalysts. The results showed an increase in the reactant conversions with an increase in the reaction time.     

Effects of Sn doping on the manufacturing,performance and carbon deposition of Ni/ScSZ cells in solid oxide fuel cells

This work demonstrates the effect of tin (Sn) doping on the manufacturing, electrochemical performance, and carbon deposition in dry biogas-fuelled solid oxide fuel cells (SOFCs). Sn doping via blending in technique alters the rheology of tape casting slurry and increases the Ni/ScSZ anode porosity. In contrast to the undoped Ni/ScSZ cells, where open-circuit voltage (OCV) drops in biogas, Sn–Ni/ScSZ SOFC OCV increases by 3%. The maximum power densities in biogas are 0.116, 0.211, 0.263, and 0.314 W/cm² for undoped Ni/ScSZ, undoped Ni/ScSZ with 3 wt% pore former, Sn–Ni/ScSZ and Sn–NiScSZ with 1 wt% pore former, respectively. Sn–Ni/ScSZ reduces the effect of the drop in the maximum power densities by 26%–36% with the fuel switch. A 1.28–2.24-fold higher amount of carbon is detected on the Sn–Ni/ScSZ samples despite the better electrochemical performance, which may reflect an enhanced methane decomposition reaction.     

Studies of tin–transition metal–carbon and tin–cobalt–transition metal–carbon negative electrode materials prepared by mechanical attrition

Samples of Sn₃₀TM₃₀C₄₀ and of Sn₃₀Co₁₅TM₁₅C₄₀, with TM = 3d transition metals, were prepared by vertical-axis attritor milling. The structure and performance of these samples were studied by X-ray diffraction (XRD) and by electrochemical testing. The XRD patterns of Sn₃₀TM₃₀C₄₀ show an amorphous-like diffraction pattern only for the sample with TM = Co. The other prepared samples show broadened Bragg peaks of their main starting material, along with an amorphous-like background, even after 32 h of milling. Samples with TM = Co and TM = Ni show stable differential capacity versus potential plots and stable cycling for at least 100 cycles with reversible capacities of 425 and 250 mAh g⁻¹, respectively. All samples prepared with 15 at.% Co show good capacity retention for at least 100 cycles ranging from 270 mAh g⁻¹ for samples with TM = Ni to 500 mAh g⁻¹ for samples with TM = Ti. The differential capacity versus potential plots for all the prepared Sn₃₀Co₁₅TM₁₅C₄₀ samples show similar structure to that of Sn₃₀Co₃₀C₄₀ except when TM = Cu. This shows the possibility of preparing tin-based negative electrode materials using a combination of cobalt and TM, especially if one looks to reduce the cobalt content.     

Effects of annealing on Zr8Ni19X2 (X = Ni,Mg, Al,Sc, V,Mn, Co,Sn, La,and Hf): Hydrogen storage and electrochemical properties

The effects of 8-h annealing at 960 °C on the gaseous phase hydrogen storage and electrochemical properties of partial-Ni substituted Zr₈Ni₂₁ alloys were studied. The substituting elements included Mg, Al, Sc, V, Mn, Co, Sn, La, and Hf. Only the main phase of the annealed Sn-substitution remained Zr₈Ni₂₁-structured while those of other substitutions turned into Zr₇Ni₁₀ or Zr₂Ni₇. The observed trend in maximum gaseous phase hydrogen storage capacity followed the increasing order of B/A ratio of the main phase as orthogonal Zr₇Ni₁₀ > tetragonal Zr₇Ni₁₀ > Zr₈Ni₂₁ > Zr₂Ni₇. After annealing, due to the increase in abundance of the main phase, the maximum gaseous phase hydrogen storage capacities of alloys with higher capacities before annealing increased while others decreased. The full discharge capacity also improved in the same increasing order of B/A ratio in the main phase. Hf-substitution showed the highest electrochemical discharge capacity at 200 mAh g⁻¹. After annealing, all alloys with the same main phase as the as-cast alloys showed degradation in full electrochemical capacity due to the reduction in both number and abundance of the catalytic secondary phases. All supplements assisted in improving surface exchange current from the base binary Zr₈Ni₂₁ alloy. Except for La- and Hf-substitutions, annealing reduced the surface exchange current density. The bulk hydrogen diffusion coefficient decreased with most of the supplements except for V- and Sn-substitutions. All supplements, except for Sc, showed improvement in the bulk diffusion after annealing. Furthermore, the maximum gaseous phase hydrogen storage capacity showed a strong correlation to the full electrochemical discharge capacity. Among all alloys in this study, the as-cast Hf-substituted Zr₈Ni₂₁ alloy demonstrated the best overall gaseous hydrogen storage and electrochemical properties.     

Hydrogenation properties of MgH2- x wt% AC (x=0, 5, 10, 15) nanocomposites

Magnesium is considered as a promising candidate for hydrogen storage due to its high storage capacity (theoretical value ~ 7.6 wt%). Nanocomposites of Magnesium hydride and activated charcoal (AC) were prepared using ball milling method. These nanocomposites were characterized by XRD, TGA, DSC and SEM techniques. The TGA analysis show that the MgH₂-5 wt% AC nanocomposite exhibits dehydrogenation capacity of 7.45 wt% (which is very close to the storage capacity of MgH₂) and starts release of hydrogen at 140 °C temperature. The results from the Kissinger plot from DSC result showed that the activation energy for hydrogen desorption of MgH₂ with 5 wt% AC was reduced compared to those of as-received.     

The recent development on MgH2 system by 16 wt% nickel addition and particle size reduction through ball milling: A noticeable hydrogen capacity up to 5 wt% at low temperature and pressure

The addition of nickel as catalyst and particle size reduction through milling process is considered as the best approach for MgH₂ properties to be thermodynamically and kinetically more favorable. The recent development in MgH₂ is done by adding Ni (14–16 wt%) and particle size reduction through simple mechanical milling at a large sample of 100 g. The research sequences are easy to adopt for the implementation and sustainable research of MgH₂. Starting from the moisture test to the milling process, continue with particle size distribution (PSD) for the milled sample and final moisture test after PSD. Some critical finding from our research includes high capacity storage of Mg₈₄:Ni₁₆ above 5 wt% H₂ within 20 min at 573 K, the effect of moisture content on system performance and the different effect of carbon (C) in the system at specific temperature and pressure that may have.     

Influences of temperature, H2SO4 concentration and Sn content on corrosion behaviors of PbSn alloy in sulfuric acid solution

The influences of temperature, H₂SO₄ concentration and Sn content on corrosion behaviors of PbSn alloys in sulfuric acid solution were investigated by potentiodynamic curve, cyclic voltammetry (CV), linear sweeping voltage (LSV), electrochemical impedance spectra (EIS), a.c. voltammetry (ACV) and Mott-Schottky analysis. The microstructure of the corrosion layer on PbSn alloy was analyzed by scanning electron microscopy (SEM). The results showed that the corrosion resistance of PbSn alloy increased with ascending Sn content and H₂SO₄ concentration, the increment of temperature can decrease the corrosion resistance of PbSn alloy in H₂SO₄ solution. The conductivity of the anodic film on PbSn alloy was enhanced with increasing temperature, ascending Sn content and descending H₂SO₄ concentration. SEM result revealed that the corrosion film after cyclic voltammetry was consisted of tetragonal crystal, the porosity enlarged with decreasing temperature, Sn content and H₂SO₄ concentration.