Oxidation Of Pb Research Articles

The role of Pb oxidation state of the precursor in the formation of 2D perovskite microplates.

Two-dimensional (2D) lead halide perovskites are an exciting class of materials currently being extensively explored for photovoltaics and other optoelectronic applications. Their ionic nature makes them ideal candidates for solution processing into both thin films and nanostructured crystals. Understanding how 2D lead halide perovskite crystals form is key towards full control over their physical properties, which may enable new physical phenomena and devices. Here, we investigate the effects of the Pb oxidation state of the initial inorganic precursor on the growth of pure-phase (n = 1) - Popper 2D perovskite BA2PbI4 in single-step synthesis. We examine the different crystallisation routes in exposing PbO2 and PbI2 powders to a BAI : IPA organo-halide solution, by combining in situ optical microscopy, UV-VIS spectroscopy and time-resolved high performance liquid chromatography. So far, works using PbO2 to synthesise 3D LHPs introduce a preceding step to reduce PbO2 into either PbO or PbI2. In this work, we find that BA2PbI4 is directly formed when exposing PbO2 to BAI : IPA without the need for an external reducing agent. We explain this phenomenon by the spontaneous reduction/oxidation of PbO2/BAI that occurs under iodine-rich conditions. We observe differences in the final morphology (rectangles vs. octagons) and nanocrystal growth rate, which we explain through the different chemistry and iodoplumbate complexes involved in each case. As such, this work spans the horizon of usable lead precursors and offers a new turning knob to control crystal growth in single-step LHP synthesis.

Synthesis of Lead Oxide Using the Oxidizing Agent (NH4)2S2O8 with Variaous Amounts of NaOH for Decolorization of Remazol Black B Solution

In this study, the lead oxide has been successfully synthesized using oxidizing agents (NH4)2S2O8 and applied to decolorize the Remazole Black B (RBB) solution. Lead oxide was synthesized by the batch method through the mechanism of reduction-oxidation and characterized using SEM-EDX and XRD. Decolorizing RBB solution was performed using a modified Fenton method. This study aims to determine the optimum performance of RBB decolorization from lead oxide. The results showed that the crystal formed contains Pb and O. Pb oxide obtained was α-PBO2 with the orthorhombic crystal system. Based on characterization, the lead oxide obtained has a surface morphology of coral flowers-like. Synthesis utilizing equilibrium composition (1:2) and a drying temperature of 100°C yielded Pb oxide, which has a better potential as a modifier in RBB decolorization with a decolorization percentage of 80.07%. The process was then carried out for advanced synthesis less and excess of molar variations. The ratio of lead oxide: NaOH (1:4) showed optimum performance in decolorizing RBB with a decolorization percentage of 80.07 %.

Electrochemical performance of novel Pb alloys reinforced with Ni-coated fly ash microballoon composite foams in Lead Acid Battery

Novel Pb composite foams comprising hybrid gas pores and Ni-coated fly ash microballoons were produced by direct melt foaming method. Pb composite foams were designed to have a lower weight and larger surface area to be used in the Lead Acid Battery (LAB) as alternative to the traditional Pb grids, offering benefits in the transportation industry. The Ni-coated fly ash microballoons were added to Pb alloy melt to serve as thickening agent and pores, which were wholly enclosed within the microballoons, as well as reinforcements. The electrochemical performance of Pb grids used in traditional LAB and Pb composite foams produced in the present work was investigated for comparing purposes. The cured plates form positive and negative electrodes of Pb grid and Pb composite foams were characterized by X-ray diffraction to identify the different Pb compounds and phases. The morphology of the cured plate was found to contain flakes and dendritic structure. Zones were formed from a network of Pb particles in the negative electrode covered with PbSO4 crystals. The PbSO4 crystals exhibited miscellaneous morphology. The matrix of lead basic sulphate crystals was converted into aggregates of PbO2 particles in the positive electrode morphology, which maintained the form of the original substance. Cyclic voltammetry measurements (CV) were conducted in 3 M H2SO4 to study the anodic oxidation and cathodic reduction peaks of Pb, PbSO4 and PbO2. The galvanostatic polarization for oxidation and reduction steps was measured at different current densities. It revealed the benefit that the Pb matrix composite foam showed a longer period for oxidation of Pb into PbSO4. The composite foams exhibited a greater specific discharge electrical capacity than the Pb alloys used in traditional LAB.

Temperature estimates of historical Pb-Ag smelting slags: A multi-methodological approach

The process temperature is a key parameter for the reconstruction of historic smelting operations since it can provide valuable information on the technological state-of-the-art as well as on intrinsically related aspects such as the type and availability of fuel (e.g. charcoal, wood) and metallurgical know-how. Slag compositions in lead-silver metallurgy can show a wide variation due to the utilisation of variable raw materials and possible addition of fluxes, but also since Pb oxide can be a major component, affecting the thermal behaviour and viscosity of the slag melt. This study presents results for liquidus temperatures determined by a range of different data-based and experimental techniques – phase diagrams, thermometry calculations, differential thermal analysis-thermogravimetry (DTA-TG) and hot stage microscopy (HSM) – applied to a suite of slags broadly representative of the compositional and mineralogical spectrum of metallurgical remains of lead-silver smelting. We propose suitable applications of the different techniques and provide generalised archaeometallurgical implications for the investigated slag types.

Response addition is more protective of biogeochemical cycles of carbon and phosphorus compared to concentration addition

In soils, enzymes are crucial to catalyzing reactions and cycling elements such as carbon (C), nitrogen (N), and phosphorus (P). Although these soil enzymes are sensitive to metals, they are often disregarded in risk assessments, and regulatory laws governing their existence are unclear. Nevertheless, there is a need to develop regulatory standards for metal mixtures that protect biogeochemical cycles because soil serve as a sink for metals and exposures occur as mixtures. Using a fixed ratio ray design, we investigated the effects of 5 single metals and 10 quinary mixtures of Zn, Cu, Ni, Pb, and Co metal oxides on two soil enzymes (i.e., acid phosphatases [ACP] and beta glucosidases [BGD]) in two acidic Canadian soils (S1: acid sandy forest soil, and S2: acid sandy arable soil), closely matched to EU REACH standard soils. Compared to BGD, ACP was generally the more sensitive enzyme to both the single metals and the metal mixtures. The effective concentration inhibiting 50% enzyme activity (EC50) estimates for single Cu (2.1–160.7 mmol kg−1) and Ni (12–272 mmol kg−1) showed that those were the most toxic to both enzymes in both soils. For metal mixtures, response addition (RA) was more conservative in predicting metal effects compared to concentration addition (CA). For both additivity models, antagonism was observed except at lower concentrations (≤10,000 mg/kg) where synergism was observed. At higher concentrations (>10,000 mg/kg), free and CaCl2 extractable Cu protected both enzymes against the toxicity of other metals in the mixture. The results suggest that assuming CA at concentrations less than EC50 does not protect biogeochemical cycling of C and P. And Cu in soil may protect soil enzymes from other toxic metals and thus may have an overall positive role.

Dissolved organic matters-enhanced Pb releases from nano- or submicron Pb sulfides and oxides

Diverse lead (Pb) particles possess different ecological risks not only due to their own toxicity differences but also because of different abilities to release toxic dissolved Pb. Dissolved organic matter (DOM) was a key factor influencing dissolution processes of metal particles. However, impacts of DOM on dissolution of different Pb nano- or submicron particles were not known yet. Herein, impacts of DOM on dissolution kinetics of lead sulfide (PbS), lead sulfate (PbSO4), lead monoxide (PbO), lead tetroxide (Pb3O4) and lead dioxide (PbO2) nano- or submicron particles were firstly investigated taking Pahokee Peat humic acid (PPHA) as an example. Results indicated PPHA improved the suspending stability of Pb particles through electrostatic repulsion, and enhanced releases of dissolved Pb. Final concentration of dissolved Pb was raised by 1.22–8.82 times with PPHA. This was attributed to ligand exchange interactions between PPHA and Pb particles. Theoretical computations indicated that not only sorption or ligand exchange energy, but also numbers of ligands on the surface of particles were key factors governing impacts of PPHA on dissolved Pb. This study provided a new mechanism insight into dissolution behavior of various Pb particles and will be beneficial to their ecological risk assessment.

Revisiting some overlooked registered Thai traditional medicine preparations: an alert to a regulatory affair

ObjectiveThis study evaluated the heavy metal identity and content of registered Thai Traditional medicine (TTM) preparations in Thailand to ensure consumer safety.MethodsBoth qualitative and quantitative information about the elemental composition of the heavy metal content in each TTM crude drug and the heavy metal content in some registered TTM preparations in Thailand was performed. Seven kinds of mineral-based TTM crude drugs, namely realgar, orpiment, Chinese powder, Sen, vermilion, natural vermilion, and cinnabar, were analyzed with X-ray diffraction and scanning electron microscopy and energy-dispersive spectroscopy techniques to determine the type of metal and elemental composition to confirm their chemical formulas. Furthermore, the number of heavy metals, such as arsenic (As), lead (Pb), and mercury (Hg), was in three samples of realgar-containing preparations; one sample of Sen-containing preparation, and eight samples of cinnabar-containing preparations. Heavy metals were determined with inductively coupled plasma-optical emission spectrometry.ResultsIt was observed that realgar and orpiment consisted of arsenic sulfide (AsS) and arsenic trisulfide (As2S3), respectively. Both crude drugs contained approximately 50% of As. Vermilion, natural vermilion, and cinnabar consisted of mercuric sulfide (HgS), with Hg accounting for approximately 66%. Sen consisted of Pb (II, IV) oxide (Pb3O4) with an approximate Pb percentage of 80%. However, Pb was absent in Chinese powder and consisted mainly of calcium carbonate (CaCO3). A traditional detoxification procedure can reduce the amount of As and Hg in processed crude drugs by at least 20%.ConclusionsPb was higher in some TTM preparations, and no CaCO3 was detected in Chinese powder. Our results raise concerns on both safety and efficacy to consumers and alert public health policymakers that they should implement regulations so that the quality (authenticity) and quantity of elemental medicine used in traditional medicine are correctly labeled and within permissible limits to prevent threats to consumers.

Metal deportment in Pb-Zn mine wastes from a historic tailings pond, Plombières, East Belgium

The exploitation of mine waste materials as secondary resources requires in-depth mineralogical analyses, with metal deportment being of particular relevance for metal recovery. Using a combination of the Scanning Electron Microscope (SEM)-based Mineral Liberation Analyser (MLA) and Electron Probe Micro-Analyser (EPMA) methods, the deportment of lead and zinc in the historic Plombières mine site (East Belgium) was investigated. The mine site comprises four different materials: soil, metallurgical waste, brown and yellow tailings. The integration of the MLA and EPMA data allowed the identification and quantification of Pb- and Zn-bearing phases, including minerals present in low abundances as well as slag phases. Different slag types and Pb oxides phases are the main sources of lead in Plombières mine waste samples. These phases host 65 to 99 % of the Pb, the rest is distributed between cerussite (0 to 37 %), and/or anglesite (0 to 17 %). Approximately 95 % of Zn is hosted by different types of slags or by fraipontite, with minor amounts contributed by sphalerite (0.1 to 3 %), gahnite (1.0 to 2.4 %), willemite (0.1 to 2.9 %), and bannisterite (0 to 3 %). The MLA/EPMA measurements were validated by comparing calculated Pb and Zn grades with bulk grades measured by X-ray fluorescence spectroscopy. The coefficients of correlation between the measured and calculated values were found to be 0.89 for lead and 0.80 for zinc. Uncertainties on the metal deportments were estimated by bootstrap resampling and are typically low. The highest uncertainties are observed when the metal-bearing phases are present in low abundances, which is particularly noticeable in the yellow tailings. Considering the promising results, the integrated approach applied in this study should be applicable to other metals and waste deposits across the globe.

Enhancement of TiO2 activity under visible light by N,S codoping for Pb(II) removal from water

This paper deals with a systematic study on the co-doping N,S on TiO2 photocatalyst to improve its activity under visible light on the removal of Pb(II) from the aqueous media. The co-doping TiO2 by N,S atoms was conducted in an autoclave by one-step hydrothermal of TiO2 mixed with nitric and sulfuric acids as the sources of N and S, respectively. The mole ratio of TiO2:nitric acid:sulfuric acid was varied as 1:1:0.5, 1:1:1, and 1:1:1.5 to find the best ratio toward the activity. The co-doped photocatalysts obtained were characterized by specular reflectance UV/Vis (SRUV), X-ray diffraction (XRD), and fourier transform infrared (FTIR) instruments. A batch experiment was carried out for oxidation of Pb(II), driven by a combination of visible light and TiO2-N,S photocatalyst. The research results attribute that co-doping N,S into TiO2 has remarkably narrowed the gap in the TiO2 structure, emerging in the visible region. It was also proven that the co-doped in TiO2 can considerably enhance its activity in the removal of Pb(II) under visible light, and the highest activity was owned by TiO2-N,S (1:1:1). Furthermore, the most effective removal of Pb(II) 10 mg/L (98%) could be reached by employing 500 mg L-1 of the TiO2-N,S (1:1:1) dose, 45 min of the time, and the solution pH at 7. The Pb(II) removed is due to the photo-oxidation induced by OH radicals to form the handleable PbO2.

Potential application of carbohydrate biomass in hydrometallurgy: one-pot reduction of metal oxides/salts under mild hydrothermal conditions.

Carbohydrate biomass can be employed as a reductant for metallic material preparation due to it possessing diverse reducing functional groups. The reported studies focused on reduction of metal ions in acidic solution with the aid of biomass. However, we found alkali hydrothermal conditions are favorable to metal compound reduction, even direct conversion of metal oxides to metals. Based on our previous research on direct reduction of CuO and NiO into the corresponding metals, herein, conversion of other metal oxides (Fe2O3, MnO2, Co3O4, PbO2) with glucose was investigated to illustrate the universal applicability of direct reduction of metal oxides with carbohydrates under alkali hydrothermal conditions. Furthermore, metal salt reduction by carbohydrates was studied and the reduction performance of glucose and cellulose with and without alkali was compared. The results showed an alkaline hydrothermal environment is more conducive to metal reduction. Unlike the complete reduction of CuO and NiO, oxides of Fe(iii), Mn(iv), Co(iii) and Pb(iv) can only be partially reduced under the experimental conditions. Not only carbohydrates but also decomposed intermediates can reduce metal oxides or salts. In addition, due to the formation of stable complexes between the anions of salts and the decomposition products of carbohydrates, the reduction effects of various copper salts are significantly different. This study may provide an alternative approach to metal preparation in hydrometallurgy.

Dissolved Organic Matters-Enhanced Pb Releases from Nano- or Submicron Pb Sulfides and Oxides

Dissolved Organic Matters-Enhanced Pb Releases from Nano- or Submicron Pb Sulfides and Oxides

Rapid Review of Dermal Penetration and Absorption of Inorganic Lead Compounds for Occupational Risk Assessment.

Lead (Pb) exposure continues to be a significant public health issue in both occupational and non-occupational settings. The vast majority of exposure and toxicological studies have focused on effects related to inhalation and gastrointestinal exposure routes. Exposure to inorganic Pb compounds through dermal absorption has been less well studied, perhaps due to the assumption that the dermal pathway is a minor contributor to aggregate exposures to Pb compounds. The aim of this rapid review was to identify and evaluate published literature on dermal exposures to support the estimation of key percutaneous absorption parameters (Kp, flux, diffusion rate) for use in occupational risk assessment. Eleven articles were identified containing information from both in vitro and in vivo systems relevant to percutaneous absorption kinetics. These articles provided 24 individual study summaries and information for seven inorganic Pb compounds. The vast majority of study summaries evaluated (n = 22, 92%) reported detectable amounts of dermal absorption of inorganic Pb. Data were identified for four Pb compounds (Pb acetate, Pb nitrate, Pb oxide, and Pb metal) that may be sufficient to use in evaluating physiologically based pharmacokinetic models. Average calculated diffusion rates for the pool of animal and human skin data ranged from 10-7 to 10-4 mg cm-2 h-1, and Kp values ranged from 10-7 to 10-5 cm h-1. Study design and documentation were highly variable, and only one of the studies identified was conducted using standard test guideline-compliant methodologies. Two studies provided quality estimates on the impacts of dermal absorption from water-insoluble Pb compounds on blood Pb levels. These two studies reported that exposures via dermal routes could elevate blood Pb by over 6 µg dl-1. This estimation could represent over 100% of 5 µg dl-1, the blood Pb associated with adverse health effects in adults. The utility of these estimates to occupational dermal exposures is limited, because the confidence in the estimates is not high. The literature, while of limited quality, overall strongly suggests inorganic Pb has the potential for dermal uptake in meaningful amounts associated with negative health outcomes based on upper bound diffusion rate estimates. Future standard test guideline-compliant studies are needed to provide high-confidence estimates of dermal uptake. Such data are needed to allow for improved evaluation of Pb exposures in an occupational risk assessment context.

Novel Pb alloys based composite foams containing hybrid pores produced by liquid metallurgy for lightweight batteries

High-quality novel Pb alloys based composite foams reinforced with fly ash cenospheres of different diameters in a variety of volume fractions were successfully synthesized by stir casting. Several crucial parameters such as wetting between the cenospheres and molten Pb alloy, volume fraction and size of the cenospheres, melt temperature, rate of cenosphere addition, stirring time and speed, foaming agent amount, foaming temperature and foaming time were optimized to produce high-quality composite foams. The microstructure of the composite foams revealed uniform cell distribution and size with mostly closed cell structure. The cells were measured to be of the size range of 290–430 μm. Microscopy and spectroscopy of the composite foams indicated that limited or no interfacial reaction products are formed between fly ash cenospheres and Pb alloys. The specific discharge electrical capacity of the composite foams was higher than those of the Pb alloys used in conventional Pb-acid batteries. Moreover, the weights of the composite foam electrodes were much lower than those of the conventional lead alloys, providing benefits in transportation applications. The cyclic voltammetric and galvanostatic polarization results indicated that the rates of oxidation of Pb into PbSO4 in the composite foam were much lower than those in Pb-grids and the oxidation of the Pb in the positive and negative grids occurred at much lower voltage than that in composite foams.

Gamma–ray irradiation of lead iodide precursor for enhanced perovskite crystalline properties

We describe an effective method for tuning the structure of lead iodide (PbI2) via high-energy gamma (γ)-ray irradiation. The chemistry of the precursor used in preparing the solution critically determines the quality of the perovskite films and the photovoltaic performance. We investigated the dependence of the precursor crystal structure and morphology on the γ-ray irradiation dose without by-products. The crystal orientation of PbI2 gradually changed when PbI2 was exposed to γ-ray radiation, causing it to form high-valent iodoplumbates with organic solvents because of the increase in the Pb oxidation number required to maintain a planar structure. The iodoplumbates suppress rapid crystallization and limit the space available for the grains to grow, thereby improving perovskite crystallinity. We also analyzed the optical and electrical properties of a perovskite film containing the irradiated precursor and compared them with those of a film containing the pristine PbI2 precursor. The detailed analysis of the crystal structure of the film revealed the effects of γ-ray irradiation. The PSC devices produced with γ-irradiated precursor material displayed improved performance. The direct treatment of precursors with high energy sources, such as γ-rays, which does not involve fabrication, is efficient in improving perovskite structures.

An investigation on characterization and floation behavior of a transitional ore containing Galena and Pb Oxide minerals

Bu çalışmada hem sülfürlü hem de oksit yapıdaki Pb minerallerini barındıran, geçiş zonuna ait bir kurşun cevherinin flotasyon davranışı incelenmiştir. Detaylı bir mineraloji analizi yapılarak kurşun ve gang mineralleri tespit edilmiştir. Kurşun minerallerinden galen ve serüzit ile birlikte plumbogummit belirlenmiş olup, oksit ve sülfürlü kurşun minerallerinin birlikte bulunduğu bir yapı görülmektedir. Flotasyon testlerinde, öncelikle tane boyutunun etkisi incelenmiş, daha sonra sülfürleştirici, toplayıcı ve köpürtücü reaktiflerin türlerinin kurşun flotasyon üzerindeki etkisi araştırılmıştır. Flotasyon testlerinde potasyum amil ksantat, modifiye merkaptan (Aero 412) ve köpürtücü (Dow250) birlikte kullanıldığı durumda en yüksek verime ulaşılmıştır. Flotasyon süresini kısaltmak ve görece iri boyutta serbestleşen kurşun tanelerinin yüzdürülmesi amacıyla flaş flotasyonun etkisi araştırılarak en uygun açık devre tasarımı yapılmıştır. En iyi flotasyon performansının elde edildiği koşularda kapalı devre flotasyon testi yapılmış ve tesis koşullarında elde edilebilecek nihai konsantre tenör ve verimleri belirlenmiştir.

Improving water electrolysis assisted by anodic biochar oxidation for clean hydrogen production

Biochar-assisted water electrolysis (BAWE) for hydrogen production is an effective way to integrate renewable electricity and biomass utilization. But it is limited by slow biochar oxidation reaction (BOR). Here we adopted the biochar derived from pyrolysis (PB) and hydrothermal carbonization (HB) of rice husk. Replacement of oxygen evolution reaction with BOR leaves a significantly reduced onset potential (Eonset) and an increased current density. Strongly related to carbonization temperature, the physicochemical properties of biochar markedly affected BOR. The abundant –OH groups in HB contributed to a low Eonset, while the well-developed pore structure and high specific surface area of PB enhanced its reactivity at higher potential. Exposure of functional groups on PB surface after pickling made an increase in current density, but the simultaneous elimination of easily oxidized solutes in HB dominated and caused current density decline. H2SO4 electrolyte of 1 mol/L was most appropriate for the uniform dispersion of biochar particles. The oxidation of PB derived at 800 °C with a slurry concentration of 10 g/L showed the lowest charge-transfer resistance and a favorable kinetics. Continuous BAWE indicated that PB was more superior than HB in increasing current density and H2 production. This work provides favorable strategies for improving BAWE.

Selective Leaching Trace Elements from Bauxite Residue (Red Mud) without and with Adding Solid NH4Cl Using Microwave Heating

Bauxite residue (red mud), which is an industrial byproduct, contains valuable trace elements. Solid NH4Cl was used as a chlorinating agent during the microwave heating of red mud to convert trace elements into soluble metal chloride. Red mud was heated using microwave ovens under various conditions (i.e., with the addition of solid NH4Cl and with a range of microwave output powers and microwave heating times). Leaching tests were then conducted using deionized (DI) water on the microwave-heated red mud to leach trace elements from red mud. V, Cr, and As were selectively leached from the microwave heated red mud slurry (30% water content), whereas Mn, Cu, Co, Ni, Zn, and Pb were selectively leached from the microwave-heated red mud with the addition of solid NH4Cl. The oxides of V, Cr, and As in red mud could be transformed into metal chlorides by chlorination, which are insoluble in water, or could be easily volatilized when red mud was microwave-heated in the presence of solid NH4Cl. On the other hand, the oxides of Mn, Cu, Co, Zn, Ni, and Pb in red mud could be heated rapidly by microwave irradiating, resulting in metal chlorides in the presence of solid NH4Cl. Those metal chlorides are relatively soluble in water, leading to higher leaching efficiency for microwave-heated red mud with the addition of solid NH4Cl. Experimental results suggest that trace elements from red mud can be selectively leached by microwave heating of red mud without or with the addition of solid NH4Cl.

Photocatalysis over N-Doped TiO2 Driven by Visible Light for Pb(II) Removal from Aqueous Media

The photocatalysis process over N-doped TiO2 under visible light is examined for Pb(II) removal. The doping TiO2 with N element was conducted by simple hydrothermal technique and using urea as the N source. The doped photocatalysts were characterized by DRUVS, XRD, FTIR and SEM-EDX instruments. Photocatalysis of Pb(II) through a batch experiment was performed for evaluation of the doped TiO2 activity under visible light, with applying various fractions of N-doped, photocatalyst mass, irradiation time, and solution pH. The research results attributed that N doping has been successfully performed, which shifted TiO2 absorption into visible region, allowing it to be active under visible irradiation. The photocatalytic removal of Pb(II) proceeded through photo-oxidation to form PbO2. Doping N into TiO2 noticeably enhanced the photo-catalytic oxidation of Pb(II) under visible light irradiation. The highest photocatalytic oxidation of 15 mg/L Pb(II) in 25 mL of the solution could be reached by employing TiO2 doped with 10%w of N content 15 mg, 30 min of time and at pH 8. The doped-photocatalyst that was three times repeatedly used demonstrated significant activity. The most effective process of Pb(II) photo-oxidation under beneficial condition, producing less toxic and handleable PbO2 and good repeatable photocatalyst, suggest a feasible method for Pb(II) remediation on an industrial scale.

Extending cycle life of the soluble lead redox flow battery with an auxiliary gas-diffusion electrode: a proof-of-concept study

Development and demonstration of soluble lead redox flow battery (SLRFB) is hindered due to its limited cycle life caused by the formation of lead dendrites, oxygen evolution reaction (OER), and accumulation of PbO2 sludge. OER leads to an imbalanced deposition of Pb metal at anode and PbO2 at cathode. As a result, complete oxidation of Pb is stalled during discharge of SLRFB. Besides, sluggish kinetics of cathode reaction results in accumulation of PbO2. Due to incomplete dissolution and accumulation of both active materials, concentration of Pb2+ decreases continuously in the electrolyte. Under such conditions, repeated charge–discharge cycling leads to the failure of SLRFB. In this study, we propose and demonstrate a novel route of using an auxiliary gas-diffusion electrode to obviate these problems to help in extending the cycle life of SLRFB. The auxiliary electrode is operated either as an air electrode or a hydrogen electrode. When the auxiliary electrode is an air electrode, it is used as positive electrode, and on coupling with anode of SLRFB, it forms a galvanic Pb–air flow cell that on discharge helps in oxidizing Pb metal to Pb2+ ions. When the auxiliary electrode is a hydrogen electrode, it is used as negative electrode, and on coupling with cathode of SLRFB, it forms a galvanic H2–PbO2 flow cell which on discharge reduces PbO2 to Pb2+ ions and mitigates the adverse effect of sludge accumulation in SLRFB.

Effect of strain and stoichiometry on the ferroelectric and pyroelectric properties of the epitaxial Pb(Zr0.2Ti0.8)O3 films deposited on Si wafers

Properties of epitaxial PbZr0.2Ti0.8O3 (PZT) films deposited on Si substrates were investigated for integration in the present CMOS technology. Polarization is downward oriented, in association with the presence of an internal electric field, and has a lower value compared to the PZT films deposited on single crystal perovskite SrTiO3 (STO) substrates (40 µC/cm2 versus 80 µC/cm2), while the dielectric constant is larger (180 versus 120). Large value for the pyroelectric coefficient was also found, 1.22 × 10−3C/m2K, as for PZT grown on single crystal STO. The macroscopic ferroelectric and pyroelectric properties appear to be affected by the structural quality and stoichiometry of the PZT film. The changes in the electric properties are an effect of the strain gradients induced by the large difference between the thermal expansion coefficients of PZT and Si substrate, leading in turn to Pb oxidation and antisite defect formation compared to PZT films deposited on STO substrates.