Fundamentals of lead-acid cells. X. The formation of PbO2 on lead and antimonial lead

The electrochemical oxidation of films of lead sulphate formed by the cyclic sweep method has been examined using the potential step technique. Gross differences in behaviour are observed between the lead and antimonial lead alloy, the most important being the appearance of an additional peak in the transient response of the antimony alloy. An interpretation is given in terms of the structure of the grown lead sulphate film. The oxidation behaviour of the lead sulphate deposits depends on the length of time the electrode is held potentiostatically controlled in the lead sulphate region before being stepped to the PbO₂ region. The results can be readily interpreted in terms of the density of nucleation sites and the formation of the PbO₂phase by the two-dimensional growth of instantaneously nucleated layers.     

锌电积用PbO_2复合惰性阳极材料制备及性能研究

以3Cr13不锈钢为基体,在由PbO45g/L和NaOH160g/L组成的镀液中加入20g/LCeO2(平均粒径30nm)或/和20g/LB4C(平均粒径6μm),采用阳极电沉积的方法制备了α-PbO2–B4C、α-PbO2–CeO2、α-PbO2–CeO2–B4C等3种复合惰性阳极材料,观察了其表面微观组织特征,测试了其电沉积时的阳极极化曲线以及在ZnSO4–H2SO4溶液中的循环伏安曲线和塔菲尔曲线,并与纯α-PbO2电极进行了对比。结果表明,CeO2、B4C或其两者与α-PbO2的共沉积改变了阳极沉积电位和α-PbO2的电结晶形貌,使晶粒尺寸减小,并导致α-PbO2在ZnSO4–H2SO4溶液中的阴极还原峰电位正移,及有助于提高α-PbO2的耐蚀性。α-PbO2–CeO2和α-PbO2–CeO2–B4C复合惰性阳极材料分别在低电位区和高电位区具有良好的析氧电催化活性。     

Electrochemical phenomena in aqueous electrowinning of lead

Attempts have been made to electrowin smooth and compact lead deposits from a medium containing glycine and hydrochloric acid, since this solution was recommended for its capacity to dissolve lead salts. Numerous factors such as electrolyte composition, current density, temperature, stirring and working electrodes were considered in the search for better quality deposits. Linear and cyclic sweep voltammetry, and potentiostatic and galvanostatic perturbations were employed in order to examine the processes at the cathode and to interpret the influence of some organic compounds added to the bath. Surface analyses of the lead deposit were performed by X-ray diffraction, scanning electron microscopy and Auger electron spectroscopy.     

Electrocatalysis of polyaniline formation by PbO2 in acetonitrile

Electrocatalytic effects on electropolymerization of aniline were investigated. It was determined that surface catalysis by β‐PbO₂ causes formation of higher amounts of polyaniline than catalysis by α‐PbO₂ and Pb²⁺ ions. β‐PbO₂ surfaces decreased the upper potential limit of aniline electropolymerization about 400 mV. The catalytic effect of PbO₂ is highly dependent upon the crystal structure of PbO₂. Dry conductivity values of polyaniline samples obtained under different conditions were also compared. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 599–605, 2003     

Electrochemical noise studies of the corrosion behaviour of lead anodes during zinc electrowinning maintenance

Following anodic polarisation of lead anodes with different silver contents (0.5-0.7%) during Zn electrowinning, the discharge and corrosion of lead anode during the decay period at open circuit potential in sulphuric acid bath have been studied by electrochemical noise analysis (ENA) method. Potential and current decay behaviour over 16 h shows 4 and 2 main characteristic regions, respectively. The wavelet transform has been employed to analyse the ENA data. The results of wavelets have demonstrated that energy distribution plot “EDP” was a powerful tool to provide useful information about the dominant process for different discharge and corrosion stages and mechanisms. The discharge is predominant than corrosion for all anodes for the regions I, II and III, and ENA feature of events changes from large timescale to low timescale, diffusion control or exfoliation to metastable pitting and pit growth, respectively. Region IV, only observed for 0.6% and 0.7%Ag, corresponds to general and metastable pitting corrosion under diffusion control. It has been found that anode containing lower silver content have more corrosion products even after 16 h of decay (discharge and attack dominated by pitting corrosion type with the highest corrosion due to the longest period of pitting during the 16 h).     

废铅酸蓄电池中二氧化铅还原技术研究进展

废铅酸蓄电池中的二氧化铅（PbO2）是一种两性氧化物,主要呈酸性,性质比较稳定,难以回收利用,但其含量仅次于硫酸铅,其还原回收率对铅的总回收率具有重大影响,使得人们对废铅酸蓄电池中二氧化铅的还原技术愈加重视。对国内外废铅酸蓄电池回收技术中二氧化铅的还原方法及研究现状进行了综述,分析了各种方法的优缺点,指出湿法还原优于火法还原,尤其是用草酸还原二氧化铅的方法比较理想,对环境无污染,并具有工业应用价值,值得做进一步的试验研究。     

Solid state electro-oxidation processes on lead and lead alloys in the PbO2/PbSO4 regions

The results are presented of potential step experiments in 5M sulphuric acid on lead and two lead alloys of some commercial importance. Differences in the nucleation and growth processes of PbO₂ on PbSO₄ are observed as a result of the presence of the alloying ingredient. The effect of Sb is very marked. Some reasons for the observations are discussed.Nomenclature A time dependent rate of nucleation - F Faraday constant - i _m maximum current - k ₁ parallel rate constant - k ₂ orthogonal rate constant - M molecular weight - n ₀ initial number of nuclei - t _m time corresponding to maximum current - z number of electrons transferred - density On study leave from Department of Chemistry, Helsinki University of Technology, Finland.     

Influence of Co2+ ions on cathode behaviour during zinc electrowinning

The effect of Co2+ ions on zinc deposition from acidic sulfate electrolytes is investigated on the basis of steady-state polarization curves and impedance measurements. Hydrogen evolution is shown to be enhanced by adsorbed cobalt on both the zinc deposit and the aluminium substrate, and this stimulation occurs in combination with the catalytic effect of adsorbed species originating from anodic products. Hydrogen evolution involves a diffusion-controlled step and a slow adsorption process which is the rate-determining step. It also induces the redissolution of the zinc deposit observable from the potential dependencies of current, charge transfer resistance and double layer capacitance.     

Bubble characteristics and aerosol formation in electrowinning cells

The nature of the aerosol emitted from a scale model zinc electrowinning system, operated under industrial conditions, has been established as a function of bubble formation rate, electrode surface characteristics, coalescence of bubbles, and control strategies. The emitted aerosol was collected and characterized using an Andersen Ambient Impactor. The effect of the relative humidity of the ambient air on the composition and density of the aerosol droplets was determined, permitting comparison of emissions on a standard basis. The size distribution of the aerosol was found to be of a bimodal nature indicating the presence of both film and jet droplets of geometric mean size 2 and 30m respectively. The amount and distribution of the aerosol were found to depend on the bubble size distribution in the cell which in turn depends on the anode surface, the amount and nature of the MnO₂ scale and surface active substances in the electrolyte. The gross emission rate was about 2–3 mgm^–2 s^–1 without any control. A new method of control of the acidic emissions is proposed based on observations made and results obtained from the study of the aerosol characteristics. Providing means of enhancing bubble coalescence below the electrolyte surface results in fewer and larger bubbles which yield less aerosol. The method has been evaluated in both zinc and copper electrowinning and leads to reduction of aerosol emission by over 90%.Paper presented at the International Meeting on Electrolytic Bubbles organized by the Electrochemical Technology Group of the Society of Chemical Industry, and held at Imperial College, London, 13–14 September 1984.     

Influence of Co2+ and Mn2+ ions on the kinetics of lead anodes for zinc electrowinning

The influence of Co²⁺ and Mn²⁺ ions on the kinetics of lead and lead–silver alloy anodes is analysed using impedance spectroscopy and steady-state polarisation curves. With lead–silver anodes, increasing the Mn²⁺ concentration catalyses the oxygen evolution current by stimulating the reaction rate. Impedance data reveal a transient inhibition of the reaction, ascribed to the adsorption of a silver-salt containing manganese. The addition of Co²⁺ catalyses oxygen evolution, mainly on the pure lead anode. For lead–silver anodes, the small catalytic effect of Co²⁺ ions implies an increase in the Tafel coefficient for the oxygen reaction. The transient inhibiting process suggests the formation of a cobalt-containing adsorbate on the pure lead anode.     

PbWO4 formation during controlled crystallization of lead borate glasses

Lead borate glasses were prepared and then heat treated in order to obtain transparent glass-ceramics. Controlled crystallization of precursor lead borate glass at appropriate annealing temperature and time led to formation of the PbWO₄ crystallites. The observed broad blue emission band is related to the PbWO₄ crystallites. The influence of PbX₂ content (X=F, Cl, Br), PbF₂ concentration and lanthanide doping (Eu, Dy) on the excitation and emission spectra of lead borate glass-ceramics containing PbWO₄ phase was examined. The relationship between Pb–X bond and spectral line width of the blue emission can be successfully observed, when halogen X ions (X=F, Cl or Br) are also present in the distorted PbWO₄ crystallites.     

A note on the impedance of reduced PbO2 layers on some lead alloys in sulphuric acid

The impedances of reduced layers of PbO₂ in sulphuric acid are measured at potentials in the range between initial discharge and complete reduction to lead. The electrode behaviour is fairly polarizable when the electrode is remote from the PbSO₄/Pb potential. Near the reversible potential the electrode behaves as a porous electrode under charge-transfer and diffusion control.     

Corrosion rates of lead based anodes for zinc electrowinning at high current densities

The corrosion rates of anodes made from various lead/silver alloys have been determined during electrolysis in sulphuric acid solution, pure and containing additives, using current densities in the range 2500 to 10 000 A m^–2. An increase in acid concentration, and in some cases temperature, caused an increase in the corrosion rate. In the absence of manganese in the bath, the corrosion rate was effectively independent of current density in the range studied, whereas in the presence of manganese, the corrosion rate decreased with decreasing current density. The corrosion rates of various calcium, tin and thallium alloys of lead were also determined. The presence of chloride ions in the electrolyte increases the corrosion rate, whereas potassium ions and strontium carbonate have a negligible effect. Pre-treating silver/lead anodes with a solution of acidic potassium fluoride at 500 A m^–2 prior to testing markedly decreased the corrosion rate in the presence of manganese, but increased the corrosion rate with manganese absent. The effect of zinc on the corrosion rate in synthetic electrolyte solutions, with and without manganese present, has also been determined for silver/lead alloys at 10 000 A m^–2. At zinc levels over 1 M, the corrosion rate increased with and without added manganese. As the work has been undertaken in an attempt to improve the electrowinning of zinc, an electrolyte based on acidified industrial solution has also been tested. The rates observed were similar to those obtained for synthetic zinc-containing solutions.     

Influence of lead dioxide surface films on anodic oxidation of a lead alloy under conditions typical of copper electrowinning

Cyclic voltammograms, current transients at constant potential and potential decay transients have been used to study the formation of lead dioxide surface films in the presence of cobalt ions and their role in decreasing the oxidation rate of a lead alloy under steady state conditions typical of copper electrowinning. The observations in the present work indicate, consistent with the surface film model, that the formation of a continuous PbSO₄ + α-PbO₂ film on the surface of the lead alloy in the presence of cobalt ions hinders further oxidation of the metal. The protectiveness of the film is dynamic in the steady state; the film is continuously forming and dissolving. Also studied was the potential of the oxygen evolution reaction on α-PbO₂ and β-PbO₂ in 170 g L⁻¹ H₂SO₄ with and without cobalt ions. The steady state potential for oxygen evolution on β-PbO₂ in 170 g L⁻¹ H₂SO₄ at 285 A m⁻² decreased in the presence of cobalt ions and the steady state potential of β-PbO₂ was essentially the same as that of (i) the Pb–Ca–Sn alloy and (ii) α-PbO₂. The implication is that the potential of the Pb–Ca–Sn alloy is determined by the α-PbO₂ and/or β-PbO₂ on its surface.     

The influence of PbO modification on the kinetics of the 4PbO·PbSO4 lead-acid battery paste formation

The influence of PbO modification on the formation of 4PbO·PbSO₄ paste is determined by X-ray diffraction analysis and scanning electron microscopy. The paste was prepared from tetragonal PbO, orthorhombic PbO and several mixtures of both oxides at 80° C and a H₂SO₄/PbO ratio of 6 wt%.The reaction scheme of 4PbO·PbSO₄ formation depends on the PbO modification. When tetragonal PbO is used, 3PbO·PbSO₄·H₂O crystals are obtained first and then 4PbO·PbSO₄. If the initial oxide is orthorhombic PbO, PbSO₄, PbO·PbSO₄ and 3PbO·PbSO₄·H₂O are formed successively. When the correct ratio of 3PbO·PbSO₄·H₂O, orthorhombic PbO and tetragonal-PbO is achieved in the paste then 4PbO·PbSO₄ formation begins. This ratio is reached most quickly if tetragonal PbO is present at 30–60wt% in the initial mixture of both modifications.     

Zinc electrowinning with 2-butyne-1,4-diol

The beneficial effect of 2-butyne-1,4-diol on zinc current efficiency in the presence of nickel impurity has been examined. Several techniques including HPLC, absorption spectrophotometry and constant current deposition experiments have shown that a trimer of 2-butyne-1,4-diol is responsible for the removal of Ni ions from the electrolyte, thus increasing the current efficiency of the zinc electrowinning process from sulphate solutions (60 g/L Zn + 200 g/L H₂SO₄) in the presence of Ni ions.     

The perchlorate-assisted formation of lead dioxide on lead

Perchloric acid affects the phase formation process during the oxidation of lead to PbO₂ in dilute sulphuric acid. In sulphuric acid, the reaction involves a two-dimensional instantaneous nucleation process for the production of PbO₂. In the mixed acid, the growth of PbO₂ in low concentrations (20 mM) of added perchlorate ion remains two-dimensional but the nucleation becomes progressive and at higher perchlorate concentrations phase formation occurs by three-dimensional growth. A range of perchlorate concentration (30–40 mM) exists where the attack is on an advancing front (analogous to the electrodeposition of a metal from solution), in which the PbO₂ steadily advances into the metal. A mechanism is proposed for the Planté reaction process.     

The breakdown of PbO2-Ti anodes

Lead dioxide-titanium electrodes have been tested as oxygen evolving anodes in 1 mol dm^–3 H₂SO₄, at high current densities. Three modes of failure, shedding, thinning and deactivation have been identified. The first two are the result of stresses produced during electrodeposition, compounded by the thermal effects of polarization. Some improvements in these aspects of performance have been made by manipulation of the plating conditions. Deactivation has been modelled by considering the diffusion of special sites from the bulk material. There is continuous redeposition of PbO₂ from the solution.     

The effect of Co2+, Cu2+, Fe2+ and Fe3+ during electrowinning of nickel

The effects of the impurities Co²⁺, Cu²⁺, Fe²⁺, Fe³⁺ on the current efficiency, physical appearance, purity, crystallographic orientation and surface morphology of the deposit and on nickel deposition polarization behaviour during nickel electrowinning were determined. The current efficiency did not change significantly in the presence of these impurities over the concentration range studied, but certain changes in the purity and physical appearance of the deposit were observed. Based on the physical appearance of the electrodeposited nickel, the tolerance limits of the impurities in the electrolyte are reported. The tolerance limit of Co²⁺ was a maximum at 500 p.p.m. and a minimum at 5 p.p.m. in the case of Fe²⁺. No deviation of nickel structure from fcc was observed in the presence of any of these impurities but the peak height values for different orientations showed variations with all the impurities and the values also changed with increase in the impurity concentrations. The surface morphology of electrodeposited nickel also changed in the presence of the impurities. The potentiodynamic scan curves for electrodeposition of nickel showed deviations in the presence of all the impurities except Cu²⁺. Based on the results, an attempt is made to correlate the effects of the various factors investigated.     

二氧化铅电极的制备及应用现状

二氧化铅电极具有耐腐蚀性好、导电性强、析氧过电位高、催化性好、成本低等优点，是性能良好的阳极材料。介绍了二氧化铅电极的电化学性能及其在无机化学工业、有机化学工业和环保领域的应用现状；综合评述了国内外不同二氧化铅复合电极的制备方法、过程和不足；介绍了目前国内外最新的二氧化铅／SPE复合膜电极的发展现状、优点及制备方法。指出随着电化学工艺的发展，二氧化铝电极的应用将更加广泛，拥有更多优越性的二氧化铅／SPE复合膜电极的研究也将更加深入。