Porous PbO2 Research Articles

Electrochemical Behaviour of Porous PbO2 Layers Prepared by Oxygen Bubble Templated Anodic Deposition

Porous PbO2 layers were produced from methanesulfonic acid or perchloric acid media, through an oxygen bubble templated anodic deposition process, i.e. by oxidizing Pb2+ ions at large current densities, with simultaneous oxygen evolution. The effect of deposition current density, Pb2+ concentration and nature of the acid on the deposit porosity (assessed through number of pores per unit surface area, average pore diameter, and void volume fraction) were investigated. Porous PbO2 deposits obtained from both media consisted of the same mixture of α- and β-phases, although the corresponding compact deposits had significantly different structures (pure α-PbO2 from methanesulfonic acid, a mixture of α- and β- PbO2 from perchloric acid). The cycling behaviour of compact and porous PbO2 layers in 1.0M H2SO4 was compared. During the first cycle, the reduction charge was much higher for porous than for compact layers, as a consequence of the different electrochemically active areas. For the former it depended on the layer thickness, while it was independent of it for the latter. Upon cycling, the charges exchanged by compact layers steadily increased, whereas those of porous layers, after an initial increase, slowly declined, but remained markedly higher.

Oxygen bubble–templated anodic deposition of porous PbO 2

The oxygen bubble–templated deposition of porous PbO2 was realized by anodizing Pb(II) solutions (in nitrate-acetate, sulfamate or methanesulfonate media) at large current density. This process is the anodic analogue of the more common hydrogen bubble–templated electrodeposition of porous metals. The porous PbO2 layers consisted of a mixture of α- and β-phases, in contrast to compact layers deposited at low current density (pure α-PbO2). The void volume fraction and surface roughness factor of porous PbO2 were estimated.

Theoretical and Experimental Insights into the Electrochemical Mineralization Mechanism of Perfluorooctanoic Acid

The electrochemical mineralization mechanism of environmentally persistent perfluorooctanoic acid (PFOA) at a Ce-doped modified porous nanocrystalline PbO2 film anode was investigated using density functional theory (DFT) simulation and further validated experimentally. The potential energy surface was mapped out for all possible reactions during electrochemical mineralization reaction of PFOA. The hydroxyl radical (·OH), O2 and H2O took part in the mineralization process and played different roles. The ·OH-initiated process was found to be the main degradation pathway, and the existence of O2 obviously accelerated the degradation process of PFOA in aqueous solution. On the basis of the DFT calculations, an optimal electrochemical mineralization mechanism of PFOA was proposed, which involved the electronic migration, decarboxylation, radical reaction, hydrogen abstraction reaction, and radical fragmentation reaction. The proposed mechanism was verified by the dynamics and intermediate determination experiments. Furthermore, the observed ·OH concentration showed that the electrolysis system could produce enough ·OH for PFOA mineralization process, indicating that the proposed ·OH-initiated process derived from DFT calculations was feasible. These insightful findings are instrumental for a comprehensive understanding of the mineralization of PFOA in the electrolysis system.

Correction to Electrochemical Mineralization of Perfluorocarboxylic Acids (PFCAs) by Ce-doped Modified Porous Nanocrystalline PbO2 Film Electrode

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionCorrection to Electrochemical Mineralization of Perfluorocarboxylic Acids (PFCAs) by Ce-doped Modified Porous Nanocrystalline PbO2 Film ElectrodeJunfeng Niu*, Hui Lin, Jiale Xu, Hao Wu, and Yangyang LiView Author Information State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, P.R. China*Phone: +86-10-5880 7612; fax: +86-10-5880 7612; e-mail: [email protected]Cite this: Environ. Sci. Technol. 2013, 47, 9, 4959Publication Date (Web):April 22, 2013Publication History Published online22 April 2013Published inissue 7 May 2013https://doi.org/10.1021/es401587yCopyright © 2013 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views918Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (120 KB) Get e-Alerts Get e-Alerts

Cyclic voltammetry and passivation behaviour of lead in Na2HPO4 solution

Abstract The electrochemical and passivation behaviour of lead electrode in 0.10 mol dm−3 Na2HPO4 solution was studied using cyclic voltammetric technique and complemented by X-ray surface analysis. The anodic half-cycle of the voltammogram exhibits active, pre-passive, passive and transpassive regions before the oxygen evolution. Passivity is due to the formation of thick porous PbO film by three-dimensional nucleation and growth on the electrode surface. The transpassive region is attributed to the electroformation of PbO2. The cathodic half-cycle shows two cathodic peaks as well as a small shoulder at the extreme negative potential just before the hydrogen evolution. The mechanism of formation of the passive film is discussed.

Preparation of porous PbO 2 electrodes by electrochemical deposition of composites

Porous PbO 2 electrodes have been prepared by anodic codeposition of PbO 2 particles with an electrochemically grown PbO 2 matrix, with the aim of illustrating how composite deposition may be a suitable method for obtaining electrodes of large and controlled surface roughness. By exploiting the different crystal structures of PbO 2, the composition of α-PbO 2+β-PbO 2 composites (i.e. composites with an α matrix and a β dispersed phase) has been determined by X-ray diffraction. It has been found that reliable indications on composition of deposits may be also obtained by measuring the current efficiency of the deposition process, which largely exceeds unity in the case of composites. This way, the dependence of the dispersed phase concentration in the deposits on current density and suspended particles concentration has been determined. The surface roughness of the composite electrodes has been estimated by electrochemical impedance spectroscopy. It was found to increase almost linearly with the deposition charge and reach limiting values as either the deposition current density or the suspended particles concentration are increased.

How to understand the reversible capacity decay of the lead dioxide electrode1Dedicated to: Prof. August Winsel, the father of the Agglomerate-of-Spheres Model, on the occasion of his 70th birthday in August 1998.1

Unfavourable cycling conditions may successively lead to a porous PbO2 structure with poor mechanical and electrical connection between the particles of which the porous electrode is built. Increasing active material resistance of this skeleton will induce a more and more inhomogeneous current distribution over the active mass, with successive restriction of the discharge/recharge processes to the active material area near to the grid. This leads to excessive mass utilisation in this very region, which aggravates the situation from cycle to cycle. The results are active material softening and shedding. This change of PbO2 structure can be reverted, when cycling is continued with modified regimes. By this and by other means, lost capacity may be recovered. This effect is called reversible capacity decay or reversible insufficient mass utilization (RIMU). The Aggregate-of-Spheres Model (AOS), based on the behaviour of sintered bodies, describes semi-quantitatively the phenomena at the connecting sites of the particles of the PbO2 active material, explaining the experimental findings of reversible capacity decay. The main features of reversible capacity loss are discussed in terms of AOS explanations, in order to work out strategies and limits for the improvement of lead/acid battery performance.

Potentiostatic step experiments on pasted Pb-Sb and Pb-Sn-Ca electrodes

A range of cyclic electrochemical experiments have been carried out on electrodes of porous PbO2 supported on a number of Pb-Sb and Pb-Sn-Ca alloys using micro-computer controlled potentiostatic stepping techniques. The results show that, in certain cases, the differences in electrochemical behaviour of the PbO2 can be interpreted as being due to the effect of the support alloy.

Application of the galvanostatic interrupter method to the study of the polarization during the discharge of PbO 2 electrodes

The discharge curves of porous PbO 2 electrodes have been studied by application of the galvanostatic interrupter technique. The necessary modifications of commercially available measuring devices are described. The differences of electrode potential 50 and 1000 μs after current interruption are presented as a function of the discharge time or overdischarge time. From these measurements and the corresponding time constants of the cut-off curves, conclusions can be made about the reactions during the discharge process. Unpretreated electrodes were investigated as well as thermally pretreated ones.

The impedance of porous PbO 2 supported on lead alloy bases in sulphuric acid

The impedance of porous PbO 2 on various lead alloy supports in H 2SO 4 has been measured over a large potential region. An analogue previously developed for pure-lead-supported systems was used to describe the discharge behaviour of the electrodes. The behaviour of systems on the various alloy electrode bases is comparable with that for lead-based systems. Bismuth addition to the support alloys does not appear to donate desirable properties to the electrode systems.

The a.c. impedance of porous PbO 2 on a lead support in sulphuric acid

The impedance of the porous PbO 2 layer formed by electro-oxidation of a complex “paste” on a PbO 2-covered lead support has been measured over a range of potential. Differences were observed as the potential was shifted. An analogue has been developed which represents the behaviour of the electrode.

Morphological study of porous PbO 2 formed in aqueous H 2SO 4 on Pb-Sb and Ca-Sn-Pb alloys

A morphological study of the PbO 2 matrix formed by the oxidation of pasted Pb-Sb and Ca-Sn-Pb electrodes in 0.3 M H 2SO 4 and then subjected to microcomputer-controlled potentiostatic pulse experiments in 5 M H 2SO 4 is presented. After a reductive pulse into the PbSO 4 region, a complete discharge and a re-step back into the PbO 2 region, it was found that with the Pb-Sb ‘positive’ a considerable amount of α-PbO 2 was produced. This was very different from the case of the Ca-Sn-Pb-supported PbO 2 matrix where β-PbO 2 was predominantly formed.

The formation of PbSO 4 at the PbO 2 planté electrode

The development of PbSO 4 in porous PbO 2 electrodes formed by the Planté process was investigated by the impedance method. The results were significantly different from those reported earlier for thin films of PbO 2 formed on lead by potentiostatting in the PbO 2 region. The data allow for deductions to be made regarding the effect of the porous structure.

Discharge profiles in the porous PbO 2 electrode

The macrohomogeneous model of porous PbO 2 positive plates indicates that a curving discharge profile should be observed with the majority of current arising from the front of the electrode. These expectations were investigated by electron microscopy. The results are not consistent with the theory. Explanations are given in terms of phenomenological observations.

Fundamentals of lead acid cells part IV. The reduction of porous PbO2 electrodes in sulphuric acid

The reduction behaviour of porous lead dioxide electrodes is shown to be independent of rotation speed in a large excess of 5 M H2SO4. The reduction peak is broadened by the porosity. This porosity broadening is interpreted in terms of the reaction being driven more deeply into the pore structure as the front of the electrode becomes progressively more ressstive. The effect of different potential sweep rates on the current response and the effects of progressive redox cycles can be fully explained on this model.

Fundamentals of lead acid cells: Part IV. The reduction of porous PbO 2 electrodes in sulphuric acid

The reduction behaviour of porous lead dioxide electrodes is shown to be independent of rotation speed in a large excess of 5 M H 2SO 4. The reduction peak is broadened by the porosity. This porosity broadening is interpreted in terms of the reaction being driven more deeply into the pore structure as the front of the electrode becomes progressively more ressstive. The effect of different potential sweep rates on the current response and the effects of progressive redox cycles can be fully explained on this model.

Hydrodynamic instabilities in a lead acid battery

WE demonstrate here the feasibility of the observations of hydrodynamic instabilities in a lead acid battery during the discharge process. We use a system comprising two horizontal electrodes immersed in a transparent cell. The electrodes contain in the charged state porous PbO2, the ‘positive’ electrode, and porous Pb, the ‘negative’ electrode. The electrodes were prepared to commercial standards using common industrial processes.