PbO2 Deposition Research Articles

Effect of CH3NH3I/CH3NH3Br precursors on the structural and surface morphology properties of the electrodeposited methylammonium lead–mixed halide perovskite films

Organometallic halide perovskites have been arisen as a class of multi-purpose materials with exciting applications in optoelectronic devices such as solar cells, light-emitting diodes, photo detectors, and laser diodes. In spite of a significant hope in performance, still production process in ambient air and its stability must be addressed as the main issues for this type of material. In this work, a versatile and scalable fabricating process of halide mixed perovskite layers through electrochemical deposition of PbO2 on FTO (fluorine-doped tin dioxide–coated glass) substrates and double-vapor transformation with HX and CH3NH3X (X = I & Br) vapors without using a glove box or a high vacuum system is demonstrated. Highly crystalline hollow-free electrodeposited perovskite layers on FTO substrate were achieved. Treatments with CH3NH3Br/CH3NH3I precursors were also investigated to check the possible impact on the quality of the final perovskite layer. It was illustrated that the use of CH3NH3I or CH3NH3Br precursors in the last step of the electrochemical synthesis can determine the properties of the perovskite film. When PbI2 and PbBr2 films exposed to CH3NH3Br vapor, bromine-treated perovskites were achieved with uniform grain size of ~ 1.5 to 2.3 μm. Similar treatment with CH3NH3I vapor led to the smaller grain size perovskite layers (~ 0.7 μm). Final properties of all fabricated layers, including optical absorption, bandgaps the crystalline phases, and chemical composition, were characterized and compared.

Reaction Selectivity of IrO2-Based Nano/Amorphous Hybrid Oxide-Coated Titanium Anodes in Acidic Aqueous Solutions: Oxygen Evolution and Lead Oxide Deposition

The present study demonstrated that novel IrO2-Ta2O5/Ti anodes prepared by thermal decomposition at a low temperature of 380 °C have high reaction selectivity for oxygen evolution and metal oxide deposition in acidic aqueous solutions. Conventional IrO2-Ta2O5/Ti anodes are generally prepared at a temperature between 450 °C and 500 °C. However, if Pb(II) ions are present as an impurity in the electrolyte, the oxidation of Pb(II) ions occurs as an anodic side reaction, leading to deposition of PbO2 onto the conventional anodes. Herein, we prepared IrO2-Ta2O5/Ti anodes by thermal decomposition at the low temperature of 380 °C and investigated their crystallographic structure, surface morphology, and polarization behaviors for oxygen evolution as well as their suppression effect for anodic PbO2 deposition in sulfuric acid/lead sulfate solutions. SEM observations with low accelerated incident electrons revealed that the nano/amorphous hybrid structure consisting of nanosized IrO2 particles highly dispersed in the amorphous Ta2O5 matrix can be prepared at 380 °C. Oxygen evolution was accelerated with an increasing Ir ratio in the anodes prepared at 380 °C in sulfuric acid solutions. Anodic PbO2 deposition on the anodes prepared at 380 °C in lead sulfate solutions, which assumed the conditions of practical use, was completely suppressed.

Development of a two-dimensional, moving mesh treatment for modelling the reaction chamber of the soluble lead flow battery as a function of state of charge for Pb and PbO2 deposition and dissolution

Abstract During cycling of the soluble lead flow battery, solid layers of lead (Pb) and lead dioxide (PbO2) are deposited and stripped from the electrode surfaces. As such, there is a change in geometry of the flow field within the battery. A detailed two-dimensional numerical model which simulates this change in geometry using a moving mesh technique is developed. The model accounts for deposition of Pb, PbO2 along with the formation of lead oxide (PbO) during discharge of the PbO2 deposit due to a side reaction which is commonly assumed in the literature. Over short time scales of around 1 hr charge/discharge periods, which are typically reported in the literature, the effect of this is small. However, over more realistic time scales (>1 hr), by applying this technique, significant differences are seen in the cell resistance and in the mass flow rate of electrolyte. As a result, a difference in cell voltage of up to 65 mV is seen over a 24 h period. The numerical results are validated against experimental data, showing an agreement in the voltage-time profile and a close fit for the moving mesh approach.

Electrosynthesis and catalytic activity of PbO2‐fluorinated surfactant composites

AbstractBACKGROUNDThe effect of the potassium salt of nonafluorobutanesulfonic acid (C4F9SO3K) on the kinetic regularities of electrodeposition of lead dioxide (PbO2) from nitrate electrolytes has been investigated. Obtained results concerning synthesis and physicochemical properties can contribute substantially to a fundamental understanding of the relationship between coating structure and catalytic activity, important to all fields of catalysis.RESULTSThe introduction of C4F9SO3K into the PbO2 deposition electrolyte leads to insignificant inhibition of the Pb2+ electro‐oxidation process, whereas the mechanism of the process does not change. Upon deposition of coatings from electrolytes containing surfactants, a composite coating is formed. Depending on the electrolyte composition and electrolysis conditions, the surfactant content in the composite can vary from 2.00 ± 0.05 to 17.00 ± 0.05 wt%. The inclusion of surfactants in the coating composition with subsequent overgrowth with PbO2 leads to a decrease in the size of PbO2 crystals and prevents the formation of polycrystalline blocks. The composite material is a PbO2 matrix with submicron and nanoscale crystals into which surfactant particles are embedded.CONCLUSIONIt was shown that the electrocatalytic activity of composite PbO2‐surfactant materials depends on the nature and content of the latter in the composite. The use of PbO2 doped with C4F9SO3K as an anode leads to an inhibition of the process of oxygen evolution and an almost three‐fold increase in the rate of electrochemical conversion of 4‐chlorophenol to aliphatic compounds. © 2020 Society of Chemical Industry

An in-depth study of lead dioxide formation in nitrate and methanesulfonate solutions by in situ analysis and numerical model

An in-depth understanding of PbO2 formation is critical for the development of PbO2 electrodes preparation and battery applications. In this study, incorporating in situ atomic force microscopy, electrochemical quartz crystal microbalance and numerical modelling technologies, the details in nitrate and methanesulfonate electrolytes are observed and simulated during electrodeposition. The behavior of PbO2 deposition in soluble media is observed in situ by atomic force microscopy for the first time in this study. Both in nitrate and methanesulfonate solutions, the PbO2 deposits are initially formed only by circle-like phase alone, and then pyramidal phase is formed or the two phases are identical. If the deposition is carried out for longer time, the growth centers of phase with slower grow rate can be covered by another phase. The ratio of mass to electrical charge for PbO2 deposition onto gold in methanesulfonate electrolyte attains 0.85 mg C−1, which is bigger than nitrate electrolyte. Variations of species concentration distribution and oxygen evolution current density are simulated in this study. The influence and concentration distribution of Pb(CH3SO3)+ are investigated probably for the first time in model.

Significance of PbO deposition ratio in activated carbon-based lead-carbon composites for lead-carbon battery under high-rate partial-state-of-charge operation

Lead-carbon composites are effective additives in lead-carbon negative electrode due to their beneficial influences on the performance of negative electrode of lead-carbon battery operated under high-rate partial-state-of-charge duty. In this paper, to further investigate the effects of the lead monoxide (PbO) deposition ratio of activated carbon (AC) based lead-carbon composite additives, we prepared lead-carbon composites (termed as PbO@AC) with different controllable PbO deposition ratios successfully through a facile coupled chemical-deposition/pyrolysis strategy. The hydrogen evolution reaction of AC and lead-carbon electrode is effectively inhibited through the deposition of PbO. PbO@AC-2 sample with a PbO deposition ratio of 9.9% exhibits the best electrochemical performances when used as the negative electrode additive. The evidently enhanced performances of lead-carbon electrodes, such as rate capability and cycling life under high-rate partial-state-of-charge operation, indicate the beneficial effects of deposited PbO. Particularly, PbO@AC-2 battery exhibits the longest cycling life of more than 10,000 cycles which is 1.956 times that of lead-carbon battery with AC as the negative electrode additive. The improved performances of lead-carbon electrode enabled by PbO@AC-2 originate from both the inhibition of hydrogen evolution reaction and the enhanced electrochemical reversibility of the Pb/PbSO4 redox reaction. PbO@AC-2 exhibits the best trade-off between inhibiting hydrogen evolution and building extra electrochemical active area for the deposition of Pb.

Composite Electrodes PbO2-Nafion®

PbO2-polyelectrolyte composite materials with a content of polyelectrolyte up to 13 wt% are formed by electrochemical deposition of PbO2, depending on the solution composition and the deposition conditions. Several assumptions concerning the mechanism of the formation of composites that taking into account the oxygen-containing species of lead non-fixed on the surface, located in the near-electrode zone have been proposed. The shape and size of the PbO2 crystals is altered by the presence of polyelectrolyte. The surface is more uniform and the crystals are smaller, there is not a pronounced crystallographic orientation, however the phase content remains practically the same as in the undoped sample. When using composite materials based on lead dioxide containing polyelectrolyte, selective changes in the overvoltage of oxygen evolution and electrochemical conversion of organic substances into aliphatic non-toxic compounds are observed. In this case, the electrocatalytic activity of composite materials depends on the nature and content of the polyelectrolyte additive in the oxide.

Effects of additives on the morphology and stability of PbO2 films electrodeposited on nickel substrate for light weight lead-acid battery application

Abstract This work investigated the effects of NaF and sodium dodecyl sulfate (SDS) on the morphology and stability of electrodeposited PbO2 film. The PbO2 electrodeposition was conducted on the Ni-substrate by galvanostatic anodic deposition in acidic Pb(NO3)2 solution to be employed as a positive electrode in the lightweight lead-acid battery. The stability and electrochemical properties of the film were investigated by cyclic voltammetry in 4.7 mol L−1 H2SO4. Phase constituents and microstructures of the deposited PbO2 before and after cycling was characterized using atomic force microscope (AFM), scanning electron microscope (SEM), and X-ray diffraction spectroscopy. Experimental results show that current density and the concentration of Pb(NO3)2 and NaF positively affected the current efficiency for PbO2 deposition. A mixed-phase (ɑ-PbO2 and β-PbO2), relatively less stable (persist up to 80 cycles) and larger-grained deposit with low charge-discharge density was produced in the absence of SDS. The addition of a small amount of SDS in the electrolyte increased the proportion of β-PbO2 having compact and small-grained crystals resulting in the improvement of the stability (persist up to 300 cycles) and charge-discharge density of the PbO2 film in the battery environment. The density functional theory (DFT) calculation confirmed that the higher binding energy of H2O to the defected PbO2 sites caused by high cycling was mainly responsible for enormous oxygen evolution which eventually resulted in the failure of the positive electrode and water loss of the battery during operation.

Determination of the lead oxide fouling mechanisms in lead bismuth eutectic coolant

An increased interest in the use of liquid metals for novel energy conversion systems is present today. The Accelerator Driven System (ADS) called MYRRHA under design at the Belgian Nuclear Research Centre (SCK-CEN) is an example of such an innovative system. The use of Lead-Bismuth Eutectic (LBE) as a coolant for this reactor implies that an accurate knowledge on the chemical properties of the coolant needs to be available. An important factor is the risk of coolant oxidation due to oxygen ingress in the system. Although the formation of lead oxide (PbO) is well understood, the deposition mechanism and kinetics are not yet studied. In this work the deposition mechanism of PbO on 316L stainless steel is investigated. The evolution of the dissolved oxygen concentration during thermal cycling of LBE indicates that fouling of isothermal surfaces by PbO can only proceed by particle deposition. On the other hand, the fouling of non-isothermal surfaces by PbO is dominated by crystallization fouling. A real-time measurement of the PbO deposition rate shows an asymptotic behavior of PbO crystallization fouling. By predicting the onset of PbO nucleation and subsequent growth, a kinetic model for the crystallization fouling is put forward. Quantitative agreement between deposition rate predictions and validation measurements is obtained around 673 K.

(Invited) Energetic Hole Ejection Involved in Plasmon-Induced Charge Separation: Local Oxidation and an Application to Near IR Photovoltaics

Plasmon-induced charge separation (PICS)1-3 involves electron transfer from plasmonic nanoparticles of Au, Ag, or Cu to a semiconductor such as TiO2.1-4 PICS of Ag-TiO2 systems often involve oxidation of Ag to Ag+,5 and that this reaction occurs preferentially at resonance sites, at which optical near fields are localized.6-8 This cannot be ascribed to thermal acceleration of reaction,9 but can be explained in terms of ejection of energetic holes from the nanoparticles as Ag+ ions. This hole ejection has been investigated further for Au nanocubes on TiO2 by using other reactions; Pb2+ oxidation to PbO2 and pyrrole oxidation to polypyrrole. Au nanocubes on TiO2 show distal mode, in which electron oscillation is localized at the top face of the nanocube, and proximal mode, in which electron oscillation is localized at the bottom face. In the case of Pb2+ oxidation, PICS for the distal mode and proximal mode resulted in PbO2 deposition at around the top face and the bottom face, respectively.10 However, in the case of pyrrole oxidation, both of the distal mode PICS and proximal mode PICS resulted in polypyrrole deposition at the whole surface of the nanocube. On the basis of those results, we conclude that the localized oxidation and the delocalized oxidation are ascribed to energetic hole ejection mechanism and positive charge accumulation mechanism, respectively. We have applied energetic hole ejection to fabrication of chiral plasmonic nanostructures11 and near IR photovoltaics.12 Y. Tian and T. Tatsuma, J. Am. Chem. Soc., 127, 7632 (2005).Y. Tian and T. Tatsuma, Chem. Commun., 2004, 1810.T. Tatsuma, H. Nishi, and T. Ishida, Chem. Sci., 8, 3325 (2017) [review].E. Kazuma and T. Tatsuma, Adv. Mater. Interfaces, 1, 1400066 (2014).Y. Ohko, T. Tatsuma, T. Fujii, K. Naoi, C. Niwa, Y. Kubota, and A. Fujishima, Nat. Mater., 2, 29 (2003).E. Kazuma, N. Sakai, and T. Tatsuma, Chem. Commun., 47, 5777 (2011).I. Tanabe and T. Tatsuma, Nano Lett., 12, 5418 (2012).K. Saito, I. Tanabe, and T. Tatsuma, J. Phys. Chem. Lett., 7, 4363 (2016).K. Saito, K. Setoura, S. Ito, H. Miyasaka, Y. Mitsuda, and T. Tatsuma, ACS Appl. Mater. Interfaces, 9, 11064 (2017).H. Nishi, M. Sakamoto, and T. Tatsuma, Chem. Commun., 54, 11741 (2018).K. Saito and T. Tatsuma, Nano Lett., 18, 3209 (2018).S. H. Lee, H. Nishi, and T. Tatsuma, Nanoscale, 10, 2841 (2018).

Remarkable Visible-Light Photocatalytic Activity Enhancement over Au/p-type TiO2 Promoted by Efficient Interfacial Charge Transfer.

Metal-induced photocatalysis has emerged as a promising approach for exploiting visible-light-responsive composite materials for solar energy conversion, which is generally hindered by low photocatalytic efficiency. Herein, for the first time, an Au/p-TiO2 (p-type TiO2) strategy with the hole transfer mechanism is developed, remarkably promoting visible-light photocatalytic performance. An efficient acetone evolution rate (138 μmol·g-1·h-1) in the photocatalytic isopropyl alcohol (IPA) degradation under λex = 500 nm light (light intensity, 5.5 mW/cm2) was achieved over Au/p-TiO2, which is approximately 5 times as high as that over Au/n-TiO2 under the same conditions. Photoluminescence and electrochemical impedance spectroscopy measurements indicate enhanced charge carrier separation and transfer for Au/p-TiO2. In an elaborate study, apparent quantum efficiency and transmission electron microscopy characterization on selective PbO2 deposition over p-TiO2 revealed that visible-light-excited holes other than electrons generated in the Au interband transition transferred to p-TiO2, which is opposite to the general route in Au/n-TiO2 (n-type TiO2). Energetic holes generated in the d band of Au led to a fluent transfer across the Schottky barrier, which is further confirmed by the IPA photodegradation mechanism study with different scavengers over Au/p-TiO2. This discovery opens up new opportunities in designing and developing efficient metal semiconductor composite materials with visible-light response.

High-Temperature Pb Doping of SnO2 and Growth Limitations of PbxSn1–xO2 Nanowires Versus Low-Temperature Growth of PbxSn1–xO for Energy Storage and Conversion

Pb doping of SnO2 nanowires grown by the vapor–liquid–solid mechanism on 1 nm Au/Si has been investigated between 500 and 1000 °C via the reaction of Sn-containing Pb with O2 at 10–1 mbar. The SnO2 nanowires have diameters of 50 nm, lengths up to 100 μm, and a tetragonal rutile crystal structure, but they do not contain Pb because of its significant depletion during the temperature ramp and re-evaporation from the surface of the SnO2 nanowires. Consequently, we do not observe a semiconductor to semimetal transition and band gap narrowing. Instead, the Pb reacts with O2, leading to the deposition of PbO directly on Si but not on the SnO2 nanowires, which have carrier densities of ≈1016 cm–3. Furthermore, one-dimensional growth was completely suppressed by increasing the amount of Pb in Sn. As such, Pb doping of SnO2 and the growth of PbxSn1–xO2 nanowires is difficult, if not impossible, because PbO2 nanowires cannot be grown by the vapor–liquid–solid mechanism irrespective of the growth temperature. In con...

Memristive behavior of TiOx obtained via Pb(II)-assisted anodic oxidation process

Memristive devices are of promising systems enabling the potential applications of neuromorphic circuits, logical operations, and non-volatile memories. This study introduces a low-cost and feasible TiOx formation process for memristive devices with Cu/TiOx/Ti/Cu and Pt/TiOx/Ti/Pt layers. In the proposed device, active material TiOx is produced by anodic oxidation of Ti using cyclic voltammetry in 100 mM Methane sulfonic acid (CH3SO3H) aqueous solution containing Pb(CH3SO3)2. The influence of Pb2+ content in the anodic oxidation process is evaluated using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Particularly, EIS results indicate that an increase in the Pb2+ content in the solution improves the conductivity of TiOx films. The conductivity improves with the insertion of more oxygen deficiency to TiOx. The structural identity and oxide thicknesses are worked out using Scanning Electron Microscopy, Low Angle X-Ray Diffraction (XRD) and Ellipsometry. Addition of Pb2+ to CH3SO3H solution significantly improves the oxidation rate and increasing the amount of Pb2+ in the solution produces a thicker oxide layer. Low Angle XRD analysis suggests the TiOx formation, including oxygen-deficient (Magneli) phase, on Ti. Our findings indicate that during the anodic oxidation, a soluble oxygenated Pb4+ compound, (Pb(OH)22+), occurs and instead of contributing to PbO2 deposition, it shows a catalytic effect on TiOx formation. I–V measurements are conducted to investigate memristive behavior. Increasing the amount of Pb2+ content in the anodization solution yields wider hysteresis referring to more distinguishable ON/OFF states for electronic applications.

Photocatalytic behaviors of epitaxial BiVO4 (010) thin films

Photocatalytic studies performed on well-defined epitaxial thin films and heterostructures allow the direct investigation of crystallographic-dependent reactivity, and can provide fundamental insights into the reaction mechanisms. In this work, we show that phase-pure, monoclinic BiVO4 nanoislands with a truncated pyramid shape with the (010) top surface and {110} sidewalls can be grown on (001)-oriented yttria-stabilized zirconia (YSZ) substrates with an epitaxial relationship of BiVO4(010)[001] // YSZ(001)[100]. The resulting nanostructures show a strong size-dependent mass-normalized photocatalytic activity, with highly dispersed nanoislands at low coverage being the most active. Pb(NO3)2 photooxidation or photoreduction reactions can be controlled in aqueous solution with and without adding NaIO3 as a electron scavenger, leading to the selective deposition of PbO2 or Pb on {110} or (010) surfaces of BiVO4, respectively.

Physicochemical characterization of PEG-modified PbO2 coatings electrodeposited from a methanesulfonate bath

This study explores the preparation and application of polyethylene glycol (PEG)-modified PbO2 electrodes. The PEG-modified PbO2 coatings were electrodeposited on a Ti/SnO2-Sb substrate from a methanesulfonate electrolytic bath containing different amounts of PEG. Structural and morphologic characterization was carried out for the deposited electrodes. The presence of PEG in the deposition bath represses the nucleation process and grain growth process in PbO2 deposition. Increasing PEG addition results in an increased [Formula: see text]-PbO2 content and decreased crystallite size. At a limited PEG addition [Formula: see text]4 g/L, a rough and pyramidal surface morphology is presented in the PbO2 coatings. A higher PEG addition at 6 g/L leads to a dense and smooth coating surface yet with less uniformity. Electrochemical characterization reveals a great electrocatalytic activity for the modified PbO2 electrodes when the PEG addition is [Formula: see text]4 g/L.

Accelerated site-selective photooxidation on Au nanoparticles via electrochemically-assisted plasmonic hole ejection.

In order to induce electrochemical reactions by localized surface plasmon resonance (LSPR), semiconductors have been employed as electron or hole acceptors for plasmon-induced charge separation (PICS) in most cases. Here we replaced a semiconductor with a potential-controlled transparent electrode, and achieved accelerated photooxidation reactions at selected local sites on plasmonic metal nanoparticles. We demonstrate site-selective PbO2 deposition at the tips and sides of Au nanorods and PbO2 deposition and Au dissolution at the top and bottom of Au nanocubes, through the selective excitation of different LSPR modes. Energetic electron-hole pairs are generated at a plasmonic resonance site, and oxidation reactions are driven by hole ejection at the site. The complementary electrons are removed via the positively biased electrode, and consumed at a counter electrode by reduction reactions. In the case of the PbO2 deposition, formation of PbO2 nuclei is triggered by the hole ejection, and PbO2 is grown further in an electrochemical manner at an improved rate.

A Comprehensive Study on Nano-Diamond Doped β-PbO2 Electrode: Preparation, Properties and Electrocatalytic Performance

In this study, a nano-diamond modified β-PbO2 electrode with the efficiently electrochemical performance was successfully prepared by electrodeposition method (marked as Ti/SnO2-Sb/PbO2-ND). Chronoamperometric curves for PbO2 deposition reveals that the addition of nano-diamond particles could promote the growth of β-PbO2 crystallites. This can be ascribed to the enhancement in the electrochemical generation of •OH in the presence of nano-diamond. Additionally, the presence of nano-diamond could effectively improve the electromigration of Pb2+ toward the anode surface by the formation of negatively charged [Pb2+-nano-diamond] complex. The optimum doping concentration of nano-diamond for β-PbO2 preparation was 1.5 g/L. As compared with blank β-PbO2 electrode, Ti/SnO2-Sb/PbO2-1.5ND electrode has smaller grain size, more compact film and higher ratio of Oad/(Oad+OL). The electrochemical active area for Ti/SnO2-Sb/PbO2-1.5ND electrode was increased to 4.55 cm2, while it was only 2.73 cm2 for β-PbO2 electrode. Notably, the oxygen evolution overpotential of Ti/SnO2-Sb/PbO2-1.5ND electrode was approximately 2.1 V/SCE, which was higher than blank β-PbO2 electrode (1.81 V/SCE). The almost complete removal of methylene blue could be attained within 60 min at a current density of 30 mA cm−2. Generally, the Ti/SnO2-Sb/PbO2-1.5ND shows promise as an efficient and low-cost electrode for electrochemical treatment of industrial wastewater.

Effects of deposition time and current density on PbO2 electrosynthesis from methanesulfonate electrolyte

This work investigated the effects of current density and deposition time on the properties of electrodeposited PbO2. The PbO2 preparation was conducted on Ti/SnO2–Sb substrates by galvanostatic anodic deposition in a newly proposed methanesulfonate electrolytic solution. Phase constituents and microstructures of the deposited PbO2 coatings were characterized. Increasing current density in the range ≤ 100 mA cm− 2 leads to the formation of highly textured coatings with an increased content of α-PbO2 phase. Concurrently, a high current density favors a compact and flat surface morphology. The study of deposition time indicates a change of crystallite growth manner from an initially random growth to a later-stage preferred growth along distinct orientations. The change of crystallite growth is corroborated by the cross-sectional microstructures of the PbO2 deposits. The microstructural transition occurs only in the initial deposition stage. After a brief period, prolonged electrodeposition barely changes the surface morphology of PbO2 coatings.

Stabilization of Electrodeposit in Soluble Lead Flow Batteries with Acetate Additive

The emerging of renewable energy demands energy storage. Redox flow batteries are inherently suited for large-scale applications, but their market penetration is thwarted by the high materials cost. In contrast, membrane-less and single-flow soluble lead flow batteries (SLFBs) are more economical to scale up and free of expensive noble metals. However, lifespan of SLFBs reported so far is limited to approximately 200 cycles under normal flow conditions, which is insufficient for long-term operation in utility applications. Failures of SLFBs are believed to be associated with PbO2 deposition/dissolution at the positive electrode. Although failure mechanisms are not well understood, passivation and shedding of PbO2 are suggested to decrease efficiency of SLFBs. Formation of a passivation layer of non-stoichiometric PbOx is found to be correlated to proton activities. PbO2 deposits of poor adherence and low quality are also observed to occur when the electrolyte is high in acidity. We therefore employ sodium acetate (NaOAc) as electrolyte additive, and successfully extend the cycle life of SLFBs by over 50%. In this study, effects of acetate additive on electroplating of PbO2 are investigated. Surface morphology and mechanical strength of electroplated PbO2 via electrolyte with and without NaOAc are examined by scanning electron microscopy (SEM) and nano-indentation, respectively. Acetate-assisted electrolyte is found to substantially enhance deposited film strength and leads to a more integrated and smoother surface. Crystal structures, grain sizes, and grain orientations of plated PbO2 are analyzed via x-ray diffraction (XRD) and electron back scatter diffraction (EBSD), and very different phase distributions and grain orientations are observed for electrolyte with and without NaOAc. Electroplating and oxygen evolution kinetics are further investigated by rotating disk electrode (RDE) experiments. Our findings elucidate acetate additive effects on electroplating of PbO2 in SLFB systems and shed lights on battery life extension.

Local trapping of energetic holes at gold nanoparticles on TiO2.

Oxidation sites for plasmon-induced charge separation at gold nanocubes and nanorods on TiO2 were visualized by PbO2 deposition, and the sites were localized at plasmonic resonance sites. This indicates that energetic holes generated at those sites dominate the reactions, which can be applied to photo-nanofabrication beyond the diffraction limit.