Simple electrode assembly engineering:Toward a multifunctional lead-acid battery

Electrochemical energy storage is a promising technology for the integration of renewable energy.Lead-acid battery is perhaps among the most successful commercialized systems ever since thanks to its excellent cost-effectiveness and safety records.Despite of 165 years of development,the low energy density as well as the coupled power and energy density scaling restrain its wider application in real life.To address this challenge,we optimized the configuration of conventional Pb-acid battery to integrate two gas diffusion electrodes.The novel device can work as a Pb-air battery using ambient air,showing a peak power density of 183 mW cm^(−2),which was comparable with other state-of-the-art metal-O_(2)batteries.It can also behave as a fuel cell,simultaneously converting H_(2)and air into electricity with a peak power density of 75 mW cm^(−2).Importantly,this device showed little performance degradation after 35 h of the longevity test.Our work shows the exciting potential of lead battery technology and demonstrates the importance of battery architecture optimization toward improved energy storage capacity.

Mn-doped perovskite-type oxide LaFeO3 as highly active and durable bifunctional electrocatalysts for oxygen electrode reactions

Perovskite oxides based on the alkaline earth metal lanthanum for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)in alkaline electrolytes are promising catalysts,but their catalytic activity and stability remain unsatisfactory.Here,we synthesized a series of LaFe1-xMn2O3(x=0,0.1,0.3,0.5,0.7,0.9 and 1)perovskite oxides by doping Mn into LaFeO3(LF).The results show that the doping amount of Mn has a significant effect on the catalytic performance.When x=0.5,the catalyst LaFeo.sMno.sO3(LFM)exhibits the best performance.The limiting current density in 0.1 mol·L^-1 KOH solution is 7 mA·cm^-2,much larger than that of the commercial Pt/C catalyst(5.5 mA·cm^-2).Meanwhile,the performance of the doped catalyst is also superior to that of commercial Pt/C in terms of the long-term durability.The excellent catalytic performance of LFM may be ascribed to its abundant 0^2-/0^-species and low charge transfer resistance after doping the Mn element.

Electrodeposition of Ir on platinum in NaCl-KCl molten salt

The reduction mechanism of Ir in the NaCl-KCl-IrCl3 molten salt was investigated by cyclic voltammetry and chronopotentiometry, and Ir film was deposited effectively on platinum in potentiostatic mode. The morphology and constitution of Ir film were examined by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD）. It is found that the reduction mechanism of Ir（III） is a three-electron step and electro reaction is a reversible diffusion controlled process; the diffusion coefficients of Ir（III） at 1083, 1113, 1143 and 1183 K are 1.56×10-4, 2.23×10-4, 2.77×10-4 and 4.40×10-4 cm2/s, respectively, while the activation energy of the electrode reaction is 102.95 kJ/mol. The compacted Ir film reveals that the applied potential greatly affects the deposition of Ir, the thickness of Ir film deposited at the potential of reduction peak is the highest, the temperature of the molten salt also exerts an influence on deposition, the film formed at a lower temperature is thinner, but more micropores would occur on film when the temperature went too high.

Characterization methods of organic electrode materials

The development of novel organic electrode materials is of great significance for improving the reversible capacity and cycle stability of rechargeable batteries.Before practical application,it is essential to characterize the electrode materials to study their structures,redox mechanisms and electrochemical performances.In this review,the common characterization methods that have been adopted so far are summarized from two aspects:experimental characterization and theoretical calculation.The experimental characterization is introduced in detail from structural characterization,electrochemical characterization and electrode reaction chara cterization.The experimental purposes and working principles of various experimental characterization methods are briefly illustrated.As the auxilia ry means,theoretical calculation provides the theoretical basis for characterizing the electrochemical reaction mechanism of organic electrode materials.Through these characterizations,we will have a deep understanding about the material structures,electrochemical redox mechanisms,electrochemical properties and the relationships of structure-property.It is hoped that this review would help researchers to select the suitable characterization methods to analyze the structures and performances of organic electrode materials quickly and effectively.

The j–pH diagram of interfacial reactions involving H+ and OH-

For aqueous interfacial reactions involving H+and OH-, the interfacial pH varies dynamically during the reaction process, which is a key factor determining the reaction performance. Herein, the kinetic relevance between the interfacial pH and reaction rate is deciphered owing to the success in establishing the transport equations of H+/OH- in unbuffered solutions, and is charted as a current(j)–pH diagram in the form of an electrochemical response. The as-described j–pH interplay is experimentally verified by the oxygen reduction and hydrogen evolution reactions. This diagram serves to form a panoramic graphic view of pH function working on the interfacial reactions in conjunction with the Pourbaix’s potential–pH diagram, and particularly enables a kinetic understanding of the transport effect of H+and OH-on the reaction rate and valuable instruction toward associated pH control and buffering manipulation.

THE CALCULATION OF RATE CONSTANT OF ELECTRON TRANSFER REACTION AT ELECTRODES

After the electron transfers from the metal electrode to the Fe3+(H2O)(6) ion, the free energy of activation of this electron transfer reaction is calculated, then using the transition probability which is calculated by the perturbed degeneration theory and the Fermi golden rule,, the rate constant is gotten. Compared with the experimental results, it is satisfactory.

Carbon nanotube-supported mixed-valence Mn_(3)O_(4) electrodes for high-performance lithium-oxygen batteries

Lithium-oxygen batteries(LOBs)have extensive applications because of their ultra-high energy densities.However,the practical application of LOBs is limited by several factors,such as a high overpotential,poor cycle stability,and limited rate capacity.In this paper,we describe the successful uniform loading of Mn_(3)O_(4) nanoparticles onto multi-walled carbon nanotubes(Mn_(3)O_(4)@CNT).CNTs form a conductive network and expose numerous catalytically active sites,and the one-dimensional porous structure provides a convenient channel for the transmission of Li+and O2 in LOBs.The electronic conductivity and electrocatalytic activity of Mn_(3)O_(4)@CNT are significantly better than those of MnO@CNT because of the inherent driving force facilitating charge transfer between different valence metal ions.Therefore,the Mn_(3)O_(4)@CNT cathode obtains a low overpotential(0.76 V at a limited capacity of 1000 mAh g^(-1)),high initial discharge capacity(16895 mAh g^(-1) at 200 mA g^(-1)),and long cycle life(97 cycles at 200 mA g^(-1)).This study provides evidence that transition metal oxides with mixed-valence states are suitable for application as efficient cathodes for LOBs.

XPS and Cyclic Voltammetric Surface Characterization of Terbium Oxide Electrocatalysts

The surface characteristics and electrochemical behaviors of Tb 4O 7 layers deposited on graphite by thermal decomposition were investigated by means of XPS and cyclic voltammetry at 700 ℃ in NaCl KCl melts. XPS analysis indicates that thermal decomposition products are mainly non stoichiometric and defective structurally oxide. Cyclic polarization on oxide electrode reflects the specific adsorption of Cl - and structural modification of oxide surface. Analysis based on the features of the voltammograms reveals the redox behaviors of Tb oxide layer with different valency states and its correlation to electrocatalytic active. The variation of voltammetric charge was used to characterize the affection of temperature, measure the electrochemical active surface area and monitor the modification of active surface.

Voltammetric Behavior of Degradation Product and Determination of Cefdinir

The electrochemical behavior of the degradation product of cefdinir（CDR） was studied in a 0.05 mol/L NaOH solution by means of linear sweep voltammetry（LSV） and cyclic voltammetry（CV）. The results indicate that the C=N bond in the oxime group was reduced. Moreover, a saturated adsorption amount of 1.32× 10^-10 mol/cm2 at Hg electrode was obtained. The adsorption coefficient β was 1.56× 10^5 L/mol. Gibbs standard energy of adsorption AGO at 25 ℃ was -29.63 kJ/mol and the number of electrons transferred n was 2. A method for the determination of CDR was proposed by differential pulse voltammetry（DPV）. The reduction peak currents of the CDR＇s degradation product were found to be linear in a concentration range of 4.0×10^-7--4.0×10^- 6 mol/L and that of 4.0× 10^-8-4.0× 10^-7 mol/L, respectively. The detection limit was found to be 3.0× 10^-8 mol/L under the optimized conditions. The applica- bility of this approach was illustrated by the determination of CDR in capsules. In addition, the mechanism about the degradation of CDR in 0.2 mol/L NaOH was discussed by UV spectrophotometry.

Synthesis and Electrochemical Study of Water-Soluble Lanthanide Porphyrins

The water soluble tetra p sulfonatophenylporphyrinatolanthanide, [Ln·TPPS·OH ·2imidazole] ·3H 2O(Ln=Tb～Yb), were synthesized and characterized. Their stability and complex constants were also studied and determined. The structural formula of the lanthanide porphyrins was proposed too. The lanthanide atom is sitting above the porphyrin plane. For the lanthanide porphyrin complexes, the complex becomes more stable and the reduction potential has a slight shift to more positive values as the atomic number increases from Tb to Yb. The mechanism of electrode processes for these lanthanidee porphyrin complexes were investigated in details.

pH Overpotential for Unveiling the pH Gradient Effect of H^(+)/OH^(−)Transport in Electrode Reaction Kinetics

The pH gradient caused by H^(+)/OH^(−)transport on an electrode surface is the key factor determining reaction performance,but its detailed impact on the electrode reaction kinetics has yet to be clarified.Here,the pH gradient effect was determined by developing electrode reaction equations,considering the overpotential assigned to the pH gradient called pH overpotential.The pH gradient effect was revealed to involve two aspects:(1)the Nernst pH overpotential,accounting for the common Nernst relationship with pH,and(2)the pH-dependent function of the electron-transfer coefficient(α_(pH)).Both parts were verified experimentally using oxygen reduction reaction and hydrogen evolution reaction,obviously,with differentα_(pH) functions.Detailedα_(pH) function effect was clarified based on numerical calculations of the electrode reaction equations.We found that the effect could be assessed suitably by an apparent constant(α_(app))and a nonlinear fitting method proposed forα_(app) value estimation.The results of this study provide the kinetic fundamentals of electrode reactions involving H^(+)/OH^(−)and contribute to the understanding and assessment of their performance with the H^(+)/OH^(−)transport effect.

Efficient molten salt CO_(2)capture and selective electrochemical transformation processes toward carbon neutrality:advances,challenges,and prospects

Atmospheric carbon dioxide(CO_(2))concentration has reached record levels due to excessive anthropogenic CO_(2)emissions from massive industrial productions.Renewable-energy-driven CO_(2)electroreduction is an effective method of directly converting CO_(2)into various value-added chemicals or materials without subsequent geological disposal treatment.Owing to their promising thermal stability,wide electrochemical window,tunable oxo-basicity,and nontoxic nature,molten salt electrolytes endow intrinsic advantages,such as fast CO_(2)absorption and selective electrochemical transformation,among different electrolyte species,wherein advanced carbon materials,CO,and hydrocarbons can be generated at relatively high current densities.Herein,we review the recent advances in molten salt CO_(2)capture and electrochemical transformation(MSCC-ET)technologies,including reaction mechanisms,CO_(2)absorption kinetics,electrode reaction kinetics,and product selectivity.This review highlights feasible strategies for regulating nanostructures,carbon product crystallinity,energy efficiency,overall CO_(2)conversion efficiency,and MSCC-ET adaptability toward practical flue gases.Moreover,suitable cost-effective inert anode candidates for the oxygen evolution reaction are discussed.