Novel Sn Doped Co3O4 Thin Film for Nonenzymatic Glucose Bio‐Sensor and Fuel Cell

A facile chemical solution deposition via two‐step spin coating technique was used to fabricate nano‐particulate novel Sn doped Co₃O₄ thin film for glucose sensor and fuel cell applications. Substitution of Sn into Co₃O₄ host lattice lead to a remarkable increase in the electrocatalytic activity of the Co₃O₄ electrode material. Film thickness played a significant role in enhancing the charge transferability of the electrode as was observed from electrochemical impedance spectroscopy (EIS). The best sensor exhibited two wide linear response ranges (2 μM up to ∼0.5 mM and 0.6 mM up to ∼5.5 mM respectively) with sensitivities of 921 and 265 μA cm⁻² mM⁻¹ respectively and low limit of detection of 100 nM (S/N=3). The sensor was very selective towards glucose in the presence of various interference and showed long term stability. Moreover, the developed thin film modified electrode could generate one electron current in nonenzymatic fuel cell setup at room temperature.     

NiCr x Fe2-x O4 as cathode materials for electrochemical reduction of NO x

Solid solutions of spinel-type oxides with the composition NiCr _x Fe_2-x O₄ (x = 0.0, 0.5, 1.0, 1.5, 2.0) were prepared with the glycine–nitrate combustion synthesis. Four-point DC resistivity measurements show an increase in the conductivity as more Cr is introduced into the structure, whereas dilatometer measurements show that the linear thermal expansion decreases with increasing Cr content. The oxides were used as electrode materials in a pseudo-three-electrode setup in the temperature range of 300–600 °C. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electrochemical behavior in 1% NO, 1% NO₂, and 10% O₂. NiCr₂O₄ shows high activity in NO and NO₂ relative to O₂ and can therefore be considered as a possible electrode material. Peaks were detected in the voltammograms recorded on NiCr₂O₄ in 1% NO. The origin of the peaks seems to be related to the oxidation of Cr or the formation of nitrogen-containing species formed on the surface of the electrode.     

In situ soft X-ray absorption spectroscopy investigation of electrochemical corrosion of copper in aqueous NaHCO3 solution

A novel electrochemical setup has been developed for soft X-ray absorption studies of the electronic structure of electrode materials during electrochemical cycling. In this communication we illustrate the operation of the cell with a study of the corrosion behavior of copper in aqueous NaHCO₃ solution via the electrochemically induced changes of its electronic structure. This development opens the way for in situ investigations of electrochemical processes, photovoltaics, batteries, fuel cells, water splitting, corrosion, electrodeposition, and a variety of important biological processes.     

From a Molecular 2Fe‐2Se Precursor to a Highly Efficient Iron Diselenide Electrocatalyst for Overall Water Splitting

A highly active FeSe₂ electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe‐2Se precursor. The as‐synthesized FeSe₂ was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen‐evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm⁻², representing outstanding catalytic activity and stability because of Fe(OH)₂/FeOOH active sites formed at the surface of FeSe₂. Remarkably, the system is also favorable for the HER. Moreover, an overall water‐splitting setup was fabricated using a two‐electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting.     

花瓣状Co-Al双金属硫化物/泡沫镍电极材料的制备及其超级电容性能的研究

采用低成本的两步水热法直接将Co-Al双金属硫化物生长在泡沫镍上,成功制备了CoAl₂S₄/Ni电极材料,利用X射线衍射(XRD)、扫描电镜(SEM)和电化学测试等手段对其结构、形貌和超级电容性能进行了表征。结果表明,CoAl₂S₄/Ni电极材料呈现花瓣状的三维多孔结构,且表面粗糙,这种结构有利于电解液和电极材料的充分接触,具有良好的导电性和比电容性能;当电流密度为1A/g时,电极的放电比容量高达2187.1 F/g, 循环100次后比电容的保持率为90.1%,相关研究为超级电容器电极材料的制备及性能研究提供思路。     

On the Mediated Electron Transfer of Immobilized Galactose Oxidase for Biotechnological Applications

The use of enzymes as catalysts in chemical synthesis offers advantages in terms of clean and highly selective transformations. Galactose oxidase (GalOx) is a remarkable enzyme with several applications in industrial conversions as it catalyzes the oxidation of primary alcohols. We have investigated the wiring of GalOx with a redox polymer; this enables mediated electron transfer with the electrode surface for its potential application in biotechnological conversions. As a result of electrochemical regeneration of the catalytic center, the formation of harmful H₂O₂ is minimized during enzymatic catalysis. The introduced bioelectrode was applied to the conversion of bio-renewable platform materials, with glycerol as model substrate. The biocatalytic transformations of glycerol and 5-hydroxymethylfurfural (HMF) were investigated in a circular flow-through setup to assess the possibility of substrate over-oxidation, which is observed for glycerol oxidation but not during HMF conversion.     

Photocurrent response of the passive film on iron in a high-temperature aqueous electrolyte

An experimental setup for in situ photoelectrochemical measurements of passive films in high-temperature, high-pressure electrolytes are described. The setup enables photovoltammetric and photocurrent spectroscopic measurements at temperatures up to 300 °C and at pressures up to 10 MPa. The first results on the photocurrent response of the passive film on Fe in 0.05 M Na₂B₄O₇ (pH 9.3) are presented. The dependences of the photocurrent on photon energy and electrode potential are explored. The results are discussed in terms of the effect of temperature and potential on the nature of the photoactive layer in the passive film on Fe. It can be concluded that despite the increase in the overall thickness of the film on Fe with increasing temperature, the thickness of the photoactive layer seems to remain constant.     

Layered silicate magadiite–derived three-dimensional honeycomb-like cobalt–nickel silicates as excellent cathode for hybrid supercapacitors

Developing low-cost electrode materials with high performance is the priority among priorities for large-scale application of supercapacitors (SCs). Magadiite, the most ubiquitous material on Earth, is half-abandoned and half-forgotten, and it is extremely valuable for development to useful materials, such as ‘a potential stock’ to be developed. Herein, we conceive the transformation of magadiite to electrode materials, pursuing the aim ‘waste can be turned into treasure’. Fortunately, three-dimensional honeycomb-like cobalt–nickel silicate (Co_xNi_2-xSiO₄) as high-performance electrode material for SCs is achieved via two simple steps of exfoliation and hydrothermal process. The bimetallic synergistic effect derived from Co/Ni can improve the reactivity of the material, and the honeycomb-like morphology can facilitate ion migration, so the electrochemical properties are enhanced. As a consequence, the Co_xNi_2-xSiO₄ electrode exhibited a specific capacitance of 1,097 F/g (548 C/g) at 0.5 A/g, as well as excellent cyclic stability of 101% retention after 10,000 cycles. The hybrid SC device is assembled by Co_xNi_2-xSiO₄ and active carbon (Co_xNi_2-xSiO₄//AC), and it delivers an excellent energy density of 15.5 Wh/m² at a power density of 1.34 W/m² and cycling stability (100% after 10,000 cycles). This work not only realizes the transformation of magadiite to transition metal silicates (TMSs) as electrode materials for high-performance SCs but also broadens the application of magadiite and opens up a novel strategy for synthesizing TMSs.     

Tuning the Chemistry of Organonitrogen Compounds for Promoting All‐Organic Anionic Rechargeable Batteries

The ever‐increasing demand for rechargeable batteries induces significant pressure on the worldwide metal supply, depleting resources and increasing costs and environmental concerns. In this context, developing the chemistry of anion‐inserting electrode organic materials could promote the fabrication of molecular (metal‐free) rechargeable batteries. However, few examples have been reported because little effort has been made to develop such anionic‐ion batteries. Here we show the design of two anionic host electrode materials based on the N‐substituted salts of azaaromatics (zwitterions). A combination of NMR, EDS, FTIR spectroscopies coupled with thermal analyses and single‐crystal XRD allowed a thorough structural and chemical characterization of the compounds. Thanks to a reversible electrochemical activity located at an average potential of 2.2 V vs. Li⁺/Li, the coupling with dilithium 2,5‐(dianilino)terephthalate (Li₂DAnT) as the positive electrode enabled the fabrication of the first all‐organic anionic rechargeable batteries based on crystallized host electrode materials capable of delivering a specific capacity of ≈27 mAh/g_electrodes with a stable cycling over dozens of cycles (≈24 Wh/kg_electrodes).     

Engineering Fast Ion Conduction and Selective Cation Channels for a High‐Rate and High‐Voltage Hybrid Aqueous Battery

The rechargeable aqueous metal‐ion battery (RAMB) has attracted considerable attention due to its safety, low costs, and environmental friendliness. Yet the poor‐performance electrode materials lead to a low feasibility of practical application. A hybrid aqueous battery (HAB) built from electrode materials with selective cation channels could increase the electrode applicability and thus enlarge the application of RAMB. Herein, we construct a high‐voltage K–Na HAB based on K₂FeFe(CN)₆ cathode and carbon‐coated NaTi₂(PO₄)₃ (NTP/C) anode. Due to the unique cation selectivity of both materials and ultrafast ion conduction of NTP/C, the hybrid battery delivers a high capacity of 160 mAh g^?1 at a 0.5 C rate. Considerable capacity retention of 94.3 % is also obtained after 1000 cycles at even 60 C rate. Meanwhile, high energy density of 69.6 Wh kg^?1 based on the total mass of active electrode materials is obtained, which is comparable and even superior to that of the lead acid, Ni/Cd, and Ni/MH batteries.     

Intermetallic insertion electrodes derived from NiAs-, Ni2In-, and Li2CuSn-type structures for lithium-ion batteries

The implications of designing intermetallic insertion electrodes for lithium-ion cells are discussed in terms of materials with the NiAs-, Ni₂In-, and Li₂CuSn-type structures. Specific reference is made to a recent announcement that lithium can be inserted topotactically into η-Cu₆Sn₅ at approximately 400 mV above the potential of metallic lithium. These materials hold promise for developing a new family of electrode structures to replace carbon as the negative electrode in state-of-the-art lithium-ion cells.     

In situ neutron powder diffraction studies of lithium-ion batteries

Neutron powder diffraction (NPD) offers many advantages in the analysis of battery materials. Understanding the relationship between the structural transformations of electrode materials and their electrochemical performance within lithium-ion batteries is crucial for further development of these technologies and is the overall goal of in situ NPD experiments. In this work, we present NPD data of electrode materials within batteries that are collected in situ during electrochemical cycling, including the commercially available materials LiCoO₂, LiMn₂O₄, LiFePO₄ and graphite and the YFe(CN)₆ and FeFe(CN)₆ materials that are not commercially available. Using these data, we illustrate the experimental approach and requirements for the collection of in situ NPD data of sufficient quality for detailed structural analyses of the electrode components of interest within batteries.     

Effect of Cathodic and Anodic Polarization in a Lithium Sulfate Solution on the Electrical Conductivity of Carbonized Fibrous Carbon Materials

The effect of cathodic and anodic polarization of carbonized fibrous carbon materials of the KNM and NT-1 types in a Li₂SO₄ solution on their properties: electrical conductivity, steady-state electrode potential, electrical conductivity profile across the electrode thickness in relation to the electrolysis time, current density, Li₂SO₄ concentration, electrode thickness, and current reversal, was studied. The stability of the resulting electrical conductivity profile across the electrode thickness with time and in the course of the subsequent electrolysis was assessed. The reduction of Fe³⁺ in the ferri-ferrocyanide system on electrically iso- and nonisoconducting fibrous carbon electrode was considered.     

A Microwave Synthesis of Mesoporous NiCo2O4 Nanosheets as Electrode Materials for Lithium‐Ion Batteries and Supercapacitors

A facile microwave method was employed to synthesize NiCo₂O₄ nanosheets as electrode materials for lithium‐ion batteries and supercapacitors. The structure and morphology of the materials were characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller methods. Owing to the porous nanosheet structure, the NiCo₂O₄ electrodes exhibited a high reversible capacity of 891 mA h g^?1 at a current density of 100 mA g^?1, good rate capability and stable cycling performance. When used as electrode materials for supercapacitors, NiCo₂O₄ nanosheets demonstrated a specific capacitance of 400 F g^?1 at a current density of 20 A g^?1 and superior cycling stability over 5000 cycles. The excellent electrochemical performance could be ascribed to the thin porous structure of the nanosheets, which provides a high specific surface area to increase the electrode–electrolyte contact area and facilitate rapid ion transport.     

Comparative Study of Special Features of the Oxygen Reaction (Molecular Oxygen Ionization and Evolution) in Aqueous and Nonaqueous Electrolyte Solutions (a Review)

Studies of the oxygen reaction, including the oxygen ionization and evolution processes occurring at typical electrode materials in aqueous and nonaqueous electrolytes, are analyzed. A connection between the problematics of the oxygen electrode reaction in nonaqueous media and the developing of novel batteries, in the first place, Li–O₂ batteries, is emphasized. Unlike aqueous solutions, the oxygen reduction in aprotic electrolytes was shown to occur without breaking of the O–O bond; it is accompanied by formation of poorly soluble product of two-electron reaction (Li₂O₂) in the pores of positive electrode. The effect of the solvent donor number and the anion composition on the oxygen reduction mechanism and the lithium peroxide deposit structure is described. A marked reduction of the Li₂O₂ oxidation overvoltage when passing from carbonaceous materials to platinum-containing catalysts in the positive electrode is elucidated; in the latter case, the effect of electrocatalyst type upon the Li₂O₂ formation reaction is somewhat reduced. The elucidation of the contribution of processes occurring at the free and lithium-peroxide-covered electrode surface during the oxygen reaction for wide variety of active materials is formulated as the main basic problem of the future research.     

Electrochemical properties of ordered mesoporous carbon and its electroanalytical application for selective determination of dopamine

The electrochemical properties of one novel carbon material, ordered mesoporous carbons (OMC), synthesized by templating SBA-15 mesoporous silica materials and the electrocatalytic behaviors of OMC modified electrode towards the oxidation of dopamine (DA) and ascorbic acid (AA) were studied. Cyclic voltammetry was used to evaluate the electrochemical behaviors of OMC in 5 mM K₃Fe(CN)₆/0.1 M KCl solution. OMC showed a faster electron transfer rate, as compared with glass carbon (GC) electrode. The higher electron transfer kinetics can be attributed to the existence of a large amount of edge plane defect sites in the OMC materials, which was verified by Raman spectroscopy. The cyclic voltammetric studies also showed the presence of oxygen-containing functional groups on the surface of OMC. Furthermore, the OMC modified electrode showed high electrocatalytic activities toward the oxidation of DA and AA, and resolved their voltammetric responses into two well-defined peaks with peak separation of ca. 0.210 V. The OMC modified electrode could be effectively used for the selective electrochemical determination of DA in the presence of AA.     

Metal-organic framework derived Co3O4/PPy bifunctional electrocatalysts for efficient overall water splitting

In this work, we report Co₃O₄@PPy hybrid structured electrode materials for overall water splitting. The as-synthesized Co₃O₄/PPy-120 samples present excellent electrocatalytic performances for OER and HER and long durability. It only requires an operating potential of 1.67 V to deliver a current density of 10 mA/cm² with a remarkable durability for 28 h. The superior electrocatalytic performances mainly can be attributed to the unique heterostructures and the synergistic effects between PPy and Co₃O₄ electrode materials.     

A study on structure-performance relationship of overcharged 18650-size Li4Ti5O12/LiMn2O4 battery

The electrochemical properties and thermal generation behavior of 18650 Li₄Ti₅O₁₂/LiMn₂O₄ batteries were tested before and after overcharge. The experimental results showed that after overcharge, the specific capacity decreased obviously. The higher the current density was, the more obvious the capacity decreased. For instance, the overcharged battery had almost no capacity when the current density increased to 5C. At the same time, the overcharged battery presented a much more apparent thermal runaway trend compared to the normal battery. After measuring the electrochemical impedance spectroscopy of the batteries and characterizing the crystal structure/nanostructure of the electrode materials, these phenomena could be attributed to the following two reasons: (1) the decomposition of the electrolyte arisen from the overcharge process resulted in increased internal resistance; (2) the thermal runaway due to the increased internal resistance resulted in the damage to crystal structure/nanostructure and aggregation of the electrode materials, thus leading to the secondary decrease in capacity.     

All-solid-state rechargeable lithium batteries using SnX-P2X5 (X = S and O) amorphous negative electrodes

SnS-P₂S₅ and SnO-P₂O₅ amorphous materials were prepared by a mechanical milling technique. The SnO-P₂O₅ milled materials worked as a reversible electrode with higher capacity than SnO crystal in rechargeable lithium cells with conventional liquid electrolytes. All-solid-state cells with a SnX-P₂X₅ (X = S and O) amorphous electrode and the Li₂S-P₂S₅ glass-ceramic electrolyte were charged and discharged at room temperature. The sulfide electrodes exhibited better charge-discharge performance than the oxide electrodes, suggesting that SnS-P₂S₅ electrodes are more compatible with Li₂S-P₂S₅ sulfide solid electrolytes. All-solid state batteries 80SnS·20P₂S₅/LiCoO₂ showed a charge-discharge plateau of about 3.4 V and high reversible capacity of over 400 mAh/g, even after 50 cycles. The SnX (X = S and O)-based amorphous materials are promising negative electrode materials with high capacity for rechargeable lithium batteries using not only liquid electrolytes but solid electrolytes.     

Doping-induced memory effect in Li-ion batteries: the case of Al-doped Li4Ti5O12

In Li-ion batteries (LIBs), a memory effect has been revealed in two-phase electrode materials such as olivine LiFePO₄ and anatase TiO₂, which complicates the two-phase transition and influences the estimation of the state of charge. Practical electrode materials are usually optimized by the element doping strategy, however, its impact on the memory effect has not been reported yet. Here we firstly present the doping-induced memory effect in LIBs. Pristine Li₄Ti₅O₁₂ is free from the memory effect, while a distinct memory effect could be induced by Al-doping. After being discharged to a lower cutoff potential, Al-doped Li₄Ti₅O₁₂ exhibits poorer electrochemical kinetics, delivering a larger overpotential during the charging process. This dependence of the overpotential on the discharging cutoff leads to the memory effect in Al-doped Li₄Ti₅O₁₂. Our discovery emphasizes the impact of element doping on the memory effect of electrode materials, and thus has implications for battery design.