Fabrication and electrochemical properties of the Sn–Ni–P alloy rods array electrode for lithium-ion batteries

A new ternary Sn–Ni–P alloy rods array electrode for lithium-ion batteries is synthesized by electrodeposition with a Cu nanorods array structured foil as current collector. The Cu nanorods array foil is fabricated by heat treatment and electrochemical reduction of Cu(OH)₂ nanorods film, which is grown directly on Cu substrate through an oxidation method. The Sn–Ni–P alloy rods array electrode is mainly composed of pure Sn, Ni₃Sn₄ and Ni–P phases. The electrochemical experimental results illustrate that the Sn–Ni–P alloy rods array electrode has high reversible capacity and excellent coulombic efficiency, with an initial discharge capacity and charge capacity of 785.0 mAh g^?1 and 567.8 mAh g^?1, respectively. After the 100th discharge–charge cycling, capacity retention is 94.2% with a value of 534.8 mAh g^?1. The electrode also performs with an excellent rate capacity.     

Electrochemical oxidation of primary amine in ionic liquid media: Formation of organic layer attached to electrode surface

Electrochemical oxidation of primary amine in ionic liquid media has been investigated. The ionic liquid chosen for this study was 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Two primary amine compounds are used for this study; 4-nitrobenzylamine and 2-aminoethylferrocenylmethylether. The oxidation of the amino compounds in ionic liquid conduces to the modification of the electrode surface. The modified electrodes were characterized by cyclic voltammetry and XPS analysis. Both techniques support the presence of an organic layer strongly attached onto the electrode surface. The surface concentration of the attached group obtained in this media was found to be around 1 to 3 × 10^?10 mol cm^?2. The use of ionic liquid as media for the grafting leads to decrease of the surface concentration of the grafted layer; and the formation of less dense layer compared with classical solvent such as acetonitrile.     

Electro-reduction of cuprous chloride powder to copper nanoparticles in an ionic liquid

Cyclic voltammetry of the CuCl powder in a cavity microelectrode revealed direct electro-reduction in solid state in 1-butyl-3-methylimidazolium hexafluorophosphate. Potentiostatic electrolysis of the salt powder (attached to a current collector) in the ionic liquid produced Cu nanoparticles as confirmed by X-ray diffraction, energy dispersive X-ray analysis, scanning and transmission electron microscopy. The particle size decreased down to 10 nm when the electrode potential was shifted from −0.9 V to −1.8 V (versus Ag/Ag⁺). The electro-reduction and the nanoparticle formation mechanisms were investigated in the ionic liquid and also in aqueous 0.1 mol L⁻¹ KClO₄ in which larger Cu particles were obtained.     

Modification of carbon electrode in ionic liquid through the reduction of phenyl diazonium salt. Electrochemical evidence in ionic liquid

Electrochemical reduction of the 4-nitrophenyl diazonium salt in ionic liquid media has been investigated at carbon electrode. The ionic liquid chosen for this study was 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][TFSI]. The cyclic voltammetry study demonstrated the possibility of the electrochemical grafting of the nitrophenyl groups onto carbon electrode after the reduction of its corresponding diazonium in ionic liquid. The electrochemical characterization of the modified electrode achieved on ionic liquid displays the presence of the nitrophenyl group at the carbon surface. Moreover, the surface concentration of the attached group obtained in this media was found to be around 1.7 × 10⁻¹⁰ mol cm⁻², this value may suggest the possibility of the formation of monolayer. Furthermore, the characterization of the modified electrode in [EMIM][TFSI] showed the conversion of some NO₂-phenyl groups to NHOH-phenyl. This observation could indicate the presence of surface interaction between the reduced NO₂-phenyl and the ionic liquid cation, thanks to the presence of acidic proton in the ionic liquid cation.     

Li/LiFePO4 batteries with room temperature ionic liquid as electrolyte

Room temperature ionic liquid (RTIL) was prepared on basis of N-methyl-N-butylpiperidinium bis(trifluoromethanesulfonyl)imide (PP₁₄TFSI), which showed a wide electrochemical window (?0.1–5.2 V vs. Li⁺/Li) and is theoretically feasible as an electrolyte for batteries with metallic Li as anodes. The addition of vinylene carbonate (VC) improved the compatibility of PP₁₄TFSI-based electrolyte towards lithium anodes and enhanced the formation of solid electrolyte interphase film to protect lithium anodes from corrosion. Accordingly, Li/LiFePO₄ cells initially delivered a discharge capacity of about 127 mAh g^?1 at a current density of 17 mA g^?1 in the ionic liquid with the addition of VC and showed better cyclability than in the neat ionic liquid. Electrochemical impedance spectroscopy disclosed that the addition of VC enhanced Li-ion diffusion and depressed interfacial resistance significantly.     

Cost-effective electrodeposition of platinum nanoparticles with ionic liquid droplet confined onto electrode surface as micro-media

We report here for the first time on the use of a droplet of water-immiscible ionic liquid (IL) containing metallic precursor confined onto electrode surface as new micro-media for cost-effective electrodeposition of platinum nanoparticles. 1-n-Butyl-3-methylimidazolium hexafluorophosphate (BmimPF₆), a typical water-immiscible IL, is found to be able to form a stable droplet onto electrode surface in which the metallic precursor (i.e., chloroplatinic acid hexahydrate (H₂PtCl₆)) for electrodeposition of Pt nanoparticles can be stably dissolved when the prepared electrode is used in aqueous solutions. The electrodeposition of Pt nanoparticles is carried out in the aqueous solution of 0.1 M KPF₆ with the H₂PtCl₆-containing IL droplet-confined glassy carbon electrode as working electrode at −1.5 V vs. Ag/AgCl. The Pt nanoparticles electrodeposited from the IL droplet micro-medium are characterized to have a uniform morphology and to possess an excellent electrocatalytic activity toward the oxidation of methanol. Compared with the existing methods for the electrodeposition of metals with ILs as the solvents, the method demonstrated here requires a less amount of ILs and metallic precursors and is thus anticipated to provide a new and cost-effective approach to the deposition of metallic nanoparticles onto conducting substrate.     

Micro-electrodeposition in the presence of ionic liquid for the preconcentration of trace amounts of Fe,Co, Ni and Zn from aqueous samples

The paper presents the preconcentration of trace elements via electrodeposition onto a (micro)aluminum cathode in the presence of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆] as a supporting electrolyte. The advantages of the proposed method include very simple instrumentation for the preconcentration of trace elements and low-cost reagents. The experiment showed that the use of ionic liquid in the electrodeposition process significantly improves sensitivity, recovery and detection limits for the determination of trace amounts of iron, cobalt, nickel and zinc. The preconcentrated metals were determined using X-ray fluorescence spectrometry. The optimum parameters for electrodeposition such as pH, the volume of the analyzed solution, the voltage and the deposition time were studied. Under the optimized conditions, the detection limits were 5, 2, 3 and 6 μg L^− 1 for iron, cobalt, nickel and zinc, respectively. The precision and recovery of the method were in the range of 3–5.5%, and 92–103%, respectively. The calibration was performed using aqueous standards of Fe(III), Co(II), Ni(II) and Zn(II) in the range 0.01–0.25 mg L^− 1. The method was applied successfully in water analysis.     

Thermodynamic study of the mixed system (CsCl + CaCl2 + H2O) by EMF Measurements at T = 298.15 K

This work reports the results of a thermodynamic investigation of the ternary mixed-electrolyte system (CsCl + CaCl₂ + H₂O). The activity coefficients of this mixed aqueous electrolyte system have been studied with the electromotive force measurement (EMF) of the cell: Cs ion-selective electrode (ISE)|CsCl(m_A), CaCl₂(m_B), H₂O|Ag/AgCl at T = 298.15 K and over total ionic strengths from (0.01 to 1.50) mol · kg^?1 for different ionic strength fractions y_B of CaCl₂ with y_B = (0, 0.2, 0.4, 0.6, and 0.8). The cesium ion-selective electrode (Cs-ISE) and the Ag/AgCl electrode used in this work were made in our laboratory and had a good Nernst response. The experimental results obey the Harned rule, and the Pitzer model can be used to describe this ternary system satisfactorily. The osmotic coefficients, excess Gibbs free energies and activities of water of the mixtures were also calculated.     

A sensitivity-controlled hydrogen peroxide sensor based on self-assembled Prussian Blue modified electrode

In this communication, a hydrogen peroxide (H₂O₂) sensor based on self-assembled Prussian Blue (PB) modified electrode was reported. Thin film of PB was deposited on the electrode by self-assembly process including multiple sequential adsorption of ferric ions and hexacyanoferrate ions. The as-prepared PB modified electrode displayed sufficient stability for practical sensing application. At an applied potential of ?0.05 V vs. Ag/AgCl (sat. KCl), PB modified electrode with 30 layers exhibited a linear dependence on H₂O₂ concentration in the range of 1 × 10^?6–4 × 10^?4 M (r = 0.9998) with a sensitivity of 625 mA M^?1 cm^?2. It was found that the sensitivity of H₂O₂ sensors could be well controlled by adjusting the number of deposition cycles for PB preparation. This work demonstrates the feasibility of self-assembled PB modified electrode in sensing application, and provides an effective approach to control the sensitivity of PB-based amperometric biosensors.     

Macroporous Co3O4 platelets with excellent rate capability as anodes for lithium ion batteries

This paper reports the microwave-assisted synthesis of Co₃O₄ nanomaterials with different morphologies including nanoparticles, rod-like nanoclusters and macroporous platelets. The new macroporous platelet-like Co₃O₄ morphology was found to be the best suitable for reversible lithium storage properties. It displayed superior cycling performances than nanoparticles and rod-like nanoclusters. More interestingly, excellent high rate capabilities (811 mAh g^?1 at 1780 mA g^?1 and 746 mAh g^?1 at 4450 mA g^?1) were observed for macroporous Co₃O₄ platelet. The good electrochemical performance could be attributed to the unique macroporous platelet structure of Co₃O₄ materials.     

Amperometric biosensors based on deposition of gold and platinum nanoparticles on polyvinylferrocene modified electrode for xanthine detection

In this study, new xanthine biosensors, XO/Au/PVF/Pt and XO/Pt/PVF/Pt, based on electroless deposition of gold(Au) and platinum(Pt) nanoparticles on polyvinylferrocene(PVF) coated Pt electrode for detection of xanthine were presented. The amperometric responses of the enzyme electrodes were measured at the constant potential, which was due to the electrooxidation of enzymatically produced H₂O₂. Compared with XO/PVF/Pt electrode, XO/Au/PVF/Pt and XO/Pt/PVF/Pt exhibited excellent electrocatalytic activity towards the oxidation of the analyte. Effect of Au and Pt nanoparticles was investigated by monitoring the response currents at the different deposition times and the different concentrations of KAuCl₄ and PtBr₂. Under the optimal conditions, the calibration curves of XO/Au/PVF/Pt and XO/Pt/PVF/Pt were obtained over the range of 2.5 × 10^?3 to 0.56 mM and 2.0 × 10^?3 to 0.66 mM, respectively. The detection limits were 7.5 × 10^?4 mM for XO/Au/PVF/Pt and 6.0 × 10^?4 mM for XO/Pt/PVF/Pt. The effects of interferents, the operational and the storage stabilities of the biosensors and the applicabilities of the proposed biosensors to the drug samples analysis were also evaluated.     

Evaluation of a platinum electrode modified with hydroxyapatite in the lead(II) determination in a square wave voltammetric procedure

The behavior of a modified carbon platinum electrode (Pt) for lead(II) determination by square wave voltammetry (SWV) was studied. The modified electrode is obtained by electrodeposition of hydroxyapatite (HAP) on the surface of a bare platinum electrode. The new electrode (HAP/Pt) revealed interesting electroanalytical detection of lead(II) based on the adsorption of this metal onto hydroxyapatite under open circuit conditions. After optimization of the experimental and voltammetric conditions, the best voltammetric responses-current intensity and voltammetric profile were obtained in 0.2 mol L^?1 KNO₃ with: 30 min accumulation time, 5 mV pulse amplitude and 1 mV s^?1 scan rate. The observed detection (DL, 3σ) and quantification (DL, 10σ) limits in pure water were 2.01 × 10^?8 and 6.7 × 10^?7 mol L^?1, respectively. The reproducibility of the proposed method was determined from five different measurements in a solution containing 2.2 × 10^?6 mol L^?1 lead(II) with a coefficients of variation of 2.08%.The electrochemical of hydroxyapatite at platinum surfaces was characterized, after calcinations 900 °C, by X-ray diffraction, infrared spectroscopy, chemical and electrochemical analysis.     

Highly mesoporous and high surface area carbon: A high capacitance electrode material for EDLCs with various electrolytes

Activated carbon fibers (ACFs) with high surface area and highly mesoporous structure for electrochemical double layer capacitors (EDLCs) have been prepared from polyacrylonitrile fibers by NaOH activation. Their unique microstructural features enable the ACFs to present outstanding high specific capacitance in aqueous, non-aqueous and novel ionic liquid electrolytes, i.e. 371 F g⁻¹ in 6 mol L⁻¹ KOH, 213 F g⁻¹ in 1 mol L⁻¹ LiClO₄/PC and 188 F g⁻¹ in ionic liquid composed of lithium bis(trifluoromethane sulfonyl)imide (LiN(SO₂CF₃)₂, LiTFSI) and 2-oxazolidinone (C₃H₅NO₂, OZO), suggesting that the ACF is a promising electrode material for high performance EDLCs.     

Electrodeposition of PtCo alloy nanoparticles on inclusion complex film of functionalized cyclodextrin–ionic liquid and their application in glucose sensing

Platinum–cobalt (PtCo) alloy nanoparticles (NPs) are successfully fabricated by ultrasonic-electrodeposition method, using an inclusion complex (IC) film of functionalized cyclodextrin (CD)–ionic liquid (IL) as support. The morphology and composition of the PtCo alloy NPs are characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. It is found that they are well-dispersed on the CD–IL surface and exhibit many unique features. The resulting modified glassy carbon electrode shows excellent catalytic activity for glucose oxidation. Under the physiological condition, the oxidation current of glucose is linear to its concentration up to 20 mM with sensitivity of 13.7 μA mM^?1 cm^?2. In addition, the interference from the oxidation of ascorbic acid and uric acid could be effectively avoided. Therefore, it is promising as a nonenzymatic glucose sensor.     

An SFG/DFG investigation of CN− adsorption at an Au electrode in 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ionic liquid

In this paper we report an SFG/DFG investigation of the adsorption of CN^? – used as a probe molecule to study the electrochemical double-layer structure – at a polycrystalline Au electrode in 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ([BMP][TFSA]) room-temperature ionic liquid (RTIL). The adsorption of CN^? yielded single SFG and DFG bands in the range from ca. 2125 to 2135 cm^?1, exhibiting a Stark tuning of ca. 3 cm^?1 V^?1. Vibrational resonances – corresponding to modes of the RTIL coadsorbed with CN^?, were found in the range from ca. 1200 to 1500 cm^?1. The study of the double-layer structure was complemented by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements, from which the differential double-layer capacity (C_DL) was estimated.     

Structural and electrochemical properties of a porous nanostructured SnO2 film electrode for lithium-ion batteries

A B₂O₃-doped SnO₂ thin film was prepared by a novel experimental procedure combining the electrodeposition and the hydrothermal treatment, and its structure and electrochemical properties were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, energy dispersive X-ray (EDX) spectroscopy and galvanostatic charge–discharge tests. It was found that the as-prepared modified SnO₂ film shows a porous network structure with large specific surface area and high crystallinity. The results of electrochemical tests showed that the modified SnO₂ electrode presents the largest reversible capacity of 676 mAh g^?1 at the fourth cycle, close to the theoretical capacity of SnO₂ (790 mAh g^?1); and it still delivers a reversible Li storage capacity of 524 mAh g^?1 after 50 cycles. The reasons that the modified SnO₂ film electrode shows excellent electrochemical properties were also discussed.     

Design of a bioelectrocatalytic electrode interface for oxygen reduction in biofuel cells based on a specifically adapted Os-complex containing redox polymer with entrapped Trametes hirsuta laccase

The design of the coordination shell of an Os-complex and its integration within an electrodeposition polymer enables fast electron transfer between an electrode and a polymer entrapped high-potential laccase from the basidiomycete Trametes hirsuta. The redox potential of the Os^3+/2+-centre tethered to the polymer backbone (+ 720 mV vs. NHE) is perfectly matching the potential of the enzyme (+ 780 mV vs. NHE at pH 6.5). The laccase and the Os-complex modified anodic electrodeposition polymer were simultaneously precipitated on the surface of a glassy carbon electrode by means of a pH-shift to 2.5. The modified electrode was investigated with respect to biocatalytic O₂ reduction to H₂O. The proposed modified electrode has potential applications as biofuel cell cathode.     

Complexation study and spectrofluorometric determination of the binding constant for diquat and p-sulfonatocalix[4]arene

The interactions between diquat (DQ) and p-sulfonatocalix[4]arene (C4S) were studied in an aqueous solution as a function of the ionic strength. Evidence for the formation of a complex between DQ and C4S was obtained using fluorescence measurements, while the stoichiometry of the complex was confirmed as 1:1 for DQ/C4S using UV–vis spectroscopy. The ionic strength had no influence on the stoichiometry of the complex, but exerted a significant influence on the complexation constant, K_c, decreasing with an increase in the ionic strength. The thermodynamic complexation constant, K_c′, was computed as 5.25±1.11×10⁷ using the extended Debye–Hückel law. The rate constants for the heterogeneous electron transfer for the reduction of DQ at an electrode surface were evaluated as 0.150±0.010 cm s^?1 in the absence of C4S and 0.065±0.010 cm s^?1 when C4S was added to the solution in a 1:1 ratio.     

High capacity and excellent cyclability of vanadium (IV) oxide in lithium battery applications

A VO₂ · 0.43H₂O powder with a flaky particle morphology was synthesized via a hydrothermal reduction method. It was characterized by scanning electron microscopy, electron energy loss spectroscopy, and thermogravimetric analysis. As an electrode material for rechargeable lithium batteries, it was used both as a cathode versus lithium anode and as an anode versus LiCoO₂, LiFePO₄ or LiNi_0.5Mn_1.5O₄ cathode. The VO₂ · 0.43H₂O electrode exhibits an extraordinary superiority with high capacity (160 mAh g^?1), high energy efficiency (95%), excellent cyclability (142.5 mAh g^?1 after 500 cycles) and rate capability (100 mAh g^?1 at 10 C-rate).     

Crucial effect of rubidium cation on catalytic activity of a polycrystalline gold electrode toward oxygen reduction reaction in alkaline media

Catalytic activity of a polycrystalline gold electrode toward oxygen reduction reaction (ORR) in aqueous alkaline media in the presence of various alkali-metal sulfates (M₂SO₄, M = Li, Na, K, Rb and Cs) was investigated by hydrodynamic voltammetry. The fraction of 4e^? pathway in low overpotentials (? 0.1 to ? 0.3 V) depended on the alkali-metal cations (Rb ? Na, K, Cs, Li). A complete 4e^? reduction of O₂ was only attained in the presence of Rb⁺ cation in the solution, which was comparable or even superior to that reported at the Au(100) single crystal electrode.