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.     

Electrodeposited PbO2 thin film on Ti electrode for application in hybrid supercapacitor

PbO₂ thin films were prepared by pulse current technique on Ti substrate from Pb(NO₃)₂ plating solution. The hybrid supercapacitor was designed with PbO₂ thin film as positive electrode and activated carbon (AC) as negative electrode in the 5.3 M H₂SO₄ solution. Its electrochemical properties were determined by cyclic voltammetry (CV), charge–discharge test and electrochemical impedance spectroscopy (EIS). The results revealed that the PbO₂/AC hybrid supercapacitor exhibited large specific capacitance, high-power and stable cycle performance. In the potential range of 0.8–1.8 V, the hybrid supercapacitor can deliver a specific capacitance of 71.5 F g^?1 at a discharge current density of 200 mA g^?1(4 mA cm^?2) when the mass ratio of AC to PbO₂ was three, and after 4500 deep cycles, the specific capacitance remains at 64.4 F g^?1, or 32.2 Wh Kg^?1 in specific energy, and the capacity only fades 10% from its initial value.     

Low-temperature growth of vertically aligned In2O3 nanoblades with improved lithium storage properties

Vertically aligned Indium oxide (In₂O₃) nanoblades are successfully obtained through plasma enhanced chemical vapor deposition (PECVD) approach. By using plasma, the reaction between InCl₃ and O₂ was able to take place, yielding vertically aligned blade like nanostructure. The novel In₂O₃ nanostructures exhibit improved electrochemical properties when used as anode materials for lithium-ion batteries. The In₂O₃ electrode reveals reversible capacity of 580 mAh g^?1 after 100 cycles, much higher than that of the In₂O₃ thin films. The result suggests that proper structural modification of In₂O₃ thin film may contribute to the improvement of electrochemical properties. The In₂O₃ electrodes with large reversible capacity and stable cycling performance may provide new insight of anode materials applied in thin film lithium-ion batteries.     

Polarized Raman study on the lattice structure of BiFeO3 films prepared by pulsed laser deposition

Polarized Raman spectroscopy was used to study the lattice structure of BiFeO₃ films on different substrates prepared by pulsed laser deposition. Interestingly, the Raman spectra of BiFeO₃ films exhibit distinct polarization dependences. The symmetries of the fundamental Raman modes in 50–700 cm⁻¹ were identified based on group theory. The symmetries of the high order Raman modes in 900–1500 cm⁻¹ of BiFeO₃ are determined for the first time, which can provide strong clarifications to the symmetry of the fundamental peaks in 400–700 cm⁻¹ in return. Moreover, the lattice structures of BiFeO₃ films are identified consequently on the basis of Raman spectroscopy. BiFeO₃ films on SrRuO₃ coated SrTiO₃ (0 0 1) substrate, CaRuO₃ coated SrTiO₃ (0 0 1) substrate and tin-doped indium oxide substrate are found to be in the rhombohedral structure, while BiFeO₃ film on SrRuO₃ coated Nb: SrTiO₃ (0 0 1) substrate is in the monoclinic structure. Our results suggest that polarized Raman spectroscopy would be a feasible tool to study the lattice structure of BiFeO₃ films.     

A novel anode material of antimony nitride for rechargeable lithium batteries

Antimony nitride thin film has been successfully fabricated by magnetron sputtering method and its electrochemistry with lithium was investigated for the first time. The reversible discharge capacity of Sb₃N/Li cells cycled between 0.3 V and 3.0 V was found above 600 mAh/g. By using transmission electron microscopy and selected area electron diffraction measurements, the conversion reaction of Sb₃N into Li₃Sb and Li₃N was revealed during the lithium electrochemical reaction of Sb₃N thin film electrode. The high reversible capacity and the good cycleability made Sb₃N one of promising anode materials for future rechargeable lithium batteries.     

Mesoporous silica thin film mechanized with a DNAzyme-based molecular switch for electrochemical biosensing

A novel electroanalytical strategy for copper and ascorbic acid detection was developed by using a nanostructured electrode surface mechanized with a DNAzyme-based molecular gate. This sensing interface was constructed by first electrodeposition of a mesoporous silica thin film on Au electrodes and further assembly of a Cu(II)-specific DNAzyme. The biosensing assay was based on the Cu(II) and ascorbic acid responsible activation of the DNAzyme, which acted as a molecular switch able to control the diffusion of the Fe(CN)₆^{3 −/4 −} electrochemical probe through the nanochannels of the mesoporous film.     

Demonstration of a novel,flexible, photocatalytic oxygen-scavenging polymer film

The preparation of a novel, flexible, photocatalytic, oxygen-scavenging polymer film is described. The film incorporates nanocrystalline titania particles in an ethyl cellulose polymer film, with or without an added sacrificial electron donor of triethanolamine. When coated on the inside of a glass vessel its UV-driven light-scavenging action is demonstrated by platinum octaethyl porphyrin coated glass beads sealed inside, since their luminescence increases with increasing UV-irradiation time. When used as a flexible film, work with an oxygen electrode shows that the film is able to scavenge oxygen at an average rate of 0.017 cm³ O₂ h⁻¹ cm⁻² over a 24 h period, which compares favourably to other, well-established oxygen-scavenger systems. The potential of using such as system for oxygen scavenging in packaging is discussed briefly.     

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.     

InP as new anode material for lithium ion batteries

InP thin film has been successfully fabricated by pulsed laser deposition (PLD) and was investigated for its electrochemistry with lithium for the first time. InP thin film presented a large reversible discharge capacity around 620 mAh g^?1. The reversibility of the crystalline structure and electrochemical reaction of InP with lithium were revealed by using ex situ XRD and XPS measurements. The high reversible capacity and stable cycle of InP thin film electrode with low overpotential made it one of the promise energy storage materials for future rechargeable lithium batteries.     

Self-assembled Li4Ti5O12/TiO2/Li3PO4 for integrated Li–ion microbatteries

This work aims to maximize the number of active sites for energy storage per geometric area, by approaching the investigation to 3D design for microelectrode arrays. Self-organized Li₄Ti₅O₁₂/TiO₂/Li₃PO₄ composite nanoforest layer (LTL) is obtained from a layer of self organized TiO₂/Li₃PO₄ nanotubes. The electrochemical response of this thin film electrode prepared at 700 °C exhibited lithium insertion and de-insertion at 1.55 and 1.57 V respectively, which is the typical potential found for lithium titanates. The effects of lithium phosphate on lithium titanate are explored for the first time. By cycling between 2.7 and 0.75 V the LTL/LiFePO₄ full cell delivered 145 mA h g^− 1 at an average potential of 1.85 V leading to an energy density of 260 W h kg^− 1 at C/2. Raman spectroscopy revealed that the γ-Li₃PO₄/lithium titanate structure is preserved after prolonged cycling. This means that Li₃PO₄ plays an important role for enhancing the electronic conductivity and lithium ion diffusion.     

Switchable electrode functionalized with an azobenzene-containing copolymer thin film using the Langmuir–Schaefer technique for a “smart” uric acid/air fuel cell

A new photoswitchable electrode triggered by a brief light signal was fabricated by depositing an azobenzene-containing copolymer on an indium tin oxide substrate decorated with gold nanoparticles. The polymer formed a compact, complete thin film on the electrode surface using the Langmuir–Schaefer technique and offered reversible and stable switching performance. The conductivity and hydrophilicity of the electrode changed under UV/visible light due to the photoisomerization of the azobenzene moieties in the polymer film, influencing electron transfer and mass transport at the electrode. The electrochemical characterization demonstrated that the electrode exhibited reversibly switchable electrochemical behavior. In its active state, the as-prepared electrode possessed efficient electrocatalytic capability towards uric acid oxidation with a maximum anodic current density of 0.97 mA·cm^− 2. The uric acid/air fuel cell assembled from the photo-triggered anode and a Pt/C-modified cathode operated with an open circuit voltage of 0.12 V and a maximum power density of 41.33 μW·cm^− 2. The cell exhibited reversible switching performance (four cycles) and high stability: after one month the power output was 94.2% of the original maximum value.     

A study on solution deposited CuSCN thin films: Structural,electrochemical, optical properties

A cost-effective successive ionic layer adsorption and reaction (SILAR) method was used to deposit copper (I) thiocyanate (CuSCN) thin films on glass and steel substrates for this study. The deposited thin films were characterized for their structural, morphological, optical and electrochemical properties using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectroscopy and VersaSTAT potentiostat. A direct band gap of 3.88 eV and 3.6 eV with film thickness of 0.7 μm and 0.9 μm was obtained at 20 and 30 deposition cycles respectively. The band gap, microstrain, dislocation density and crystal size were observed to be thickness dependent. The specific capacitance of the CuSCN thin film electrode at 20 mV/s was 760 F g⁻¹ for deposition 20 cycles and 729 F g⁻¹ for deposition 30 cycles.     

Direct electrochemistry of hemoglobin and glucose oxidase in electrodeposited sol–gel silica thin films on glassy carbon

This work points out that electrogeneration of silica gel (SG) films on glassy carbon electrodes (GCEs) can be applied to immobilize biomolecules – hemoglobin (Hb) or glucose oxidase (GOD) or both of them in mixture – without preventing their activity. These proteins were physically entrapped in the sol–gel material in the course of the electro-assisted deposition process applied to form the thin films onto the electrode surface. SG films were prepared from a precursor solution by applying a suitable cathodic potential likely to induce a local pH increase at the electrode/solution interface, accelerating thereby polycondensation of the silica precursors with concomitant film formation. Successful immobilization of proteins was checked by various physico-chemical techniques. Both Hb and GOD were found to undergo direct electron transfer, as demonstrated by cyclic voltammetry. GCE–SG–Hb gave rise to well-defined peaks at potentials E_c = −0.29 V and E_a = −0.17 V in acetate buffer, corresponding to the Fe^III/Fe^II redox system of heme group of the protein, while GCE–SG–GOD was characterized by the typical signals of FAD group at E_c = −0.41 V and E_a = −0.33 V in phosphate buffer. These two redox processes were also evidenced on a single voltammogram when both Hb and GOD were present together in the same SG film. Hb entrapped in the silica thin film displayed an electrocatalytic behavior towards O₂ and H₂O₂ in solution, respectively in the mM and μM concentration ranges. Immobilized GOD kept its biocatalytic properties towards glucose. Combined use of these two proteins in mixture has proven to be promising for detection of glucose in solution via the electrochemical monitoring of oxygen consumption (decrease of the oxygen electrocatalytic signal).     

Selective determination of uric acid with DNA doped polymers modified carbon fiber microelectrode

New biocomposite materials, based on the incorporation of DNA doped p-aminobenzensulfonic acid, was fabricated by electrochemical method. A carbon fiber microelectrode modified by this thin film was fabricated for selective determination of uric acid (UA) in the presence of a larger amount of ascorbic acid (AA). It was found that the voltammetric oxidation peak separation between UA and AA is about 260 mV at the modified electrode. A linear response of the peak current versus the concentration was found in the range of 8 × 10⁻⁷–6 × 10⁻⁴ M with correlation coefficient of 0.9991 and the detection limit was 5 × 10⁻⁷ M (s/n = 3) at the 5 × 10⁻⁴ M AA. The presence of high concentration AA did not interference the determination. The electropolymerized film was characterized by SEM techniques. The modified electrode shows good sensitivity, selectivity and stability.     

Synthesis of nickel selenide thin films for high performance all-solid-state asymmetric supercapacitors

As a significant semiconductor, nickel selenide shows enormous potential and extensive application prospects in the field of sensor, photocatalysis and supercapacitor. In this paper, nickel selenide (Ni₃Se₂, NiSe) thin films were successfully fabricated on stainless-steel sheet using a facile, effective electrodeposition technique. The morphologies, microstructures and chemical compositions of the thin films are characterized systematically. Electrochemical tests exhibit that the Ni₃Se₂ and NiSe possess high specific capacitance of 581.1 F/g and 1644.7 F/g, respectively. A flexible, all-solid-state asymmetric supercapacitor is assembled by utilizing NiSe film as positive electrode and activated carbon as negative electrode. The solid device delivers a high areal capacitance of 27.0 mF/cm² at the current density of 0.7 mA/cm². The maximum volumetric energy density and power density of the NiSe//AC asymmetric SCs can achieve 0.26 mWh/cm³ and 33.35 mW/cm³, respectively. The device shows robust cycling stability with 84.6% capacitance retention after 10,000 cycles, outstanding flexibility and satisfactory mechanical stability. Moreover, two devices in series can light up a red light-emitting diode, which displayed great potential applications for energy storage.     

Electrochemical fabrication of novel fluorescent polymeric film: Poly(pyrrole–pyrene)

We describe herein the electrochemical characterization and polymerization of 4-pyren-1-yl-butyric acid 11-pyrrol-1-yl-decyl ester (pyrrole–pyrene) in CH₃CN. The electrochemical oxidation of the pyrrole group at 0.77 V vs Ag/Ag + 10 mM in CH₃CN led to the first example of a fluorescent polypyrrole film. The mechanism of deposition on platinum electrode was studied by voltammetry and chronoamperometry. The optical properties of the polymeric films electrogenerated on ITO electrodes were examined by UV–visible spectroscopy and fluorescence microscopy indicating an increase in fluorescence properties by increased polymer thickness. The electrochemical oxidation of pyrenyl group linked to the polypyrrole backbone was carried out at 1.2 V. This additional polymerization was demonstrated by UV–visible spectroscopy and induced the loss of the fluorescence properties of the resulting polymeric film.     

Novel electrocatalysts for generating oxygen from alkaline water electrolysis

We have obtained spinel-type Co₃O₄ and La-doped Co₃O₄ in the form of thin film on Ni, using microwave-assisted synthesis, which dramatically exhibit very low overpotentials for the oxygen evolution reaction (OER). Investigations have shown that at the apparent current density of 100 mA cm⁻² in 1 mol dm⁻³ KOH at 25 °C, the new electrodes, Co₃O₄ (oxide loading = 3.4 ± 0.3 mg cm⁻²) and La-doped Co₃O₄ (oxide loading = 2.8 ± 0.4 mg cm⁻²), produce overpotentials, 235 ± 7 and 224 ± 8 mV, respectively. Such low overpotentials for the OER, to our knowledge, have not been found on any mixed oxide electrode material reported in literature till today. Small La addition improved the BET surface area and porosity of the oxide catalyst powder and reduced the charge transfer resistance for the OER on the electrode made of oxide powder.     

Electrochemical and FTIR spectroscopic study of CO2 reduction at a nanostructured Cu/reduced graphene oxide thin film

Here we report a facile approach to synthesize a novel nanostructured thin film comprising Cu nanoparticles (NPs) and reduced graphene oxide (rGO) on a glassy carbon electrode (GCE) via the direct electrochemical reduction of a mixture of cupper and graphene oxide (GO) precursors. The effect of the applied potential on the electrochemical reduction of CO₂ was investigated using linear sweep voltammetric (LSV) and chronoamperometric (CA) techniques. Carbon monoxide and formate were found as the main products based on our GC and HPLC analysis. The electrochemical reduction of CO₂ at the Cu/rGO thin film was further studied using in situ ATR-FTIR spectroscopy to identify the liquid product formed at different applied cathodic potentials. Our experimental measurements have shown that the nanostructured Cu/rGO thin film exhibits an excellent stability and superb catalytic activity for the electrochemical reduction of CO₂ in an aqueous solution with a high current efficiency of 69.4% at − 0.6 V vs. RHE, promising for the efficient electrochemical conversion of CO₂ to valuable products.     

A binder-free thin film anode composed of Co2 +-intercalated buserite grown on carbon cloth for oxygen evolution reaction

We present a binder-free catalytic anode for highly efficient and stable oxygen evolution reaction in alkaline media. The catalyst consists of a thin film of buserite-type layered manganese dioxide (MnO₂) intercalated with Co^2 + ions, resulting from electrodeposition of the layered MnO₂ film with tetrabutylammonium (Bu₄N⁺) ions on a carbon cloth, followed by ion-exchange of the initially incorporated Bu₄N⁺ with Co^2 + in solution. The electrode is capable to produce a current density of 10 mA cm^− 2 at an overpotential (η) of 377 mV with a Tafel slope of 48 mV dec^− 1, much superior to the layered MnO₂ without Co^2 +.     

EDL structure and peculiarities of ferricyanide cyclic voltammetry for silver deposits on gold

The evolution of electrochemical characteristics of a gold electrode upon the deposition of one and more atomic silver layers was studied by means of cyclic voltammetry and the method of potential temperature jump induced by the laser irradiation. Characteristics of the electric double layer on Ag monolayer are determined to be close to those of a massive silver electrode. Meanwhile, the electron-transfer parameters for the model redox system Fe(CN)₆^{3 −/4 −} correspond to a gold electrode. The silver beyond the first atomic layer in multilayer deposits was shown to transform into Ag hexacyanoferrate (II) due to the spontaneous chemical reaction with K₃Fe(CN)₆ from the solution. For the Fe(CN)₆^{3 −/4 −} redox system, the difference between oxidation and reduction peak potentials on a cyclic voltammogram increases with the growth of the silver layers number. This effect results from the corresponding increase in the ohmic resistance of the silver hexacyanoferrate (II) film and is not attributed to the changes in the electron-transfer kinetics.