Patterned Si thin film electrodes for enhancing structural stability

A patterned film (electrode) with lozenge-shaped Si tiles could be successfully fabricated by masking with an expanded metal foil during film deposition. Its electrochemical properties and structural stability during the charge-discharge process were examined and compared with those of a continuous (conventional) film electrode. The patterned electrode exhibited a remarkably improved cycleability (75% capacity retention after 120 cycles) and an enhanced structural stability compared to the continuous electrode. The good electrochemical performance of the patterned electrode was attributed to the space between Si tiles that acted as a buffer against the volume change of the Si electrode.     

A comparative study of thin film insulation techniques for gold electrodes

The increasing use of microelectrodes in small sample volumes and biological environments require the use of thin film insulators. The insulating ability of the thin film insulators electrophoretic paint, polyimide, allylphenol phenol copolymer and an epoxy dip coat have been assessed using gold wires coated in the relevant film. Insulation was assessed by recording the current from the wires in a solution of known redox couple. The effect of prolonged storage in aqueous solutions was also investigated. The most successful insulating approach, with regards to insulative ability, prolonged use in aqueous environments and speed of application, was the combination of cathodic electrophoretic paint followed by polyimide.     

In situ X-ray absorption spectroscopy of germanium evaporated thin film electrodes

The understanding of germanium Li-ion insertion/extraction reaction mechanism is drawing more and more attention in the field of Li-ion batteries. When a germanium thin film electrode is inserted with Li ions, the material remains amorphous until it crystallizes into Li₁₅Ge₄ as evidenced by X-ray diffraction. The local coordination environment of the Ge atoms of the intermediate amorphous phases was investigated by in situ X-ray absorption spectroscopy. Li-ion insertion and extraction were electrochemically controlled by continuous and intermittent galvanostatic methods. The evolution of the coordination number and interatomic distance of Ge–Ge and Ge–Li shells was determined as a function of Li composition. From a short range ordering perspective, it was observed that the first Ge–Ge interatomic distance increases and the Ge–Ge coordination number decreases with increasing Li content. The opposite is observed for the first Li–Ge interaction. Moreover, it was found that electrochemical lithiation is reversible at the atomic scale.     

Studies of electrochemical interfaces of thin PT film electrodes by surface conductance

In this paper the dc conductance of thin Pt films has been measured with respect to film thickness and to the surface effects as a function of the electrode potential in the “ideal” double layer, platinum “oxygen” and adsorbed hydrogen regions. The change in the value of dc conductance has been correlated with the electric charge as potential is scanned in these regions. Tentative mechanistic suggestions are offered to explain the data including some results on the deposition of copper on platinum.     

Influence of thin film properties on the electrochemical performance of diamond electrodes

The electrochemical properties of nanocrystalline diamond films grown by microwave-enhanced chemical vapour deposition from a helium–hydrogen–methane gas phase mixture on Ti substrates are explored. A range of important redox systems are examined in aqueous solution including the oxidation of hydroquinone and ascorbic acid, and the electrodeposition and stripping of Au and Cu. Compared to boron-doped diamond materials, the nanodiamond is found to be a highly active electrode material, with low overpotentials and high adherence of metallic electrodeposits, for the redox systems studied.     

使用光刻法在金刚石台面制备金属薄膜电极

金刚石对顶砧是实验室常用的产生流体静力学压力的装置,其核心部件是两颗对顶的金刚石.金刚石具有其它材料难以比拟的超高硬度和对电磁波的高透过率,所以金刚石压砧在高压研究中扮演着重要的角色.文章介绍一种光刻法在金刚石台面上制备金属薄膜电极用以测量材料电阻率的工艺.     

X-ray absorption spectroscopy studies of nickel oxide thin film electrodes for supercapacitors

Nickel oxide films were synthesized by electrochemical precipitation of Ni(OH)₂ followed by heat-treatment in air at various temperatures (200-600 °C). Their structure and electrochemical properties were studied by cyclic voltammetry, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). XRD results showed that the nickel oxide obtained at 250 °C or above has a crystalline NiO structure. The specific capacitance of the oxide depends on the heat-treatment temperature, showing a maximum value at 300 °C. XAS results revealed that the non-stoichiometric nickel oxide (Ni_1−xO) approached the stoichiometric NiO structure with increasing heat-treatment temperature due to the defect healing effect. The defective nature of the nickel oxide could be utilized to improve its specific capacitance for supercapacitor application.     

Electrochemical preparation of peroxodisulfuric acid using boron doped diamond thin film electrodes

We have investigated the electrochemical oxidation of sulfuric acid on boron-doped synthetic diamond electrodes (BDD) obtained by HF CVD on p-Si. The results have shown that high current efficiency for sulfuric acid oxidation to peroxodisulfuric acid can be achieved in concentrated H₂SO₄ (>2 M) at moderate temperatures (8-10 °C). The main side reaction is oxygen evolution. Small amounts of peroxomonosulfuric acid (Caro's acid) have also been detected. A reaction mechanism involving hydroxyl radicals, HSO₄⁻ and undissociated H₂SO₄ has been proposed. According to this mechanism electrogenerated hydroxyl radicals at the BDD anode react with HSO₄⁻ and H₂SO₄ giving peroxodisulfate.     

染料敏化太阳电池介孔薄膜电极的研究进展

介绍了染料敏化太阳电池多孔二氧化钛薄膜电极的结构、工作原理及其制备方法,并进一步阐述了减小电荷复合速率、改进薄膜电极性能、提高器件的光电转化效率的方法,主要涉及多孔二氧化钛薄膜电极的复合、掺杂和表面包覆等表面改性处理技术。指出了基于有序二氧化钛薄膜电极、柔性二氧化钛薄膜电极的染料敏化太阳电池和叠层薄膜结构的太阳电池高效的转化效率和应用方便的特点,并在此基础上展望了未来的研究方向。     

Correlation of film structure and molecular oxygen reduction at nitrogen doped amorphous carbon thin film electrochemical electrodes

Nitrogen doped amorphous carbon (a-C:N) thin film electrodes with a range of film structures have been deposited using a filtered cathodic vacuum arc system. The correlation between film structure and electro-reduction of molecular oxygen in aqueous media at the electrodes has been explored. In aqueous 0.1 M NaOH, dioxygen reduction is inhibited at all the a-C:N electrodes compared with that at glassy carbon electrodes. The potential of the dioxygen reduction current peak shifts negatively at a-C:N electrodes as the sp³ C fraction in the a-C:N materials increases, while the current peak height decreases simultaneously. The a-C:N electrodes possess high sensitivity for investigating the mechanism of dioxygen reduction. It was found that the catalytic H₂O₂ reduction to H₂O on carbon materials is attributed to oxygen species at sp² C sites.     

Fabrication of boron doped diamond microband electrodes for electrochemical detection in a microfluidic channel

The manufacturing and electrochemical characterisation of an array of 20 boron doped nanocrystalline diamond (BNCD) microband electrodes for use in a poly(dimethylsiloxane) (PDMS) based microfluidic system are described. The electrodes were fabricated by plasma etching of a silicon oxide- and BNCD thin film coated silicon wafer and the resulting surface structured silicon wafer was subsequently bonded to the PDMS so that the BNCD microband electrodes were located within the PDMS microchannel. The electrochemical performance of the BNCD electrodes was studied and the electrodes were found to exhibit significantly better stability than previously employed gold microband arrays.     

Semiconductor properties and redox responses at a-C:N thin film electrochemical electrodes

The semiconductor capacitances of the nitrogen-doped amorphous carbon (a-C:N) materials with different sp³/sp² C ratios were studied as a function of electrode potential in a-C:N/aqueous electrolyte systems. This dependence of capacitance on electrode potential in aqueous 0.1 M NaOH shows that the investigated a-C:N materials are intrinsic semiconductors. The space-charge layers inside the a-C:N electrodes behave similar to a Helmholtz layer because of the presence of surface states when the electrolytes contain O₂ or anions other than OH⁻. The lower density and mobility of carriers of materials with a higher sp³ C fraction within the a-C:N material causes a suppression of redox reactions, and the lower density of carriers contributes to a lower capacitance.     

Transfer-printed thin film metal electrodes for high-performance ferroelectric P(VDF-TrFE) devices

Electrodes formation method has been found to be very important in electronic devices using ferroelectric P(VDF-TrFE) copolymer. Depending on the deposition system used, vacuum-based deposition methods such as e-beam or thermal evaporation of metal electrodes has resulted in the performance deterioration, due to damages on the fragile organic surface by highly energetic particles such as intensive short-wavelength radiation, secondary electrons, etc. On the other hand, the transfer-printing of electrodes, which is formed on other substrates, onto the organic surface does not involve any such damages, leading to high-performance devices. Further, the transfer-printing process allows additional advantages of electrode surface tailoring or device fabrication on non-flat micro-rough surfaces. The proposed technique has led to much better performance of InGaZnO-based non-volatile memory transistors, compared to devices based on the direct evaporation of metal electrode. Transfer-printing of electrodes, instead of direct vacuum-based deposition, may lead to higher performing devices based on other organic electronic materials.     

The hydrogen electrode reaction characteristics of thin film electrodes of Ni-based hydrogen storage alloys

Film-type electrodes of hydrogen absorbing intermetallic compound and alloys, LaNi₅, Ni_0.11 Ti_0.89, Ni_0.50 Ti_0.50 and Ni_0.76 Ti_0.24 were prepared by a flash evaporation method. The hydrogen electrode reaction characteristics of the LaNi₅ and NiTi alloy films in 1 M NaOH are very similar to each other. The reaction proceeds via the Volmer-Tafel reaction route with mixed rate-determining characteristics. The exchange current densities of the constituent steps, as well as the overall reaction, are in the range of 10^?6 A cm^?2 (true). Surface analysis by an XPS technique has shown that La or Ti on the electrode surface exists as an electrocatalytically innert oxide of La₂O₃ or TiO₂. Close similarities of these electrodes with pure Ni electrodes indicate that Ni is responsible for the electrocatalytic activity. No synergistic effect is thus noticeable.     

Dopant induced effect on electrocatalytic reduction of nitrobenzene using conducting polypyrrole thin film electrodes

Conducting polypyrrole electrodes were prepared by electrochemical polymerization of pyrrole on vacuum‐metallized glass substrates. These electrodes were modified by doping with a range of metal halides as dopant ions having different electronegativity. Electrochemical reduction of nitrobenzene using these electrodes was studied by means of cyclic voltammetry technique in acetonitrile medium containing aqueous HClO₄ (0.1M) as supporting electrolyte. It was found that the electronegativity of the dopant ion played a very important role in the electrocatalytic activity. Polypyrrole doped with nickel chloride gave the highest anodic current at the reduction potential of nitrobenzene. The results were explained on the basis of charge transfer efficiency at the electrode–electrolyte interface, which was associated with the acceptor state created by the dopant in the semi‐conducting polymer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Ruthenium dioxide-based film electrodes

Oxygen evolution from acid solutions has been investigated on two kinds of RuO₂-based electrodes; compact and cracked (porous) films. The kinetic study has been carried out by means of potentiostatic curves. A method is suggested to estimate the surface concentration of active sites. The reaction order with respect to active sites and the activation energy have been determined. The mechanism is shown to differ on the two kinds of film in relation to theS(site)-OH bond strength and the surface concentration of intermediates. The behaviour of films on silica glass substrates is reported for the first time.Presented at the Euchem Conference on the Electrochemistry and Chemistry of Solids, 8–12 May 1977, Strasbourg (Le Howald), France. Part of this paper was first presented at the XI National Congress of the Italian Association of Physical Chemistry, 9–11 December 1976, S. Margherita Ligure, Italy.     

Fabrication of Cu-modified boron-doped diamond microband electrodes and their application for selective detection of glucose

We describe a simple bench top method for fabricating boron-doped diamond (BDD) microband electrodes and copper-modified BDD microband electrodes. The method described here is inexpensive, robust, renewable, simple, and the BDD microband electrodes and the copper-modified BDD microband electrodes are very easy to fabricate. An advantage of the method is not only its simplicity but also the renewability. That is, even if the surface of the electrode is deactivated after an electrochemical reaction, it can be renewed by simply cutting off the end. As one of the example of application, we report on the selective detection of glucose in solution containing interference species such as Ascorbic acid (AA) and Uric acid (UA) by preparing Cu-modified BDD microband electrodes. Even in solutions containing 2 or 3 times the amount of interfering species compared to the glucose concentration, the Cu-modified BDD microband electrodes showed good selectivity and high durability.     

Electrochemical impedance spectroscopy investigation of spinel type cobalt oxide thin film electrodes in alkaline medium

Spinel type Co₃O₄ thin films, for the oxygen evolution reaction (OER) in 1 M KOH, have been prepared, on stainless steel supports, using the thermal decomposition method at 400 °C. The electrochemical behaviour of the oxide film/1 M KOH interface was investigated by cyclic voltammetry and impedance techniques. The impedance measurements were carried out at different positive potentials, from the open circuit potential to a potential in the OER region and the electrical equivalent circuit, L (R₁Q₁) (R₂Q₂) (R₃Q₃) was used to fit the experimental results. At each potential, a good correlation between experimental and simulated data is found, thereby validating the proposed equivalent circuit model. The roughness factor value determined in the potential region where the charge transfer reaction is negligible is similar to that obtained by cyclic voltammetry, with a value of 70 ± 2.