Electrochemical Behaviour Of Thin Films Research Articles

MBE Grown Vanadium Oxide Thin Films for Enhanced Non‐Enzymatic Glucose Sensing

AbstractIn the search for non‐enzymatic alternatives to glucose oxidase, reliable and microchip‐compatible approaches to catalyst development are highly desirable. Herein, the electrochemical behavior of thin films of VOx deposited by molecular beam epitaxy (MBE) on glassy carbon electrodes is reported . A process of partial etching during polarization is observed. Thereafter, highly active and stable traces of VOx act as catalytic centers for glucose electrooxidation. A mechanistic description of the electrochemical process is proposed based on evidence provided by voltammetric measurements. The sensors are calibrated both with potentiometric and amperometric techniques, the former showing a wide linear range (1–10 mM), good sensitivity (14.93 ± 0.39 µA cm−2 × mM–1) and a limit of detection (0.32 m‐M). Unlike most metal oxides, it is shown that VOx on glassy carbon is capable of successfully oxidizing glucose at −0.4 V. Such a one‐of‐kind behavior can have important ramifications for energy‐efficient integrated electrochemical sensors and non‐enzymatic glucose sensing as a whole.

Effect of copper concentrations on microstructure, residual stress and corrosion behavior of Ni100−x-Cux alloy films processed by magnetron co-sputtering

Nickel based alloys have gained importance due to their very good mechanical properties as well as their electrochemical behavior in different environmental conditions. In this regard, thin films of nanocrystalline Ni-Cu alloys have been processed by RF / DC magnetron co-sputtering in Ar gas environment for different copper concentration (10 %, 21 %, 28 % and 39 %). Grain size determination, phase identification and residual stress measurement have been done using an X-ray diffraction technique. A compressive residual stress has been observed and the value of the compressive stress increases with an increase in the Cu concentration in the Ni100−x-Cux alloy films. The electrochemical behavior of thin films of the Ni100−x-Cux alloy has been investigated with the help of potentiodynamic polarization experiments which revealed susceptibility towards pitting corrosion. The rate of corrosion decreases from 0.92 ×10−2 to 0.26 ×10−2 mm / year with the increase in Cu concentration from 10 % to 39 %. The microstructure of thin films of the Ni100−x-Cux alloy has been investigated using a field emission scanning electron microscope (FESEM). The FESEM micrograph shows the formation of pits, and the size of pits decreases with increasing concentration of doped Cu. Experimental results also reveal that the increase in corrosion resistance can correlate with the developing residual stress in the films.

Effect on Durability and Electrochemical Response of the Addition of a Non-noble Transition Metal in Mixed Ruthenium and Manganese Oxide Thin-film Electrodes

Mixed metal oxide (MMOx) thin films-based electrodes have been widely used in the treatment of polluted solutions. To limit costs while exploring new electrocatalytic potentials, novel mixtures are being proposed.In this paper, the electrochemical behavior of thin films obtained by co-deposition of Ruthenium, Manganese, and a third transition metal among Copper, Iron, and Cobalt was investigated with the scope of finding optimal compositions and long stability for applications as the anodes in environmental treatments.The binary and ternary oxides coated electrodes were prepared by thermal decomposition on titanium foils from alcoholic solutions.The morphological properties of the thin films were analyzed through scanning electron microscopy (SEM) while the electrochemical performance was evaluated by potentiodynamic polarization curves and cyclic voltammetry (CV). The service time was assessed by accelerated life tests.The results show that the combination of Ruthenium with one or two different metals results in evident modifications of the morphology, both kinetic and thermodynamic electrochemical properties as well as the service lifetime.In particular, a combination of Iron and Manganese was to be excluded because of the poor solubility which affected both the coating homogeneity and electrochemical response. The Cobalt-containing electrodes outperformed the others in terms of stability. The addition of Copper implied a reduced susceptibility to corrosion and higher charge storage.

Optimisation of electrochromic properties of titanium doped V2O5 film

V2O5 is a versatile material that have controllable transmission, absorption and reflectance that are suitable for electrochromic applications. In this report, the Vanadium pentoxide is modified by doping with titanium using its propoxide precursors. Thin films were fabricated over Florine doped Tin Oxide (FTO) coated glass plate by spin coating technique. Electrochromic properties of V2O5 film is improved by doping with Titanium. X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM) analysis and UV Visible absorption and transmission of the prepared films were taken. To study the electromagnetic properties of the thin films, they were annealed at different temperatures for 30 min. Temperature dependence on optical properties of Ti-V2O5 films were analysed by absorbance and transmittance spectrum. We optimised the fabricated films for its electrochromic properties at temperatures of 350 °C, 450 °C and 550 °C. Among this the thin film annealed at 450 °C shows better oxidation and reduction peaks. Thus the electrochemical behaviour of thin films (V2O5 doped with Titanium) were studied by the cyclic voltammeter.

Preparation of well-ordered hexagonal particles of synthetic cobalt smectites containing electrochemically active cobalt(II) sites

The preparation of ordered cobalt smectites consisting of regular hexagonal platelets, up to 300 nm in diameter, is described. They were obtained by hydrothermal treatment at 250 °C of reaction mixtures prepared by adding silicic acid to cobalt hydroxide suspensions produced by the addition of NaOH to cobalt(II) chloride solutions. Selected area electron diffraction gave well-resolved spots in hexagonal arrangements showing that the platelets consisted of ordered coherent stacks of several clay layers, rather than the turbostratic stacking of layers usually found for natural smectites. Simply inverting the order of addition of NaOH and silicic acid during the preparation of the reaction mixture gave a smectite composed of much smaller particles and containing no regular hexagonal platelets. Lowering the temperature used in the hydrothermal treatment produced less regular clay particles. Increasing the pressure during the hydrothermal treatment by adding argon to the autoclave did not affect the morphology of the clay particles. These differences in the morphology of the clay particles were found to affect the electrochemical behavior of thin films of the clays. The voltammetric waves obtained for [Ru(bpy) 3] 2+ cation adsorbed in films of the clays containing the large hexagonal particles was much larger than in films of clays containing no such particles. The fraction of the adsorbed cations that were electrochemically accessible increased from 8.5% in clays containing no hexagonal particles to more than 50% in clays containing the hexagonal particles.

Electrochemical behaviour of thin films deposited by plasma DBD torch on copper: An O 2-diffusion barrier

In the field of corrosion protection, the research of environmentally friendly coating processes is one of the research topics. The use of gaseous atmospheric plasma, especially dielectric barrier discharge (DBD) plasma is an interesting way to rapidly form a thin protective coating. The aim of this work is to characterize the electrochemical behaviour of a SiO x C y N z film, formed from different organosilicon precursors, in neutral corrosive environment on copper. The film morphology and composition were determined by transmission electron microscopy (TEM) observations and X-ray photoelectron spectroscopy (XPS). The electrochemical behaviour of the different treated copper was studied by stationary techniques and electrochemical impedance spectroscopy (EIS). With the same plasma parameter, the kind of organosilicon precursor determines the chemical stability of the coatings in water, then their protective properties. When the SiO 2-like structure contains a low carbon level, the SiO x C y N z films present a good stability in water, and acts clearly as an O 2 barrier membrane.

Electrochemical behaviour of thin films of Co/Al layered double hydroxide prepared by electrodeposition

Thin films of controlled thickness of Co/Al layered double hydroxide with different Co and Al percentages have been electrosynthesized by the cathodic reduction of a 0.03 M Co and Al nitrate solution. The electrochemical behaviour of the films deposited on Pt or ITO electrodes has been deeply studied in 0.1 M NaOH solution. Our findings demonstrate that as soon as a potential is applied in the anodic direction, the films undergo an irreversible change of phase.

Thin films of amorphous nitrogenated carbon a-CN x: Electron transfer and surface reactivity

The electrochemical behaviour of thin films of nitrogenated amorphous carbon a-CN x is similar to that of boron-doped diamond, with a wide potential window in aqueous media. They are elaborated by cathodic sputtering of a graphite target in an Ar-N 2 active plasma for varying nitrogen contents, determined by XPS (0.06 ≤ x ≤ 0.39). Their electrochemical reactivity is sensitive to the surface state. The present study reports on the influence of electrochemical pre treatment on the electronic transfer rate of a fast redox system ferri-ferrocyanide, by focusing on the direction of the potential excursion. On the other hand, the role of both the pH and the potential on the interfacial capacitance in the presence of Na 2SO 4 without redox species is documented. The results show up the sensitivity of the film surface to the electrochemical conditions.

Thin layers of iron corrosion products electrochemically deposited on inert substrates: synthesis and behaviour

The deterioration of iron-based materials due to corrosion is a well-known problem. A variety of corrosion products can be formed depending on the species present in the medium (soil, water, etc.). Understanding the transformation pathways during the evolution of a corrosion layer is a hard challenge since it is difficult to clearly identify the contributions of each corrosion product. That is why the development of electrodes with only one iron corrosion product deposited as thin layers on inert substrates (gold, silver) presents many advantages to carry out electrochemical studies. In this way, the present paper reports successful electrochemical synthesis of thin layers deposited on inert substrates (gold, silver) of commonly occurring iron corrosion products as siderite, green rusts incorporating carbonate or sulphate anions, magnetite and goethite. The films are characterised by usual ex-situ techniques: FTIR, SEM, and XRD. The study of the electrochemical behaviour of thin films of green rust deposited on silver illustrates the potential application of such electrodes.

Electrochemical behaviour of iron and iron oxide thin films in alkaline (1 m KOH) aqueous solution: a voltammetry study for cathodic instability of coating/metal interface

The electrochemical behaviour of thin film metallic iron and the iron oxides in 1 m KOH anaerobic aqueous solution was studied by cyclic voltammetry technique. The material studied was of thin film (50 nm) iron supported on a glass substrate, and the oxide thermally formed on the iron film. The voltammetry of thin film iron on glass was similar to that of low carbon steel and gave a convenient means for preparing specimens for obtaining information relevant to the degradation of structural steel. In this report, the formation of various types of oxides on the iron surface are identified, and the electrochemical stability of the oxides and their relevance to the cathodic disbonding of organic coating from cathodically protected steel pipelines are discussed.

(CeO 2) x-(TiO 2) 1− x: Counter electrode materials for lithium electrochromic devices

Since 1989, (CeO 2) x -(TiO 2) 1− x have been considered as possible counter electrode materials for electrochromic devices using lithium conducting electrolytes and WO 3 as electrochromic material. The electrochemical behaviour of thin films of these materials depends on the structure of the films and on the electrolyte composition. According to X-ray diffraction data, the films seemed to be composed of an amorphous matrix of TiO 2 including nanocrystallites of CeO 2. After a short review of the data previously obtained, new data obtained on materials made up by using either sol-gel processes (Ti(OPr i) 4 + Ce(OPr i) 4 or CeCl 3 or Ce(NH 4) 2(NO 3) 4) or sputtered from oxide targets are presented. The influences of the nanocrystalline structure, of the electrolyte type (polymer based solid electrolyte or liquid organic electrolyte) and of the water content are discussed.

Comparative behavior of electrodes coated with thin films of structurally related electroactive polymers

General methods are described for the synthesis of electroactive polymers and the preparation of uniform, stable, polymer-coated electrodes. The electrochemical behaviour of thin films of eight different functionalized polystyrenes, differing in the identity and amount of attached electroactive species, and polyvinylferrocene is presented. A wide range of electrochemical properties can be observed by varying parameters such as film thickness, nature of the bound redox couple, extent of polymer functionalization and oxidation state. The deviations from ideal surface behavior are investigated in detail. These are shown to be consequences of cooperative electronic interactions, structural reorganization or uncompensated resistance within the film, depending upon the material. The film resistance varies greatly among the polymer films studied and is shown, in some cases, to be a sensitive function of the extent of oxidation and prior treatment of the film. This variable resistance is shown to be a consequence of slow ion transport through the film. The mechanism of electron transport in such materials is considered and a model of the metal/polymer/electrolyte interface is proposed.