High rates of oxygen reduction over a vapor phase-polymerized PEDOT electrode

The air electrode, which reduces oxygen (O₂), is a critical component in energy generation and storage applications such as fuel cells and metal/air batteries. The highest current densities are achieved with platinum (Pt), but in addition to its cost and scarcity, Pt particles in composite electrodes tend to be inactivated by contact with carbon monoxide (CO) or by agglomeration. We describe an air electrode based on a porous material coated with poly(3,4-ethylenedioxythiophene) (PEDOT), which acts as an O₂ reduction catalyst. Continuous operation for 1500 hours was demonstrated without material degradation or deterioration in performance. O₂ conversion rates were comparable with those of Pt-catalyzed electrodes of the same geometry, and the electrode was not sensitive to CO. Operation was demonstrated as an air electrode and as a dissolved O₂ electrode in aqueous solution.

Double layer structure of ionic liquids at the Au(111) electrode interface : an atomic force microscopy investigation

The double layer structure of two ionic liquids (ILs), 1-butyl-1- methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([Py ₁,₄]FAP) and 1-ethyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate ([EMIm]FAP) at the polarized Au(111) electrode interface is probed using Atomic Force Microscopy force measurements. The force-separation profiles suggest a multilayered morphology is present at the electrified Au(111)-IL interface, with more near surface layers detected at higher potentials. At the (slightly negative) open circuit potential, multiple ion layers are present, and the innermost layer, in contact with the Au(111) surface, is enriched in the cation due to electrostatic adsorption. Upon applying negative electrode potentials (-1.0 V, -2.0 V), stronger IL near surface structure is detected: both the number of ion layers and the force required to rupture these layers increases. Positive electrode potentials (+1.0 V, +2.0 V) also enhance IL near surface structure, but not as much as negative potentials, because surface-adsorbed anions are less effective at templating structure in subsequent layers than cations. This interfacial structure is not consistent with a double layer in the Stern-Gouy-Chapman sense, as there is no diffuse layer. The structure is consistent with a capicitative double-layer model, with a very small separation distance between the planes of charge.

MoO3 nanoparticles dispersed uniformly in carbon matrix : a high capacity composite anode for Li-ion batteries

A MoO₃-carbon nanocomposite was synthesized from a mixture of MoO₃ and graphite by a controlled ball milling procedure. The as-prepared product consists of nanosized MoO₃ particles (2-180 nm) homogeneously distributed in carbon matrix. The nanocomposite acts as a high capacity anode material for lithium-ion batteries and exhibits good cyclic behavior. Its initial capacity exceeds the theoretical capacity of 745 mA h g^-1 in a mixture of MoO₃ and graphite (1:1 by weight), and the stable capacity of 700 mA h g^-1 (94% of the theoretical capacity) is still retained after 120 cycles. The electrode performance is linked with the unique nanoarchitecture of the composite and is compared with the performance of MoO₃-based anode materials reported in the literature previously (nanoparticles, ball milled powders, and carbon-coated nanobelts). The high value of capacity and good cyclic stability of MoO₃-carbon nanocomposite are attractive in respect to those of the reported MoO₃ electrodes.

Transient temperature distribution in functionally graded graphite/Polymer nanocomposites based on temperature dependent properties

Transient heat conduction in a functionally graded graphite/polymer nanocomposite (FGN) plate is analyzed using finite element method (FEM). Stepwise gradient structure consisted of four different nanocomposite layers with 0, 5, 10 and 20 wt% of graphite. Thermal conductivity and specific heat capacity of the individual layers were determined using C-Therm TCi Thermal Conductivity Analyzer (Canada) in temperature range of -20 to 100 °C. Temperature history and temperature distribution across the thickness of the plate with two different configurations for two positive and negative temperature gradients are presented.

Transition metal nitrides as electrode materials for supercapacitors

This data comprises a collection of Scanning Electron Microscope (SEM) images of transition metal nitrates. Research was conducted to assess the size and morphology of particles

Morphology of ball milled graphite

The Scanning Electron Microscope (SEM) is used to characterize the morphology of ball milled graphite samples, which can be helpful for the further understanding of the samples' spectroscopic and absorptive properties.

Selective excitation of concomitant electrochemiluminophores : tuning emission color by electrode potential

ECL in 3D: Selective electrogenerated chemiluminescence (ECL) of several ruthenium and iridium complexes simultaneously in solution can be controlled by electrode potential (see picture; λem=emission wavelength). These luminescent redox systems create a range of new possibilities for multi-analyte ECL detection, assessment of interdependent electrochemical/spectroscopic properties, and color tuning in light-emitting devices.

Identification of surface heterogeneity effects in cyclic voltammograms derived from analysis of an individually addressable gold array electrode

Voltammetric behavior at gold electrodes in aqueous media is known to be strongly dependent on electrode polishing and history. In this study, an electrode array consisting of 100 nominally identical and individually addressable gold disks electrodes, each with a radius of 127 µm, has been fabricated. The ability to analyze both individual electrode and total array performance enables microscopic aspects of the overall voltammetric response arising from variable levels of inhomogeneity in each electrode to be identified. The array configuration was initially employed with the reversible and hence relatively surface insensitive [Ru(NH₃)₆]^3+/2+ reaction and then with the more highly surface sensitive quasi-reversible [Fe(CN)₆]^3−/4− process. In both these cases, the reactants and products are solution soluble and, at a scan rate of 50 mV s⁻¹, each electrode in the array is assumed to behave independently, since no evidence of overlapping of the diffusion layers was detected. As would be expected, the variability of the individual electrodesʼ responses was significantly larger than found for the summed electrode behavior. In the case of cytochrome c voltammetry at a 4,4′-dipyridyl disulfide modified electrode, a far greater dependence on electrode history and electrode heterogeneity was detected. In this case, voltammograms derived from individual electrodes in the gold array electrode exhibit shape variations ranging from peak to sigmoidal. However, again the total response was always found to be well-defined. This voltammetry is consistent with a microscopic model of heterogeneity where some parts of each chemically modified electrode surface are electroactive while other parts are less active. The findings are consistent with the common existence of electrode heterogeneity in cyclic voltammetric responses at gold electrodes, that are normally difficult to detect, but fundamentally important, as electrode nonuniformity can give rise to subtle forms of kinetic and other forms of dispersion.

Studying and evaluating anti-corrosion coatings and inhibitors using the wire beam electrode method in conjunction with electrochemical noise analysis

Purpose – To provide a summary of research work carried out mainly in the authors' group for evaluating various protective coatings including rustproofing oils, and also for studying corrosion inhibitors using the wire beam electrode (WBE) method.

Design/methodology/approach – A range of published papers published during the past 15 years was summarised and reviewed. Recent research work in the authors' group was also included, which involved the combined use of the WBE with electrochemical noise analysis and the scanning reference electrode technique.

Findings – The WBE method has been developed into a very useful tool of evaluating the performance of coatings and inhibitors. In particular, The WBE is uniquely applicable for determining the performance of coatings and inhibitors to control localised corrosion.

Research limitations/implications – Focusing mainly on recent research.

Practical implications – A useful source of information for researchers and graduate students working in the areas of organic coating and inhibitor research.

Originality/value – The first summary or review on this research topic.