Anthony Kucernak

Electrochemical supercapacitor material based on manganese oxide: preparation and characterization

A novel class of electrochemical supercapacitor electrode material has been electrochemically synthesized from a manganese halide complex in water-containing acetonitrile electrolyte at room temperature. This material has been physically and chemically characterized by scanning electron microscopy, X-ray photoelectron microscopy (XPS), FT-Raman microscopy and cyclic voltammetry. XPS and FT-Raman characterization suggest that this material is composed of manganese oxide with a chemical composition of Mn3O4 and containing a moderate amount of carbon. Cyclic voltammetric characterization indicates that this material has higher electronic conductivity than usually seen for manganese oxide and that it shows fast kinetics for the charge–discharge process in both aqueous and acetonitrile electrolytes. The material provides a large pseudocapacitance over a potential window of about 1 V in aqueous electrolyte and about 2 V in acetonitrile electrolyte. It is therefore a good candidate as a material for an electrochemical supercapacitor electrode.

Aspects of the anodic oxidation of methanol

Abstract This paper describes some aspects of recent investigations into the anodic oxidation of methanol. Methanol has long been proposed as an anode fuel for a fuel cell, chiefly because of its ease of carriage, distribution and manipulation. However, methanol is very much more difficult to oxidise anodically than hydrogen, the more conventional anode fuel, and this has hampered development of commercial direct methanol fuel cells. Platinum-ruthenium catalysts are the most active discovered to date. Some advances in electrocatalysis of the methanol reaction by non-noble materials are discussed.

Electrooxidation of small organic molecules on mesoporous precious metal catalysts: II: CO and methanol on platinum–ruthenium alloy

Abstract Mesoporous Pt–Ru alloy has been successively prepared by the chemical co-reduction of hexachloroplatinic acid and ruthenium trichloride both dissolved in aqueous domains of the liquid crystalline phases of an oligoethylene oxide surfactant using Zn metal reductant. The resultant material containing mesoporous structures has a high specific electrochemical surface area and has been examined as an electrocatalyst towards the electrooxidation of CO and methanol using cyclic voltammetry and chronoamperometry. The rate of electrooxidation of adsorbed CO on the mesoporous Pt–Ru electrode can be modelled by the nucleation and growth of CO free holes under a process that involves 2D nucleation and 2D surface diffusion-controlled growth. Methanol is oxidized mainly via a direct pathway to soluble products on the mesoporous Pt–Ru electrode and steady-state kinetics can be attained even at low potentials. The electrocatalytic activity of the mesoporous PtRu towards methanol oxidation is favourable compared to an ultrafine Pt–Ru electrocatalyst with similar bulk composition.

Nanostructured platinum as an electrocatalyst for the electrooxidation of formic acid

Nanostructured platinum prepared by the chemical reduction of hexachloroplatinic acid dissolved in aqueous domains of the liquid crystalline phases of oligoethylene oxide surfactants, was examined as an electrocatalyst for the electrooxidation of formic acid. The electrocatalytic properties of the catalyst combining highly specific surface areas and a periodic mesoporous nanostructure were accessed in sulfuric acid solution containing 0.5 mol dm − 3 formic acid using cyclic voltammetry (CV) and chronoamperometry. The electrocatalytic activity of the material at 60 °C, is characterised by a mass activity of 8.6 A g −1 and a specific surface area activity of 26 Ac m − 2 at 0.376 V (vs. RHE). The resistance to CO poisoning was found to depend upon electrode potential. At hydrogen adsorption potentials, the material is easily poisoned, while the material shows high resistance to CO poisoning at potentials positive of the hydrogen region. These facts suggest that the decomposition of HCOOH on the mesoporous platinum is likely to proceed through a dual-path mechanism and the high surface area material is a potential electocatalyst towards the electrooxidation of small organic molecules.

Measurement of the current distribution along a single flow channel of a solid polymer fuel cell

We present a method of performing high spatial and time-resolution, non-intrusive and dynamic current measurements along the length of a single flow channel in a solid polymer fuel cell. Current profiles at different cell polarisations and reactant flow rates are examined along with the dynamic response of the fuel cell upon introduction of reactant gases.

Nickel phosphide: the effect of phosphorus content on hydrogen evolution activity and corrosion resistance in acidic medium

Transition metal phosphides possess novel, structural, physical and chemical properties and are an emerging new class of materials for various catalytic applications. Electroplated or electrolessly plated nickel phosphide alloy materials with achievable phosphorus contents <15 at% P are known to be more corrosion resistant than nickel alone, and have been investigated as hydrogen evolution catalysts in alkaline environments. However, there is significant interest in developing new inexpensive catalysts for solid polymer electrolyte electrolysers which require acid stable catalysts. In this paper, we show that by increasing the phosphorus content beyond the limit available using electroplating techniques (∼12 at% P), the nickel based phosphides Ni12P5 and Ni2P with higher levels of phosphorus (29 and 33 at% P) may be utilised for the hydrogen evolution reaction (HER) in acidic medium. Corrosion resistance in acid is directly correlated with phosphorus content – those materials with higher phosphorus content are more corrosion resistant. Hydrogen evolution activity in acid is also correlated with phosphorus content – Ni2P based catalysts appear to be more active for the hydrogen evolution reaction than Ni12P5. Electrochemical kinetic studies of the HER reveal high exchange current densities and little deviation in the Tafel slope especially in the lower overpotential regime for these nickel phosphide catalysts. The electrochemical impedance spectroscopy response of the respective system in acidic medium reveals the presence of two time constants associated with the HER.

Water in polymer electrolyte fuel cells : Friend or foe?

If fuel cells are to do for the 21st century what combustion engines did for the 19th and 20th, designers must wrestle with the complex role of water—as reaction product, proton shuttle, and asphyxiant.

Electrocatalytic activity of some carburised nickel, tungsten and molybdenum compounds

Carburisation of some compounds of nickel, tungsten and molybdenum produces powders which show considerable passivity in sulphuric acid at elevated temperature, and which also show some catalytic activity towards the electro-oxidation of methanol and of hydrogen. Of those materials examined, carburised nickel-tungsten, prepared by reduction of nickel tungstate, shows a wide potential range of passivity, and is electroactive towards the anodic oxidation of methanol. The corresponding nickel-molybdenum material shows higher corrosion rates, and some electrocatalytic activity towards the anodic oxidation of hydrogen, but with little detectable catalysis of the methanol oxidation reaction. Reduced nickel and reduced iron on their own give high corrosion rates with no detectable electrocatalytic activity for fuel oxidation. Tungsten carbide on its own shows a high degree of passivity in sulphuric acid, but no electrocatalytic activity for methanol oxidation.

Upper bounds on cold fusion in electrolytic cells

Experiments using three different calorimeter designs and high-efficiency neutron and γ -ray detection on a wide range of materials fail to sustain the recent claims of cold fusion made by Fleischmann et al.1 and Jones et al.2. Spurious effects which, undetected, could have led to claims of cold fusion, include noise from neutron counters, cosmic-ray background variations, calibration errors in simple calorimeters and variable electrolytic enrichment of tritium.

Fabrication of carbon microelectrodes with an effective radius of 1 nm

Abstract A method for producing insulated nanometer-sized carbon electrodes is presented. These electrodes are produced using electrochemical etching of carbon fibers followed by deposition of electrophoretic paint. A new deposition approach for insulating the tips, the so-called “inverted deposition” technique, is introduced. This technique allows complete insulation of the whole body of the etched carbon fiber except for the very tip, leaving an electrochemical active area with effective diameters as small as a few nanometers. The process overcomes pinhole formation that can be a problem with the normal electrophoretic paint deposition process. The fabricated electrodes show ideal steady-state voltammetric behavior. The voltammetric response corresponding to the reduction of hexacyanoferrate(III) and hexaammineruthenium(III) is investigated on these small electrodes in the absence and presence of supporting electrolyte. For these two multiple-charged ions the steady-state voltammetric behavior in the absence of supporting electrolyte is found to deviate from expected behavior, especially at very small electrodes.