Versatile electrochemical coatings and surface layers from aqueous methanesulfonic acid

Ever tightening environmental pressure together with the continued need for coatings able to meet challenging service environments have stimulated advances in coating technology. In the case of electrochemical techniques, the classical techniques of electrodeposition and anodising are being upgraded to meet the need for modern surface engineering coatings (including nanostructured films) on metals. A major challenge is to retain conventional processing, including aqueous solutions, simple power supplies and existing electrolyte tanks while using cost effective, ‘green’ electrolytes. One successful direction has been the emergence of electrolytes based on methanesulfonic acid, MSA which has good electrolytic conductivity and is capable of dissolving many metals as well as acting as a useful medium for dispersion of solids prior to electrophoretic coating. A range of application methods result, including electroplating, anodising and electrophoretic deposition from a stable, aqueous sol. A diverse range of coating materials is emerging, including metals, alloys, porous metal oxide films, conductive polymers and many composites. This review illustrates the usefulness and applications of MSA electrolytes using recent examples from the authors' laboratories and others. Developing coatings, including alternating multilayers of Sn and Cu, nanostructured metals, hierarchical pores, nanotubular metal oxides and graphene composites are briefly considered. This is a review with 94 references

Photocurable Polymers for Ion Selective Field Effect Transistors. 20 Years of Applications

Application of photocurable polymers for encapsulation of ion selective field effect transistors (ISFET) and for membrane formation in chemical sensitive field effect transistors (ChemFET) during the last 20 years is discussed. From a technological point of view these materials are quite interesting because they allow the use of standard photo-lithographic processes, which reduces significantly the time required for sensor encapsulation and membrane deposition and the amount of manual work required for this, all items of importance for sensor mass production. Problems associated with the application of this kind of polymers in sensors are analysed and estimation of future trends in this field of research are presented

The influence of cell design and electrolysis parameters on the electrosynthesis of carboxylic acids from carbon dioxide and 1,3 - butadiene

The electrochemical reduction of carbon dioxide in acetonitrile in the presence of excess 1,3-butadiene is studied. The electrolysis products obtained consist mainly of a mixture of pentenoic, C5, acids (two isomers), hexenedioic, C6, acids (two isomers) and decadienedioic, C10, acids (three isomers). It is found that the total current yield and the ratio of the acids are strongly dependent on cell design and other experimental parameters. The electrolysis is investigated in several reactors, namely a dividend and an undivided batch cell and three undivided flow cells (a parallel plate cell, a swiss-roll and a fluidized bed used in monopolar and bipolar configurations). In all undivided cells the supporting electrolyte is a mixture of ditetraethylammonium oxalate and tetraethylammonium formate, which also provide the anode reactions by being oxidized to carbon dioxide and CO2 and protons, respectively. The current yield and product distribution of the unsaturated acids are investigated as a function of the electrolyte composition (salt and water contents), electrode material and form, electrolyte flow rate, electrode potential or current density and electrolysis duration. The total current yield of the three acids is higher in the flow cells. With the parallel plate configuration, using a reticulated carbon foam cathode, it can exceed 60% at high current densities (42mA.cm-2) when both electrolyte salts are present; the selectivity to the decadienedioic acids can be as high as 50%. Similar current yields can be obtained in a bipolar fluidized bed made of carbon spheres with the C10 acids initially formed with a selectivity of about 80%. The space time yield is also very high but as the electrolysis continues, the formation of the C10 acids decreases drastically and C5 acids become the major products. It is shown that the behaviour of the electrolysis depends on the electrode material and structure and on the supporting electrolyte but little on hydrodynamic parameters. It is therefore concluded that the process proceeds via species adsorbed at the electrode surface. (D72866/87)</p

Electrochemically deposited polypyrrole films and their characterization

Ionically conductive polypyrrole films have been deposited at 295 K from anhydrous acetonitrile, acetonitrile/H2O and NaBF4 aqueous solutions onto platinum, mild steel and stainless steel discs, using cyclic voltammetry, potentiostatic and galvanostatic techniques. Cyclic voltammetry of the polymer films has been studied as a function of water content of the acetonitrile solvent, polypyrrole concentration and potential sweep rate. Potentiostatic growth of thicker (&lt;30 micron) films on stainless steel allowed free-standing polypyrrole membranes to be produced. Well adherent and conductive films were deposited at constant potential in stirred solutions from acetonitrile electrolytes containing 1% (v/v) of water. The membrane resistivity of the reduced films in 0.5 mol dm-3 KCl(aq) at 295 K was ? 1 x 106 ohm cm, while the resistivity of the oxidised membrane was 2700 ohm cm