Hydrophilic Electrode Research Articles

Peroxidase-incorporated hydrophilic polythiophene electrode for the determination of hydrogen peroxide in acetonitrile

Peroxidase-incorporated conducting polymer electrodes are examined as hydrogen peroxide sensors in acetonitrile. An aqueous solution containing horseradish peroxidase (HRP) and chemically polymerized poly(3-(3'-thienyl)propanesulfonic acid) (PTS) was cast on SnO 2-coated glass plates to obtain HRP/PTS electrodes. The electrode exhibits cathodic current responses to hydrogen peroxide (≥ 1 μM) at +100 to +700 mV vs. Ag Ag + in acetonitrile containing 4% water and 0.1 M supporting salt (NaClO 4 or tetra- n-butylammonium perchlorate).

Permselectivity and High Sensitivity at Ultrathin Monolayers. Effect of Film Hydrophobicity

The effect of monolayer structure and solution composition on electrochemical response at ultrathin monolayers formed by self-assembly has been investigated. The monolayers studied consisted of thioctic acid (1,2-dithiolane-3-pentanoic acid) and 1-hexanethiol, where different degrees of surface hydrophobicity were obtained through the coassembly of these two molecules. On the more hydrophilic thioctic acid monolayers, fast kinetics and high electrochemical sensitivity were obtained for hydrophilic probes Fe(CN) 6 3- and Ru(NH3) 6 3+ . Permselectivity at the hydrophilic monolayer electrodes could be achieved by controlling the extent of dissociation of the monolayer COOH head groups. As the hydrophobicity of the film increased with the coadsorption of hexanethiol, the kinetics of the hydrophilic probes became slower. For more hydrophobic catecholamines and quinone probes, slower kinetics (lower sensitivity) were consistently observed at the monolayer electrodes, independent of the monolayer composition. A simple modified Stern model is proposed to represent the relationship between the probe response, the monolayer structure, and the electrolyte composition. The role of the Donnan potential in controlling film permselectivity is addressed, and the roles of monolayer stability and substrate quality on the monolayer electrode response are discussed.

Analysis of the influence of the surface wettability on the quartz sensor response

Abstract Acoustic impedances of water and Brij-58 (a nonionic detergent) in contact with hydrophilic and hydrophobic electrodes of thickness shear mode resonators were studied. Measurements were performed at the fundamental, third and fifth overtone resonances of the AT quartz. Discrepancies were observed between the real and imaginary parts of the acoustic impedance, Re( Z L ) and Im( Z L ), for the hydrophilic quartz as well as the chemically modified quartz (hydrophobic surface). Moreover for this latter surface, the imaginary component of the acoustic impedance was lower than for the native resonator. This difference is especially due to the surface wettability. The extent of liquid rigidly coupled to the quartz surface was thus quantified, and it was shown that it was lower for a hydrophobic quartz than for a hydrophilic one. Furthermore it has been observed that for both components of the acoustic impedances, a significant transient signal appears before equilibrium whatever the liquid used.

The silver catalyst in the hydrophobic oxygen electrode

Ten sorts of silver powder were tested as the catalysts for hydrophobic air electrodes in an alkaline electrolyte. The fine grain catalysts meet the demands of the electrodes better than the catalysts with large surface area which proved not to be satisfactory. The catalyst prepared by reduction of the aqueous suspension of a solid silver salt has the best properties. Electrochemical electrode behaviour is improved by using pure oxygen. The characteristics of some silver catalysts in hydrophilic electrodes were also determined.

Methanol-air fuel cell with hydrophilic air electrodes

A methanol-air fuel cell system with alkaline electrolyte and hydrophilic air electrodes was built and tested. Heat and fuel losses as well as auxiliary system power demand have been measured. Information is gained about attainable temperatures and voltage efficiencies as a function of the number of cells delivering a given electrical output. The effects of some stack imperfections are discussed.

The silver catalyst in the hydrophobic oxygen electrode

Ten sorts of silver powder were tested as the catalysts for hydrophobic air electrodes in an alkaline electrolyte. The fine grain catalysts meet the demands of the electrodes better than the catalysts with large surface area which proved not to be satisfactory. The catalyst prepared by reduction of the aqueous suspension of a solid silver salt has the best properties. Electrochemical electrode behaviour is improved by using pure oxygen. The characteristics of some silver catalysts in hydrophilic electrodes were also determined.

Behavior of Hydrophilic Porous Oxygen Electrodes with Silver Electrocatalyst

An experimental study of the behavior of porous hydrophilic oxygen electrodes shows the important influence of the electrochemical reaction on the shape of the i‐E curves at low current densities. A correlation between mass transport properties of the electrolyte, , and the slope of the polarization curve is found at medium current densities. Convection appears to be important at high current densities. The depth of the effective reaction zone has been calculated under varying conditions.