Nicholas E. Vanderborgh

Thin Film Electrode Arrays for Mapping the Current‐Voltage Distributions in Proton‐Exchange‐Membrane Fuel Cells

An array of reference electrodes was fabricated on a polyperfluorosulfonic acid membrane using microlithographic techniques. This array was used to map the current-voltage distribution at a proton exchange membrane fuel cell anode. Inhomogeneity in the voltage distribution was attributed to nonuniform humidification of the electrode, resulting in a decrease in halt-cell performance. Details of the fabrication method and the theory behind the array concept are presented.

Heterogeneous Charge Transfer Rates of the Ferrocene Oxidation in Sulfolane

Large deviations were found between predicted and observed rates of charge transfer for ferrocene oxidation in sulfolane; the measured rates were low. Reduction rates of nitrobenzene in sulfolane were also of the same order of magnitude. It is suggested that similar retardation might occur in other structured solvents such as DMSO or hexamethylphosphoamide. (DLC)

Electrochemistry at thin solid films

Recently, several techniques have been developed to simultaneously examine species formed during electrochemical reactions. For exmaple, in situ spectroscopic−electrochemical methods yield data to characterize electrode processes and possibly elucidate electrocatalytic reactions. Spectroelectrochemistry utilizes optically transparent electrodes (OTE) to measure with transmission, internal reflectance, or reflection spectroscopy the rates of formation and disappearance of electrogenerated species. These OTE’s are either metal or semiconductor thin films which are chemically inert and have optical properties compatible with the experiment. Optical data gives a clearer picture of the electrochemistry at the solution/electrode interface. These types of electrochemical data may also be used to characterize surfaces of the thin film electrodes. Application of thin deposited films to spectroelectrochemical studies are reviewed. Simultaneous spectroscopic and voltametric results are shown for Pt films deposited u...

Studies of the Ag‐Pt Interface Formed by Ag Deposition from Sulfolane Solutions on Thin Film Electrodes

Vapor deposition, thin film fabrication techniques have been applied to the preparation of Pt electrodes of various topographies. Large variations were observed in the electrical resistivities of these electrodes as a function of porosities. The effect of these film preparation techniques on Ag electrodeposition from solutions of AgClO/sub 4/ in sulfolane was examined. Analysis of cyclic voltammetric data and double potential step chronocoulometric results indicate silver deposition occurs without underpotential deposition in sulfolane in contrast to behavior found in aqueous medium. Auger electron spectroscopy and argon ion sputter etching were used to examine the surface and depth profile of controlled potential-deposited thin layers of Ag. Porous films showed deep penetration of all monitored species (Ag, Pt, S, Cl). The degree of penetration decreases rapidly with increasing film density. The surface analysis results have been correlated to the electrochemical behavior and interpreted in terms of the extent of solvent, solute interaction prior to electrodeposition.

Auger electron spectroscopic depth profiling techniques applied to ultrathin electrochemically deposited metal layers

The Auger electron spectroscopic depth profiling technique is applied to the study of the initial equivalent monolayer of electrodeposited Ag on thin‐film Pt electrodes. The ultimate depth resolution of this technique is determined by examining ultrathin layers of Ag which have been ion deposited from a zeolite source in ultrahigh vacuum. The exponential decay apparent in the examination of such layers is explained from elementary considerations of the sputtering process. These are seen to be the resolution‐limiting factor for these layers. The depth resolution is shown to be on the order of 5 A. Examination of monolayer and submonolayer films of Ag electrodeposited from an AgClO4/sulfolane solution shows that there is an adsorbed overlayer of S (of solvent origin) followed by the electrodeposited Ag film, which is rich in Cl (of solute origin), followed by the Pt substrate, which also contains high levels of Cl. The absence of underpotential deposition is clearly demonstrated. There appears to be two che...

Three‐transducer differential phase‐shift method for the measurement of ultrasonic velocity in liquids

A new method for determining ultrasonic velocity (500 kHz) is described. Differential phase shift measurements are made with a three‐transducer cell to a precision of ± 0.2%. Calibration data are given for aqueous solutions of NaCl and with mixtures of water and tertiary butyl alcohol.

Laser Induced Pyrolysis Gas Chromatography

Although pulsed lasers have been commercially available for only one decade, they have been utilized in chemical analysis as highly monochromatic light sources, as intense, short duration sources for photolysis, and during the last few years, as thermal sources for degradation processes. Pulsed laser energy offers unique properties for the initiation of thermal degradation. Especially sensible is the combination of laser induced thermal degradation with gas chromatography. This paper reviews some applications and experimental possibilities of this new pyrolysis method. It should be noted that only a few papers have appeared on this topic and certainly much still needs to be done to fully characterize the potentialities of this technique.