Coatings on surgical instruments & eyeglasses, catalysts for control of air pollution & water pollutions, sensors that detect common hazardous gases, coatings on pigments that could make paints last longer, & diverse possible applications in optics, electronics & magnetic materials are just some of the potential applications for this research. |
Oxygen Sensors, they're in your car, in factories, in just about anything with emissions. Making the sensors work better will help control air pollution and pockebook inflation. |
Could Fuel Cells someday be powering everything from cars to cooking ranges? That's what our research is about. |
The primary objective of an ARPA-sponsored research program is to develop an efficient proton exchange membrane (PEM)-based methanol/air fuel cell capable of operating at 200C to provide a compact and reliable energy source for military and civilian applications. Such a high temperature is expected to minimize catalyst poisoning effects and enhance significantly the overall electrochemical performance over more conventional PEM-based fuel cells operating at ca. 80C. New polymeric materials with desired thermal, chemical and electrochemical stability as well as optimized ionic conductivity and processing characteristics are being synthesized. Binary and ternary alloys, including electrocatalyst/co-catalyst composites and metal macrocycles for methanol oxidation and methanol-tolerant oxygen reduction are being identified and tested. Structure-activity relations are being elucidated based on theoretical calculations and experimental information involving model systems. These studies are being complemented by the development of new strategies for the fabrication of electrodes with optimized utilization of catalytic materials. All advances are being integrated and tested in a fuel cell system. This program is a cooperative effort among three departments on the CWRU campus: Chemical Engineering; Chemistry and Macromolecular Science and Engineering, and involves 8 faculty, 12 research associates, 21 graduate students, 2 undergraduate students and 2 visiting scholars. There are also two subcontracts, one to Clemson University and other to the University of Iowa. During this past year of the ARPA sponsored project on methanol fuel cells, the polymer synthesis effort has produced a number of perfluorinated polymers with some identified to be very promising candidates for low and for high temperature fuel cell operation. Two proton conducting polymers have been identified as being able to conduct protons at temperatures of 200C under low humidity conditions [Nafion/phosphoric acid and H3PO4 doped polybenzimidazole(PBI)]. Films of PBI also have low methanol permeation so fuel crossover is low (~10 mA/cm2 for a 3 mil film). In another advance,a new one-step method of doping and casting the PBI membrane resultsis not just a simpler process, but yields conductivity greater by factors of more than four to five. The new PBI/phosphoric acid polymer has high temperature conductivity equivalent or better than the state-of-the-art commercial materials at their optimum condition. PBI/acid films were demonstrated to be stable in 200 and 600 hour H2/O2 fuel cell tests at 150C. Also, good methanol electrode performance was demonstrated with PBI/H3PO4 as the electrolyte. Experiments have been designed to elucidate the conductivity mechanism of this electrolyte and to further examine its thermal and electrochemical stability. Several oxometallates of the Keggin-type structure were found to significantly lower the potential for methanol oxidation compared to dispersed Pt catalyst alone. Theoretical ASED-MO theory is elucidating the role of Ru and Sn atoms on Pt surfaces in catalyzing methanol oxidation. Experimental efforts to clarify the mechanism of methanol oxidation have progressed with the development ofa novel technique to place Ru clusters on Pt surfaces. Also, an in situ probe (ATR/FTIR) has been developed which will identify products and intermediates at the Pt/polymer interface. Another in situ technique which combines electrochemical and mass spectrometric analysis has been developed (DEMS - Differential Electrochemical Mass Spectrometry) which has been useful for elucidating methanol oxidation mechanisms under practical operating conditions. This system has been modified to provide the first on-line MS analysis of fuel cell gas products. In situ EXAFS is being developed as a powerful tool to probe catalyst structure while electrochemical reactions are taking place under actual operating conditions. Two catalysts, iron tetramethoxyphenyl porphyrin and octylethyl porphyrin have been identified as methanol-tolerant oxygen reduction catalysts. These catalysts have activity approaching platinum. The successes of this program has attracted the attention of industry and government. The Defense Department has announced its intention to continue funding of this program for two moreyears at a level of $1.63 million per year. A consortium lead by Eltech Research Corporation of northeast Ohio has been selected by the Defense Department to develop a PBI methanol fuel cell. CWRU has entered into a licensing arrangement with one company and is negotiating other licenses to specific applications. |
A spectroelectrochemical cell/environment-controlled chamber has been designed and constructed to conduct in situ attenuatedtotal reflection Fourier transform infrared (ATR/FTIR) spectroscopy of Li/PEO(LiClO4) electrolyte. For these experiments, Li is electrodeposited in situ onto a thin Au layer sputtered on the surface of a Geinternal reflection element. This assembly enables variable temperature measurements to be performed under conditions of utmost cleanliness. Preliminary results have shown that in the case of PEO/LiClO4 this ATR/FTIR technique has sufficient sensitivity to observe changes in the composition of the surface and near surface region, including reaction products and perchlorate anions, which contribute to the transport of charge in the electrolyte phase. (Prof. D.Scherson and his research group.) |
| A rapid-scan spectrophotometer has been coupled to a rotating disk electrode (RDE) to enable acquisition of potential-difference near-normal incidence UV-vis reflection-absorption spectra of electrogenerated species in the diffusion boundary layer. The(correlated) noise associated with the wobbling of the RDE, and other imperfections, could be eliminated by synchronizing the rotation angle of the disk, with respect to an arbitrary fixed point, and the initiation of each spectral scan. This strategy was implemented by employing a signal generated by an optical sensor coupled to the rotating shaft as a primary source to drivethe grating/galvanometer unit of a Harrick rapid scan spectrophotometer. Quantitative agreement between theory and experiment was able to be obtained using the oxidation of ferrocyanide to ferricyanide ions on the surface of a Pt RDE in an aqueous electrolyte as a model system. Calculations based on the observed signal-to-noise ratios indicate that this in situ spectroscopic/forced convection method can resolve potential-difference spectral features on the order of 0.005 absorbance units. (Prof. D. Scherson and his research group.) |
A low cost, selective and user-friendly tin oxide-based H2S gas sensor has been developed using the microfabrication and micromachining facilities available on the CWRU campus. The device will detectlow concentrations of hydrogen sulfide in effluent gases to monitor H2S concentration in sulfur recovery processes. The sensor has been successfully evaluated by Keithley Instruments and they are exploring commercializing this technology. (Profs. R. Savinell and C.C. Liu and their research groups.) |
A CO sensor is being developed using Nafion as a supporting electrolyte at room temperature. This method is based on the electrocatalytic oxidation of CO. The advantages of this approach are higher reproducibility, greater sensitivity and linear dependence. Several electrode structures have been successfully tested in the CO concentration range 45-500ppm. Similar approaches are being pursued for developing an azide sensor, which is of interest to the automotive air-bag industry. (Profs. R. Savinell and C.C. Liu and their research group.) |
A research program is underway to develop sensors to measurethe aggressiveness of local environments. An extensive study is underway to understand the Ir/IrOx system, which is used as apH sensor. Sensors have been developed at CWRU to measure suchcorrosion-related parameters as Cl- ion concentration, redox potential,conductivity, time-of-wetness, and temperature. (Prof. J. Payer and his research groups.) |
Microelectronic circuitry typically used in the computer and communications industries is susceptible to failure resulting from corrosion of copper interconnects. Copper coupons were exposed to various corrosive atmospheres. The nature and the extent of species formed in the resulting tarnish films were determined electrochemically using coulometric reduction and spectroscopically using X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS). The morphology of the corrosion products was determined using transmission electron microscopy (TEM) and high resolution scanning electron microscopy (SEM). (Prof. J.Payer and his research group.) |
The exterior of buried steel pipeline is protected from corrosion by coating the steel with fusion bonded epoxy (FBE) and applying cathodic protection to any steel that might be exposed due to defects in the coating. The epoxy is cured on a thermally oxidized (iron oxides) steel surface. The accelerated disbonding of epoxy coatings from steel under cathodic polarization is a major reason for the degradation of these protected surfaces. The effects of polarization have been observed for the steel surface in 1M aqueous KOH using subtractively normalized-interfacial Fourier Transform infrared spectroscopy (SNIFTIRS). The formation and breakdown of various iron oxides on the surface were observed. In addition the rate and conditions of disbonding were studied. The degradation of the FBE coating and remnants of the coating on the steel were examined using Fourier transform infrared spectroscopy. (Prof.J. Payer and his research group.) |
The electrochemisty of boron doped diamond films and high energy implanted diamond films (prepared by R. Kalish, Technion,Israel) have been examined in several media. The boron doped films are more stable and wide ranging in electrochemical behavior than high energy ion implanted films that are partially graphitized. The latter have the advantage of high lithographic selectivity. (Prof. B. Miller and his research group.) |
II-VI Semiconductors have been successfully deposited in TiO2 nanostructures as confirmed by photospectra and energy conversion response. (Prof. B. Miller and his research group.) |
Spatially averaging electrochemical microsensors have been designed and microfabricated for diagnostic measurements in 1-20L biomedical samples. Integrating Pt, Au, Au|Hg, Af and Pd|PdO sensors are used to detect ions and molecules in model body fluid microsamples. Calcium, magnesium, copper, zinc ions, pH and enzyme activities are measured. A spatially integrating pH microsensor combined with a microfabricated noble metal electrode and a feedback control loop is designed to operate as a miniature pH-stat to determine enzyme activity in 1-20 L enzyme samples at preset constant pH values. (Prof. M. Gratzl and his research group.) |
Microvoltammetry with carbon fiber electrodes was shown to be able to detect anticancer drugs after adsorptive stripping in the 10-10 - 10-4 M range. This detection scheme was used in a unique set of experiments to characterize drug-sensitive versus drug-resistant single live human cancer cells in terms of activedrug efflux, to elucidate mechanisms of drug resistance that is an all-too-frequent cause of failure of cancer chemotherapy. (Prof.M. Gratzl and his research group.) |