Swathy Swathirajan

Corrosion resistant PEM fuel cell

The present invention contemplates a PEM fuel cell having electrical contact elements (including bipolar plates/septums) comprising a titanium nitride coated light weight metal (e.g., Al or Ti) core, having a passivating, protective metal layer intermediate the core and the titanium nitride. The protective layer forms a barrier to further oxidation/corrosion when exposed to the fuel cells operating environment. Stainless steels rich in CR, Ni, and Mo are particularly effective protective interlayers.

Rotating Disk Electrode Investigations of Fuel Cell Catalyst Degradation Due to Potential Cycling in Acid Electrolyte

Fuel cells operated under automotive cyclic conditions are more vulnerable to membrane and electrode degradation. Degradation of Pt catalyst due to potential cycling was characterized by loss of hydrogen adsorption (HAD) area and shift in the half-wave potential for oxygen reduction at a thin film catalyst rotating disk electrode. It is shown from an analysis of the assumptions involved in calculating the HAD area that uncertainty in the potential dependence of hydrogen coverage and the inability to separate a priori the double layer charging current at Pt can lead to a 34% underestimation of the HAD area of Pt. Potential cycling between 0 and 1.2 V (RHE) for 500 cycles caused about a 20-30% decrease in HAD area for two carbon-supported platinum catalysts. This decrease followed second order kinetics, indicating that the loss of surface area is probably caused by agglomeration of Pt particles due to carbon corrosion. Analysis of oxygen reduction kinetic losses shows an increase in Tafel slope probably due to a change in the morphology of the carbon support caused by corrosion reactions. Three mechanisms are discussed for the loss of surface area and activity of Pt catalyst due to cycling.

Methanol Oxidation on Platinum‐Tin Catalysts Dispersed on Poly(3‐methyl)thiophene Conducting Polymer

Platinum-tin catalysts were prepared by electrodeposition on poly(3-methyl)thiophene to investigate the effect of catalyst support and Pt loading on the electrochemical oxidation of methanol. The polymer-catalyst assembly was characterized by SEM/EDX, surface area measurements, and Rutherford backscattering spectrometry (RBS). The Pt-Sn catalyst deposited in the hydrogen adsorption potential region showed an order of magnitude higher surface area. RBS studies enabled the estimation of the thickness and the distribution of the catalyst layer in the conducting polymer support

Electrochemical Oxidation of Methanol at Chemically Prepared Platinum‐Ruthenium Alloy Electrodes

Chemically prepared Pt-Ru alloy catalysts were investigated to study the effects of temperature, Pt loading, and heat-treatment on the kinetics of methanol oxidation in acid electrolyte. The maximum current density obtained for the Pt-Ru catalyst, dispersed on Vulcan XC-72R carbon, was about 600 mA/cm 2 at 60°C and a Pt loading of 2.05 mg/cm 2 . The maximum catalytic shift due to the Ru modification of Pt was 200 mV at a current density of 160 mA/cm 2 . The activation energy for methanol oxidation is similar for both Pt and Pt-Ru

Characterization of New Corrosion Resistant Nickel‐Zinc‐Phosphorus Alloys Obtained by Electrodeposition

The electrodeposition of a family of NiZnP coatings was studied at a rotating cylinder electrode by varying the temperature (45 o -80 o C) and the applied current density (0.03-0.95 A/cm 2 ). Two of the coatings were nickel-rich, two were zinc-rich, and a fifth coating had approximately equal amounts of Ni and Zn. The coatings were characterized using SEM/EDX and Auger depth profile techniques

Anode Materials for Mitigating Hydrogen Starvation Effects in PEM Fuel Cells

Localized hydrogen starvation at a polymer electrolyte membrane (PEM) fuel cell anode can lead to the formation of local cells in the membrane electrode assembly, which cause performance degradation at the fuel cell cathode due to carbon corrosion. We propose using hydrogen spillover materials as a hydrogen reservoir in the fuel cell anode in order to compensate for any temporary proton deficit caused by local flooding of the anode channels. We tested composite electrodes containing TiO 2 , WSi 2 , and WO 3 , and compared their behavior to that of commercial Pt/Vulcan XC-72 carbon (Pt/Vu) benchmark catalysts, using gas-diffusion electrodes in a 0.1 M HClO 4 solution and pellet electrodes in a 0.5 M H 2 SO 4 solution. While TiO 2 yields no benefits, both WSi 2 and WO 3 can significantly delay the voltage excursion of the gas-diffusion electrode into the oxygen evolution region upon the cessation of hydrogen flow. X-ray data indicate that the beneficial effect of WSi 2 may be caused by WO 3 , because we observed conversion of WSi 2 to W0 3 during voltage cycling, without a significant loss in the apparent hydrogen adsorption―desorption area. Electrodes with WO 3 yielded the best results, with a hydrogen storage charge higher by a factor of 6 than for the Pt/Vu benchmark.

A High Surface Area Platinum Catalyst Prepared from Uranium Platinum Carbide for the Electrochemical Oxidation of Methanol

This patent describes a high surface area platinum catalyst which has been prepared by the electrochemical processing of uranium platinum carbide. This Raney-type catalyst has a roughness factor exceeding 3000. The methanol oxidation current at this catalyst was about 1.8 A/cm{sup 2} at 60{degrees}C and a polarization of 1.2 V. Due to the high activity of the catalyst, the inhibition of methanol oxidation at more positive potentials and the consequent hysteresis in the oxidation response were not observed. The preparation, characterization, and evaluation of this catalyst material are also described.