| The mutual interferences of carbon monoxide and hydrogen oxidation reactions at different anodic potentials on a Pt electrode have been investigated. Two types of response curves are observed in the cases we studied and termed as additive and inhibitive. A site model for the CO and H2 adsorption-oxidation on the Pt electrode is proposed and the ratio of sensitivities for CO to H2 at +478mV vs. Pt/air is 32.45. The selectivity for CO verses H2 oxidation reaction increases 365 times, (from 0.149 to 54.5) as the potential increased from 0mV to +478mV.; The Shared Sensor Technology User Facility (SSTUF) is a sensor test station designed to simulate environments for operational process of PEM fuel cells capable of temperature, pressure, RH, gas composition and flow controls. Three types of AGS, Devices I, II, and III, were constructed and evaluated for hydrogen measurements in atmospheres containing carbon monoxide. Device I had a porous PT composite working electrode deposited on a porous Teflon substrate. An FEP membrane was mounted on the gas inlet for Device II, which increased the cross sensitivity to gases such as CO, NH3, and H2S to nearly 100%. A Nafion RTM coated Ag/AgCl was applied as the new RE in Device III and showed a good stability to high levels of H2. Device I response to CO at varies flow rates were analyzed and diffusion control or electrochemical redox reaction control regions were defined. The hydrogen reaction order on Device III was found to be first order. By using SSTUF, isobaric measurements performed in pressure range of 1 to 3 atm absolute for Device III produced sensor signals proportional to the [H2] from 0 to 8%. The [H2] sensitivities at these pressures were linearly dependent on the total pressure and the background signals were also found linear to the pressures and also O2 levels. |
