NITRIC-OXIDE REDUCTION USING PLATINUM-ELECTRODES ON YTTRIA-STABILIZEDZIRCONIA

Porous platinum and platinum/ceria electrodes deposited on yttria-stab ilized zirconia (YSZ) are used to reduce electrochemically nitric oxid e in inert gases at temperatures between 500 and 600 degrees C. A cycl ic voltammetric study indicates that nitric oxide reduction occurs mor e rapidly on an electrode thermodynamically predicted to exist as redu ced platinum and not as platinum dioxide. The steady-state nitric oxid e decomposition rate increases with temperature, NO concentration, and cathodic polarization. Nitric oxide is also reduced on the platinum-b ased electrodes in streams containing both nitric oxide and oxygen. Th e currents at a given electrode potential and temperature are more tha n an order of magnitude higher in the NO/O-2 streams than in the NO/in ert gases due to simultaneous oxygen reduction. The yield factors, def ined as the relative rate of NO reduction compared to O-2 reduction (c orrected for species concentrations), are between 0.2 and 0.6 for both electrodes. The yield factors are insensitive to ceria addition, oxyg en concentration, applied current, and temperature in the ranges inves tigated in this study.