Effect of Electrode Composition and Microstructure on Impedancemetric Nitric Oxide Sensors Based on YSZ Electrolyte

The role of metal (Au, Pt, and Ag) electrodes in yttria-stabilized zirconia (YSZ) electrolyte-based impedancemetric nitric oxide sensors is investigated using impedance spectroscopy and equivalent circuit analysis. Focus on the metal/porous YSZ interface is based on previous studies using a symmetric cell (metal//metal) and attempts to further elucidate the important processes responsible for sensing. The current test cell consists of a rectangular slab of porous YSZ with two metal-wire loop electrodes (metal//metal), both exposed to the same atmosphere. Of the electrode materials, only Au was sensitive to changes in concentration. The impedance behavior of porous Au electrodes in a slightly different configuration was compared with dense Au electrodes and was also insensitive to . Although the exact mechanism is not determined, the composition and microstructure of the metal electrode seem to alter the rate-limiting step of the interfering reaction. Impedance behavior of the reaction that is limited by processes occurring away from the triple-phase boundary may be crucial for impedancemetric sensing.