Layered Au,Pt-YSZ mixed potential gas sensing electrode: Correlation among sensing response, dynamic electrochemical behavior and structural properties

Morphological and structural properties of layered Au,Pt-YSZ mixed-potential gas sensing electrodes (APE) prepared under different temperature treatments were studied by environmental scanning electron microscopy (ESEM), X-ray crystallography (XRD) and glow-discharge optical emission spectroscopy (GD-OES), and correlated with open-circuit potential (OCP) and cyclic voltammetry (CV) measurements under gas exposures at elevated temperatures. The electrode sintered at 1050 °C for 4 h provides a more uniform Au distribution both on the surface and in the inner part of the electrode. Correspondingly, the OCP response of this electrode to CO is clearly higher than that of the electrode sintered at 850 °C for 10 min. This can be well correlated with a smaller oxygen reduction reaction (ORR) observed in the related CV diagrams. Moreover, a transition from the diffusional transport to the charge transfer reaction kinetics controlled mixed-potential formation was observed between 20 and 5 vol.% O2 at the APE sintered at 1050 °C for 4 h.