YSZ-based electrochemical sensors: From materials preparation to testing in the exhausts of an engine bench test

Planar sensors based on tape-cast YSZ layers with parallel Pt finger electrodes, one coated with WO3 thick film as sensing electrode, were fabricated. The sensors were tested in the laboratory at various concentrations of NO2 and CO at different temperatures and oxygen partial pressures. Field tests were also performed; planar sensors were located close to a commercial oxygen sensor, downstream the three-way catalytic converter of a FIAT fire 1242 c.c. spark ignition engine coupled to a dynamometer. The performance of the gas sensors was measured at the air/fuel ratio stoichiometric point (A/F ∼ 14.3) at different engine regimes (RPM and torque) and thus at different operating temperatures. The response of gas sensors was compared with the response of the commercial lambda probe and related to the exhaust gas concentrations measured by spectroscopic analytical equipment at the engine exhaust end. Preliminary measurements showed promising results in terms of sensitivity, stability and reproducibility.