An amperometric solid-state gas sensor using a LaGaO₃-based perovskite oxide electrolyte for detecting hydrocarbon in exhaust gas. A bimetallic anode for improving sensitivity at low temperature

For the first time, an amperometric electrochemical sensor based on LaGaO₃ was demonstrated as highly sensitive to detect hydrocarbon (C₃H₆) at low temperature (423-773 K). At this temperature range, it is very important to estimate hydrocarbon pollution of automobile exhaust gas (the cold start condition). In the present study, using La _0.5Sr_0.5-MnO₃ as the oxygen reduction electrode, various hydrocarbon (C₃H₆) oxidation electrodes of Pt-based alloy systems were investigated. Addition of Co and subsequently cermet LDC [(CeO₂)_0.8(LaO_1.5)_0.2] produced very high sensor response and improved the performance of the sensor with respect to that using only Pt paste as the electrode. The sensors were hardly influenced by the oxygen concentration variation (0.5-5%). At the best operating temperature (623 K) the C₃H₆ sensitivity was above 800 μA/decade, and the lowest temperature of detection was 423 K. The sensors were fast, highly selective in the presence of coexisting gases, e.g., NO, NO₂, CO, and H₂, in the exhaust, and stable too. Sensors studied in the potentiometric mode and with impedance analysis of the hydrocarbon oxidation electrodes revealed the importance of the electrolyte/electrode interface and the related sensing mechanism.